Detection of African Swine Fever Virus Genotype II in West Africa (2020) and Its Co-Circulation With Endemic Genotype I: Implications for Pig Production

Abstract

African swine fever (ASF) is a highly devastating disease of domestic pigs caused by the ASF virus (ASFV). Historically, only ASFV Genotype I was known to circulate in West Africa. However, Genotype II has recently emerged in Nigeria, Ghana, and Benin for the first time. Between 2017 and 2023, suspected ASF outbreaks were reported in Burkina Faso, Côte d’Ivoire, Nigeria, and Mali. The source, extent, and spread of these ASF outbreaks remain unknown. Samples collected from 2017 to 2023 were analyzed using real-time qPCR and characterized using five ASFV gene segments: partial gene of the B464L (p72), full length E183L (p54), central variable region (CVR) within B602L, EP402R (CD2v), and intergenic region (IGR) between I73R and I329L genes. ASF was confirmed in 12 Nigerian states and in seven, eight, and two provinces of Burkina Faso, Côte d’Ivoire, and Mali, respectively. Phylogenetic analysis of B646L (p72), E183 (p54), and CD2v genes of ASFV revealed that Genotype I, Serogroup 4, caused the initial outbreaks in these countries, followed by Genotype II, Serogroup 8. CVR profile analysis showed ASFV Genotype I with different variants, while Genotype II presented only one CVR variant. This is the first report of ASFV Genotype II in Burkina Faso, Cote d’Ivoire, and Mali. The introduction of ASFV Genotype II and its co-circulation with Genotype I in pig populations in these West African countries threatens food security and complicates control measures. Therefore, increased surveillance at international ports of entry, restrictions on live pig movements within the countries, and improved farm-level biosecurity measures are needed to control the further spread of the disease.