Effect of Booster Vaccination with Inactivated Porcine Epidemic Diarrhea Virus on Neutralizing Antibody Response in Mammary Secretions.

Porcine epidemic diarrhea virus (PEDV) causes acute diarrhea, dehydration in pigs, and high mortality rates in piglets <3 weeks of age. Maternal immunity protects piglets, but information on vaccination before or after natural infection in endemically exposed sow herds is limited. Currently, the recovery goal in sow units infected with PEDV is to become fully naive again or use natural virus infection to develop immune gilts through a feedback program before introduction into the sow herd. Since neutralizing antibodies in the gut are critical for protection against enteric viral infections such as PEDV, we evaluated the effect of a conditionally licensed, adjuvanted inactivated PEDV vaccine on neutralizing antibody levels in milk and colostrum in both naive and previously naturally exposed sow herds. The results illustrate that intramuscular vaccination increased neutralizing antibody titers, and anti-PEDV IgA and IgG in milk and colostrum of sows that were previously infected. Thus, inactivated PEDV vaccines may provide increased protection to piglets nursing on previously infected sows against exposure to PEDV through increased delivery of lactogenic neutralizing antibodies to the enteric site of infection.

A prolonged outbreak of polioencephalomyelitis due to infection with a group I porcine enterovirus.

A commercial swineherd in Indiana experienced high death loss of nursery pigs with neurologic disorders for a prolonged period. Polioencephalomyelitis was the consistent histopathological lesion in affected animals. A porcine enterovirus (PEV) classified to group I was isolated from spinal cords and brains collected from the affected animals. The isolate (ISUVDL 200103183) was determined to belong to either serogroup 5 or 6 at the National Veterinary Services Laboratories, Ames, IA. No other significant viral or bacterial agents were isolated from or detected in the animals. A prospective longitudinal serological monitoring of pigs in the index herd for the PEV isolate revealed that colostrum-derived neutralizing antibodies to the virus rapidly declined, and by the age of 21 days the majority of piglets had no or minimal neutralizing antibody against the virus. Seroconversion to the virus then coincided with increased mortality in the herd. Results of diagnostic and cohort observations supported a diagnosis of PEV infection as the cause of the prolonged outbreak of "polio." Investigation into factors that may be contributing to the prolonged problem is currently in progress.