Senecavirus A in pigs: Epidemiology, Transmission, and Diagnosis

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Senecavirus A in pigs: Epidemiology, Transmission, and Diagnosis

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2022-11

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Abstract

Senecavirus A (SVA) has been linked to several swine vesicular disease outbreaks worldwide. Several countries have already reported the presence of the virus, and the risk of new cases is constant due to the movement of animals, people, and materials, among other potential SVA-carrying agents, between pig herds. Despite the disruptions and confusion that SVA can cause due to its clinical similarities to high-consequence foreign animal diseases, such as foot-and-mouth disease, little is known about its epidemiology and control. The main objective of this thesis was to provide new information on the epidemiology, transmission, and detection of this virus.Understanding the extent of SVA spread within a country and the risk factors associated with its exposure are the first steps toward building control strategies. Therefore, a study was designed to estimate the seroprevalence of the virus in the United States (U.S.). The seroprevalence of SVA in breeding and growing pig farms was relatively low, with 17.3% of breeding and 7.4% of growing pig farms being classified as positive. Among sow farms, the disposal of dead animal carcasses through rendering was associated with SVA seropositivity. The information about how SVA transmits between farms is scarce. Therefore, another study was conducted to evaluate the role of fomites in the indirect transmission of SVA between pig populations. Study personnel carrying fomites had direct contact with SVA-infected pigs and moved to different rooms housing SVA-naïve animals under low, medium, and high biosecurity standards. The virus was successfully transmitted to the rooms under low biosecurity standards, evidencing the role of fomites in the indirect transmission of SVA between pig populations. A third study focused on understanding the methods to detect the virus at different stages of infection, which is crucial for developing control and surveillance efforts. It is known that SVA-infected pigs shed the virus for approximately 21 to 28 days after infection. The study was designed to compare the results from oral swabs, rectal swabs, tonsil swabs, and tonsil scrapings in diagnosing SVA in experimentally-inoculated animals up to 48 days after infection. Tonsil scrapings were the only sample type where SVA was found at the late stages of the infection. At the same time, other sample types, such as rectal swabs, were easier to collect and had higher chances of SVA detection at earlier stages of infection. Developing an alternative aggregate sampling method would facilitate the detection of SVA at the population level. The fourth study in this chapter aimed to estimate the average number of SVA-positive weeks in processing fluids (PF) after an SVA outbreak. After longitudinally sampling 10 breeding farms, PF samples were estimated to remain positive on average for 11.8 weeks after an outbreak. Testing of PF may be a cost-effective method to detect SVA presence in breeding farms. In summary, this thesis has uncovered and provided novel information on the epidemiology of SVA and the knowledge gaps that remain. The information generated will serve as the foundation work for the development of further studies as well as monitoring, surveillance, and control strategies.

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University of Minnesota Ph.D. dissertation. November 2022. Major: Veterinary Medicine. Advisors: Fabio Vannucci, Cesar Corzo. 1 computer file (PDF); xi, 128 pages.

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Milanez Preis, Guilherme. (2022). Senecavirus A in pigs: Epidemiology, Transmission, and Diagnosis. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/257097.

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