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Detailed Explanation of the Pathogen and Epidemiological Characteristics of Swine Vesicular Disease

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This disease is an acute infectious disease caused by the swine vesicular disease virus. Usually, only pigs can be naturally infected by this disease, while other animals such as cattle and sheep are not easily infected, so it can be distinguished from foot-and-mouth disease. The disease is characterized by vesicles on the skin of hairless parts of the pig's body and on the oral mucosa. Vesicles and erosions also occur on the skin of the coronary band, interdigital space, and heel, and around the teats of sows. This disease is widely distributed and spreads rapidly. It was first discovered in Italy in 1966. By the 1970s, after successively becoming epidemic in the United States, Austria, Hungary, and other Eastern and Western European countries, it also occurred in Japan

This disease is an acute infectious disease caused by the swine vesicular disease virus. Usually, only pigs can be naturally infected by this disease, while other animals such as cattle and sheep are not easily infected, so it can be distinguished from foot-and-mouth disease. The disease is characterized by vesicles on the skin of hairless parts of the pig's body and on the oral mucosa. Vesicles and erosions also occur on the skin of the coronary band, interdigital space, and heel, and around the teats of sows. This disease is widely distributed and spreads rapidly. It was first discovered in Italy in 1966. By the 1970s, after successively becoming epidemic in the United States, Austria, Hungary, and other Eastern and Western European countries, it also became epidemic in Japan, and this disease also occurred in Hong Kong, China.

1. Pathogen The pathogen is the swine vesicular disease virus of the genus Enterovirus, which has an antigenic relationship with the human enterovirus Coxsackie B. The virion is cubically symmetric, roughly spherical, and non-enveloped. The virus has a certain resistance to heat. At 50°C for 30 minutes, it still has infectivity; 56°C for 30 minutes or 85°C for 1 minute can inactivate the virus. When diseased pigs are scalded and soaked in water at 65°C-67°C for 3-5 minutes, the vesicle skin still has infectivity. The virus can survive for a long time in feces and cured meat, and also has strong resistance to alkalis and disinfectants. In 3% caustic soda at 33°C it can survive 24 hours, or in 2% formalin at 13°C-18°C for 24 hours; 5% formalin requires 1.5 hours to inactivate it. A bleaching powder solution containing 0.5% available chlorine requires 20 minutes at 10°C-25°C to inactivate it. 70% alcohol, 4% cresol soap, and 10% quicklime and slaked lime milk can all inactivate it.

2. Epidemiology This disease can infect pigs of different breeds and ages. In natural epidemics, only pigs develop the disease, while cloven-hoofed animals such as cattle and sheep are not infected. There is no obvious seasonality in its occurrence. It is prone to occur in pig farms with high concentration and high stocking density, and in places with wet and dirty ground. Under generally scattered feeding conditions, it rarely causes infection and disease. Humans have a certain susceptibility. However, vesicles do not necessarily form. The symptoms of the disease are similar to those caused by the human enteric Coxsackie virus group. This disease is mainly transmitted through the digestive tract, respiratory tract, and wounds of the skin and mucous membranes. The affected parts of pig heads and hooves contain a very high amount of virus and are highly infectious. Pigs in the same group after the onset of disease and their products are the main sources of infection. The feces and urine of diseased pigs, as well as transport vehicles, feed, and water contaminated by the virus, are all transmission vectors. This disease can occur in all four seasons. The general incidence rate can reach 70%-80%, while the mortality rate is very low.

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