Biologia comparada de carrapatos Amblyomma parvum (Acari: Ixodidae) do Brasil e da Argentina

Abstract

The study of tick-parasite relationships can provide a range of information, including those necessary for the prevention of parasitic and/or infectious diseases. Widely distributed in the Neotropics, Amblyomma parvum ticks can feed in several animal species, including man, besides being a potential reservoir and/or vector of pathogens. Populations of A. parvum from Brazil and Argentina have significant genetic divergence (3.0 - 3.7%) and contrasting reports of host species. This study evaluated the reproductive compatibility between ticks from Argentina and from Brazil and compared the biology of parasites from the two sources in a few animal species. In addition, we also evaluated the capacity of guinea pigs to develop resistance to successive infestations with ticks from both sources, as well as the skin reaction in sensitized guinea pigs by infestation with parasites from Brazil. It was observed that the descendants of crosses between ticks from different origins are fertile, demonstrated by the hatching rate of eggs of hybrid ticks. Guinea pigs were the best hosts for immature forms, and dogs and bovines for adult ticks from both sources, given the highest recovery rate of larvae, the greatest weight of engorged nymphs and the highest number of larvae produced by a female on these hosts. It was also observed that bovines are more suitable hosts for larvae from Argentina than for Brazilian cohorts, which may indicate an adaptation and possibly stabilization of a surrogate life cycle in this non-Neotropical host. Guinea pigs did not develop resistance to repeated infestation by A. parvum ticks from Brazil, as shown by the enhancement of the immature performance on these animals in the third infestation. Also, these hosts did not express hypersensitivity to the tick extract, as seen in the development of reduced skin reactions in test animals, like the control animals. We conclude that the biology of A. parvum ticks from Brazil and from Argentina is very similar. It was evident that cavies can act as primary hosts for immature forms of Brazilian A. parvum as they are for those from Argentina, and its true role in the maintenance of larvae and nymphs of this parasite should be better investigated in Brazil. Finally, we emphasize that the genetic divergence found between ticks from the two sources is not enough to isolate them reproductively and the importance of reevaluate the mitochondrial 16S rDNA gene for distinguishing species of ticks.