An updated survey of African swine fever in Malawi

Abstract

SUMMARYCases of African swine fever (ASF) confirmed in the laboratory in 1985 and 1986 and other data obtained since 1984, in particular an extension of the serological survey of free-ranging domestic pigs undertaken from 1981 to 1984, are presented to give an updated survey of the ASF situation in Malawi and a revised estimate of the ASF enzootic area. Evidence is presented that the area may include some border areas in Dedza and Ntcheu districts and may be expanding in some localities.

Isolation of African swine fever virus from ticks of the Ornithodoros moubata complex (Ixodoidea: Argasidae) collected within the African swine fever enzootic area of Malawi

“…Burning infested premises, although possible for pig kholas, would clearly not be acceptable for houses and, since the ticks in houses may be infected and could reinfest new pig kholas, this would not be an effective means of eradication. These ticks occur over a much wider area than the present ASF enzootic area and there is a danger that the enzootic area could become larger in future (Haresnape & Mamu, 1986;Haresnape, Lungu & Mamu, 1987). It is difficult to see any way in which ASF could be eradicated altogether but it is possible that it could be prevented from becoming enzootic over a wider area through imposition of strict control of pig movements from the enzootic area and special efforts to detect the spread of ASF outbreaks in those areas outside the enzootic area where 0. moubata occur.…”

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

“…It is suggested that Malawian isolates of ASF virus mav be less virutlent in African than European breeds of (lomestic pig. 1981(Haresnape, 1984 Haresnape, Lungu & Mamu, 1985;Haresnape, Lungu & Mamu, 1987). One of these was in Bongera locality in 1983 where at least 130 pigs died, but estimates of the numbers of pigs affected have always been difficult to obtain.…”

“…ASF infected 0. moubata from enzootic Malawi have been reported in the district every year since 1982, but generally with mortality substantially less than 100%, and only a very small proportion of reported outbreaks have been confirmed by laboratory tests. Laboratory confirmation was obtained for only 2 of the 19 outbreaks which are believed to have occurred in the district between 1981 and 1986 (Haresnape, 1984;Haresnape, Lungu & Mamu, 1985;Haresnape, Lungu & Mamu, 1987). One of these was in Bongera locality in 1983 where at least 130 pigs died, but estimates of the numbers of pigs affected have always been difficult to obtain.…”

Molecular epidemiology of African swine fever in East Africa

“…ASF outbreaks have been reported on regular basis in the neighbouring districts of Zambia (Northern Rhodesia) and Malawi, in Chipata and Mchinji Wilkinson, 1989). The latter area was declared enzootic for ASF as early as 1933 (Turnbull, 1933 (Haresnape, 1984;Haresnape et al, 1985Haresnape et al, , 1987. Wild pigs were implicated in the first report of the disease in East Africa, and these wild suids, especially warthogs, and Ornithodoros ticks, are present, in many of the localities where ASF outbreaks occur in the region.…”

“…The role played by wild pigs and Ornithodoros ticks could not be established (Haresnape, 1984). ASF disease surveys in the same country also identified enzootic localities in which the sylvatic hosts were irrelevant (Haresnape et al, 1985(Haresnape et al, , 1987). An ASF enzootic situation in domestic pigs was thus reported for the first time in Mchinji, and the enzootic area was later extended to include Ntcheu and Dedza with the discovery of seropositive ASF survivor pigs at least nine months after the outbreaks.…”