The effect of Babesia microti on feeding and survival in its tick vector, Ixodes trianguliceps.

Evidence is presented that Babesia microti may promote its transmission amongst rodents by enhancing the feeding success and survival of its tick vector, Ixodes trianguliceps. Both the mean engorged weight of larval ticks and the percentage moult of larvae to nymphs increased as larvae fed on naive hosts later in the parasitaemic cycle up to a point a few days beyond the loss of a patent infection. This increased feeding success and survival was not dependent on the level of infection by B. microti. Two possible, host-mediated mechanisms for the observed parasite-vector interactions are suggested, the antihaemostatic effects induced by babesiosis and the interaction of the immunosuppressive effects of Babesia and the development of immunity to ixodid ticks by their vertebrate hosts.