Evaluation and application of neutralizing antibodies for porcine epidemic diarrhea virus

Abstract

Porcine epidemic diarrhea virus (PEDV) continues to plague pork producers and veterinarians. PEDV can result in high mortality of neonatal pigs and clinical disease in older swine leading to decreased production. The objectives of this research were to describe the shedding patterns of PEDV following infection and vaccination, evaluate the use of diagnostic assays for the detection of PEDV neutralizing antibodies, describe the antibody status of a herd following a PEDV outbreak, and to evaluate and compare neutralizing antibody levels in serum and milk samples from affected herds. Shedding patterns were evaluated in Chapter 2, and it was found that even in the face of prior infection or vaccination, female pigs will shed PEDV after exposure. However, previously exposed gilts shed virus for a shorter duration compared to vaccinated gilts. Two diagnostic assays, fluorescent focus neutralization (FFN) and high throughput neutralization test (HTNT), for the detection of PEDV neutralizing antibodies were evaluated in Chapter 3. It was demonstrated that the assays, HTNT and FFN, agree and demonstrate that the HTNT could be used to objectively measure neutralizing antibody in gilt serum samples. This study also showed that vaccination does elicit a neutralizing antibody response that can be measured in serum. The use of the HTNT was demonstrated in Chapter 4 by evaluating two farms following outbreaks of PEDV. Neutralizing antibody levels in sow serum samples decayed over time on both farms as expected. Sow serum, piglet serum, and milk samples were compared to evaluate correlations between the sample neutralizing antibody levels as determined by the HTNT. Correlations were observed; however, we are unable to predict piglet or milk neutralizing antibody levels based off the magnitude of PEDV neutralizing antibodies in sow serum alone. Altogether, this research shows that producers and practitioners can monitor neutralizing antibody levels in serum to monitor PEDV intervention strategies such as vaccination or natural planned exposure. However, more research is needed to determine what level of systemic neutralizing antibody levels would correlate with protection from clinical disease.