126
Chemotherapy of Helminthic Infections of Domestic Animals
been tried in vitro only, have been avoided, for
when tried in vivo, they undergo dilution below
the therapeutic threshold, a change occurs in
their chemical composition, and the manner
of excretion alters their efficiency.
DISTOMIASIS OF RUMINANTS
Hall [1921] used carbon tetrachloride as an
anthelmintic with excellent results. Recently
it has been proved very efficacious and suffi-
ciently cheap for adoption in mass treatment,
the cost working out at about half-an-anna per
dose. The dose for sheep is 1 c.c. and for
larger ruminants 5 to 10 c.c. It is given in
liquid paraffin in the proportion of 1:4. Other
cheap oils, such as groundnut oil or cotton seed
oil, may be substituted for paraffin. As only
the adult worms in the liver are destroyed by
this drug, the dose should be repeated about a
month later. It is usually administered orally,
but Pegreffi [1939] recommends intra-ruminal
injection. He states that pregnancy is not a
contra-indication to its use in oily solution.
Obitz and Wadowski [1939] treated 3,000 fluke
infested sheep by subcutaneous injection of
carbon tetrachloride in liquid paraffin. The
average time of treatment was one minute per
head and the cost was one dollar per 100 sheep.
1,600 sheep were cured with only five acci-
dents.
The drug is an excellent remedy for fascio-
liasis of ovines, but it is somewhat toxic to
bovines. In our experience, however, the
bovines recover from the toxic symptoms in
about a couple of days. Its toxicity is of a
complex nature and mainly consists of the re-
tention in the blood of bile pigments which
combine with the ionised blood-calcium and are
excreted as such, causing hypocalcimia. It
also causes the retention of guanidine in the
blood; this interferes with the conversion of
glycogen into blood-sugar and causes hypo-
glycæmia. The pathological effect is chiefly on
the liver, resulting in central necrosis and fatty
degeneration.
Guanidine and calcium are antagonistic to
each other in their behaviour and the ad-
ministration of calcium controls its toxicity;
75 to 150 c.c. of calcium gluconate is administer-
ed by injection, or calcium chloride with
ammonium
chloride
or
calcium
lactate
given orally. Injections of sodium xanthine
(liver extract) is said to protect animals against
carbon tetrachloride poisoning.
Before and after the treatment, the animal
should be fed on a carbohydrate diet. Fats
and proteins should be strictly withheld, as fats
increase the solubility of the drug and cause
its absorption through the lymphatics, while
proteins cause an increase in the production
of guanidine. As there is a heavy drain on
calcium in animals during lactation, greater
care has to be exercised in such cases. To
decrease the toxicity and to promote a rapid
excretion, a dose of magnesium sulphate may
be given.
Hexachlorethane (Igitol, Distol) is as effec-
tive as carbon tetrachloride and is much safer,
but it is somewhat costly. The dose for sheep
is 6-8 gm. The doses recommended for the
treatment of cattle are 20 gm. per 50 kil. of
body-weight, to be given for four successive
days in the morning, three to four hours before
feeding. The milk of cows undergoing treat-
ment may become slightly tainted, and milch
cows fed on concentrates may develop symp-
toms of colic.
Sprehn (1936) recommends two intra-mus-
cular injections of 20 c.c. of Fuadin for
Dicrocælium dendriticum
of sheep. On the
10th to 12th day the fæces is completely free
from eggs.
GASTRO-INTESTINAL HELMINTHS IN RUMINANTS
These chiefly consist of Hæmonchus contor-
tus, Mecistocirrus digstatus, Osteriagia spp.,
Bunostomum
spp., Trichostrongylus
spp.,
Chabertia sp., Trichuris sp., Oesophagostomum
spp., Cooperia spp. and tapeworms.
Carbon tetrachloride is very effective against
Hæmonchus,
Bunostomum,
etc., but not
against Trichostrongylus.
This drug can pro-
fitably be employed for the combined treat-
ment for fasciohasis and parasitic gastritis.
Carbon tetrachloride in combination with
copper sulphate has been used with very good
results, and regular monthly treatment pro-
duces a marked improvement in the quality of
the wool of sheep [Ross and Graham, 1933].
A drug that has come into great prominence
during the past four years is Phenothiazine
(Thiodiphenylamine—C 6 H 4 NHC 6 H 4 S). This
drug has been known since 1885, but Harwood
and collaborators [1938] were the first to use
it against nodular worms and ascarids of swine.
During the last four years it has been used
very extensively in the treatment of gastro-
intestinal helminths. It has been remarked
that the employment of this drug for the treat-
ment of helminths of domestic animals is one
of the seven outstanding advances in veterinary
medicine. This is borne out by the publication
by Professor Leiper [1942] of a special biblio-
graphy of 120 references regarding the use of
this drug as an anthelmintic. The drug is