Amblyomma variegatum (Acari: Ixodidae), an African tick in the Caribbean: preliminary phylogeographic data

Amblyomma variegatum (Fabricius, 1794) the tropical bont tick, is a widespread species in sub-Saharan Africa. It is the known vector of Ehrlichia ruminantium, the agent of heartwater in cattle and of Rickettsia africae, agent of human African tick-bite fever. This tick was imported to the Caribbean in the 18th or 19th century presumably from Senegal. Several efforts at eradicating it from the Caribbean have resulted in the reduction of the number of infested islands. Nevertheless, this tick, which can be carried over long distances not only on cattle, but also on one of their immature host, the cattle egret, is very likely to disperse again from the areas were it was not eradicated.The hypothesis that this tick was imported from the western coast of Africa is historically sound, but has never been tested by molecular methods. Here, we present data on genetic variability of three genes (mitochondrial 12srDNA and control region genes, and nuclear ITS2) of A. variegatum collected from 6 African countries, and 4 Caribbean islands. The 12SrDNA gene was not informative in determining any phylogeographic pattern, whereas the dloop and the ITS2 gene sequences, are more informative and their analysis revealed that the Caribbean populations of A. variegatum are, indeed, more closely related to the ticks collected from the West African countries than to the eastern African ones. When compared with data collected from a number of other Amblyomma species, the relative low level of genetic variability observed between and within populations of A. variegatum would indicate that either this tick lineage originated and evolved recently, or it radiated very rapidly form a common source.