Virological and Histopathological Findings in Boars Naturally Infected With Porcine Reproductive and Respiratory Syndrome Virus Type 1

Kasper Pedersen; Sophie Amalie Blirup-Plum; Charlotte Sonne Kristensen; Lise Kirstine Kvisgaard; Lotte Skade; Henrik Elvang Jensen; Lars Erik Larsen

doi:10.3389/fmicb.2022.874498

Virological and Histopathological Findings in Boars Naturally Infected With Porcine Reproductive and Respiratory Syndrome Virus Type 1

Front Microbiol. 2022 May 11:13:874498. doi: 10.3389/fmicb.2022.874498. eCollection 2022.

Authors

Kasper Pedersen^{1

2}, Sophie Amalie Blirup-Plum², Charlotte Sonne Kristensen¹, Lise Kirstine Kvisgaard², Lotte Skade¹, Henrik Elvang Jensen², Lars Erik Larsen²

Affiliations

¹ SEGES Danish Pig Research Centre, Aarhus, Denmark.
² Department of Veterinary and Animal Sciences, University of Copenhagen, Frederiksberg, Denmark.

Abstract

Major geographical transmission of porcine reproductive and respiratory syndrome virus (PRRSV) occurs via semen when a boar stud is infected. This happened in Denmark in 2019, providing an opportunity to compare previous experimental PRRSV boar studies with natural PRRSV-1 infection in boars. The aim of this study was to investigate the association between the presence of PRRSV RNA in serum, semen, testicles, and epididymis of boars naturally infected with PRRSV and to describe the histological lesions in the testes and epididymis combined with direct visualisation of PRRSV-infected cells by immunohistochemical staining (IHC). The exact timing of infection of each boar was not determined, but based on serology the boars were divided into two groups: acute and late infections. All boars included were sampled the same day. In this study, 35 boars and 10 healthy boars from another PRRSV-negative boar stud were included as histological controls. PRRSV RNA was found most often in serum (51%) and least frequently in semen (22%) and was more often detected in the reproductive tract in the acute phase of infection (p < 0.0001; RR: 2.58). Mononuclear cells and multinuclear giant cells were present in the adluminal compartment of the testis and epididymis in PRRSV-infected boars, but not in control boars (p < 0.05), which supports the hypothesis that macrophages are involved in the venereal spread of the virus.

Keywords: RT-PCR; boar; immunohistochemistry; natural infection; porcine reproductive and respiratory syndrome virus.