Genetic profile of African swine fever virus responsible for the 2019 outbreak in northern Malawi

Abstract

Background African swine fever (ASF) is an infectious transboundary animal disease which causes high mortality, approaching 100% in domestic pigs and it is currently considered as the most serious constraint to domestic pig industry and food security globally. Despite regular ASF outbreaks within Malawi, few studies have genetically characterized the causative ASF virus (ASFV). This study aimed at genetic characterization of ASFV responsible for the 2019 outbreak in northern Malawi. The disease confirmation was done by polymerase chain reaction (PCR) followed by molecular characterization of the causative ASFV by partial genome sequencing and phylogenetic reconstruction of the B646L (p72) gene, nucleotide alignment of the intergenic region (IGR) between I73R and I329L genes and translation of the central variable region (CVR) coded by B602L gene. Results All thirteen samples collected during this study in Karonga district in September 2019 were ASFV-positive and after partial genome sequencing and phylogenetic reconstruction of the B646L (p72) gene, the viruses clustered into ASFV p72 genotype II. The viruses characterized in this study lacked a GAATATATAG fragment between the I173R and the I329L genes and were classified as IGR I variants. Furthermore, the tetrameric amino acid repeats within the CVR of the B602L gene of the 2019 Malawian ASFV reported in this study had the signature BNDBNDBNAA, 100% similar to ASFV responsible for the 2013 and 2017 ASF outbreaks in Zambia and Tanzania, respectively. Conclusions The results of this study confirm an ASF outbreak in Karonga district in northern Malawi in September 2019. The virus was closely related to other p72 genotype II ASFV that caused outbreaks in neighboring eastern and southern African countries, emphasizing the possible regional transboundary transmission of this ASFV genotype. These findings call for a concerted regional and international effort to control the spread of ASF in order to improve nutritional and food security.

One hundred years of African swine fever in Africa: Where have we been, where are we now, where are we going?

“…Recently the first full genome sequence of an African genotype II virus isolate from an outbreak in Rukwa, Tanzania in 2017 has been published (Njau et al., 2021). Genotype II has been reported from eight countries in the African region (Bastos et al., 2003, 2004; Hakizimana, Kamwendo et al., 2020; Lubisi et al., 2005; Misinzo, Kasanga et al., 2012; van Heerden et al., 2017), most recently and likely due to an introduction from Asia, Nigeria (Adedeji et al., 2021).…”