Abstract
BackgroundUnion of the Comoros suffered a severe East Coast Fever epidemic in 2004. Rhipicephalus appendiculatus was probably involved in pathogen transmission as this competent tick species, although previously absent from Comoros, was sampled on 4 animals on one geographical site during the epidemic. We carried out an entomological survey on all three islands of Union of the Comoros to establish cattle tick species distribution with a special emphasis on R. appendiculatus. We investigated R. appendiculatus intraspecific diversity as this species has been previously shown to be split off into two main cytoplasmic lineages with different ecology, physiology and vectorial competence. This survey also included sampling of live cattle imported from Tanzania to investigate the possibility of tick introduction through animal trade.ResultsOur data show that Comoros cattle are infested with Amblyomma variegatum, Rhipicephalus microplus and R. appendiculatus. This latter species has established throughout Grande Comore but is absent from Anjouan and Moheli. Interestingly, 43 out of the 47 sequenced R. appendiculatus ticks belong to one single highly competent lineage while ticks from the other lineage where only found on imported cattle or on cattle parked at the vicinity of the harbor. At last, 2 ticks identified as R. evertsi, a species so far virtually absent on Comoros, were sampled on imported cattle.ConclusionsThis survey shows that importation of live cattle is clearly a source of vector introduction in Comoros. The wide distribution of one highly competent R. appendiculatus lineage on Grande Comore, together with the absence of this species on the two neighbouring islands is in accordance with the rapid and disastrous spread of East Coast Fever epidemics on Grande Comore Island only. Whether the other R. appendiculatus lineage as well as R. evertsi species will succeed in establishing permanently on Grande Comore needs to be monitored.
Highlights
The Comoros archipelago lies in the north entrance of the Mozambique Channel, roughly 180 miles East of Tanzania and 180 miles West of the North Western tip of Madagascar
Phylogenetic studies carried out on Chikungunya [3], the timing of spreading of both Chikungunya and Rift Valley Fever viruses in the region together with T. parva genotyping in Grande Comore [1] strongly suggest that Comoros are a main entrance gate for pathogens introduced from East Africa
Entomological investigations on Comoros and the neighbouring islands, together with a dedicated surveillance of human and animal exchanges between East Africa and Comoros are of primary importance in controlling emerging vector-borne diseases in the whole South Western Indian Ocean region
Summary
The Comoros archipelago lies in the north entrance of the Mozambique Channel, roughly 180 miles East of Tanzania and 180 miles West of the North Western tip of Madagascar. Phylogenetic studies carried out on Chikungunya [3], the timing of spreading of both Chikungunya and Rift Valley Fever viruses in the region together with T. parva genotyping in Grande Comore [1] strongly suggest that Comoros are a main entrance gate for pathogens introduced from East Africa. The emergence of these pathogens to the other island states probably depends on human and trade exchanges among these islands, as well as on the presence of competent vectors and putative reservoirs in the newly colonized areas. This survey included sampling of live cattle imported from Tanzania to investigate the possibility of tick introduction through animal trade
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