Diversity of the African Swine Fever Virus Genome

Abstract

African swine fever is caused by a cytoplasmically located virus particle that, although structurally similar to the Iridoviridae, has a number of similarities with Poxviridae. The genomes of African swine fever virus (ASFV) isolates from ticks inhabiting warthog burrows in different areas of Zambia were genetically very diverse. Differences between genomes of isolates from ticks inhabiting neighbouring warthog burrows were also detected and probably resulted from point mutations that had occurred at various positions along the virus genome. The genomes of isolates from domestic pig outbreaks in two regions where disease is endemic (Europe/W. Africa and E. Zambia/Malawi) were also compared. Genomes of viruses within each of these areas were closely related to each other and usually varied as a result of additions or deletions of sequences at positions close to both termini. Restriction enzyme mapping defined seven regions of the genome where length variations occurred. In most of these regions length variations were quite small (<2kb) but in a region between 7 and 20kb from the left hand terminus large variations (up to 9kb) were found. Two other variable length regions contained tandemly repeated sequences. The results are discussed in terms of the selective constraints imposed by virus replication in ticks and warthogs compared to domestic pig populations.