African swine fever (ASF) was first described by Montgomery in a report published in 1921 based on his observations in Kenya from 1909 to 1915 when 15 outbreaks occurred involving 1366 pigs, of which 1352 died. He established the viral nature of the disease, and studied the host range, mode of transmission, and the stability of the virus under a variety of environmental conditions and explored methods of immunization. The first attempts to incriminate ticks as vectors of ASF virus in Africa failed. Ixodid ticks commonly found on warthogs or in their burrows were free of virus and were also unable to experimentally transmit the virus when fed sequentially on infected and healthy susceptible pigs. In 1957, ASF appeared in Portugal. It was contracted by pigs fed on food wastes from the airport in Lisbon and was believed to have come from Angola. Natural infections with ASF virus have been found only in porcine species and ticks of genus Ornithodoros.