Detection and localization of atypical porcine pestivirus in the testicles of naturally infected, congenital tremor affected piglets

Abstract

Atypical porcine pestivirus (APPV) belongs to the genus Pestivirus within the family Flaviviridae. Recently, APPV has been identified as the causative agent of congenital tremor (CT) type AII. The disease is a neurological disorder that affects newborn piglets and is characterized by generalized trembling of the animals and often splay legs. CT is well known worldwide, and the virus seems to be highly prevalent in major swine producing areas. However, little is known about the epidemiology of the infection, transmission and spread of the virus between herds. Here, we show the high prevalence of APPV in processing fluid samples collected from Hungarian pig herds which led us to investigate the cellular targets of the virus in the testicles of newborn piglets affected by CT. By the development of an RNA in situ hybridization assay and the use of immunohistochemistry on consecutive slides, we identified the target cells of APPV in the testicle: interstitial Leydig cells, peritubular myoid cells and smooth muscle cells of medium‐sized arteries. Previous studies have shown that APPV can be found in the semen of sexually mature boars suggesting the role of infected boars and their semen in the transmission of the virus similar to many other members of the Flaviviridae family. As in our case, the virus has not been identified in cells beyond the Sertoli cell barrier, further studies on infected adult boars’ testicles and other reproductive glands are needed to analyze the possible changes in the cell tropism of APPV that might contribute to its prolonged extraction by the semen beyond the period of viraemia.

Congenital tremor and splay leg in Swedish piglets : a study of the viral causes and routes of transmission

“…The viral distribution was similar in 2-day-old piglets with signs of CT type A-II and in clinically recovered boars (Buckley et al 2021). The other study investigated the testes of new-born piglets with signs of CT type A-II (Dénes et al 2021). This study detected APPV within the walls of medium-sized arteries, the testicular interstitium, and fusiform cells around the primitive, non-functional seminiferous tubules (Dénes et al 2021).…”

“…Thus, the results from these two studies are not congruent. In the study by Buckley et al (2021), APPV was detected beyond the Sertoli cell barrier (blood-testis barrier), whereas Dénes et al (2021) reported that no virus was detected in cells beyond the blood-testis barrier of the new-born piglets.…”

“…The other study investigated the testes of new-born piglets with signs of CT type A-II (Dénes et al 2021). This study detected APPV within the walls of medium-sized arteries, the testicular interstitium, and fusiform cells around the primitive, non-functional seminiferous tubules (Dénes et al 2021). However, no viral RNA was found in the lumen of the seminiferous tubules.…”

High Prevalence of Porcine Circovirus 3 in Hungarian Pig Herds: Results of a Systematic Sampling Protocol

“…Using processing fluids to monitor the presence of different infectious agents has a lot of well-known advantages and it has been used for the detection of various porcine pathogens, including PRRSV [42], APPV [43] or Mycoplasma hyopneumoniae [44]. A retrospective study from the USA commonly detected PCV3 in clinical cases of PDNS and PMWS and tissue samples from aborted fetuses.…”

Prevalence Estimation and Genetic Characterization of Porcine Parainfluenza Virus 1 (PPIV-1) in Hungary and the First Report of the Virus in Slovakia

“…The participation in the sampling campaign was voluntary of all farms regardless of their health status, and no significant clinical disease was reported in the herds during the sampling period. On most farms, according to the protocol, 100 blood samples were drawn from animals of different age groups, 5 pen-based oral fluid samples were collected from weaned pigs (8-12 weeks of age; WOA), and 5 samples from fatteners (18-20 WOA) [14]. More details of the sampling protocol can be found in the study of Igriczi et al [15].…”