Questions and

Answers on Spring

Viremia of Carp for

Producers

Q. What is spring viremia of carp (SVC)? 

A. SVC is a contagious and potentially fatal viral 

disease of cyprinid fish, including common carp, koi

carp, and goldfish. The number of North American

fish species susceptible to SVC is not yet known. As

its name implies, SVC is usually seen in the spring

but it may also be seen in other seasons and in fish

species other than carp. High fish mortality is 

generally seen in water with temperatures that range

between 50–63 degrees F (10–17 degrees C). At

high water temperatures, infected fish may develop

immunity to the disease.

Q. What signs will I see in my fish if they are

infected with SVC?

A. The first signs of SVC disease may be a change

in behavior. Diseased fish may breathe and move

more slowly, form groups in slow–flowing water near

the pond bank, or lie on their sides at the pond 

bottom. The fish may have darkened skin, a swollen

belly, bulging eyes, bleeding in the skin, and a 

protruding vent. However, these are nonspecific

signs and may be caused by several other diseases

as well.

Q. Could my fish have the virus and appear 

normal? 

A. Yes. Fish that do not die from SVC may recover

and appear healthy, but these fish actually may

remain infected with the SVC virus and continue to

shed and spread the virus to other fish. Other 

infected fish may develop immunity without ever

showing obvious signs, but may still carry the virus.

This outcome is more likely if fish are infected when

water temperatures are greater than 63 degrees 

F (17 degrees C).

Q. How is the virus spread?

A. The virus is excreted (shed) in the feces, urine,

and mucus of the infected fish and may remain 

infectious in the water for more than 4 weeks and in

mud for 6 weeks or more (depending upon the 

temperature). The virus may also be spread through

contaminated equipment, fish parasites, predatory

birds, and on the outside of an infected fish’s eggs.

Q. Why is SVC testing done in the fall and the

spring?

A. During the fall and spring, water temperatures are

within the appropriate range (10–17 degrees C) for

maximal virus replication and reduced immune

response in the fish. Testing that is conducted at

least 2 weeks after water temperatures are within the

appropriate range are most likely to give accurate

and diagnostic results.

Q. What type of testing is done on the fish?

A. Internal organs, such as the kidney and spleen or

brain, are used to detect SVC virus. Fish tissues are

homogenized, and then placed in small flasks that

contain a layer of healthy fish cells. If the virus is

present, the healthy cells begin to die. These

changes can be seen with a microscope.

Q. What can I do to protect my fish from becoming infected with SVC?

A. There are several recommendations for 

preventing SVC from becoming established on 

commercial farms. Developing a good, thorough,

complete biosecurity plan for your fish is the best way

to protect them. Some components of this type of

plan may include:

• Purchase susceptible species of fish from 

sources known to be free of the SVC virus.

• New fish should be quarantined in water that is 

between 50 to 63 degrees F for as long as 

possible (at least 2 weeks) before introducing 

them into a pond or tank that contains other 

susceptible fish.

• Use a water source that is free of virus, such as 

well water or first–use spring water.

• Limit contact with wildlife and other predators.

• Chemically disinfect eggs by iodophore 

treatment.

• Disinfect ponds between crops and equipment 

between ponds or tanks.

• Dispose of all dead fish in a manner that 

prevents contact with other fish.

• Avoid contact with other fish, especially at shows.

• Avoid shared equipment.

Q. What can be done to cure my fish if the virus

is isolated?

A. Once SVC virus is established in pond fish, it may

be very difficult to eradicate without destroying all

kinds of life on the fish production site. Antiviral

drugs are not available or approved to treat SVC or

other viral diseases of cultured fish. Vaccine 

development has been attempted, but further studies

are necessary.

Factsheet

Veterinary Services January 2004

APHIS
Q. How can the virus be destroyed?

A. SVC virus is destroyed by changing the pH of the

water to below 3 or greater than 12. It is also 

susceptible to lipid solvents (such as detergents), and

heat above 56 degrees C. It can be inactivated by

several disinfectants including chlorine, iodine, sodium

hydroxide, and potassium peroxomonosulphate known

by its trade name Virkon. Ultraviolet light also inactivates the virus.

Q. What should I do if I think my fish have SVC?

A. SVC is an Office International des Epizooties

(OIE) List B, reportable disease. The U.S.

Department of Agriculture (USDA) is required to

report any outbreaks to the OIE, the international

standard–setting body for animal health. If you 

suspect SVC in your fish, you should contact, as soon

as possible, the State veterinarian or the local Animal

and Plant Health Inspection Service’s (APHIS)

Veterinary Services (VS) office in your State. See

http://www.aphis.usda.gov/vs/area_offices.htm for a

list of your State contacts.

Q. What should I do if my fish are positive for

SVC?

A. Do not ship or transport fish from the farm site or

pond.

• Contact State official/APHIS.

• Be prepared to take samples of fish from your 

ponds and facilities to determine where the virus 

is present.

• Request USDA SVC indemnification assistance if 

your fish must be destroyed and also assistance 

for payment of cleaning and disinfection of your 

farm/ponds if needed.

Q. Is SVC a new disease?

A. No. It has been well–known in Europe for many

years. However, it was first definitively identified in

commercial fish in the United States in the spring of

2002.

Q. What activities is APHIS undertaking?

A. APHIS–VS is conducting surveillance throughout

the United States to determine how widespread the

disease might be. It is developing import protocols to

ensure that SVC–susceptible species from other

countries do not enter the United States without a 

certificate of veterinary inspection showing they are

free of the disease. There is a voluntary export 

certification program for producers who have their fish

tested and declared as being SVC–free.

Q. Where can I get more information on SVC?

A. Current information on aquatic animal diseases is

available on the Internet at 

http://www.aphis.usda.gov/vs/aqua/aquaphis.html. If

you have additional questions contact:

USDA, APHIS, VS

Emergency Programs Staff

4700 River Road

Riverdale, MD 20737

Phone (301) 734–8073

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United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture