Key result
Jeju LOM strains induced abortion and stillbirth in pregnant sows, resulting in the same adverse effects and viral characteristics as the MLV-LOM strain.
Why the study?
Following reports of reproductive failure and piglet mortality in a non-vaccinated region, the authors investigated whether circulating classical swine fever viruses isolated in Jeju Island had recovered pathogenicity.
Jeju LOM strains of classical swine fever virus retain pathogenicity similar to the MLV-LOM vaccine, causing reproductive failure in pregnant sows.
Raises safety concerns for LOM strains in breeding sows; leaves open need for targeted attenuation and field safety studies.
In Jeju island of South Korea, a classical swine fever (CSF) non-vaccinated region, many pig farmers insisted on abortion and stillbirth in pregnant sows and high mortality of suckling/weaning piglets by circulating CSF virus from 2014 to 2018. We investigated whether CSF viruses isolated from pigs in Jeju Island (Jeju LOM) have recovered their pathogenicity by conducting experiments using pregnant sows and specific pathogen-free (SPF) pigs. The CSF modified live LOM vaccine (MLV-LOM) and Jeju LOM strains induced abortion and stillbirth in pregnant sows. Viral antigens were detected in the organs of fetuses and stillborn piglets in the absence of specific pathological lesions associated with the virulent CSF virus in both groups (MLV-LOM and Jeju LOM strain). However, antigen was detected in one newborn piglet from a sow inoculated with a Jeju LOM strain, suggesting that it may cause persistent infections in pigs. SPF pigs inoculated with the MLV-LOM or Jeju LOM strains were asymptomatic, but virus antigen was detected in several organ and blood samples. Virus shedding in both groups of animals was not detected in the feces or saliva until 21 days post inoculation. The serum concentration of the three major cytokines, IFN-α, TNF-α, and IL-10, known to be related to lymphocytopenia, were similar in both groups when the MLV-LOM or Jeju LOM strains were inoculated into SPF pigs. In conclusion, Jeju LOM strains exhibited most of the characteristics of the MLV-LOM in pigs and resulted in the same adverse effects as the MLV-LOM strain.
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Choe et al. (2019) studied Classical swine fever. Jeju LOM strains vs. CSF modified live LOM vaccine (MLV-LOM) was evaluated on Pathogenicity including abortion, stillbirth, and viral antigen detection. Jeju LOM strains induced abortion and stillbirth in pregnant sows, resulting in the same adverse effects and viral characteristics as the MLV-LOM strain.
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