Abstract
Senecavirus A (SVA) is an emerging picornavirus that has been associated with outbreaks of vesicular disease in swine. In 2015, neonatal mortality affecting piglets of 07 days of age correlated with SVA, was reported in Brazil. Here, we present an investigation carried on during 20152016 in five farrowtofinish swine operations in Southern Brazil showing an increased neonatal mortality and also vesicular disease that have been associated to SVA infection. Piglets were lethargic and had a watery diarrhea. The mortality rate increased in 23% and in some littermates a 100% of mortality was observed. Despite of a relatively fast onset of wasting syndrome progressing to mortality, all herds recovered to baseline mortality levels within 410 days. Piglets were necropsied and tissue samples were collected for histopathology, RTPCR for SVA detection targeting the VP1 VP3 region, and for viral isolation in H1299 cell culture. Genome sequences of VP1 gene of five SVA isolates were compared to other SVA sequences available on GenBank. Necropsy of six piglets revealed empty stomach and mesocolonic edema. In general, it was observed enlargement and edema of inguinal lymph nodes, pulmonary edema, ascites and ulcerative lesions on the snout and coronary band. Microscopic lesions were characterized by necrotic epidermitis and dermatitis of coronary band, mild enteritis with villus degeneration on small intestine, marked mesocolon edema and multifocal hemorrhage with lung edema. Senecavirus A was detected by RTPCR in tonsil, lung, liver, intestine and coronary band. SVA was isolated in cell culture from tonsil, lung, intestine and coronary band from piglets of all farms. Sequence comparisons based on a region of the VP1 gene (541 base pairs) revealed that the Brazilian isolates characterized here share 96- 99% of nucleotide (nt) identity with contemporary Brazilian isolates, 9598% nt identity with US and 9093% nt identity with the prototype strain SVV001. SVA was associated with neonatal mortality based on RTPCR, virus isolation and sequencing results. The genetic analysis shows the diversity of the Brazilian SVA isolates and that more studies are needed to demonstrate if there are differences between SVA from neonatal mortality and vesicular cases. SVA is clinically and economically important due to its resemblance with vesicular diseases, so the diagnosis tools are critical to confirm the initial investigation.