Colonization of Grande Comore Island by a lineage of Rhipicephalus appendiculatus ticks

Our 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.This 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.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. The archipelago is composed of 4 islands, one of them, Mayotte, being under French administration. The islands of Grande Comore, Moheli and Anjouan, compose Union of the Comoros. In the last 10 years, the country has been affected by three successive epidemic waves whose causative agents were highly suspected to spread from East Africa. In 2002/2004, an East Coast Fever epidemic, a tick-borne disease transmitted by Rhipicephalus appendiculatus, led to the death of 10% of cattle on Grande Comore [1]. The isolated Theileria parva strains, once genotyped, were shown to be closely related to the strain Muguga, widely used for vaccination in East Africa. In the following year, a severe Chikungunya epidemic hit