A four-year survey of African swine fever in Malawi

Abstract

SUMMARYA serological survey of free-ranging domestic pigs in the Central and Southern Regions of Malawi, together with laboratory data on confirmed cases of African swine fever (ASF) and data from interviews with pig owners, undertaken over a four-year period from 1981-4, has enabled the ASF enzootic area of Malawi to be identified. The area covers much of the western part of the Central Region and includes Mchinji district and parts of Kasungu, Ntchisi, Dowa and Lilongwe districts. Mortality is substantially less than 100 % in outbreaks within the enzootic area but approaches 100 % in outbreaks outside this area, as shown by both the serological investigation and the interview data.

The distribution of ticks of the Ornithodoros moubata complex (Ixodoidea: Argasidae) in Malawi, and its relation to African swine fever epizootiology

“…Although it was not possible to cover the entire country, a great many areas in the Central and Southern Regions of Malawi were visited by staff of the CVL during 1983 and 1984 during an ASF serological survey (Haresnape, Lungu & Mamu, 1985). At the same time, searches were made for tampans in both houses and pig kholas in each area visited.…”

“…The ASF enzootic area was taken to be that in which seropositive domestic pigs had been identified as reported previously (Haresnape et al 1985).…”

Role of Wild Suids in the Epidemiology of African Swine Fever

“…Despite suspecting that bushpigs can, on some occasions, play a significant role in the epidemiology of the disease (Haresnape et al, 1985), the extent of their involvement remains unclear. Outbreaks of ASF in domestic pigs have occurred in some areas of Malawi in the presence of bushpigs, and absence of warthogs and soft ticks (Wilkinson, 1984;Haresnape et al, 1985).…”

“…Outbreaks of ASF in domestic pigs have occurred in some areas of Malawi in the presence of bushpigs, and absence of warthogs and soft ticks (Wilkinson, 1984;Haresnape et al, 1985). As bushpigs attracted by crops come close to communal lands, they could encounter dead infected pigs and possibly become infected by ingesting pig carcasses.…”

“…Serology is not the method of choice for detecting ASF in bushpigs. Indeed, ASFV infection in Potamochoerus results in a diminished immune response against the virus (Oura et al, 1998), and could explain why many authors have failed to detect circulating antibodies in bushpigs (Haresnape et al, 1985;Anderson et al, 1998;Jori et al, 2007). In warthogs, virus is usually only isolated from warthog lymphatic tissue, with the exception of viremic neonate warthogs (Plowright, 1981;Thomson, 1985).…”