Pseudorabies in Pigs: Nervous System Signs, Tremors, and Paralysis

Pseudorabies, also called Aujeszky disease, is a contagious viral infection caused by a herpesvirus that primarily affects pigs. Despite the name, it is not rabies. In pigs, it can cause nervous system disease, breathing problems, fever, poor growth, and major reproductive losses. The exact signs often depend on the pig's age.

Piglets are usually hit the hardest. Very young pigs may develop severe central nervous system signs such as tremors, paddling, seizures, circling, or hind-limb weakness and paralysis. Mortality can be extremely high in newborn piglets. In older growing pigs, respiratory disease is often more obvious, while adult breeding animals may show fever, cough, abortion, stillbirths, or weak piglets.

This disease matters beyond the individual pig. Pseudorabies is a reportable disease, and suspected cases need prompt veterinary attention and laboratory confirmation. In the United States, commercial swine herds have remained pseudorabies-free since 2004, but the virus is still present in feral swine, so outdoor pigs and herds with wildlife exposure still need careful prevention planning.

Pseudorabies is caused by pseudorabies virus (PRV), a DNA herpesvirus. Pigs are the natural reservoir host. The virus spreads most often from an infected pig that is shedding virus to an uninfected pig through close contact. It can also spread through respiratory secretions, breeding, contaminated equipment, boots, clothing, bedding, feed, and other shared farm items.

One of the biggest modern risk factors in the United States is contact with feral swine. Although commercial swine herds have been free of pseudorabies for years, the virus still circulates in wild pig populations. Outdoor pigs, backyard pigs, and herds with weak perimeter fencing are at higher risk if feral swine can reach fences, feed, water, or breeding animals.

Age changes how the disease looks. Young piglets are very susceptible and may develop severe brain and spinal cord signs with high death loss. Weaned and growing pigs are more likely to show respiratory disease, while adult pigs may have fever, reduced appetite, and reproductive failure. Pigs that recover can remain latently infected, which is one reason herd-level control and veterinary oversight are so important.

Your vet will start with the herd history, age groups affected, and the pattern of signs. A combination of neurologic disease in piglets, respiratory disease in older pigs, or reproductive losses in sows can raise concern. Because several serious swine diseases can look similar, diagnosis cannot be made by signs alone.

Confirmation usually requires laboratory testing. Common options include PCR, virus isolation, fluorescent antibody testing, and serology such as ELISA or serum neutralization. In acutely affected pigs, your vet may collect nasal swabs, blood, or tissues. In pigs that died, diagnostic labs may request tissues such as brain, spleen, lung, or tonsil. Maternal antibodies and prior vaccination history can affect how some antibody tests are interpreted, so your vet may recommend paired samples or herd-level testing.

In the United States, suspected pseudorabies cases are handled through veterinary diagnostic and regulatory channels. Your vet may submit samples to the State veterinary diagnostic laboratory, and non-negative results may be forwarded for confirmatory testing. Because this is a reportable disease, herd movement, isolation, and follow-up steps should be discussed right away with your vet and animal health officials.

Prevention starts with strong biosecurity. Keep domestic pigs separated from feral swine with secure fencing, and use extra barriers for pigs that live outdoors. Avoid shared nose-to-nose contact through fences. Limit visitors, clean boots and equipment, and do not share trailers, feeders, or handling tools without proper cleaning and disinfection.

Be careful when bringing in new pigs. Source additions from herds with documented health status, and ask your vet about quarantine and testing before mixing new arrivals with the rest of the herd. USDA APHIS notes that buying from validated-qualified pseudorabies-negative herds lowers the risk of introducing disease.

Work with your vet to build a herd health plan that fits your setup. That may include quarantine protocols, breeding management, wildlife risk reduction, and a response plan for sudden neurologic or reproductive disease. Vaccines exist, but in the United States their use for pseudorabies requires APHIS and State animal health official approval, usually during an outbreak or emergency situation. For most pet parents and producers, day-to-day prevention depends much more on biosecurity than routine vaccination.