African swine fever (ASF) is the most lethal disease of pigs caused by ASF virus (ASFV) with severe economic implications and threat to food security in endemic countries. Between 2016 and 2018, several ASF outbreaks were reported throughout pig producing States in Nigeria. This study was designed to identify the ASFV genotypes responsible for these outbreaks and the transmission pathways of the virus during this period. Twenty-two ASFV-positive samples collected during passive surveillance in eight States of Nigeria were characterized using 3 partial genes sequences of the virus. The genes were: p72 capsid protein of the B646L, p54 envelope protein of E183L, and the central variable region (CVR) within B602L of ASFV. Phylogenetic analysis based on p72 and p54 revealed ASFV genotype I as the circulating virus. Sequence analysis of the CVR of B602L revealed genetic variations with six ASFV variants namely: Tet-15, Tet-20a, Tet-21b, Tet-27, Tet-31 and Tet-34, thus increasing the overall genetic diversity of ASFV in Nigeria. Three of these variants: Tet-21b, Tet-31 and Tet-34 were identified for the first time in Nigeria. The new variants of ASFV genotype I were identified in the States of Enugu, Imo, Plateau and Taraba, while co-circulation of multiple variants of ASFV genotype I were recorded in Plateau and Benue States. The high genetic diversity, emergence and increasing recovery of new variants of genotype I in Nigeria should be a concern given that ASFV is a relatively stable DNA virus. The epidemiological implications of these findings require further investigation.

Livestock trading through live animal markets are potential pathways for the introduction and spread of economically important pathogens like the African swine fever virus (ASFV) to new areas in several countries. Due to the high demand for live pigs in Nigeria both for restocking and slaughter, live pigs are sold at designated live pig markets (LPM) in the country. This involves movement of pigs over long distances. Despite, reports of ASF outbreaks following restocking of pigs bought from LPMs, there is paucity of information on the role of LPMs in the epidemiology of ASF. In this study, data and pig samples (whole blood, sera, tissue) were collected from 4 selected LPMs in Nigeria (Dawaki, Katsit, Numan & Pandam) between 2019 and 2020. Samples were analysed by polymerase chain reaction (PCR) and Enzyme-linked Immunosorbent Assay (ELISA). Four genes of ASFV positive samples were characterized to identify the circulating genotypes. Results revealed trade activities involving transportation of pigs from these selected markets to 42 major cities and towns in thirteen (13) States of Nigeria. PCR results revealed an overall ASF prevalence of 10.77% (66/613). ASFV was confirmed by PCR in all the selected LPMs with a prevalence rate of 3.13%-23.81%. The phylogeny revealed genotype I and serogroup 4 based on the p72 protein that encodes the B646L gene and the EP402R gene encoding the CD2V. While sequence analysis of CVR of B602L gene revealed 8 tetrameric repeats variants, six of which have never been reported in Nigeria. Analysis of sera samples recorded a seroprevalence of 6.9% (16/217) within the study period. Findings from this study show that LPM are hotspots and channels for transmission and continuous spread of ASFV in Nigeria. Therefore, for ASF to be controlled in Nigeria, disease surveillance and regulation at LPMs are critical.