Ecologia da interação entre carrapatos e hospedeiros no pantanal: o papel do porco monteiro, do gado nelore e de pequenos mamíferos para a ixodofauna na sub-região da Nhecolândia, MS

Abstract

With alternation of parasitic and free-living periods ticks establish complex interaction nets with hosts and environment. Human interference in the environment alters such relationships with unpredictable consequences. In this work ecological aspects of tick-host relationships within natural areas of Pantanal of Nhecolândia, Mato Grosso do Sul was investigated. For this purpose tick associations with feral pigs (Sus scrofa), Nelore cattle (Bos indicus), both exotic mammals in the region, and small non-flying mammals were studied. In the environment Amblyomma cajennense tick was the most prevalent tick followed by Amblyomma parvum. Adult ticks predominated in the rainy season and nymphs in the dry season. Uneven distribution of ticks was observed in the environment with forestall phytophysiognomies harboring almost all ticks. Furthermore within this phytophysiognomy the bromelia caraguatá vegetation (Bromelia balansae) was the most infested with A. parvum. Areas with cattle were infested with more adult ticks during rainy season than those without cattle. Feral pigs were infested predominantly with A. cajennense adults, specially males (73.9% of all ticks) in the summer and with adults and nymphs, many engorged (33.1% of all ticks) of the same species in the winter. Domestic pigs were observed to feed successfully A. cajennense nymphs and adults in experimental infestations. Natural infestations of cattle were dominated by Rhipicephalus microplus (65.1% of all ticks), but with a high proportion (31.2%) of A. cajennense ticks as well. Infestation of this host with A.cajennense occurred overwhelmingly in winter and engorged nymphs were observed in highest proportion (59.7% of ticks from those of Amblyomma genus). Experimental infestations showed that Nelore cattle are suitable hosts for A. cajennense nymphs. A. parvum ticks were found in much smaller amount and always on the bovines head, but many of the A. parvum females were engorged (28.6% of all ticks from Amblyomma genus). Small mammals (Monodelphis domestica, Oecomys mamorae, Clyomys laticeps e Thrichomys pachyurus) were infested with A. parvum larvae and nymphs, most of which engorging. Echimyidae rodents, specially T. pachiurus were the ones with more regular and with higher tick infestations. Noticeably A. cajennense was virtually absent on small mammals in sharp contrast with high environmental infestation. Overall results from this work displayed a net of interactions with an important but unequal role for both exotic hosts in the population dynamics of ticks, especially that of A. cajennense.