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Animal and Plant Health Inspection Service
U.S. Department of Agriculture
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Swine: Pseudorabies

What is Pseudorabies?

Pseudorabies is a disease of swine that can also affect cattle, dogs, cats, sheep, and goats. Pseudorabies virus (PRV) is a contagious herpesvirus that causes reproductive problems, (abortion, stillbirths), respiratory problems and occasional deaths in breeding and finishing hogs. Infected newborn pigs may exhibit central nervous system clinical signs.

PRV is primarily spread through direct animal-to-animal (nose-to-nose) contact between an infected, shedding pig and a noninfected pig. It may also be spread by sexual contact. If present on inanimate objects, such as boots, clothing, feed, trucks, and equipment, the virus can also spread from herd to herd and farm to farm.

Pseudorabies can be prevented primarily through biosecurity, and sound management practices that include disease control and prevention.

Clinical signs in pigs depend on the age of the affected animal. In piglets central nervous systems signs, incoordination, sneezing, coughing, and high mortality. In adult pigs coughing, fever, pneumonia, central nervous systems signs, and reproductive signs such as failure to breed, abortions, mummified piglets, stillbirths, and small litters. Adult pigs often have low mortality and the virus can remain hidden in the pig in a carrier state for long periods of time.

There is no treatment but antibiotic medications can control secondary bacterial infections. PRV vaccines are available, require USDA approval for use, and can be used to assist in outbreak response efforts.

PRV is known to have existed in the United States for at least 150 years. Although feral swine remain as a reservoir for PRV in the United States, currently, all 50 States are considered free of PRV in commercial production swine herds. Commercial swine herds are defined as those herds which have adequate measures in place to prevent contact and potential infection from feral and transitional production swine which are known potential carriers of the PRV virus.

A pseudorabies-infected herd contains animals that have tested positive serologically or have had the virus isolated in an official test conducted by an approved laboratory.

No commercial total confinement production herds have been found to be infected with PRV since early 2003. Sporadic infections have been found in outdoor production herds or swine that have access to the outdoors, especially where contact with feral swine is possible. Any infected herds have been promptly depopulated when found, and intense epidemiological investigations have been conducted to ascertain that no viral spread to commercial production swine has occurred.

Indemnity Information: for questions in regards to pseudorabies indemnity contact:

Nicki Humphrey, DVM
Veterinary Medical Officer-Swine Staff-ASEP
USDA-APHIS-Veterinary Services


John A. Korslund, DVM
Swine Commodity Health Specialist
USDA, APHIS, VS, Surveillance, Preparedness, and Response Services
301-851-3468 Office
301-821-7406 Cell

If an accredited veterinarian suspects PRV in an animal or herd, blood samples should be collected and sent to the state diagnostic laboratory, usually a National Animal Health Laboratory Network (NAHLN) lab. The lab will conduct screening tests for PRV and submit any non-negative results to the National Veterinary Services Laboratories (NVSL) in Ames, IA for confirmatory testing. PRV is a reportable disease in all states.

PRV can be devastating to your breeding animals and young piglets in particular. If you have any serious breeding, nervous, respiratory or sudden unexplained death issues with sows and newborn piglets in particular, call your veterinarian to investigate. The veterinarian will most likely get blood samples and tissues (from dead piglets, for example) to submit to the veterinary diagnostic lab to help determine a diagnosis. If the cause turns out to be PRV state and federal animal health officials will also become involved in the investigation. Contact with feral swine is by far the most common method of PRV getting into your swine herd, so be sure this cannot happen through double fencing and other measures if feral swine are present in your area.  Prevention is the key to dealing with this disease.

Federal: VS District Offices Points of Contact
State: State Animal Health Officials

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