Why Keep Testing?

Barry Whitworth, DVM Area Food/Animal Quality and Health Specialist for Eastern Oklahoma

The month of December is when spring pig shows begin. One requirement that accompanies the swine show season in a negative pseudorabies virus (PRV) test. Many exhibitors question the need to continue testing for this disease. It is a fair question. According to the United States Department of Agriculture (USDA), pseudorabies has not been a problem in commercial swine since 2004. Unfortunately, in surveillance testing conducted by USDA Wildlife Services, feral swine in the Oklahoma continue to harbor the virus. State Veterinarian Rod Hall reports that the chance of show pigs and herds that produce show pigs being exposed to feral swine is high enough to warrant continued testing.

Although not known as pseudorabies, the disease was first described in the US and later Europe in the 1800s. Because of similar clinical signs, the disease was mistaken for rabies which is why it is called pseudorabies (pseudo means false). Dr. Aujeszky was the first to describe the infectious nature of the pathogen. He demonstrated that the disease was not rabies. For this reason, the disease is sometimes referred to as Aujeszky’s disease (AD).

 The term used to describe the disease in animals other than pigs is “mad itch”. Several different species of animals have been diagnosed with PRV. Animals that develop clinical signs of the disease have close contact with pigs or consume raw pork products. These animals develop a severe pruritus (severe itching) around the head and neck area. The scratching results in self-mutilation. Death follows shortly after clinical signs appear.

In pigs, which are the natural host of the virus, the virus causes respiratory, neurological, and reproductive issues. Pigs that recover from infection are latent carriers of the virus. The virus may be re-activated if the animal is stressed.

Clinical disease depends on the age of the pig. When exposure to the virus occurs in young pigs, large numbers of pigs may become ill and/or die. Neurological signs seen in young pigs may be paddling, shaking, disorientation, and lameness. Sick piglets with respiratory symptoms may demonstrate coughing, sneezing, and nasal discharge. Diarrhea and vomiting may be seen in some strains of the virus. In feeder pigs, the clinical signs will be similar but less severe and with far fewer deaths. In sows, respiratory, reproductive, and anorexia may be seen. Reproductive clinical signs seen will depend on the stage of gestation. In early gestation, early embryonic death and resorption of the fetus is common. In mid to late gestions, abortion and mummified fetuses are found.

Read more in the January 2022 issue of Oklahoma Farm & Ranch.