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The objectives of this study were to develop a multiplex real-time PCR assay for porcine astrovirus (PoAstV) genotypes 4 and 5 and to determine the prevalence of Torque teno sus virus (TTSuV1 and TTSuV2), PoAstV4 and PoAstV5 in cases of diarrhea in pigs collected in the United States.
Eighty-eight fecal samples were collected during 2011 from routine submissions to the Veterinary Diagnostic Laboratory at Iowa State University. All samples originated from different farms. All samples were from pigs of varying ages with a history of diarrhea. There were 13 samples from suckling pigs, 39 samples from nursery pigs, 16 samples from grow-finish pigs, and the age of pigs for 19 samples was not available. A novel multiplex real-time PCR was developed capable of detecting and differentiating between the five PoAstV groups.
The highest prevalence was found for PoAstV4 (53.4% of the samples positive), followed by TTSuV2 (48.9% positive), TTSuV1 (31.8% positive), and PoAstV5 (4.5% positive). Concurrent PoAstV4 and TSuV1 infection was identified in 81.2% (13/16) of the samples obtained from growfinisher pigs, in 23.1% (9/23) of the samples obtained from nursery pigs, and in 7.7% (1/13) of the samples from suckling pigs.
The results of this study indicate that both TTSuV1 and PoAstV4 have a high prevalence in fecal samples from pigs with clinical diarrhea in the United States. Based on the limited samples size, both agents were more prevalent in grow-finish pigs compared to suckling or nursery pigs. The clinical relevance of this finding is unknown. Both agents could be causally associated with the observed enteric disease or may be transmitted by the enteric route and the finding of these agents in feces is incidental. Future work should include testing more field samples from affected and unaffected pigs and studies to experimentally inoculate naïve pigs need to be done.
Prevalence of porcine astrovirus and Torque teno sus virus in fecal samples from pigs with diarrhea collected in the United States. T Opriessnig, CT Xiao, PG Halbur. IIPVS, 2012.
