Senecavirus A: First clinical case in an Ontario commercial swine herd

Josepha DeLay, Ryan Tenbergen, Margaret Stalker, Tim Blackwell, Davor Ojkic, Jim Fairles

Animal Health Laboratory, University of Guelph, ON (DeLay, Stalker, Ojkic); Demeter Veterinary Services, St. Nicolas, ON (Tenbergen); Ontario Ministry of Agriculture, Food, and Rural Affairs, Elora, ON (Blackwell)

AHL Newsletter 2019;23(4):9-10.

In June 2019, Senecavirus A (SVA) was detected in a farrow-to-finish, multi-site Ontario herd. Initially, 40% of lactating sows were acutely anorexic and pyrexic, and 10% of affected sows developed vesicles and ulcers on snouts and at coronary bands (Fig. 1A and 1B). Concurrently, diarrhea was identified in 50% of neonatal litters <7days of age, with high mortality (70%) among affected piglets.  The Canadian Food Inspection Agency (CFIA) was immediately notified when vesicles were observed, and a full investigation excluded foreign animal diseases, including: foot and mouth disease, swine vesicular disease, and vesicular stomatitis.  SVA was confirmed by PCR as the cause of vesicular lesions. 

Biofeedback was initiated to control the outbreak.  Clinical disease continued in the sow herd and among nursing piglets but gradually resolved, with increases in preweaning mortality, sow mortality and stillborn and mummified fetuses over the next 3-4 weeks.  Progression and monitoring of herd infection were accomplished by SVA PCR on oral fluids, carried out at the Animal Health Laboratory. Among piglets infected during the initial outbreak, PCR-based evidence of infection persisted for variable time periods and through all stages of production, although vesicular lesions were identified only in nursing and gestating sows and in gilts in the developer unit, and diarrhea was seen only in neonates.  Surviving nursing and nursery pigs were unthrifty, with uneven growth.  In a sample of piglets euthanized at weaning, postmortem examination identified lymphoplasmacytic inflammation in multiple organs including kidney, heart, liver, and brain.

Figures 1A and 1B. Snout (A) and coronary band (B) ulceration in Senecavirus A-infected sows.

Pathology investigation is ongoing into the association of widespread inflammatory lesions in nursery pigs with SVA. Animal and environmental monitoring continues for SVA elimination in the herd. Further investigation is in progress to determine the source of SVA infection in this outbreak. Although SVA has been detected at assembly yards in Ontario since 2016 and lesions have been observed in cull sows at these sites, this is the first case of SVA-associated disease in a commercial swine herd in Ontario.

References

1. Canning P et al. Neonatal mortality, vesicular lesions, and lameness associated with Senecavirus A in a U.S. sow farm. Transboundary and Emerg Dis 2016;63: 373-378.

2. Leme RA et al. Pathological, immunohistochemical, and molecular findings associated with Senecavirus  A-induced lesions in neonatal pigs.  J Comp Path 2016;155: 145-155.

3. Segalés J et al. Senecavirus A: An emerging pathogen causing vesicular disease and mortality in pigs? Vet Pathol 2017;54(1): 11-21.