Experimental infection of the argasid tick, ornithodoros moubata porcinus, with African swine fever virus

Plowright, W.; Perry, C.T.; Peirce, M. A.; Parker, John

doi:10.1007/bf01241664

Cited by 80 publications

(67 citation statements)

References 9 publications

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“…In general, titres decreased with the passage of time but it appears that virus multiplied to high titres in a small proportion of infected ticks including adult females in the Chalaswa area in November 1983 and in Tikoliwe in March 1982, and also in the three nymphae identified in this study in July 1984, 8 months after the ASF outbreak. It is unlikely that the higher titres observed in these ticks was residual virus from recently ingested blood meals since it was so long after the last reported cases of ASF, and because the time between collection in Malawi and assay at Pirbright w ould have resulted in considerable reduction in the amount of infectious virus in the ticks (Plowright et al 1970 or that virus can cross the placenta (Schlafer, McVicar & Mebus, 1984), newborn piglets may be passively protected by antibodies in colostrum which do not prevent infection but reduce the clinical course, duration and titres of viraemia after challenge (Schlafer, Mebus & McVicar, 1984). Since recovered sows are frequently used for breeding in Malawi, their piglets may be seropositive, anid produce only mild clinical disease when exposed to challenge virus.…”

Section: Discussionmentioning

confidence: 99%

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

Haresnape¹,

Wilkinson

1989

Epidemiol. Infect.

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SUMMARYA detailed study was made in 1983-5 in three villages in Mchinji district in the African swine fever (ASE) 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 240/ 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 titne 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 t 00( following the outbreak, with many apparently healthy pigs beiing seropositive. 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. Since many more outbreaks probably go unreported, it is likely that several thousand village pigs have died as a result of ASF in the enzootic area of Malawi over the last few years, and many more in epizootics outside the enzootic area which are characterized by a mortality approaching 100% (Haresnape, Lungu & Mamu, 1985). INTRODIU(TIONA serological survey undertaken between 1981 and 1984 included 10 localities in Mchinji district, and seropositive pigs were identified in all of them. Between 21 and 74 % of the pigs were seropositive and highest proportion was in the southwest part of the district. Mortality was estimated from serological data to be between 47 and 83 % for one locality in the district and between 77 and 92 % for another (Haresnape, Lungu & Mamu, 1985).It has been suggested that most outbreaks of ASF outside the enzootic area probably start following introduction of infected meat from an affected area, but that some outbreaks within the enzootic area may represent new incursions of virus from a natural reservoir (Haresnape, Lungu & Mamu, 1985). The soft tick, Ornithodoros moubata, which is known to be a reservoir of ASF virus and vector of the disease (Plowright, Parker & Pierce, 1969; Thomson et al. 1983), is common both in houses and pig pens (kholas) in the enzootic area, particularly in Mchinji district (Haresnape & Mamu, 1986). Collections of these ticks were started in 1982, and examined for the presence of ASF virus. Up to November 1983, 1262 ticks collected from pig kholas in eight villages in Mchinji district were tested, and only three were infected. None of the 977 ticks collected from houses in the same villages were infected. The three infected ticks were from kholas in three different villages in the west part of Mchinji district and there had been suspected ca...

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Section: Discussionmentioning

confidence: 99%

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

Haresnape¹,

Wilkinson

1989

Epidemiol. Infect.

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“…Transmission of the virus sexually, trans-ovarially and trans-stadially in Ornithodoros (reviewed by Kleiboeker and Scoles, 2001), facilitates maintenance of the virus in colonies for periods of up to 15 months (Plowright et al, 1970), in the absence of an infectious vertebrate blood meal. While it has been suggested that they may even be capable of maintaining the virus indefinitely (Plowright, 1977), definitive estimates of the upper time limit of virus clearance from tick colonies are lacking and it remains unclear to what extent virus transmission and survival may be facilitated by soft ticks alone.…”

Section: Warthog/tick Cyclementioning

confidence: 99%

Role of Wild Suids in the Epidemiology of African Swine Fever

2009

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There is presently no vaccine to combat African swine fever (ASF), a viral hemorrhagic fever of domestic pigs that causes up to 100% morbidity and mortality in naive, commercial pig populations. In its endemic setting, ASF virus cycles between asymptomatic warthogs and soft ticks, with persistence in exotic locations being ascribed to the almost global distribution of susceptible soft tick and suid hosts. An understanding of the role played by diverse hosts in the epidemiology of this multi-host disease is crucial for effective disease control. Unlike the intensively studied Ornithodoros tick vector, the role of many wild suids remains obscure, despite growing recognition for suid-exclusive virus cycling, without the agency of the argasid tick, at some localities. Because the four wild suid genera, Phacochoerus, Potamochoerus, Hylochoerus, and Sus differ from each other in taxonomy, distribution, ecology, reservoir host potential, virus shedding, ASF symptomology, and domestic-pig contact potential, their role in disease epidemiology is also varied. This first consolidated summary of ASF epidemiology in relation to wild suids summarizes current knowledge and identifies information gaps and future research priorities crucial for formulating effective disease control strategies.

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“…African swine fever virus has been isolated from and demonstrated to replicate in the argasid tick Ornithodorus meubata porcinus in Uganda and Kenya, and from O. erraticus in Spain; and the virus has also been isolated from domestic and wild swine. This virus is the only ICDV demonstrated to replicate in hosts of different phyla in vivo (Plowright, 1972;Plowright, Parker & Pierce, i969 a, b;Plowright, Perry & * The term 'polyhedral cytoplasmic deoxy(ribo)virus ' has also been used synonymously with 'icosahedral cytoplasmic deoxyribovirus'. The authors of this review prefer to use the adjective icosahedral to polyhedral, so avoiding possible confusion with the polyhedrosis viruses of insects; though it is recognized that few of the viruses reviewed here have been conclusively demonstrated to be icosahedral.…”

Section: The Viruses Their Hosts and Pathologymentioning

confidence: 99%