Longitudinal study of atypical porcine pestivirus infection dynamics in pigs from birth to market reveals persistent infection in piglets with congenital tremors

Authors: Buckley, Alexandra; MORA-DIAZ, JUAN-CARLOS - Iowa State University; VAN HULZEN, AMBERLY - Iowa State University; MATIAS FERREYRA, FRANCO - Kansas State University; FALKENBERG, SHOLLIE - Auburn University; GIMENEZ-LIROLA, LUIS - Iowa State University; Arruda, Bailey

Submitted to: American Association of Swine Veterinarians Annual Meeting
Publication Type: Proceedings
Publication Acceptance Date: 1/13/2023
Publication Date: 3/5/2023
Citation: Devries, A.C., Mora-Diaz, J., Van Hulzen, A., Matias Ferreyra, F., Falkenberg, S., Gimenez-Lirola, L., Arruda, B.L. 2023. Longitudinal study of atypical porcine pestivirus infection dynamics in pigs from birth to market reveals persistent infection in piglets with congenital tremors. American Association of Swine Veterinarians Annual Meeting. AASV 2023 Proceedings, March 4-7, 2023, Aurora, Colorado.

Interpretive Summary:

Technical Abstract: Introduction Atypical porcine pestivirus (APPV) has been found to be associated with piglets demonstrating congenital tremors (CT) and clinical presentation of CT in piglets was reproduced after experimental challenge. The virus has been identified in swine of all ages globally; although, little is known about the pathogenesis and epidemiology of APPV. The objective of this research was to perform a longitudinal study following two cohorts of pigs, those born in litters with piglets exhibiting CT and those born in litters without CT, to analyze the dynamics of APPV infection from birth to market. Materials and Methods A commercial sow farm experiencing an outbreak of CT in piglets was identified. Five litters with at least one piglet exhibiting CT were selected for the study in addition to three cohort litters not demonstrating CT based on parity of sow and date of farrowing. At weaning previously enrolled piglets were co-mingled upon placement at a wean-to-finish barn. Once a month, animals were bled and observed for clinical signs of CT. When pigs were market ready, four pigs from CT positive litters and four pigs from CT negative litters were necropsied for tissue collection to evaluate viral distribution. Monthly serum samples were tested for APPV RNA by PCR and the antibody response determined by ELISA. Tissue samples were tested for APPV RNA by PCR and localization was determined by in situ hybridization. Results There was a wide range in the percentage of affected piglets (8-75%) within CT positive litters. APPV nucleic acid was detected in serum of both affected (100%) and unaffected (31%) piglets from CT positive litters, while only a single pig was PCR positive from a negative CT litter at the first sampling timepoint. After comingling at weaning, most piglets from CT negative litters tested PCR positive for APPV in the serum. Overall, a greater percentage of pigs exhibiting CT remained PCR positive throughout the growing phase compared to unaffected piglets from CT litters and those in CT negative litters. Piglets from CT negative litters had the shortest duration of viremia. In addition, CT negative litters had had evidence of maternal immunity; however, some piglets from CT positive litters did as well. The majority of unaffected piglets from CT litters and piglets from CT negative litters were positive for antibody by ELISA during sampling, while very few CT positive piglets had a detectable antibody response after maternal immunity waned. APPV nucleic acid was present in multiple tissues from pigs in CT positive and CT negative litters especially the cerebellum, tonsil, and mandibular salivary gland. Conclusion This study has shed light on infection dynamics of APPV in swine and the impact immune status and timing of infection have on the persistence of APPV in serum and tissues, which can aide control measures for the industry.