Mass-exposure and tentative elimination of Senecavirus A in a Brazilian sow farm

Senecavirus A (SVA) is an emerging pathogen first reported recently in Brazil, causing vesicular disease in sows and finishing pigs. There is still lack of information regarding the pathogenicity and dynamics of infection. The objective of this abstract is to report the previous results of a tentative protocol of Senecavirus A elimination.

The tentative protocol was conducted in a sow farm, where vesicular lesions in nostrils and snouts predominantly, of sows (approximately 1-5% incidence), late nursery piglets (15%) and finishing pigs (2-3%) were observed. No other related clinical sign or production loss was observed. After 16 weeks of the onset of infection, a mass exposure was conducted with herd closure and spraying fresh oral fluids (OF) as an inoculum in the nostrils of every female. The OF samples were collected in pens with animals showing acute vesicular disease, and all sows and replacement gilts received at least two sprays, during weeks 1 and 2 of protocol. In week 0, no more offsite replacement gilts were brought into the sow farm, and between weeks 3 and 7 all piglets were weaned offsite, and so the herd was stable. During this period, a washing and disinfection process of the empty nursery facilities was conducted in three rounds, utilizing three different disinfectants, and finalizing with full drying, fumigation with formaldehyde, followed by the return of onsite weaning.

Until the date of submission of this abstract, the laboratory results of OF PCR and serology sampled during the protocol were not available yet. The clinical evaluation of the herd showed an increase in vesicular lesions in sow herd (~10%) after the first round of exposure, and on week 3 it returned to a baseline of 2-4% of prevalence. The first piglets being weaned in nursery started showing vesicular lesions in the nostrils and snouts on the second week (week 9), incidence of 10%.

The incidence of lesions in sows stabilized in 2-4% since the prime-infection and later after the mass exposure. Also, it was expected the absence of lesions in weaned piglets, due to the colostrum protection. The observation of vesicular lesions on the first weaned piglets onsite after the mass exposure of sows and herd closure may suggest that there was low success rate of the protocol. From the diagnostics and to the beginning of the exposure there was a 16 weeks period, when the dynamics of infection became endemic, and it probably interfered on the seroconversion of the whole sow herd, and consequently on the antibody transference to piglets. Further test results are necessary to learn more about the viral excretion of sows and piglets after the mass exposure and tentative elimination.

Disclosure of Interest: None Declared.