Pestivirus infections cause significant morbidity and mortality characterized by shaking and muscular spasms that set in within the early hours of a piglet’s life. Affecting all races of swine equally, the virus responsible for this infection is called “atypical porcine pestivirus (AAPV)”. Since 2015, AAPV infections have been reported in Europe, Asia and the USA. This infection only affects piglets and is not a public health risk to humans.
Since trembling and muscular spasms are associated with many different infections, additional diagnostic tests are needed to positively diagnose AAPV. Notably, autopsies allow veterinary pathologists to observe differences in luxol fast blue dye incorporation into the spinal cord tissue of healthy piglets and those infected with AAPV. As part of a collaboration between MAPAQ researchers Drs. Martin Choinière et Fanny Dessureault and CRIPA researchers Drs. Carl A. Gagnon and Chantale Provost, a molecular test was optimised that allows researchers to detect the virus in different sample types by PCR.
In 2017, the first AAPV infection in Canada was diagnosed on a pig farm with high sanitation levels. It should be noted that all infected piglets were born to gilts that had been recently incorporated into the herd and not in sows from the same group. All of the infected piglets were symptomatic with tremors and extreme muscle spasms; illness was associated with a 25% mortality rate. Three weeks after birth, the clinical symptoms had completely disappeared. The virus was found in the saliva, nasal secretions, semen, and feces, suggesting that APPV can be easily released into the environment. Several viral transmission routes are possible (fecal-oral, venereal), but the exact mode of transmission needs to be determined. More research is needed, but studies suggest that AAPV infections only occur when naïve sows are infected during pregnancy. Generally, piglets born from subsequent pregnancies are not affected, suggesting that the development of maternal immunity plays a key role in preventing subsequent infections.
Finally, since tremors at birth are also a symptom of classical swine fever virus (CSFV), a reportable disease in Canada, it is essential that veterinarians have the diagnostic tools to distinguish CSFV from AAPV.
Source : Can Vet J. 2018 Apr;59(4):429-432. First report of atypical porcine pestivirus in piglets with congenital tremor in Canada. Dessureault FG, Choinière M, Provost C, Gagnon CA.