Two more fact sheets have been updated in the Swine Health Information Center (SHIC) Swine Disease Fact Sheet Library. As part of SHIC’s mission to protect the health of the US swine herd, providing guidance and resources for producers, practitioners, and diagnosticians who are on the front lines of swine health concerns is paramount. Updated fact sheets on porcine teschovirus (PTV) and Japanese encephalitis virus (JEV) were recently posted.
PTV is an enteric picornavirus of swine. Most infections are subclinical, but some strains cause severe central nervous system disease (polioencephalomyelitis) with high mortality. Why some PTVs cause polioencephalomyelitis and others circulate inapparently is not known. In the United States, diagnostic laboratory submissions with a history of posterior paresis seem to be increasing in pigs from a wide age range. Additionally, in other countries, sporadic outbreaks of severe polioencephalomyelitis continue to occur. Swine, including wild boar, are the only known hosts for PTV.
Severe polioencephalomyelitis (teschovirus encephalomyelitis, Teschen disease) causes high morbidity and mortality in pigs of all ages. Milder cases of polioencephalomyelitis (benign enzootic paresis, Talfan disease) occur in post-weaning pigs. More research is needed to understand why some PTVs induce severe polioencephalomyelitis, and others do not.
Transmission is mainly fecal-oral. Some PTVs are linked to SMEDI syndrome (stillbirth, mummified fetus, embryonic death, infertility). And PTV has been associated with diarrhea, but the virus can also be found in the feces of healthy pigs. PTVs are also linked to respiratory disease, pericarditis, myocarditis, and congenital microphthalmic syndrome.
JEV is a zoonotic arbovirus that is endemic in much of Asia and the western Pacific region. Pigs are an amplifying host of JEV while most other susceptible species are dead-end hosts. The virus produces neurological disease in pigs and horses as well as reproductive failure in pigs.
Most JEV infections in pigs are subclinical. In sows, infection with JEV before 60 to 70 days of gestation can cause abortion, fetal mummification or stillbirth, or the birth of weak piglets. Infected boars can have reduced sperm motility and develop testicular edema and temporary infertility. Piglets born alive may develop encephalitis, displaying tremors and convulsions.
Japanese encephalitis (JE) is currently a foreign animal disease, but its emergence in the United States is a concern due to the presence of competent mosquito vectors and susceptible hosts. Mosquito control is essential for the prevention of JE and recommended practices include removing stagnant water around pig enclosures, using insecticides, installing insect screens, and using fans inside buildings where pigs are housed to disrupt mosquito activity. Although pig-to-pig transmission of JEV has been described, its role in natural transmission is unclear.
SHIC, launched in 2015 with Pork Checkoff funding, continues to focus efforts on prevention, preparedness, and response to novel and emerging swine disease for the benefit of US swine health. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. SHIC is funded by America’s pork producers to fulfill its mission to protect and enhance the health of the US swine herd. For more information, visit http://www.swinehealth.org or contact Dr. Sundberg at psundberg@swinehealth.org.