Source: Dr Lesley van Helden, Western Cape Department of Agriculture’s epidemiology report, photo credit: Vetre Antanaviciute-meskauskiene/Dreamstime.com/Le News
African swine fever virus (ASFV) is a large and complicated DNA virus. Many of its genes encode proteins that stimulate an immune response in the host, and some suppress the immune response of the host to allow the virus to invade the cells more easily.
Variations of these proteins are present in the 24 known genotypes of ASFV in existence. All 24 genotypes are present in Africa, where the disease is endemic in many countries and has been since the virus was first recognised in the early 1900s.
Because ASF occurred only in Africa, other countries protected themselves from the disease using import regulations and, when outbreaks occurred, a policy of immediate culling to eradicate all potentially infected animals. These countries did so in order to be officially recognised as free of the disease, and using vaccination would interfere with that goal.
There was therefore little interest or financial investment in developing a vaccine. However, after 2007, genotype II of ASF broke out in the country of Georgia and from there spread to much of Eastern Europe and Asia.
Attempts to control the disease using the traditional method of culling were unsuccessful and in some countries the disease became established in wild populations of wild boar. The development of a vaccine therefore received renewed interest and work in this field has started in earnest.