A study of African swine fever virus infected ticks (Ornithodoros moubata) collected from three villages in the ASF enzootic area of Malawi following an outbreak of the disease in domestic pigs.

A detailed study was made in 1983-5 in three villages in Mchinji district in the African swine fever (ASF) enzootic area of Malawi, following an outbreak of ASF which affected all three villages. Ticks of the Ornithodoros moubata complex were collected from both pig sties and houses shortly after the outbreak, and approximately 24% contained ASF virus. The proportion of ticks infected did not differ significantly in the three villages, or more surprisingly in different types of premises, and was equivalent in all stages of ticks. The proportion infected decreased with the passage of time, but infected ticks were still present in all three villages 8 months after the outbreak, some with high titres of virus. The proportion of seropositive pigs in the three villages approached 100% following the outbreak, with many apparently healthy pigs being seropositive. It is suggested that Malawian isolates of ASF virus may be less virulent in African than European breeds of domestic pig.