Polioencephalomyelitis in Domestic Swine Associated With Porcine Astrovirus Type 3

Abstract

In the past decade, different members of the genus Mamastrovirus have been associated with outbreaks of neurologic disease in humans, cattle, sheep, mink, and, most recently, porcine astrovirus 3 (PoAstV3) in swine. We performed a retrospective analysis of 50 cases of porcine neurologic disease of undetermined cause but with microscopic lesions compatible with a viral encephalomyelitis to better understand the role and pathogenesis of PoAstV3 infection. Nucleic acid was extracted from formalin-fixed paraffin-embedded (FFPE) tissue for reverse transcription quantitative polymerase chain reaction (RT-qPCR) testing for PoAstV3. In addition, 3 cases with confirmed PoAstV3-associated disease were assayed by RT-qPCR to investigate PoAstV3 tissue distribution. PoAstV3 was detected in central nervous system (CNS) tissue via RT-qPCR and in situ hybridization in 13 of 50 (26%) FFPE cases assayed. PoAstV3 was rarely detected in any tissues outside the CNS. Positive cases from the retrospective study included pigs in various production categories beginning in 2010, the earliest year samples were available. Based on these results, PoAstV3 appears to be a recurring putative cause of viral encephalomyelitis in swine that is rarely detected outside of the CNS at the time of clinical neurologic disease, unlike other common viral causes of neurologic disease in swine.

Postweaning mortality in commercial swine production II: review of infectious contributing factors

“…In recent years, an increase in the incidence of neurological syndromes has been observed and, in many cases, associated with diagnosis of viral infectious agents. This is still an area of ongoing research efforts, but multiple viruses recently have been associated with neurological syndromes, including porcine sapelovirus ( Schock et al, 2014 ; Arruda et al, 2017b ), porcine astrovirus type 3 ( Boros et al, 2017 ; Rawal et al, 2019 ; Matias Ferreyra et al, 2020 ), and porcine teschovirus ( Bangari et al, 2010 ; Deng et al, 2012 ; Carnero et al, 2018 ). The recently described atypical porcine pestivirus has been associated with congenital tremors ( de Groof et al, 2016 ; Postel et al, 2016 ; Schwarz et al, 2017 ) but is not believed to be a major contributor to postweaning mortality ( Gatto et al, 2019 ).…”

Ecology of Porcine Astrovirus Type 3 in a Herd with Associated Neurologic Disease

“…PoAstV3 was not detected in any tissue outside the CNS although numerous sample types were assayed. The inconsistent detection of PoAstV3 in tissues, especially enteric tissues, outside the CNS at the time of neurologic disease [18][19][20] could suggest prolonged transport of PoAstV3 from the peripheral nervous system to the CNS. In humans with neurologic astrovirus disease, astrovirus has been reported to be inconsistently detected in feces and infrequently in serum/plasma and cerebrospinal fluid samples [12,[28][29][30][31][32].…”

“…Twenty-two controls were sampled from Barn-1 (Room-3; Pen-1, 3, 5, 7, 10). Additionally, four neurologic pigs (two from each barn) were selected for a diagnostic investigation that included gross and histologic evaluation and PoAstV3, Teschovirus A and Sapelovirus A RT-qPCR, as described previously [18].…”

“…The advent of next-generation sequencing (NGS) methods has provided additional insight into astroviruses and their role in disease. As technology progresses, the spectrum of astrovirus genotype species has increased significantly with concurrent growing evidence that MAstVs are involved in neurologic disease in several mammals including humans, cattle, mink, sheep, and more recently pigs [11][12][13][14][15][16][17][18][19][20]. The pathogenic significance of PoAstVs is not well characterized with the exception of PoAstV3 (MAstV22), which has been recently associated with outbreaks of polioencephalomyelitis in swine in the United States [17][18][19] and Hungary [20].…”

“…Due to the increasing evidence that PoAstV3 is a cause of encephalomyelitis in swine [17][18][19] and to better understand the ecology of PoAstV3, four studies were conducted in a growing phase swine production system with an extensive history of neurologic disease due to PoAstV3. These studies included a case-control study, pilot study, clean room study, and a prospective longitudinal investigation.…”