Clinical experiences with neonatal mortality and vesicular disease associated with Senecavirus A in Brazil and USA pig farms

Vesicular disease (VD) was reproduced with Senecavirus A (SVA) in 9 and 25 week old pigs, confirming that SVA causes VD in pigs (ISU and USDA, 2015). Between Sept 2014 and Dec 2015 a large incidence of VD associated with SVA was reported in Brazil. Likewise, between July-Dec 2015 the incidence of SVA in the USA pig industry increased significantly. Moreover, authors of this study reported the epidemic transient neonatal losses (ETNL) syndrome affecting piglets in Brazil and USA. In most cases, ETNL was associated with minor/mild VD. The objective of this case report was to describe clinical presentation and diagnostic investigation of cases of ETNL and VD associated with SVA infection in Brazil and USA herds.

We followed 4 SVA outbreaks: Farm A (8000 breed to finish), Farm B (4000 breed to wean) and Farms C and D (growing pigs). Clinical features and differential diagnosis associated with ETNL and VD in enrolled farms were described.

Farms A and B. Sudden increase in mortality rate on piglets of 0-4 days of age was reported. Farm A mortality was 72% in that age group and returned to baseline after 7 days. Farm B mortality was 38% and returned to baseline 5 days. In both cases there were affected and non affected litters. Within affected litters, close to 100% pigs were affected. Necropsy of 40 affected pigs per farm evaluated gross and histopathology lesions. No significant lesions were noticed. About 85% of piglets had stomach full of milk, indicating that starvation did not cause death. On farm A, 20% of sows developed minor VD in the foot (coronary bands, foot pad and/or interdigital area) and 2% of sows had snout vesicles - all VD healed within 2 weeks. Farm A finishing pigs developed lameness followed by VD in 30% of pigs, starting 1 week after ETNL onset and recovering in 2 weeks. No VD was observed in farm B. Lameness was reported in farms C and D. Farm C had a high incidence (80%) of pigs with lameness followed by VD lesions in foot and/or snouts within 10 days. Lesions had mild severity and recovered within 14 days. No VD was observed after the first wave. On Farm D, 20% pigs developed VD in week 1, and about 3-5% incidence per week in the next 12 weeks were reported.

A comprehensive diagnostic investigation was performed and included infectious and non-infectious etiologies. Presence of other viruses causing vesicular disease including FMDv was ruled out. SVA infection was initially associated with the disease through the identification of viral RNA by PCR. In addition, SVA was identified within the tissues by in situ hybridization.

SVA caused lameness and VD in pigs and was associated with ETNL.

Disclosure of Interest: None Declared.