Genetic Assessment of African Swine Fever Isolates Involved in Outbreaks in the Democratic Republic of Congo between 2005 and 2012 Reveals Co-Circulation of p72 Genotypes I, IX and XIV, Including 19 Variants.

Leopold Mulumba–Mfumu,Matthew Mauldin,Etienne Thiry,Noelia Moreno,Esther Blanco,Curé Tshilenge,Adama Diallo,Jenna Achenbach,Linda Dixon,Claude Saegerman,Charles Lamien

doi:10.3390/v9020031

Abstract

African swine fever (ASF) is a devastating disease of domestic pigs. It is a socioeconomically important disease, initially described from Kenya, but subsequently reported in most Sub-Saharan countries. ASF spread to Europe, South America and the Caribbean through multiple introductions which were initially eradicated—except for Sardinia—followed by re‑introduction into Europe in 2007. In this study of ASF within the Democratic Republic of the Congo, 62 domestic pig samples, collected between 2005–2012, were examined for viral DNA and sequencing at multiple loci: C-terminus of the B646L gene (p72 protein), central hypervariable region (CVR) of the B602L gene, and the E183L gene (p54 protein). Phylogenetic analyses identified three circulating genotypes: I (64.5% of samples), IX (32.3%), and XIV (3.2%). This is the first evidence of genotypes IX and XIV within this country. Examination of the CVR revealed high levels of intra-genotypic variation, with 19 identified variants.

Highlights

African swine fever (ASF) is a complex and highly lethal haemorrhagic disease of domestic swine with mortality rates reaching 100%
Introduction of ASF has not been limited to Europe, as outbreaks with putative causal links to Spain have occurred in the Caribbean and South America [7]
ASF is caused by African swine fever virus (ASFV), which is transmitted to swine through three main routes: (1) a sylvatic cycle involving wild swine and Ornithodoros ticks; (2) from the sylvatic cycle to domestic pigs; and (3) domestic pig cycle involving domesticated pig to pig transmission [3,9]

Summary

Introduction

African swine fever (ASF) is a complex and highly lethal haemorrhagic disease of domestic swine with mortality rates reaching 100%. Subsequent exportations to Europe occurred in 1960 and 2007 [5,6]. ASF has not been limited to Europe, as outbreaks with putative causal links to Spain have occurred in the Caribbean and South America [7]. Domestic pigs are most susceptible, with the disease course ranging from peracute, acute, subacute, chronic and unapparent and, mortality rates ranging from 100% to as little as 3% [8]. Due to the lack of treatment and vaccine, rapid and accurate diagnosis complemented by the genotyping of circulating ASFVs may contribute to timely improvement of prevention and control strategies. In order to identify and determine the heterogeneity of circulating ASFVs, a rapid method of polymerase chain reaction (PCR)-based sequencing of a 478 base pair (bp) fragment at the C-terminal end of the p72 gene has been commonly used to differentiate the different genotypes of ASFV [11]

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