Abstract
BackgroundAfrican Swine Fever Virus has devastated more than the half of the domestic pig population in Madagascar since its introduction, probably in 1997-1998. One of the hypotheses to explain its persistence on the island is its establishment in local Ornithodoros soft ticks, whose presence has been reported in the past from the north-western coast to the Central Highlands. The aim of the present study was to verify such hypothesis by conducting tick examinations in three distinct zones of pig production in Madagascar where African Swine Fever outbreaks have been regularly reported over the past decade and then to improve our knowledge on the tick distribution and taxonomy.ResultsOrnithodoros ticks were only found in one pig farm in the village of Mahitsy, north-west of Antananarivo in the Central Highlands, whereas the tick seemed to be absent from the two other study zones near Ambatondrazaka and Marovoay. Using 16SrDNA PCR amplification and sequencing, it was confirmed that the collected ticks belonged to the O. porcinus species and is closely related to the O. p. domesticus sub-species Walton, 1962. ASFV was detected in 7.14% (13/182) of the field ticks through the amplification of part of the viral VP72 gene, and their ability to maintain long-term infections was confirmed since all the ticks came from a pig building where no pigs or any other potential vertebrate hosts had been introduced for at least four years.ConclusionsConsidering these results, O. porcinus is a reservoir for ASFV and most likely acts as vector for ASFV in Madagascar, but its apparent restricted distribution may limit its role in the epidemiology of the disease in domestic pigs.
Highlights
African Swine Fever Virus has devastated more than the half of the domestic pig population in Madagascar since its introduction, probably in 1997-1998
Enzootic African Swine Fever (ASF) has been closely linked to the existence of Ornithodoros tick hosts interacting with wild suids, with O. moubata and O. porcinus ticks from the O. moubata species complex in East and Southern Africa [5,11], with O. erraticus in the Iberian Peninsula [6] and perhaps with O. sonrai in Senegal [12]
Presence of O. porcinus in Malagasy pig pens O. porcinus was confirmed in one farm located in Mahitsy (18°45’3’’S, 47°20’47’’E) in the Antananarivo zone (Figure 1 Figure 2)
Summary
African Swine Fever Virus has devastated more than the half of the domestic pig population in Madagascar since its introduction, probably in 1997-1998. African Swine Fever Virus (ASFV) can be transmitted by soft ticks of the genus Ornithodoros, which may either colonise pig pens in domestic areas or mammal burrows in the wild [4,5,6]. Considering their capacity to replicate and to maintain the virus over the years and to transmit the virus “from tick-to-tick” during mating and development stages [7,8,9,10], they are considered excellent reservoirs of ASFV, just like wild African suids (e.g., warthogs, bush pigs and giant forest hogs). Enzootic ASF has been closely linked to the existence of Ornithodoros tick hosts interacting with wild suids, with O. moubata and O. porcinus ticks from the O. moubata species complex in East and Southern Africa [5,11], with O. erraticus in the Iberian Peninsula [6] and perhaps with O. sonrai in Senegal [12]
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