GRICULTURE HANDBOOK

NO. 175

CURRE, r SE.,;,r,f^/

^UG 2 6 1960

^

510

AGRICUITUEAL RESEARCH SERVICE

U.S. DEPARTMENT OF AGRICULTURE
CONTENTS

Vnlít!

DISEASES OF MINKS 1

Factors in Prevention and Control 1

Ranch location 1

Shipping instructions 2

Live animal exhibitions 2

Pens and nest boxes 2

Guard fence 2

Water and feed supply 3

Disinfectants 3

Disease outbreaks 4

Disposal of dead animals 4

Bacterial Diseases 4

Botulism 4

Anthrax 5

Streptococcus infections 6

Salmonella infections 7

Tularemia 7

Tuberculosis 8

Nonspecific enteritis 8

Pneumonia 9

Pleuritis. 10

Virus Diseases 10

Distemper 10

Virus enteritis 13

Nutritional Diseases 13

Urinary calculi 13

Steatitis (yellow fat) 15

Nursing sickness 16

Pregnancy disease 17

Urinary incontinence (wet

belly) 17

Chastek's paralysis 17

Gastroenteritis 17

Fatty change of liver 18

Hereditary Diseases 18

Il3'drocephalus 18

Aleutian disease 19

Poisoning, Vices, and Miscellaneous Agents 19

Lead poisoning 19

Page

DISEASES OF MINKS—Con,

Poisoriing, Vices, and Miscellaneous Agents—Continued

Other poisoning 20

Feeding poultry waste 20

Foreign bodies 20

Tail chewing and fur clipping 21

Heat exhaustion 21

Posterior paralysis 22

PARASITES OF MINKS 23

Prevention and Control 23

External Parasites 23

The fox maggot 24

Grubs of the rodent botfly 25

Fleas and lice 26

Mange 27

Other mites 27

Internal Parasites 27

Coccidia 27

Toxoplasma 29

Roundworms of digestive

tract 29

Roundworms of kidney 29

Trichinae 30

Guinea worms 30

Tapeworms 30

Lung flukes (flat-worms) 30

Intestinal flukes 31

Liver flukes 31

Examination of feces for parasite eggs 31

Collection and preparation of

samples 31

Examination of slide 33

HOW TO PACK AND SHIP

SPECIMENS FOR LABORATORY DIAGNOSIS 33

• Shipping Dead Animals 34

The Accompanying Letter 35

Shipping Tissues in Formalin__ 35

Shipping Parasites 35

This Agriculture Handbook supersedes Farmers' Bulletin 2050, Diseases and Parasites

í -:, of Minks r'A

Washington,, D.C. Issued August^WeO

For sale, by the Superintendent of Documents, U.S. Government Printing Office,

Washington 25, D.C—Price 20 cents
MINKS: Diseases and Parasites

C- By J. R. \G(>r}iaiii, ¡Í. J.jdriffith.i, niitl R. Kcith\ Fnrrcll

Domestic raising of ininlvs on a

large scale is a relativelj' new industry in the United States. Although

minks were grown on farms as early

as the 1920"s, rapid expansion of the

industi-y did not occur until introduction of the mutation strains in

the early 19-iO's. More than 6,500

domestic mink ranchers novi- 2)roduce more than 5 million pelts annually. The industry has an annual

value in excess of $100 million.

Increasing production costs emphasize the importance of i-educing

to a minimum losses from diseases

and parasites.

This bulletin, based on nearly 15

years of researcli by Federal and

State agencies and by the fur-farming industry, is intended to provide

a useful reference manual for mink

ranchers. It is desigiied to help

ranchers recognize the more common mink diseases and thus know

when professional assistance is

needed. It is not meant to encourage ranchers to diagnose and treat

diseased miidis without the advice

of a veterinarian.

DISEASES OF MINK'

Diseases are here divided according to their cause—bacteria, viruses, nutrition, heredity, a n d

miscellaneous, including poisoning

and vices such as tail chewing.

Consult a veterinarian for specific

information if a disease breaks out

in your mink herd. There is always the possibility that an animal

may be sutfering from two or more

diseases at one time.

Factors In Prevention and

Control

Ranch Location

The ranch may be located on any

type of well-drained soil. Good

'Prepared by J. R. Gorham and R.

Keith Farrell, Animal Di.sea.se and Parasite Research Division, Agricultural

Research Service, in cooiieratiou with

the Department of Veterinary Science,

Washington State University.

drainage, as in gravelly or sandy

soil, helps to lower the incidence

of disease ; poor drainage favors the

growth and spread of bacteria and

parasites. Good soil drainage is

especially important if minks are

kept on the ground. Although the

importance of good soil drainage is

reduced if minks are reared in wirebottom pens, it is not good practice

to allow pools of stagnant water to

accumulate under tlie ])ens.

When selecting a location for a

ranch, consider the possibility of

losses due to heat exhaustion.

Minks get along very well in cold

weatlier, but they do not tolerate

extremely hot, humid conditions.

As many desirable mink-raising

areas are hot and humid, locate the

ranch Avhere tliere is a maximum

of air circulation. Good ventilation often prevents losses.

1
Shipping Instructions

Ship only iuiiiiiiils tliiit liave been

vaeciimted ajiüinst distemper and

vii'iis enteritis. For convenience in

feediiii;- and liandlin<i diirinp; shipment, expressmen often i)lace minks

next to do<i-s. If tlie doa's near tliem

have distemper, unvaccinated minks

run a serious risk of becoming

infected.

Proper feed and clean fresli water

during transit are very imj^ortant.

In the feeding instructions to the

expressman, specify the use of

fresldy ground, raw lean beef, but

never hamburger. Use of haml)urger permits too many substitutes that nniy be spoiled or

decomposed. Feeding of spoiled

hamburger has caused tlie loss of

valuable animals. Fresh water

should be availal)le to the minks at

all times.

Isolate all new or returned breeding stock. Place them in a sejjarate shed for at least 50 days. Animals should be shipped only during

the fall and winter and never before

the breeding season, when an isolation period is impracticable.

Live Animal Exhibitions

Live animal fur shows and Held

daj's are worthwhile and should be

contiiiued at their present high

standards. If a few precautions

are followed, the danger of disease

is negligible. Vaccinate all show

animals for distemper at least 2

weeks prior to the exhibition. Do

not show any minks if any animal

on your farm has had distemper

within the past year. ÎNIinks from

virus enteritis areas sliould be

barred from shows until eifective

control measures become available.

Pens and Nest Boxes

Wire-bottom pens have greatly

reduced the hazard of disease (fig.

1). Because internal jiarasites

(such ascoccidia) and external parasites (such as fleas) spend parts of

their life cycles in bedding or soil,

animals readily reinfect themselves

/*-^^^

VuiViiE 1.—A mink pen of desirable typeIt is raised uljove the ground so that

the diMippings cannot collect in the pen

hut will iall down through the wire.

and expose their pen mates when

they are kept on the ground. Furthermore, infected soil remains contaminated for some time and is

capable of infecting minks that are

later placed in the pen. Pens with

cement or board floors have the

same disadvantages. H o w e v e r,

the}^ are easier to clean ancl

disinfect.

Nest boxes and pens should be

constructed so that they are easy to

clean. Pelt in season any animals

that are poor housekeepers—as evidenced by piles of droppings and

uneaten feed—unless they are valuable breeders. This filth is a source

of disease-producing bacteria, bacterial toxins (poisons), and parasite eggs and cj'sts, and, in addition,

it attracts flies, which may carry

bacteria and viruses.

Guard Fence

A guard fence is important to

prevent loss of animals that escape

fronr their pens and to keep out

stray dogs, rats, and other animals

and visitors that might introduce

infection into the minkery.

Many mink ranchers keep dogs

within the guard fence to protect

the minks from marauders. This is

permissible if the dogs have been

vaccinated for distemper and are

not allowed to roam the neighbor-
hood, where they miirht be exposed

to it or to other diseases and carry

them back to the stoclc animals.

Eats are potential spreaders of a

large number of disease-producing

organisms; they should be eliminated from the premises to protect

the health not onlj' of the minks but

also of the workers and their

families.

It is not good practice to allow

ferrets, pet coyotes, or raccoons, in

the enclosed area. All these animals are susceptible to distemper

and, if infected, can easily spread

the virus. In a routine mink-vaccination program, all such pets

should also be vaccinated.

Water and Feed Supply

Successful ranchers realize the importance of plenty of fresh water

for their minks. The mink's luitural habitat is near lakes and along

streams and rivers. ^Slinks can occasionally miss a feeding or two

without harm, but they must have

water eveiy day. "Withholding water for about 3 days will kill a

mink. Under farm conditions, 1

day without water is likelj' to be

fatal.

Many ranchers have a watering

system in which all minks on one

side of a shed drink out of one long,

narrow trough. Since distemper

virus is excreted in nasal discharges

and virus enteritis is excreted in

the droppings, one infected mink

near the source of water might

easily infect all those drinking

along the entire row. Alwaj's provide individual water containers

when there is a disease outl^reak.

Using any feed of qi;estionalj]e

quality is unwise. For example,

meat containing botulinus toxhi

would produce botulism, which can

wipe out an entire mink herd within

2 or 3 days. Never purchase meat

from a rendering plant; it may be

contaminated or spoiled by improper handling or inadequate storage

facilities.

Disinfectants

Cleanliness in the caie of minks

cannot be overemphasized. .V disease is much easier to pi'evenl than

to cure. JNIinks are hearty, vigorous animals. They rarely get sick

if they have an adequate ration and

healthful living conditions.

To facilitate the use of disinfectants, all equipment and other construction should be as simple as

possible and easy to clean.

Fecal matter and other organic

material protect disease bacteria

and viruses; therefore, thorough

cleaning should precede disinfection. Itis advantageous to have one

agent act as both cleanser and

disinfectant.

In the routine cleaning and disinfecting of pens and sheds on a

small ranch, ordinary lye solution is

eifective and economical. One 13-

ounce can of lye is enough to make

If) gallons of cleaning and disinfecting solution. For large ranches,

it is advisable to buy the lye in the

form of caustic soda. Each pound

makes about 20 gallons of solution,

which does not need to be heated

although heating is advisable. In

aildition to acting as a disinfectant,

lye cuts grease and partly dissolves

and penetrates fecal material.

Use of lye has some disadvantages. Concentrated lye is a poison

and is destructive to aluminum

))aints, and clothing. The dilute solution recommended does not

harm wood or iron, nor is it hai-mful to the animals in the amounts

that might remain in the pens.

However, do not leave the solution

where the animals may drink it.

The lye may be slightly irritating

to the" hands and face of the operator. Consequently, take precautions to avoid excessive exposure

of the skin during the disinfecting

|n-ocess. Keep containers of lye

tightly covered.

Many ranchers use steam under

pressure to clean and disinfect pens

and equipment. The steam is sup-
plied l)y ;i steiiiii jpiiny, wliicli uses

oil iis fuel. When sleain is used, it

is a li'ood idea to lirst sf)iik theciiked

feciU iiiaterial with water. Use of

a «••ood cleaiisiiifi" coinpouiid in the

jenny boiler cleans and disinfects

very satisfactorily.

ITse of cresol componnds on fur

fanns is not I'ecoinmended. Severe inflammation of the feet of

adult minks has been reported as a

result of their use. One farmer who

sprayed the inside of his nest boxes

in the fall lost a larye number of

kits the followiiifi sprinü;. línough

of the material soaked into the

wood to bui'u the younp- minks so

severely that they died. Cresols

have a disa<ii'eeable odor and do not

mix readily with hard water.

Althoufih hot water alone is used

to clean feed houses and feedinii'

equipment on many successful fur

farms, some of the cleansinir

ag:ents, or deteraents, do a better

job. If bouirht from a distrilnitor,

they are cheap enouoh for use on

the fur farm. Theii- disinfective

action is limited, but they are effective in cutting o-rease and in general cleaning. Eoutine use of

these compounds on the mink i-anch

is recommended.

Disease Outbreaks

When disease breaks out, immediately isolate the affected minks

from the rest of the herd. Clean

and disinfe<;t all pens, nest boxes,

and feeding and other ecjuipment

with a 2-percent lye solution ( 1

pound of lye to 51/2 gallons of water). This solution is effective

against most viruses and bacteria ;

however, for anthrax, use a 5-percent solution (1/^ pound of lye to 1

gallon of water). In using lye solutions, especially in strong concentrations, care should be taken to

prevent injury to both the operator

and the animals.

Cleanliness and care in avoiding

contact M-ith infection are always

necessary, even when new disinfectants are available. Any accumulation of dirt protects bacteria and

nullilies the effectiveness of even

the most efficient disinfectant.

Disposal of Dead Animals

Evei-y ranch loses a few animals

each year. If the animals are not

submitted for autopsy, they should

be disposed of in such a way that

they will not infect the rest of the

stock. To ''throw them over the

fence" is a dangerous practice, as

rats, dogs, and flies may carry the

disease back to the minks. Probably the most efficient and sanitary

method of destroying carcasses is

to bum them.

Also, burn pelted carcasses or

sell them to rendering plants.

Never feed them to the animals.

The diseases and parasites that

might be sj^u'ead through an entire

mink ranch are too numerous and

damaging to justify the risk of infection for the small amount of

meat obtainable from the carcasses.

Bacterial Diseases

Botulism

The botulism bacterium C/o.stridium bofulilium, in the absence

of oxygen, produces a potent toxin

in contaminated meat. If an outbreak of botulism occurs in a mink

herd, losses are very high. In an

outbreak involving 13,000 minks

near Seattle, appi-oximately 6,000

minks died.

Sigih\.—From 12 to 96 hours

after minks have eaten meat containing the toxin, some dead and

some paralyzed minks will be found

in the pens. Onset of the disease is

rapid. It is characterized bj^ muscular incoordination and stiffness

followed by paralysis of the front

or hind legs. When the animal is

picked up and held over the palm

of the hand, the front and hind legs

hang limp (fig. 2). The eyes are

bright and salivation is common.
you

FIGURE 2.—When a mink affected with

bütulism is picked ui). the front and

hind (juarters hang limp.

The toxin paralyzes the muscles

used in breathing, and the minks

die.

Prevention.—Never feed the carcasses of sick animals, spoiled feed,

or feed that has had a chance to become \A-arm. Always keep the mix

cool before feeding. If you are

not sure about a certain food ingredient, feed it to a few animals before including it in the regular ration. However, the best practice is

to follow tlie axiom "when in

doubt—throw it out."

For prevention, a toxoid—j^reventive inoculation—offers excellent promise. The ñrst work on

botulism toxoids for minks was

done in Sweden. Following disastrous outbreaks of botulism in tliis

country when spoiled meat was fed,

research workers in Ttah and Wisconsin and at the Department of

Agriculture Fur Animal Disease

Station developed an experimental

toxoid, which is available commercially. Vaccinate all kits shortly

after weaning.

Treatment.—Treatment of minks

affected with botulism is seldom

successful. Pr o m p t recognition

and report of the disease when it

first appears gives the veterinarian

a better chance to save minks that

have not eaten enougji of the poisoned feed to show signs. Immediately remove from the wire or feed

boards and discard any feed

suspect is spoiled.

If the veterinarian makes a diagnosis of botulism, polyvalent antitoxin should be administered to

every mink on the ranch as soon as

iwssible. The dosage should be

from 5 to 10 cubic centimeters, depending on the size of the animals.

Anthrax

Antlirax is an acute infections

disease caused by the bacterium

BaciJlux nnthracis. JNIinks become

ill by eating infected horse, cattle,

or hog meat.

Sigri.s and aiifo¡>f<y findings.—

Within a day or two after eating

infected meat, minks often show the

following signs : Depression, loss of

a])petite, and linally muscular weakness and death. Autopsy reveals

engorged blood vessels filled with

l)lack, tarry blood. The sj^leen is

enlarged, dark red, and easily torn.

A diagnosis can be made only by

bacteriological examination, because

other conditions in minks often present a picture similar to that of

anthrax.

Pj-eeention and treatment.—Obviously, the best prevention is to

feed no meat from animals that

were sick before slaughter. A veterinai'ian who diagnoses anthrax in

a mink herd usually prescribes

penicillin or some other antibiotic.

Man is also susjiectible to anthrax. Therefore, burn dead animals; do not pelt them. It is very

easy to become infected through the

hands and arms by handling animals that have died from anthrax.

The bacteria are highly resistant to

heat and drying and can live for

years on dried material and in soil.

Do not market pelts from minks

that die of anthrax; they may infect anj'one Avho handles them.
streptococcus Infections

AH8CESSES

An abscess (boil) is an enlarpjement dne to an accumulation of pus

enclosed in a capsule. Abscesses

are usually sporadic in occurrence

and do not cause much concern.

However, on a ranch where a large

number of minks have abscesses that

resist treatment and nrany of the

animals die, the problem is not so

simple.

Oavse.—Aoscesses usually are

caused by slight injuries to the skin

or lining of the mouth by slivers of

bone or wood or bits of sharp material in poor-quality nest hay.

These injuries allow streptococci

and a variety of other bacteria to

enter. Abscesses develop from the

infection.

Faulty techniques used in vaccinating may cause an abscess. All

vaccination programs should be

supervised by a veterinarian. If

the vaccine becomes contaminated

with bacteria, each inoculated mink

will have a large abscess within 5

or 6 days.

During the breeding season, aggressive males frequently bite the

females. The resulting wounds

often become infected, and abscesses

result.

Bacteria also may be introduced

in the feed. Eating meat from a

horse aiïected with fistula of the

Avithers or with strangles may cause

an outbreak of abscesses among

minks.

Signs and autopsy findings.—

Until an animal is near death, its

appetite remains good. The affected animal can be easily picked

out by its misshapen head or neck

(fig. 3). After an abscess breaks,

a crust may form a cap over the

animal's head. Such a case is difficult to treat. Unless a mink so

affected is a valuable breeder, pelt it

in season.

The mink with an abscess usually

has a greatly swollen, dark-red

spleen. The liver is sometimes dull

red, soft, and easily torn. Sometimes small abscesses are scattered

througli the organs.

Treatment.—After the abscess

has come to a head, as evidenced by

a hot, painfulj fluctuating swelling,

make a vertical incision wáth a

FiüUHE 3.—AduU mink with an abscess

in its throat. Some of the fluid has

been talcen up in the syringe.

sharp, sterile knife at the lowest

point of drainage. Make the incision large enough to allow the pus

to flow freely. Then wash out the

cavity with a mild antiseptic and

sprinkle it with a good healing

powder. Your local veterinarian

can demonstrate this simple technique. It is well to accompany the

treatment with injections of penicillin.

SEPTICEMIA

The term septicemia refers to an

infection in which bacteria enter

the blood stream, multiply, and produce toxins. Streptococcal septicemia is a disease of young minks at

about weaning time. The usual

histoiy is sudden death of one kit

of a litter. Separate the balance of

the litter and inoculate each kit

with penicillin.

SINUSITIS

Inflammation of the nasal sinuses

is occasionally seen in minks. The

animals may have a nasal discharge

for 3 or 4 months. In this disease,
as in others in which a nasal or eye

discharge occurs, distemper must

first be eliminated as a cause of the

discharge before other diagnoses

can be made.

CELI^TJLITIS

Ranchers first note this condition

when a mink refuses feed and appears sluggish. Within a short

time its head begins to swell. The

swelling caused by cellulitis differs

from the swelling caused by abscesses. In abscesses, the inflammation is usually confined to the

side or top of the head. In cellulitis, the inflammation covers tlie

entire surface, including the top

and sides of the head, the nose,

throat, and adjoining neck region.

Here the swelling stops, and a

raised edçie circling the neck can

be felt. This edge of the swellingis a distinctive feature of the disease. Eyes may be clear or they

may show a discharge. Lids are

swollen.

Cellulitis may easily be confused

with distemper, in which a swollen

head and eyelids and an eye discharge are commonly obsen-ed. To

differentiate between the two diseases, an examination by a veterinarian or a diagnostic laboratory

may be necessaiy. In cellulitis,

cutting the skin of the liead releases

a thin water}' fluid. Opening abscesses reveals a thick exúdate that

is never clear. Streptococci can be

isolated from the exiTdate. Other

post-mortem findings are not significant. In hydrocephalus t h e

head is also swollen, but the swelling is caused by a large amount of

fluid within the skull cavity.

Salmonella Infections

Fur-farming journals often mention Salmoneila organisms as the

major cause of enteritis ( inflammation of the intestines) in minks.

Minks with diarrhea are frequently

said to have a Salmonella infection.

Such diagnoses are often made

without laboratory confirmation.

The agents leading to or causing

enteritis in minks are largely unknown. Other causes of enteritis

may be nutritioiuü or from virus

infections.

In one unusual outbreak among

pregnant females, the predominating sign was abortion; no

deaths occurred. Salrnovflla organisms were isolated from tlie

uterus and from al)orted kits in

evei-y instance. The original

source of infection was infected

pork livers.

Tularemia

In some sections of the West,

jackrabbits often are numerous

enough to use as a substitute for

horse meat in mink rations. Tularemia (rabbit fever) is a common

disease of jackrabbits; it has been

reported from all parts of the

Ihiited States. Snowshoe rabbits,

cottontails, and many other rodents

also may carry the disease, and man

may contract it.

Examination of a rabbit or mink

infected witli tularemia often reveals many small white spots on the

surface, and imbedded in the substance, of the liver, spleen, and lungs

(fig. -i). However, a rabbit may

carry the bacteria and sliow no

changes in the organs.

To prevent tularemia in minks,

do not feed them sick rabbits or rabbits that have a spotted liver and

Fli>uuE 4.—Lungs froui a mink that died

(if tularemia; tlie wliite spots are typieal of the di.sease.

537796°—60-
spleen. Fiirlliei'inore, when i-nl)l)its

are decreiisin^- in nnnihers in an

area, do not feed them (o minks;

tliey niay he (l.yin<i as a residt of an

outbreak of tuhiremia. Addin<i an

ocfasional wild rahhit to the ration

is veiy poor pructiee. Tlie amount

of meat obtained is small and the

risk is great.

Outbreaks can be conti'olled by

inchidino; in the regular ration a

treatment level of a broad-spectrum

antibiotic such as Aureomycin or

Terramycin. An a fleeted animal

may be given an injection of Streptomycin. However, this antibiotic

is very toxic to minks and should be

used with care.

Tularemia bacteria that may

enter the body through a wound,

cut, or abrasion, or directly through

unbroken skin may cause tularemia

in man. It is important, therefore,

that skinners and others handling

rabbit carcasses wear rubber gloves,

even though the disease is not suspected. The bacteria have been

found in carcasses i;^3 days after

death, and in hides as long as 40

days. However, the bacteria are

killed by thorough cooking of the

infected tissue.

Tuberculosis

Tuberculosis, one of the most

connnon diseases in minks in Europe, is rare in minks in the United

States. Kegulatory agencies, both

Federal and State, have largely controlled the disease m livestock,

which is a source of protein for

minks in this countiy.

As the signs shown by live infected minks are not characteristic,

the disease is usuallj' recognized

only at autopsy. When the animal

is opened for examination, the

spleen and lymph nodes may be

greatly enlarged. Gray spots are

often seen in the substance of the

spleen. The diagnosis is confirmed

by bacteriological procedures.

No practical herd treatment has

been found. Avoid feeding infected pork, chicken, or beef

byproducts.

Nonspecific Enteritis

An enteritis of which the definite

cause is unknown frequently affects

minks. It may be bacterial in origin, or it may be caused by a virus.

It is useless to speculate as to the

cause until more facts are known.

The disease usually breaks out in

warm weather on ranches where

sanitation is not good. The feed

house is often dirty, the meat

grinder seldom cleaned, and refrigeration poor. Uneaten feed remains on the wire or feed boards,

and old feed and feces are piled up

in the nest boxes. These practices

foster the agents that cause enteritis and often lead to and cause a

severe outbreak. However, enteritis may also appear at times on

clean, well-managed ranches.

Sifpifi.—The signs vary. In acute

cases, a mink may refuse to eat,

have bloody diarrhea, and die

within ?> or 4 days. In chronic

cases, the animal may not die for a

month, during which time it often

has an excellent appetite. However,

it apparently does not digest its

food, and it becomes badly emaciated before death. In some cases

of chionic enteritis, the feces are

light in color and mixed with mucus; in other chronic cases, the feces

are black and fluid.

Autopxy ßndings.—Contrary to

popular opinion, enteritis is often

difficult to diagnose at autopsy.

The carcass must be fresh, for if the

mink has been dead for even a

short time, post-mortem changes

(changes occurring after death)

mask changes due to the disease

and make it impossible to diagnose

the cause of death. This is particularly true in the intestinal tract,

where the walls are rather thin

and quickly become blackened.

The intestinal lining breaks down

shortly after death, and the intestinal contents become black and

8
FiGUiiE 5.—Acvite inüanunatidu (if the stoinach ami acljniuiu.i; iiart iif tlie intestine.

wliicli darkens tlie lining.

fluid. This quickl}' covers up the

changes due to enteritis.

If the mink has been dead only a

short time and the intestine is reddened and contains free blood,

acute enteritis (fig. 5) evidently

was the cause of death. If the

wall is thickened and the animal

has had intermittent diarrhea for

some time, chronic enteritis is a safe

diagnosis. Stomach ulcers are

commonly observed.

Treatment.—A veterinarian who

diagnoses enteritis in a herd will

prescribe drugs to alleviate the inflammation of the intestines of the

affected animals and to combat the

infection. Sulfaguanidine can be

used to advantage by including

it in the feed.

Pneumonia

Pasteurella multocida is found

in cases of mink pneumonia. The

disease often appears in the spring

and fall when the weather is damp

and the temperature is subject to

rapid change. Nest boxes should

be constructed so that they can be

kept dry and well ventilated.

Minks can stand freezing temperatures, but they cannot tolerate we«

nest hay and boxes.

Eapid, shallow breathing, as evidenced bj' a heaving of the flanlvs,

is the most impoi-tant clinical sign

of the disease.

For treatment, injections of penicillin, Aureomycin, or Terramycin

can be given. Treatment is not always successful because the animal

is often too far gone by the time it

looks ill.

Pseudomonas aeniginosa causes

a rare but deadly pneumonia in

minks. This bacterium is introduced into the herd through contaminated drinking water. INIost

minks are noticed to be sick only an

hour or two before they die; they

may look healthy in the evening

but are found dead the next morning. Aflected animals usually

bleed from the nose. Dark-red congested lungs are the most significant

finding at autopsy.

Streptomycin and polymyxin are

the antibiotics of choice. However, these drugs are highly toxic

to minks; information as to the

dosage and manner of treatment
should be. obtjiiiied from a

vcU'riniu-ian.

Pleuritis

Pleuritis (iiidaiuiuidioii of tlie

liiiiuü,- nieinbranes of the rhest euvitv) causes sporadic deaths iu a

mink herd, ('uttiu^i,- tlie rilw and

openinji' the chest cavity reveals a

laru'e amount of thick, o-rayisli-yellow pus. The luna'S are conipressed

and covered witli adhesions.

Animals sick with pleuritis are

seldom treated, because they usually

are found dead with no signs of

illness.

Virus Diseases

Distemper

"When distemper is mentioned,

mink ranchers everywhere haxe

cause for alarm, for it is a very

serious disease in minks throughout the United States.

Altliouu'li almost all minks become infected in any given outbreak, .some animals do not show

any signs of the disease. Deaths

vary in number from one outbreak

to another. Losses ma_v be as high

as 90 percent in young minks, but

average 30 to 40 percent in older

minks. Kits as j'oung as 3 weeks

may be infected. Outbrealis occur

at any time of the year.

Cause und fratixmission.—The

cause of distemper in minks is a

virus—the same virus that causes

distemper in dogs and foxes.

Although the distemper virus is

easily destroyed within a few hours

by heat and by most of the common

disinfectants, it resists drying and

low temperatures for several weeks.

It can survive for some time at temperatures ])elow freezing.

Tlie virus is sj^read from animal

to animal through the air. In normal breathing, minks that show distemj^er (as well as ajiparently

healthy carriers) emit millions of

small, virus-containing droplets

into the air. Shortly before and

during an attack, the virus also is

found in the saliva, nasal secretions, and skin scurf. A mink may

also shed the virus into the air

aftei' signs of the disease disappear.

The virus can also be transmitted

among minks by indirect means,

such as contaminated handling

mitts and food pans.

Signs.—A mink infected with distemper often has signs resembling

those of otlier mink diseases. In a

disease outbreak, consider first the

possibility of distemper.

The incubation ])eriod—the interval between the time the virus

first enters the mink and apj^earance of the disease—is about 9

to U days.

The first sign of the disease is

s([uinty. swollen watery eyelids. In

1 or 3 days the lids become crusty

and stick together (fig. 0). A similai' discharge appears at the nostrils,

wlieie it dries and cakes. The mink

may have an excellent appetite at

this time. The head is often swollen. These signs, which ma,y persist for a week or moi'e. usually are

accompanied by a swelling of the

foot pads. Later examination reveals granular material on the swollen red surfaces of the pads (fig. 7).

Thickening of the skin ancl loss

of hair are not uncommon. At this

time, the mink may go into a coma

and die in a terminal convulsion.

However, it may recover, the signs

of the eye, nose, and feet meanwhile suitsiding. Although it has

Figiu-e 6.—Mink shuwing signs of distemiier; the lids are stuck together

with il pussy di.scharge.

10
FIGURE 7.~Left, Footpad of a healthy mink. Rit/lit, Footpad of a miiik with advanced distemper showing swelling and, on the surface, a srauular material that

adheres to the skin.

11
new breeding

FIGURE S.—Neurotropic signs in a distemper-infected adult ; tlie liead is thrown

baclv in a violent spasm.

a good appetite and appears normal, a minlî may later die in what

ranchers term ''screaming ñts." In

this type of distemper, the virus has

invaded the brain, causing the mink

to froth at the moutii, cliew violently on the wire netting, roll

about the pen, and scream sharply

(Hg. 8). These convulsive seizui-es

may last a short or a long time. The

mink usually dies after one or two

attacks.

Atitopsy -jindingH.—Distemper is

difficult to diagnose by looking at

the lungs and the abdominal organs, {"requently, the only change

that can be seen is an enlarged

spleen. Important changes are observed, however, if a piece of bladder or trachea (windpipe) is

stained with dyes and examined

under the microscope. Distemper

leaves characteristic marks, called

inclusion bodies, in those tissues.

They are small stained ''dots," or

specks, which represent distemper

virus.

The surest way for a veterinarian

to obtain a diagnosis is to remove

the spleen from the suspected distemper-infected mink, grind it in a

liquid suspension, and inject it into

a ferret. If the spleen contains active virus, the ferret, which is

almost 100 percent susceptible to

the Adrus, will become infected.

Prevention.—Distemper is usuallv introduced into a herd of susceptible minks by

stock that carry the virus or by an

infected dog. On many isolated

farms where the source of the virus

is not apparent, some insect or an

animal other than a dog might act

as a carrier of the viras.

As preventive measures, isolate

new^ breeding stock for at least 50

days and take special care to allow

no infected dog near the minks.

Anyone who raises minks should

learn to recognize typical signs of

distemper in the dog, which are as

follows: An irregular fever, dullness, loss of appetite, and a discharge from the eyes and nose (fig.

9). The discharge at first is thin

and watery; later it becomes thick

like mucus and tends to dry in

crusts around the eyes and nose. If

the lungs and air passages are affected, tlie dog coughs and has difficulty in breathing. In some

cases, the skin has small red pustules; in others, diarrhea occurs.

As in minks, the nervous form of

the disease may appear in the later

stages. A dog may have an almost

continuous twitching of one leg,

the forehead, or ears, a blinking of

the eyes, or a champing of the jaw.

The animal usually has intermittent convulsions and may become

paralyzed. Death follows the appearance of these nervous signs m

half or more of the cases. Dogs

tltat recover are often left with permanent brain or nerve-tissue damage. However, the signs are not

always so severe ; the animal may

have only a slight eye discharge

and not feel up to par. Nevertheless, it is still capable of transmitting the virus. A few dogs that

have apparently recovered from an

attack of distemper may be carriers

and potential spreaders of the virus

for a short time.

Despite marked progress in immunizing minks against distemper,

the virus causes heavy losses each

year. Two general types of distemper vaccine are on the market^

killed-virus vaccine and living

12
FIGURE 9.—A young dog showing typical

signs of distemper—discliarge around

the eyes and nose.

modified virus vaccine. Killedvirus vaccine is safe to use but

has some disadvantages. Animals

inoculated with this type of vaccine develop immunitj' r a t h e r

slowl}'. The immunity seems to

leave the animal, and revaccination

is necessary.

Living-virus vaccine, prepared in

fertile hen eggs, has been more successful in controlling outbreaks.

Since this modified virus must be

living at the time it is administered,

ranchers should obtain the advice

of a veterinarian Ijefore they use it.

For example, if the reconstituted

vaccine becomes warm or disinfectants are used in the syringes, the

vaccine may not have any effect.

For maximum control, all kits

should be vaccinated at 10 weeks of

age.

Treatment.—Unless an early diagnosis is made and the infected

animals are isolated, control of outbreaks is often unsatisfactory. In

an outbreak, isolate each mink as it

breaks out with distemper and vaccinate the other animals in the herd.

Do not handle or shift animals more

than necessary, as such manipulations may spread the virus through

the pens. Effective treatment of an

animal with screaming fits (neurotropic distemper) is impossible.

The virus has caused irreparable

damage to its nervous system.

Virus Enteritis

Virus enteritis, a serious threat

to minks in the United States, was

first recognized in Ontaiio and has

been reported in many mink-raising

areas of the United tSates. The disease spreads rapidly on a rancli and

may kill up to 75 percent of tlie kits.

The first indication of sickness, a

sudden loss of appetite, occurs

within a week after the minks are

exposed to the disease. A slightly

pink to grayish-wliite "slug" (intestinal cast) can be noticed in the

feces. Animals that do not die

within 4 or 5 days often I'ecover but

may never reacli maximum size.

At autop.sy, the intestines appear

bright red.

Pelt in season minks that have

recovered from virus enteritis.

They may harbor the disease as

"silent" carriers and serve as a

source of virus for kits the follow^-

ing summer.

Because vii'us enteritis is related

to feline-panleukopenia virus, cats

as well as other animals and visitors should be excluded from mink

yards.

Two types of vaccine are used to

immunize minks against virus enteritis. One type is a killed-virus

vaccine prepared from the spleen of

mink dead of virus enteritis; the

other is connnercial formalized

feline-panleukopenia vaccine.

Nutritional Diseases

Urinary Calculi

Urinary calculi, commonly called

stones or gravel, are deposits of

mineral salts in the kidneys, bladder, and urethra (the tube from the

bladder to the outside) of minks.

Losses of male kits have exceeded

10 percent on a single ranch. In

females, it is most prevalent in May

and June, with losses in excess of 15

percent on some ranches.

The cause is unknown. The

stones are almost pure magnesium

13
¡iniiiioiiiuiii pliospliate. Because

calculi of Miis type are Ihou^'lit to

t'oi'ui in alkaline ni'ine, investi<>atoi'K

believe this alkalinity lias a role in

the disease.

S/f/ii.s (iiul autopsy fiidliu/x.—The

signs of cálenlas disease are often

difficnlt. to recognize and the presence of calculi in the animal may

not. be known until an autopsy is

made. Sometimes the signs are

weakness, diflicnlt urination, wet

fur between the hind legs, straddling gait, ))aralysis, and terminal

convulsions followed by death. A

diseased animal is often in good

flesh because its appetite remains

good until death. Sometimes, however, its hair coat becomes rougli

and it refuses food, tlius losing flesh

befoi'e dying.

In female minks, calculi often

hinder normal contractions of tlie

iiterns and prevent birth of tlie kits.

At post-mortem examination, the

kidneys and bladder should be examined for calculi (fig. 10). Where

calculi are present and have caused

the death of the animal, the stones

ai-e usually accom])anied by blood

and pus. Calculi range from the

size of a millet seed or smaller to a

size that fills the entire bladder. In

male minks, a very small calculus

may lodge in the urethra at the

penis bone (fig. 11) or where the

urethra curves around the pelvis

Ijone. In these cases the bladder is

often filled witli bloody fluid.

Calculi apparently fonn rapidly.

Large ones have been found in Ijladders of kits 6 to 7 weeks of age.

Prevention.—Observations indicate that feeding phosphoric acid

from the first of April through

pelting may help control the disease,

because the drug helps to establish

^.."^% ' ^m"

a^B .:;-

.1- i^ 'ílByiM

'«Ü'.-^v^ ^ éÊÊkf

W^ #^^' Ü*^^

m

^g^JfTm

^^,.Miffi^ •

''!^^'' i,wl|p fe j^. 'd^^. '

tif^^- ^

K>^ - 1

FIGURE 10.—Calculi removed from urinary tracts of minks.

14
FIGURE 11.—A small cakulus lodged in

the tube at the peuls bone.

a more neutral urine. The animal.s

should be given plenty of water.

Steatitis (Yellow Fat)

Steatitis, a sunnner-fall disease

that affects young minks only, li;is

been recognized in various parts of

the United States and Canada since

1942. It probably existed before

that time but was diagnosed as

something else. Losses from steatitis have amounted to thousands of

dollars on some ranches.

Cause.—The disease usually appears when ranchers feed a high

percentage of horse meat that has

been in storage, or ñsh scrap. Sucb

rations often have a higli content of

unsaturatecl fatty acids and are low

or delicient in vitaniin E. 01)servations of natural outbreaks and

laboratory experiments have sliown

that these two factors jirobnbly

work together to produce tlie characteristic yellow-brown color of tlie

fat.

Slf/n.<t.—Kits are first affected

sliortly after weaning and after

tliey liave eaten large amounts of

solid food. Outbreaks are most

conunon tlie last 2 weeks in July

and tlie lirst 2 weeks in August.

Some, however, begin late in September and continue until peltingtime.

Steatitis usually ap])ears without

warning. Some icits may refuse

the nigiit feeding and be dead in

the morning. Others may leave

their feed and show a peculiar unsteady hop. Tlie impaired gait

¡nay become progressively worse

until the minks are unable to move.

Tliey remain in a coma imtil death.

In a typical outbreak, 25 percent of

tlie kits may die; often the survivors do not fur out well. Nearly

all tlie kits tliat survive show yellow

discoloration of the fat and skin at

l)elting time (fig. 12).

Avfopsi/ fndings.—At autopsy,

the abdomen and groin appear

tliickened and feel doughy. When

tlie affected tissues are cut with a

knife, a thin watery fluid escapes.

The fat beneath the skin and surrounding the abdominal organs is

a characteristic brownisli yellow.

The spleen is often 2 to o times normal size and may liave darle Idotclies

on it.

'^

^•v-- -*.

í'

i^É'«*^^^^^^-y^^

y

'-/' >

i

j^ Já^^l^ i

Á»' •SW

FIGURE 12.—Dlst-olorations ou a pelt caused by steatitis in a mink kit.

537796°—60 ?j 15
FiouRK 13.—This female, affected witli nursing sickness, is very thin and weak.

Prevention and tj'eatment.—Bemuse the disease often closely follows weaning, feed the female, as

well as the kit, a ration adequate in

vitamin E and other nutrients.

Supplement the diet of young

growing kits so that the amount of

wheat-germ meal or stabilized powder provides 5 units of vitamin E

per day per mink.

In an outbreak, reduce the

amount of tish or storage horsemeat

in the ration; substitute fresh unfrozen horsemeat and liver and add

wheat-germ meal or stabilized vitamin E ])owder to the diet. Inoculate each atl'ected kit with 15 to 20

milligrams of vitamin E a day for

o days or more. The pre])aration is sold under such names as

injectable tocopherols.

Nursing Sickness

Xursing sickness, coninum in

nursing minks, ajipears before the

nth or 6th week of lactation. Affected females ai'e first noticed in

late June at about the time the

voung minks are weaned, but the

disease may appear after the kits

have been taken away.

Signs of nursing sickness include

lack of appetite, loss of flesh, weakness, and incoordination (fig. 13).

Death follows a period of coma.

Some females, although apparently

starving, fill their moutlis with feed

but do not swallow it.

The carcass is extremely thin:

there is almost no body fat. A yellow, easily torn liver is often observed, t'sually the gall bladder is

distended with bile—evidence the

animal has not been eating—and

the stoniach is empty.

Eanchers have considered prevention of this condition a management problem. Watch nui-sing females carefully. If any becomes

thin and dehydrated, give its kits

to another female if they are too

small to wean. Another help is to

make food and water easily available to young kits from an early

age onward.

' Dr. G. R. Hartsough, of the

Great Lakes Ranch Service, has observed that nureing sickness may

lesult fi'om a depletion of salt in

the diet. He has recommended the

addition of 0.5 percent of table salt

to the mixed feed from late May

until the middle of July. Some

commercial mink cereals contain

salt; therefore, use caution when

16
adding; more salt, as minks are susceptible to salt poisoning.

Pregnancy Disease

Pregnancy toxemia, usually occurs a few daj^s before Ayheli)iug.

Although the cause is not clearly

understood, it may be nutritional.

The disease is often a serious problem and causes losses of unborn kits

as well as females. Additional

fresh liAer in the ration may help

prevent the condition. The onlj'

characteristic post-mortem change

is a yellow liver.

Urinary Incontinence (Wet Belly)

Urinary incontinence, usually

called wet belly, is connnon in

minks in the I'nited States. The

cause is unknown. Constant dribbling of urine causes loss of hair

and severe inflammation of the skin

and underlying tissues in the region of the penis. Frequently 10

percent of the males on a ranch are

art'ected.

"When the animal is pelted and

the skin is stretched on the board

to drv, the damaged area is readily

visible (tig. 14). Because these

pelts bring lower prices at auction,

the condition is cause for concern.

The condition has been successfully treated liy increasing the

amount of carbohydrate in the diet.

The animals should have plenty of

water.

FiuiHE 14.—Mink i>elts sliuwins damage

(cliu-k triangular area) callí^ed liy wet

belly.

Chastek's Paralysis

C'hastek's pai-alysis is so-named

because the cause of the disease was

discoA-ered on the C'hastek fur far)n

in Glencoe, Minn. îîaw Hsh in tlie

ration was causing jjaralysis and

death in foxes on the ('hastek far)u.

Research workers discovered that

the raw fisli contained an enzyme

that caused the destruction of vitamin B] (thiamine). Daily feeding

of fish tliat contain this destructive

enzyme to either foxes or minks deprives the animals of all sources of

thiamine. Reserves of the vitamin

are soon used up. Alinks refuse to

eat and become very thin ; paralysis and coma precede death.

Carp, suckers, saugers, goldfish,

burbot, white bass, whitefish,

creeli chub, ocean herring, bullheads, and channel cats contain this

enzyme. In experiments at Oregon

State College, Chastek's paralysis

was ])roduced in minks aiul foxes

by feeding them rations composed

of .")() percent of fresh-frozen smelts.

To prevent the disease, remove all

raw fish from the ration, feed raw

fish on alternate days only, or cook

tlie fish to destroy the enzyme. Include ample amounts of brewer's

j^east in the I'ation.

In an outbreak, immediately remove micooked fish from the ration.

A veterinarian may I'ecommend intraperitoneal injections of thiamine

to treat the paralysis.

Gastroenteritis

Gastroenteritis (infiammation of

tlie stomach and intestines) has

been produced in minks in experimental studies bj' feeding rations

that lacked the factors found in

fresh liver and raw milk. Weakness, loss of appetite, and bloody

diarrhea are signs of the disease.

The cause of black dropi)ings, commonly mentioned by mink ranchers,

may be poor nutrition. Addition of

tomato pomace and fresh li\-er to the

ration has alleviated the trouble on

some ranches. Nutritional enteri17
Ms muy be more comiiidii than

been believed.

has

Fatty Change of Liver

Fiitty chiiiifie of llie li\'er, often

refen-e"d to as fatty (le<i,-eneralioii, is

fre([iiently fonnd on post-iuorlem

examination of miidvS. It is an abnoi-mul chan<ie that arconi¡)unies

many disease eondii ions i-alher than

a, separate disease. Arcumnlation

of fat in the cells of the liver causes

it to l>e yellowish or clay colored.

It may be softer than usual, and it

has à tendency to separate into

small pieces. When the liver is cut

with a cold knife, a film of grease

lemains on the blade.

Fatty change of the liver (fig.

15) is connnon in intoxications resuUing from bacterial toxins, toxic

V

FiGUHE 15.—A, Liver frtim a healthy

mink; B, light-colored showing fatty

c-liange.

])iT)dncts of metabolism, or chemical

¡joisoning. It is also common in

nursing sickness. The cluinge can

be produced experimentally by starvation and by including excessive

fal in the ration. Significant fatty

cliauge of the liver is not found in

either experimeiital or actual field

cases of steatitis (yellow-fat

disease).

Tlie diagnostic value of fatty degeneration is limited, because it occurs in many disease conditions.

Do not attempt to treat fatty

change of the liver as such, but

rather look for the actual cause to

provide a sounder basis for therapy.

Hereditary Diseases

Hydrocephalus

Hydi-ocephalus, also called water

on the brain or Ijighead, occurs in

mink kits soon after they are born.

It is characterized ]>y a great distention of the part of the skull that

covers the brain (fig. 16). Many

cases never become apparent because the affected kits die soon after

birth and are eaten bj- the females.

When the condition becomes established in the breeding stock, it is

very serious and difficult to eliminate.

C'auxe.—Hydrocephalus is noncontagious and, so far as is known,

is not caused by AWJ nutritional factor, but is hereditary. In rare cases

it is caused by accidents in development during the gestation period,

under which circumstances it is not

inherited.

Sigrifi.—The affected liit is usually first noticed when animals in

the litter are counted and examined after whelping. A^Hien the affected kit is pickeci up and the head

is examined more carefully, the part

of the skull housing the brain is

seen to be greatly distended and

fluctuates to the touch.

The underlying cause is an accumulation of fluid witliin the cavities (ventricles) of the brain. The

18
FiuuKE 10.—Ilydrot-eiiliiilas in a mink

kit ; distended, softened .skull revealed

b.v reiniival of skin.

resulting pressure forces the bi-aiu

substance against the soft developing bones of the skull, arching them

outward. The pressure on the

brain and the retention of fluid

cause the dullness and muscnlar incoordination. Cutting open the

swelling releases much colorless

fluid and reveals a large cavity.

Control.—Hj'drocephahis in

minks is, in most cases, assumed to

be a heritable lethal character produced by recessive genes. It may

appear on a ranch as suddenly as

a new color-phase mutation. Ivike

other récessives, hydrocephalus may

remain hidden for several generations, becoming apparent only when

both male and female parents cany

the hydrocéphalie genes and transmit them to their offspring togetlier.

If the malady appears, destroy

the affected kit. It will only take

nourishment from the female and

die in a short time. Then pelt the

sire, the dam, and the litter mates

of the hydrocéphalie kit. Both the

sire and the dam are carrying the

gene and all or most of the litter

mates may carry it. These practical measures, if followed each year,

should eliminate the trouble.

Aleutian Disease

A condition causing death in

adult minks that carry the Aleutian gene—that is, Aleutian and

Sapphire color-phase nuitations—

results in many losses. The affected

animal may exhibit bleeding at tlie

mouth, become extremely thin, and

succumb in a month or less. A

marked increase in water consinnption is a common sign. Nervous

signs are also observed. The most

striking finding at autopsy is an enl:;rged pale kidney with many small

Fic!Ui;iä 17.—Kidney from a mink affected

by Aleutian disease ; note the many

small dark hemorrhages.

liemorrhages (fig. 17). To increase

the hardiness of this beautiful mutation, many ranchers outcross them

with standard black minks. Howe\er, such a breeding program results in "byproduct" minks having

a lower pelt value. No effective

treatment is j-et known.

Poisoning, Vices, and

Miscellaneous Agents

Lead Poisoning

Each year a few mink ranchers

suffer disastrous losses from red

lead poisoning. Although it is a

good preservative, red lead or any

paint containing lead should never

be used on wire, water and feed

19
dishes, or on any othei' equipment

witli wliicli minks nniy come in contiict. A little red lead paint on a

wire-bottom pen, for instance, can

cause the death of healthy minks.

t^ir/iiK (iiid iiittopi^y findings.—

Acute lead poisonino- occurs when

minks are placed on wire innnediately after it has beeii painted with

red lead in oil. For 2 or 3 days

the animals ap])ear normal, Ijut soon

they act slufífíish and show no interest in their feed. These sions

are followed by muscular incoordination, stiffness, tremblino-, complete loss of appetite, dehydration

(removal of water from the Itody),

and mucopui-nlent discharoe around

the eyes. About a week after they

are placed in painted pens, the animals have a terminal convulsion

and die.

Wire treated with red lead causes

chronic lead poisoning in minks

placed on it even when it is thoroughly dry. Wire-bottom pens

may be dangerous for some time

after they have been painted.

Minks with chronic lead poisoning show no characteristic signs.

The animals lose weight gradually

and die in 25 to 40 clays. An

autopsy reveals no characteristic

changes. Diagnosis, therefore,

must be based on the report that

the animals had been kept on wire

that had been treated with red lead.

Treatment.—When a diagnosis

of lead poisoning is made, remove

the animals from the painted pens

as soon as possible. While in the

pens the minks consume a small

amount of lead each clay from chewing on the wire or other painted

equipment.

GiA^e the survivors adequate

amounts of calcium in their ration

each day. This may be in the form

of dicalcium phosphate or calcium

gluconate, obtainable from a veterinarian.

Treat animals for at least 2

months, gradually reducing the dosage. At the same time feed enough

fresh fish oil to supply vitamin T).

The calcium and vitamin D tend to

prevent the lead from circulating

in the system and to store it in the

bones, wliere it will do little haim.

After it is stored in the bones, it is

slowly eliminated from the body.

Other Poisoning

Many materials can jooison minks.

Because the animals are confined in

a small space, tlie major possil^ilities are poisoning from materials

sprayed on them or the pens, and

poisoning from some toxic material

in the feed. Poisonous spray materials include DDT, creosote, sulfur,

chlorinated phenols and benzol benzoate compounds. Poisonous material may be mistaken for a feed ingredient and added to the ration.

For example, commercial fertilizer

may be mistaken for bonemeal.

Feeding Poultry Waste

Breeding faihires on many mink

ranches have been attributed to the

feeding of poultry waste containing the heacls of chemically caponized birds, known as caponettes in

some localities. The chemical—a

hormone-producing drug, diethylstilbestrol—is implanted as a pellet

in the neck of the bird a few weeks

before it is to be marketed. The

pellet gives the same results as surgical caponization and is more

convenient.

Apparently, when the heads of

caponettes are fed to minks, enough

of the pellet remains to interfere

with reproduction and cause breeding failures in both males and females. Ranchers who must feed

poultry heads as a source of meat

shoulct be positive that they do not

include caponette heads in the diet.

Foreign Bodies

It is not uncommon foi- a mink to

get small bone splinters stuck in the

corners of its jaw in such a manner

that it is unable to close its mouth.

When fed ground turkey or chicken

lieads, a mink may get one of the

small rings of windpipe encircled

20
and lodged around its tongue. The

signs are similar in both cases. The

animal seems hungry but refuses to

eat. Saliva collects at the corners

of its month, and the mink scratches

at its mouth. The mouth should be

opened and the bone or ring of cartilage removed. Ranchers can often prevent further trouble of this

kind by using feed-grinder plates

with smaller holes.

blinks occasionally consume

quantities of bedding, splinters of

wood, or such otiier materials as

pine needles. This depraved appetite often leads to impactions or

perforations of stomach and intestine.

Tail Chewing and Fur Clipping

Nothing disgusts mink ranchers

more than an animal that chews its

tail or clips its fur. Fur journals

contain many suggestions from

ranchers and veterinarians on how

to cure or prevent this ^^ce. One

method may be successful in some

cases but not in others. I'ndoubtedly, close confinement and an inadequate ration predispose to tail

chewing and fur clipping. Few

trappers have found wild minks

that mutilate themselves in such a

manner.

Fur clippers chew off all the hair

they can reach. This gives them

a lionlike appearance (fig. 18).

Strangely, few animals show any ill

effects from their diet of hair. They

FIGURE IS.—Marked fur cliewiug by

Silver Bine male mink.

often sto[) chewing their hair for a

month or two. If they ever get a

full prime coat, it is well to pelt

tliese animals, as they may begin

chewing again at any time. A tail

chewei' first sucks its tail, nmch as a

child sucks its thumb. Soon it begins to chew the flesh and bone. It

is not uncommon for a mink to chew

off its entire tail and continue chewing until death results.

Heat Exhaustion

Pleat exhaustion is a paralysis of

the mink's heat-regulating meclianism, caused by prolonged exposure

to excessive heat either from the

sun or from confinement in a close,

hot 1)1 ace. Losses may be very high

when tlie fenu^les are whelping or

when the kits are only a few days

old if they are housed in humid,

poorly ventilated pens. Free movement of air reduces the danger

considerably.

Excessive heat afl'ects the female

at whelping time. She may not

take care of her kits, or slie may

maul and drag them from the nest

box out onto the wire, where they

may be killed by the direct rays of

the sun or they may fall througli

the wire and be lost.

Signs and autopsy findings.—If

the female is whelping and the

weather is excessively hot and humid with no air currents, the young

kits may die so rapidly that no signs

can be 'ol)served. The female does

not clean tliem properly ancHs in

distress herself. She may lie in the

doorway of the nest box, shutting

off any air currents that might

otherwise enter. The nest box then

becomes exceedingly hot and the

kits suff'ocate.

On a hot, humid day later in the

season, when the kits are older, the

rancher may find some kits dead

and others "affected. These older

animals, however, usually show typ21
FiGUüE ly.—Young miuk kit showing

signs of lieat exliaustion. It is niialile

to move rapidly; when distnrlieil it

will turn on its side and cry weakly.

First the older kits become quiet

and stretch out on their sides. As

the day progresses and l:)econies liotter and more humid, thej' look

anxiously for shade and ^vater. If

the rancher reaches for a kit at this

time, it may turn on its side and

cry weakly in protest (Hg. 19).

The kits appear extremely nervous

and bite at the wire. They breathe

rapidly and must crawl on their

stomachs to move. Saliva soon

gathers at the corners of their

mouths, and the animals may have

a terminal convulsion or go directly

into a coma and die. This chain of

signs may occur in a surprisingly

short time.

At autopsy, the lesions are often

indefinite. However, a marked con -

gestion of the lungs is usually

found. The large veins are often

distended, and the blood fails to

clot. Small hemorrhages are occasionally seen on the thymus gland.

Since the carcass is hot, decomposition is rapid.

Treat'inent and prevention.—Unfortunately, not much can be done

to help a kit at Avhelping time.

Older kits can sometimes be revived

by dipping them in lukewarm

water. After dipping, place them

in the shade, where tliere is free

circulation of air. As a stimulant

in advanced cases, place a drop or

two of aromatic spirits of ammonia

on the tongue.

Frequent watering—as often as

10 times a day dnr'ing hot, humid

weather—is a preventive.

Large lawn sprinklers aid in

cooling il small yard. Overhead

pipe s])riiiklei-s, such as those used

in nurseries, can be placed in yards

where large numbers of minks are

held. When sprinkling, do not allow any of tlie cold water to fall

on tlieyoung kits; the sudden shock

might kill them.

Many ranchers find aluminumroofed sheds very satisfactoiy.

They are durable and fairly cheap,

and they are relatively cool on the

liottest da5's. Tlie aluminum sheeting reflects the heat. If the sheds

are built in a north and south direction, clieck closely to see that the

sun, as it passes overhead, does not

I'eflect off one slanting roof onto the

young kits in the shed parallel to

it. With a certain pitch of the roof

this may occur. To block the reflection, put canvas shades or sacks

on the side of the shed.

Some niink ranchers lay burlap

bags on the wire and wet them

down. Evaporation of the water

helps to keep the pen cool. The

lid of the nest box can be opened

and the hay removed to help the

circulation of air.

Posterior Paralysis

This disease is characterized by a

sudden posterior paralysis. The

mink moves about with its front

legs dragging its rear quartere.

There is loss of control of urinary

function. The appetite remains

surprisingly good. The actual

cause is unknown; however, spinal

injuries are suspected. The numhnv of animals affected on a ranch

seldom exceeds i/^ of 1 percent;

nevertheless, it is an annoying condition. Treatment has not been

successful.

22
PARASITES OF MINKS

Minks are susceptible to a inimbei- of insect and wonu parasites.

Only a few are of great economic

importance at pi'esent. However,

those not now important may become so if methods of feeding-, handling, and housing minks are

changed. Furthermore, some of

the parasites now found only in

wild minks might cause grave concern if they become established in

ranch-raised minks.

Keep recently purchased animals

in quarantine for a few days and

check them for parasites. Whether

or not a living animal is infected

with internal parasites can usually

be determined by microscopic examination of the manure for worm

eggs and protozoan cysts (p. 31).

Prevention and Control

For profitable mink ranching,

parasite prevention is necessary.

The best preventive measures are

good sanitation, good housing, good

feeding, and a Iniowledge of the

potential parasites and their life

cycles.

On ranches where good husbandry is the rule, minks are rarely

infested with parasites. Eanchers

who practice good sanitation and

hygiene may never experience an

outbreak of coccidiosis or a flea infestation. Modern pens are so constructed that they can be kept clean

and free of infective forms of

parasites.

Few remedies for the removal of

internal parasites of minks are

either safe or eiïective. To remove

worms, drugs must be powerful.

They are not easy to administer to

minks. Prevention of infection

with parasites is far preferable to

treatment. Supply feed from reliable sources, remove manure fre-

' Prepared by H. .T. Griffiths, profes«(ir

of veterinary parasitology, University of

Minnesota.

quently, use propei- disinfectants

when necessary, fly])r()of nest boxes,

and use wire-bottom pens and sanitary water containers.

External Parasites

Fur animals frequently l)ecome

infested with the larvae—maggots

or grubs—of flies. Older animals

are rarel}' infested; young kits,

sometimes those only 1 week old,

are the more frequent victims.

Fly conti'ol on the ranch.—To reduce the number of house flies,

blowflies, and their maggots around

the ranch, conti'ol is dii'ected toward

preventing them from jjreeding.

House flies are attracted by manure

and other decaying vegetable matter. Flesh flies, bluebottles, and

greenbottle flies are attracted by decaying animal material. They lay

their eggs on carrion and on animals having soiled ai-eas around

body openings and infected Avounds.

Such maggot-infested areas should

be cleaned up and washed with a

mild disinfectant. If not treated,

the animals may die.

Sanitation continues to be the

most impoi-tant consideration in

any fly-control program. Removal

and disposal of manure, waste feed,

garbage, and decaying meat should

be carried out routinely. Feed

p r ep a r a t i o n rooms slioul d be

screened and kept scrui^ulou.sly

clean at all times. Insecticides and

fly repellants should be used irith

r'liufion around the ranch. Do not

use them on animals, on feed and

watering equipment, or on surfaces

that the minks contact.

Eliminate breeding places and

destroy adult flies and maggots

arouncl buildings by using fly

sprays that have a residual killingaction.

In addition to sanitation, the judicious use of insecticides around

the premises and exterior of animal

23
quarters sliould ussist in the control

of these, (lies. ])I)T, nietlioxydilor,

and lindane applied as "1- to 5-

percent wet sprays on wood or other

surfaces, inchidiii«;- vej^etalion, provide lonp,'-lastin^- I'esidiial action.

Do not spray the interior of animal

quarters and do not apply on minks,

or contaminate their feed or wateiwith these insecticides. Dry or ^Yet

poison baits are etfective in controllinii- house flies and some kinds

of blowñies. Baits may be scattered or sprinliled or painted

around tlie ])remises wliei'e flies

conoTe<>-ate. The poison baits consist of organic-pliosphorus i)isecticides, sucli as Äialathion. Diazinon.

and Dipterex, to which a sweeteninir apent lias been added. ^Manure

and garbage piles can be treated

with Diazinon or Älalathion sprays

to destroy maggots. These measures should assist in general fly

control.

The Fox Maggot

The fox maggot {WoMfahrtia

spp.) is widely distributed throughout the Northern United States. It

l^robably causes greater annoyance

and loss of minlv kits tlian any other

maggot-producing fly. Kits are

most frequently attacked by it when

they are about 5 weeks old.

The fly responsible for this maggot invasion of kits is about twice

tlie size of the orcbnary house fly.

It is black and gray and i-ather slow

in its movements. Adults feed on

such sweet materials as nectar of

flowers, especially that of sweet

clover. The female fly strikes at

various parts of her victim, but she

seems to prefer the face, neck, flank,

and areas around tlie natural body

ojienings. Once she flnds a suitLARVAE Clnim) BU(W)W INTO

SKIN AND FO^M

SUBCUTANEOUS CHANNELS

FIGURE 20.—Life cycle of the gray flesh fly.

24
able spot slie deposits minute maggots, which attempt to bore into the

skin. Usually they are not able to

penetrate tlie skin of the adult but

readily break through the skin of

the ne\Yborn kit (fig. 20).

Once they have penetrated tlie

skin, the maggots develop rapidiv

and in 3 or 4 days may attain "a

length of about half an inch. Tliey

remain under the skin for 9 to Í4

days. Then they leave the mink

and fall to the ground. Here they

go into the resting (pupal) stage,

and in due course become adult fiies.

The life cycle may be completed in

a month during warm weather and

under the most favorable conditions, or it may be prolonged for

7 to 8 months if it began in the fall.

The gray flesh fly is abundant

from June to September, the period

of greatest attack usually being in

June. Late-born litters are more

likely to become infested than

earlier litters.

S/ffn.9.—A small area at the point

of the maggots' penetration becomes

reddish. Serum seeps from the irritated area, and the surrounding fine

fur becomes matted. As tlie maggots grow, a boillike lesion develops.

This lesion has a small opening

through which the maggots obtain

air (fig. 21).

'^AHiile skin penetration is in progress, the young minks become extreniely restless and may whine

pitifully. The nursing mother

often drags them outside the nei-t

box, where they may die from exposure. The constant irritation,

restlessness, and lack of appetite

brought about by this maggot infestation may result in exliaustion

and emaciation of the kits; death

may occur.

Treatment.—A 11 h o ug h many

ranchers do not like to handle kits

until they are weaned, examination

of the kits every second day is necessary to control this ¡jest. This

examination entails considerable

labor, but it is the most effective

FIGURE 21.—Taking a flesh fly maggot

from a hole in a minlv liit's slvin.

method of reducing losses from the

fly.

Prevention.—To prevent the infestation of mink kits with the gray

flesh fly, screen the entire shecl.

Screening of individual pens is

costly and impractical.

Keep lids of the nest box tightly

closed. To provide adequate ventilation, remove a 2-inch strip of

wood below the lid and replace it

with a piece of fly screening.

Brush the screen occasionally to

keep it free from dust and lint.

Fly traps around the pens may help

in reducing the fly population.

Grubs of the Rodent Botfly

The grubs of the rodent botfly

(Cuterehra sp.), which frequently

infest rabbits, squirrels, field mice,

deer mice, several other rodents, and

25
(loiHcstic kiík'iis, (K'casionall}' infest

minks.

T\\v adnll fly is ]ar>j:i'. and pix'fci-s

(o lay hi'i- t'fi'^s in dark surrnnndin<>'s. Liflle is known as lo how the

i^rubs tlial hutcii from tlie eii'<rs enter the skin of the host animal.

( )nce under tlie skin, tliey frrow to be

3/1 iiK'Ii lonji- and abnost ^2 i"*^'! i"

diametei". Wlien full iirown, the

«irubs leave tlie skin, drop to the

oroimd, and later beeome adult flies.

The <:-rubs do not seem to amioy

the minks to any f^reat extent while

they are embedded beneatli the skin.

However, they may readily be removed by squeezino- them out or Ijy

pullino- them out with a pair of

thumb forceps.

Fleas and Lice

Minks are not connnonly infested

with fleas. When they are, liowever, they may sutler considerably.

When foxes and minks are kept in

the same enclosure, the connnon dooflea {CtenocephaIidcf< cdnJji) may

appear on minks. Such an invasion is transient, however, for this

flea prefei-s feeding- on foxes.

The mink flea {C'eratophynus

vlsoii), when present in lai'f^e numbeis, is very detrimental to the

healtl) of jninks. As these insects

b'ed on blood, tliey may pi'oduce a

marked anemia and also cause the

animals to become restless and gradually lose weight. Pelts may be

damaged by continuous scratching

and by the exci'eta from the fleas,

which becomes intermingled with

hair and skin excretions.

Lice on minks aie rai-e. However, a biting louse {Trirhodeetea

retufiii.'i) has attacked ranch-raised

minks. When pi'esent, lice may be

very annoying. They blemish pelts

l>y attaching their eggs to hairs, and

the ii'i'itation caused by the adults

may result in loss of fur through

i'ul)bing and biting.

f'oiifroL—Fleas reproduce by

laying eggs on an animal's body or

in the dust and litter in the nest

box. As the eggs are not sticlcy,

those laid on the animal soon drop

on' into the bedding or litter. Flea

control is aimed at killing the adult

forms on the host, as well as the

PUPA IN COCOON LARVA

FiGUiiE 22.—Life cycle of the flea.

26
immature forms in the dirt, cracks,

and crevices of nest boxes and

kennels.

To destroy the young stages—

eggs, larvae, and pupae (fig. 22) —

remove all tlie litter and debris

from the nest boxes and pens.

Burn this material. Tlien scrub

with hot water and lye; 1 pound of

lye to Si-o gallons of water makes

a suitable cleaning and disinfecting

solution.

To destroy the adult fleas and

lice, dust adult minks with a good

insect powder. Commercial preparations of pyrethrum and rotenone

are available in powder form.

Dusting should be done over a sheet

of paper that can be folded up and

burned. Kepeat dusting treatments

2 or 3 times at intervals of 2 weeks

to destroy the young lice or fleas

that hatch from eggs.

Using insecticidal powders and

dusts on and around minks is dangerous. Do not use dusts in nesting hay or in nest l:)oxes prior to

whelping and do not dust kits until

they are at least S weeks of age.

Only insecticides tliat are relatively

nontoxic, sucli as derris or pyrethrum, are recommended for tliis

purpose.

Mange

Mange is rare in minks. When

found, it has usually lieen traced to

the introduction of fitclies or ferrets

or to contamination of ranch equipment by infested fitches.

Mange mites (8arcopte-'< sp.) are

prolific. They burrow into the

skin and they are minute ; therefore,

they are not readily visible to the

unaided eye. Ordinarily, the disease they cause is not recognized

until it has gained a good foothold.

Infested areas become extremely

itchy, whereupon tlie animals bite

and scratch in an effort to get relief. Scabs form over the infested

area, and the legs and feet, which

frequently become infested early,

become greatly enlarged and covered witli brownisli scabs and

crusts.

If mange is suspected on a mink

ranch, tlie diagiu)sis slionld lie confirmed I)y microscopic examination.

As mange is a serious contagious

disease, consult a veterinarian

whenever any animal has a scabljy

skin associated with itcliing. Tlie

diagnosis, control, and treatment

should be undertaken under the direct supervision of a veterinarian.

Other Mites

Occasionally, minks liave lieen

found infested with tyroglvpliid

and cheyletid mites. Thoug"]i not

usual parasites of minks, they may

cause considerable fur damage.

Tyroglyphid mites are usually

found in stored foods, dried meats,

grains, and flour and other cereals,

but at times they may attack small

animals or even man. Cheyletid

mites may be free-living, but they

also have been found on field or

house mice and otlier small rodents,

Avhere they may be parasitic.

S o m e t i m e s these mites are

brought to a mink ranch with food

products and may be found by the

millions in litter, bedding, or'nestl3ox dust. When tlie mites get on

minks, they cause considerable irritation. The minks seek relief by

scratching and rubbing, which destroys the guard hairs on their sides

and tails.

These mites may be controlled by

scrujiulous cleaning of pens and

nest boxes. Transfer infested animals to clean quarters, remove all

litter, and scrub dirty pens.

Internal Parasites

Coccidia

Coccidiosis (a disease caused by

coccidia, minute protozoan forms)

may become rampant on mink

ranches and cause heavy mortality

among kits. The disease is most

common in summer or early fall and

appears to be equally prevalent in

27
dry und wet SOMSOHR. AUlioii^li

coceidiosis usuully alfects iiiiiiiiiils

kept on earth and hoard ñooriiifí,

it may also atFect those kept on wire

flooring»'. Before wire-hottom pens

came into <i-enera] use, losses among

minks from coccidiosis were extensive. In the early days, tliis disease probably was one of the major

sinjile factors in kit mortality.

Both ranch-raised and wild minks

may become infected. Adult

minks often act as carriers of coccidia. and may be a source of infection for the kits even though they

show no signs.

The parasite lives in the intestinal tract, and the infective forms

(oocysts) are passed out with the

manure. The oocysts develop further outside the body, and the animal becomes infected I)y swallowing

them with contaminated feed and

water. Once s w a 1 1 o w e d, the

oocysts develop rapidly and liberate great j)umbei-s of tiny bodies.

These invade the cells of the gut

wall, thereby producing much irritation and injury. The young parasites, in turn, produce oocysts that

pass out with the droppings and

i-epeat the life cycle within about

2 weeks (fig. 23).

HigiiH.—'llie severity of coccidiosis depends on the extent of infection and the mink's resistance.

The signs, therefore, are not

always clear-cut and specific. Usually tlie tirst sign noted is the

passing of droppings coated with

mucus. The appetite may become

irregular and impaired; the fur,

rough, lusterless, and frequently

faded. Progressive weakness and

loss of flesh usually follow. If the

disease is associated with distemper

or some other malady, losses may

be great. Coccidiosis may also be

chronic, especially in older animals.

It runs its course in from 4 to 10

weeks, after which the animal will

have built up an immunity. UsuCONTAMINATE

FOOD AND Wi\TER

COCCIDIA CAN BE SEEN

ONLY UNDER MICROSCOPE

OOCYSTS DEVELOPE INFECTIVE

FORM ON GROUND

FIGURE 23.—Life cycle of coccidia.

28
ally íin outbreak of coccidiosis runs

its course and the losses cease witliout treatment.

Prevention and treatment.—As

yet there is no remedy that controls

coccidiosis. If the disease has not

gained too great a footliold, good

feed and nursing, together with

good sanitation, may help greatly.

Modern ranching methods and pen

construction have aided in eliminating this disease. "When minks are

kept imder insanitary conditions,

reinfection is continuous. Use

pens with suitable types of elevated

wire floors and keep feed and water

troughs scrupulously clean.

Toxoplasma

Suspected outbreaks of toxoplasmosis have been observed in minks

in Minnesota and Ontario. The

disease may appear in the form of

a nervous disturbance involving the

brain. Afl'ected minks nuiy show

extreme nervousness, irregular feed

and water consumption, inability to

find their food and to chew and

SAvallow it in the usual manner. In

advanced stages of the infection, severe nervous disorders may be seen

prior to death.

At present there is no eiïective

treatment for this protozoan infection. T r a n s m i s s i on may be

through eating infected meat, but

this has not been proved.

Roundworms of Digestive Tract

Generally speaking, ranch-raised

minks are not seriously affected by

roundworms, a hazard of the fox

industry some years ago. Several

species of roundworms from wild

minks have been reported, but none

appear to have caused serious losses

in ranch-raised animals.

Ascarids, commonly present in

the intestines of foxes and dogs, are

seldom found in minks. However,

animals infected with intestinal roundworms may show some

diarrhea and intestinal disturbance.

A ihie threadlike worm [CapHlaria

sp.) has l)eeu ol)served as an occasional intestinal p;irasite of minks,

but the iiann done by it has not been

determined.

Roundworms of Kidney

The kidney worm (Diuefoplujina

rénale), connnonly called the giant

kidney worm (fig. 24), has been recorded from both wild and ranchraised minks. It measures up to Vi

inch in diameter and 12 inches in

lengtli and is reddish in color. Although the worm is usually found

within the kidney, it has been found

also free in the abdominal cavity.

As a rule, only one kidne}' is affected and usually only one worm

is present.

The life cj'cle of this worm is

complicated. Its eggs passed in

the urine are ingested and develop

in small leechlike worms (branchiobdellid) that are parasitic on

crayfish. The latter are eaten by

bullheads which become infected by

FiüUüE 24.—Mink kidney cut open to

slmw tlie .yiaut kidne.v w<irm within.

29
iiifíestion of the, briiiicJiiobdellid.

Minks heeonie infected l)y eatinp;

tlie encysted paiiisites in tlie bodies

of the I)ullheads.

The pi'esenee of this worm in one

kidney does not nsually pi'oduce

any sij^ns. If Ijoth kidneys become,

infected, \Yhich is unusual, tlie animal dies. Because no curative

treatment is known, control is based

on prevention of infection. Biülheads suspected of comino- from infected sources should be cooked

before being used for mink feed.

Trichinae

Tricliinosis, a serious and often

fatal human disease resultino; from

an infection with Trichinelln f<piralh, sometimes affects minks.

Tricliinae—small, slender worms—

are acquired by eatinp; raw meat

containin<ï encysted larvae. Infection may be prevented by thoroufrhly cookinof nieat and meat scraps fed

to minks.

Guinea Worms

Guinea worms {Driiru)iru?ys iiitigni.^), wliich infect dogs and

foxes, have also been found in

ranch-raised minks. This worm is

an elongated, cylindrical, white

nematode, ranging from 1 to 2 millimeters in width ; the female

ranges from 75 to 280 millimeters

in length. The worms are found

just under the skin. The female

liberates a mass of living hirvae

through a small opening in the skin

when the skin comes in contact with

water. These young worms, free in

the water, are swallowed by a water

flea ( Cyclops sp.), in wluch they

develop further. Minks become infected by drinking water containing infective cyclops. This worm

does not appear to cause much harm

or inconvenience to its host. A

closely rehited species is transmissible to man by way of contaminated water; hence, measures

.sliould be taken to destroj' and dispose of infected animals.

Tapeworms

Tapeworms of several kinds have

been recorded, but they are not

common in ranch-raised minks.

TJiey are found in the small intestine but do not appear to cause

marked signs or lesions. The muskrat may act as an inteiTnediate host

for some tapeworms. Therefore,

do not feed raw mnskrat or muskrat

livers to minks. Fish that show

any bladderlike cysts in the muscle

or other tissues sliould be thoroughly cooked before they are fed

to minks.

Lung Flukes (Flatw^orms)

As a rule, flukes are common in

wild furbearer.s, e.specially those

tliat live in and around lakes and

m a r s h e s. Occasionally, flukes

appear in ranch-raised minks, especiall}'' if they are fed raw fish, crayfish, frogs, or mice.

Tlie lung fluke {Paragonimus

Ji^ellirotti), although fairly common

in the midwestern TTnited States, is

not likely to become established

among ranch-raised animals because of its complicated life cycle.

The fluke ranges in length from 4

to 16 millimeters and in width from

4 to 8 millimeters. The parasites

live in cystlike cavities in the lungs.

The cysts are relatively large and

may appear on the lung surface as

bluish raised areas. Cutting into

the cysts may reveal one or more

parasites bathed in a dark-brownish slimy fluid.

This fluke requires two intermediate hosts to complete its life

cycle—the first a species of snail, the

second a crayfish. Minks become

parasitized by eating infected crayfish. If crayfish are used for mink

feed, they should be boiled.

As this parasite inhabits the

lungs, the usual sign is a cough.

Heavy infections may cause death

of the animal. No effective treatment is known.

30
Intestinal Flukes

Several species of flukes, ranging

in length from 1 to 3 millimeters,

may be found in both wild and

ranch-raised minks. Although

they do not seem to be very harmful,

infected animals may not do well,

may show some diarrhea, and may

have harsh, lusterless, dry pelts.

The life cycle of each of these flukes

requires one or more intermediate

hosts; the second one usually is a

fish, crayfish, or frog. Infection

among ranch-raised minks may be

prevented bj^ cooking such feed or

by subjecting it to prolonged freezing.

Liver Flukes

A liver fluke {Metorchli^ conjunctu^) occurs in both wild and

ranch-raised minks. Some ranchers have sufl'ered severe losses from

this parasite which is found in the

gall bladder and bile ducts. Signs

are irregular appetite, general unthriftiness, weakness, jaundice, and

anemia. No effective treatment is

known. As the infective stage occurs in the common sucker, infection may be prevented by cooking

this fish before feeding to minks.

Examination of Feces for

Parasite Eggs

If minks are not doing well and

there is reason to suspect parasite

infection, it is advisable to have a

specimen of feces examined for

parasite eggs or cysts. The presence of internal parasites in living

animals can usually l^e determined

by microscopic examination of

fresh droppings. Most internal

parasites produce large numbers of

eggs within the host's intestine.

Finding these eggs in the manure

confirms the presence of the parasite in the animal. Whole wonns

or parts of them may occasionally

be passed with the droppings and

can sometimes be seen.

Collection and Preparation

of Samples

For a preliminary survey or

routine check, collect composite

samples of feces from tlie pens.

Number each sample to correspond

to the pen or animal number. Samples collected should be fresh; satisfactory and reliable results cannot

be obtained with old, dried manure.

Pick up the samples with a small

wooden .stick (fig. 25) or spoon.

Tiiey should be as free as possible

from material such as dirt, liedding,

sancl, and stones. To avoid contamination, use new sticks and separate containers for each sample.

Examine the samples promptly.

Many worm eggs and protozoan

cysts develop quickly once passed to

the outside in the manure. If examination must be delayed, keep

the samples on ice or in a iO-percent

formalin solution.

Direct smear.—The direct-smear

method is the simplest and quickest

way of preparing fecal material for

examination for worm eggs. Moderate to heavy infections can be detected by this method; however,

light infections may be overlooked.

The minute parasite eggs can be

seen only with the aid of a microscope.

Place a drop of clean water on

a 3- by 1-inch glass slide. With a

match or toothpick, take small bits

of fecal material at random fi'om

several parts of the sample of droppings. Mix the fecal material with

the drop of water with a rotarj' motion. Then place a clean cover

glass over the preparation. The

smear is now ready to be examined

(fig. 26).

Straining and fiedinienting.—

Parasite eggs are easier to find if

the coarse material of the fecal

sample has been removed and if the

eggs are concentrated. This may be

accomplished by the process of

straining and sedimenting. Mix the

feces thorouglily witli about a pint

of water by shaking and stirring.

31
FIGURE 25.—Collectins with a stick a sample of inannre (left) to be placed in

container (lowe'r right) labeled with the pen number (upper left).

Then strain the mixture through a

fine sieve, or one or two thicknesses

of cheesecloth, to remove the coarse

particles. The liquid which passes

through the sieve will contain the

parasite eggs. These will settle to

the bottom of the jar in 15 to 20

ininutes. With a small glass tube

or a clean straw, transfer a drop or

two of the sediment to a glass slide

for examination under the microscope.

Flotation method.—A n o t h e r

method commonly used for separating worm eggs from coarse fecal

material is to float them to the surface of a fluid. Mix the feces with

a lifiuid of such density that the

eggs are lighter than the suspending fluid and hence float to the surface. Two fluids commonljr used

for the purpose are saturated salt

solution and a sugar solution. The

Avorm eggs will float to the top within 15 to 20 minutes and can then be

removed with a wire loop or glass

rod, transferred to a slide, and examined under the microscope. This

method is excellent for certain

roundworm eggs, but fluke eggs

may fail to rise to the surface without rupturing.

32
1 Place dr^ of clean ujaier on slide 2. Mix in small amount of sample

3. Place cover slip over maferiaJ

FIGURE 26.—Preiiaring feces fur exauiiuatiipii of worm eggs by the direct-smear

luethod.

Examination of Slide

When the material is ready for

examination, place the slide on the

microscope stage and reduce the

light so the transparent objects

stand out clearly. Beginning at the

upper right-liand corner of the

cover glass, move the slide slowl}'

back and forth from side to side;

examine systematically until the

entire slide lias been examined. The

examination will reveal many structures that can be mistaken for parasite eggs or cysts. Compare the

objects seen with drawings or

photographs of the eggs. With

practice, worm eggs and protozoan

cysts may be readily identified;

liowever, the personal aid of one

acquainted with these eggs is of

much help to the beginner.

HOW TO PACK AND SHIP SPECIMENS FOR LABORATORY

DIAGNOSIS

"Upon arrival, the carcass of your

animal was decomposed and could

not be used for examination. If

available, we suggest you send additional animals."

A veterinarian often has to send

this statement to a rancher in answer to a serious problem. Much

time is lost. Often by the time additional animals are received, properly packed, it is too late to stop

further losses. A satisfactory postmortem examination cannot be performed on a decomposed animal

because signs of disease that may

have been present are often changed

or entirely obscured.

The best way for a rancher to

obtain an accurate diagnosis is to

take the dead animals, or 2 or 3 sick

animals showing typical signs, to

the nearest laboratory. Then he

can supply any additional information the pathologist may need. If

this is not con\-enient, the dead animals may be shipped.

33
Shipping Dead Animals

It (lie cni'Cii.ss is to be sliiiiped a

short distance, cliill it thoioualily

iuid place it in the center of a box

containino'sawdust or shavings ( lifi'.

)¿7). For ]on^--distaiice shipments,

place dry ice around the carcass,

then pack it as indicated al)ove.

Never put. dry ice in an airtight jai'

or can. When the ice melts, f;as is

formed; if tlie li'as cannot escape, it

may cause an explosion. Properly

used, dry ice will prevent spoila<z'e

for 2 or o days.

If dry ice is not available, place

the animal in a can with a tiiiht lid

(1- or 2-i)ound coffee cans are a convenient size foi' minks), fi'eeze solid,

and ]3ack in crushed ice surrounded

by sawdust to take up the water. A

wooden box can be used for shipment, but if a bucket, such as a lard

container, can be substituted for a

wooden IJOX, no sawdust is necessai-y.

Many s]>ecimens decompose after

arrivin<i- at tiie laboratory because

no one is available to take care of

them pi-omptly. With this in mind,

do not send fresh specimens tliat

will arrive on a weekend; most

laboratoi-ies do not operate on

Saturday or Sunday. Address the

l>ackaire to the laboratory itself, not

to an individual employee. Tliis

will insure more immediate attention.

Do not send carcasses that have

started to decompose. It is better

to kill an animal or two that show

typical signs, or to ship them alive

FIGURE 27.—Packing a dead animal to be shipiied a short distance. The carcass,

thoroughly chilled, is placed in the center of a box containing sawdust or

shavings.

34
if there is i\ chance that they may

reach tlieir destination before death.

The Accompanying Letter

Letters that do not contain sufiicient information are a problem to

the pathologist. In some tliseases,

a complete history is more useful

than the carcass. The autops_y of an

animal affected by Chastek's paralysis or botulism, for example, ^Yill

show little. The accompanying letter should contain the following

information :

(I) Number of minks on the

ranch.

{•2) Number of animals showing signs; age of animals affected.

(3) Number dead.

(4) Dates of first losses and

subsequent losses.

(5) Description and duration

of signs before death.

(6) Feeding schedule for past

f) months.

(7) If the animal has been

pelted, give color of the pelt, condition of the eyes (whether or not a

discharge was present), and condition of the coat and foot pads.

(8) Incidence of infection

(whether it is in just one house or

pen, among one type of mutation,

or scattered throughout the ranch).

(9) What treatment, if any,

has been given.

(10) Tjq^e of housing (whether

the minks are kept on wire or in

ground pens).

(II) Any other information

that might help explain tlie outbreak.

As it is against postal regulations

to send frozen carcasses of diseased

fur animals through the mail, shipment must be made by rail or air

express. Place the written material

inside the package. If cracked ice

is used, place the letter where it

cannot become soaked and illegible.

Label the outside of the box, "Biological Specimen," "Rush," and

"Keep in a Cool Place."

Shipping Tissues in Formalin

Sending tissues or organs in a

preservative such as lO-percent

formalin is often iielpful in making

a diagnosis. This solution may be

obtained from a local veterinarian

or druggist. Send the whole bladder and brain, but only a i)iece of

the kidney, sj)leen, liver, lung, stomach, and intestine. These pieces

should be about the size of a postage

stamp and a quarter of an inch

thick. Use of 10-percent formalin

lias the disadvantage that it kills

any bacteria or virus present.

Therefore, bacterial studies or viral

inoculations cannot l)e made from

tissue thus packed.

Shipping Parasites

Ship fleas, lice, flies, maggots,

mange mites, and internal parasites

for identilicatiou in a clean tight

bottle (tig. '2^) containing 70-pei'-

FiGCUE 28.—Placing parasites tu be submitted fur ideutiflcatiou in a stout glass

jar c-ontainiiis 7()-ijer<ent aleobol. Tlie

jar can then be wraiiiied iu absurbent

cotton and iiaeked in a strong box or

niaiUng tube.

cent alcohol, obtainable from a local

veterinarian or druggist. Do not

allow the jKirasites to dry out before

mailing, and always put them in a

preserving fluid. If the animals"

feces are ito be checked for i)arasite

eggs, i)lace a small amount in 10-

percent formalin. Number each

sample and put it in a clean jar.

Tissues and feces in 10-percent

formalin, or parasites in 70-percent

alcohol, may be sent by domestic

35
mail. Postal re<ínlations require or otlier suitable absorbent material

that they be placed in stout ^'lass in sufficient quantity to absorb all

jars not more than ?> inches in the fluid m case of breakage, and

diameter wifh tip-lit-htting lids, tlien pack tliem in strong boxes or

Wrap the jars in absorl)ent cotton mailing tubes.

36

U.S. GOVCRNMEMT PRINTINi; OFFICE: I960