Among the possible infectious causes are porcine teschovirus, porcine sapelovirus and atypical porcine pestivirus. Although these viruses are not new to the United States, historically confirmed cases have been reported infrequently.
PTV is a non-enveloped, positive-sense single-stranded RNA virus in the genus Teschovirus of the family Picornaviridae. There are 13 known serotypes of PTV. Pigs can be co-infected with more than one serotype and PTV is commonly isolated in healthy swine. Highly virulent strains of PTV-1 can cause teschovirus encephalomyelitis. Less virulent strains of PTV-1, in addition to PTV-2, PTV-3, and PTV-5, are associated with Talfan disease (also known as benign enzootic paresis), a milder presentation of polioencephalomyelitis than teschovirus encephalomyelitis.
In teschovirus encephalomyelitis, fever, anorexia, listlessness and locomotor ataxia can be seen prior to paralysis/paresis. Caudal ataxia leading to paresis or paralysis can be seen as early as two to three days post infection. Commonly, death occurs three to four days after the onset of clinical signs, but recent suspected cases progressed quickly to death within 24 hours.
Abortion and SMEDI syndrome (stillbirth [S], mummified fetus [M], embryonic death [ED], infertility [I]) have been linked to the variety of reproductive disorders that can be caused by PTV serotypes. SMEDI syndrome is also seen with parvovirus infections, which more frequently cause reproductive disorders in conventional herds than PTV.
PSV is a non-enveloped, positive-sense single-stranded RNA virus belonging to the genus Sapelovirus in the family Picornaviridae. PSV is closely related to the genus Enterovirus and was previously classified as porcine enterovirus 8 (PEV-8). There are three species within the Sapelovirus genus: porcine, simian and avian. Pigs, monkeys and ducks are the only known hosts for each species.
Atypical porcine pestivirus
A study by Arruda et al., published in 2016, identified an APPV from piglets with congenital tremors. This virus was closely related to a novel pestivirus reported in serum samples from pigs involved in a PRRS metagenomics sequencing study. Phylogenetic analysis showed the greatest similarity to a newly described pestivirus in bats in China.
Just recently, an APPV was isolated from a pig with uncontrollable shaking coming from a herd in which approximately 700 affected pigs in the herd had died with no other diagnosed cause. Notably, this outbreak occurred in pigs 5 to 14 weeks-of-age, which is significantly older than piglets in which congenital tremors occur.
Help bridge the knowledge gap
Posted under the Emerging Diseases tab of the Swine Health Information Center’s website, www.swinehealth.org are fact sheets with more information about these viruses and information about SHIC financial support for additional diagnostic testing. The mission of the Swine Health Information Center is to protect and enhance the health of the U.S. swine herd through coordinated global disease monitoring, targeted research investments that minimize the impact of future disease threats, and analysis of swine health data. For more information, visit www.swinehealth.org or contact Paul Sundberg at firstname.lastname@example.org.