Senecavirus A outbreak affecting piglets and sows in Southern Brazil

Senecavirus A (SVA) is an emerging picornavirus that has been associated with outbreaks of vesicular disease and neonatal mortality in swine. Vesicular disease with unknown etiology and clinically indistinguishable of other vesicular infections have been reported in U.S, Canada and recently in Brazil. Here, we present an outbreak investigation conducted in swine herds showing an increased neonatal mortality and vesicular disease that have been associated to SVA.

Herds A and B are small farrow-to-finish (518 and 843 heads, respectively) research farms that belong to the Brazilian Agricultural Research Corporation (Embrapa Swine and Poultry) in Santa Catarina, Brazil. Herd A is located at 0.2Km from herd B. Both herds are vaccinated for PCV2, atrophic rhinitis, E. coli, PPV, leptospirosis, erysipelas and M. hyo. Brazil is free of PRRSV, and the farms are located in a Brazilian state free of CSF, PRV and FMD without vaccination. Clinical samples collected from herd A and B included nasal swabs, vesicular fluids and skin of coronary band. For herd B, three piglets were necropsied and tissues samples were collected for histopathology and for RT-PCR for SVA detection, targeting the VP1-VP3 region.

Clinical signs were first seen in Herd A on October 30th, 2015 and remained until November 8th. On Herd B, clinical signs started on November 3rd. On herd A, five gilts, 28 sows (25 in the gestation and three in the farrowing building) and two boars were affected. On herd B, two sows and piglets with 3 to 5 days-old were affected. Sows from both herds presented vesicles mainly on the snout. Gilts and boars showed lameness and ulcerative lesions on coronary bands. Fever was not observed. Piglets were lethargic and had a watery diarrhea. The mortality rate in piglets increased from 11 to 34%. At necropsy, the piglets’s stomach was empty. It was observed enlargement and edema of inguinal lymph nodes, ascites, severe edema of mesocolon and severe necrosis of coronary band. Microscopic lesions were characterized by necrotic epidermitis and dermatitis of coronary band, mild enteritis with villus degeneration on small intestine and marked mesocolon edema. Senecavirus A was detected by RT-PCR in vesicular fluids of sows, skin of coronary band of gilts; and in intestine, tonsils and coronary band of piglets.

The concomitant ocurrence of vesicles in adult pigs and watery diarrhea with increased mortality in piglets was associated with SVA. Affected adult pigs recovered completely in 10-15 days. As SVA is clinically and economically important due to its resemblance with vesicular diseases, the diagnosis tools are essential.

Disclosure of Interest: None Declared.