Global Epidemiology of African Swine Fever
ASF was first reported from East Africa in 1921 and is still present in the region (Figure 3) (Lubisi et al., 2005). It was also identified in the southern, central, and West Africa during early 1900s and has been endemic in the African continent by circulating in one of the three different transmission cycles (Lubisi et al., 2005). Portugal had the outbreak of ASF in 1957, the first time outside of Africa (Sanchez-Vizcaıno et al., 2015) and also in 1959 which was believed to be imported from Angola where it was established in the Iberian Peninsula and was only eradicated in 1994 (Mary Louise Penrith, 2009). Several other outbreaks resulted in Western Europe in the 1970s and 1980s, Sardinia in 1987 where ASF persists, Cuba, Hispaniola (Haiti and the Dominican Republic) and Brazil in a similar time frame from where it has been eradicated (Sanchez-Vizcaıno et al., 2015).
The outbreak of ASF in countries of South and North America mainly occurred in 1980s. Since then, ASF outbreak has not been reported in American countries. However, there is still threat of ASF outbreak in both north and south America. Till now, only Australian country, Papua New Guinea, has reported first outbreak of ASF in 2020 (Mary Louise Penrith, 2020; World Organisation for animal health (OIE)
, 2020b).
A resurgence in western Africa occurred in 1994 infecting various nations that were previously unaffected along with the first outbreak in Kenya in 30 years, an outbreak in ASF free region in Mozambique, and first outbreak in Madagascar in 1997 (Mary Louise Penrith, 2009). Countries like Spain, France, Madeira, Italy, and Cuba were infected from 1960 to 1971, Haiti reported the infection in 1979 and reappearance was seen in Cuba in 1980 (Wardley et al., 1983). The spread of the ASF virus can be attributed to three major factors which were: 1) increment in the pig population and production; 2) reservoir non-symptomatic pig population; and 3) globalization (Sanchez-Vizcaıno et al., 2015). Since 2007 ASF is seen in the Caucasian region with the outbreak in Georgia with spread to Armenia, Azerbaijan, and the Russian Federation, Ukraine, and northwest Russia near the Baltic Sea and Barents Sea (Table 1) (Sánchez‐Vizcaíno et al., 2019). Subsequently, various outbreaks occurred in different European, Asian, and Pacific nations on different years (OIE, 2020b; M. L. Penrith & Vosloo, 2009) (Table 1) (Figure 3). Nepal has not yet reported the case of ASF. But the recent outbreaks in the neighboring countries make it susceptible to the outbreaks in near future mainly due to the open borders with India which could lead into the transfer of infected products and animals into the nation. The first case was detected in India in January with a total of 11 confirmed outbreaks, 9 in Assam and 2 in Arunachal Pradesh, with 10,920 susceptible animals and 4,199 cases (OIE, 2020a). The total death has been reported to be 3,701 with 14,000 pigs culled in Assam alone (OIE, 2020a). To date China reported 165 outbreaks of ASF since the conformation of the first outbreak in Liaoning Province on 3 August 2018 with 1,193,000 pigs being culled (FAO, 2020).
The current ASF epidemiological situation shows that Europe holds maximum outbreak of ASF (66.87%), Asia (32.72%) and Africa (0.41%) respectively (Table 2) (OIE, 2020b). Asian pig industry is highly affected by ASF with more than 80% losses compared to that in Europe (16.86%) and Africa (1.04%). Asian and African countries mainly report cases of domestic pigs while the European countries also reported a larger number of the cases of wild boar (Table 2). The increasing trend in spread of ASF brought a serious threat to animal health, pig production, and swine population globally and therefore, affect economies and trade. ASFV remains endemic in many sub‐Saharan countries on the African continent.