Abstract
The development of acquired resistance to Amblyomma cajennense ticks was evaluated. A total of 18 rabbits were uniformly distributed into three groups named GL, GN, and GA that were submitted to three consecutive infestations with, respectively, larvae, nymphs, and adults of A. cajennense. After the infestations, the parasitic and reproductive parameters of recovered instars were evaluated. A significant reduction of recovery rates of inoculated ticks was observed only after the third infestation of animals in groups GL and GN (P<0.01). The modal day for drop-off of engorged larvae and nymphs increased along the infestations. The recovered engorged nymphs presented a significant reduction of the mean body weight between the first and the third infestations (P<0.01). A significant reduction in the mean recovery rate of engorged females was only observed during the third infestation. However, significant reductions (P<0.05) in body weight, egg mass weight, and larva eclosions were observed for recovered engorged females after the second infestation onwards. The results suggest the occurrence of resistance of rabbits to A. cajennense infestations, being more evident against the adult stage.
Highlights
Known in Brazil as “micuim”, “star tick”, or “rodoleiro” (Guimarães et al, 2001), Amblyomma cajennense ticks were first described in 1787, in Cayenna city, in French Guyana.It is a three host ixodide that primaly infests horses (Borges et al, 2002)
The evaluated parameters were statistically similar among the ixodides recovered from primarily infested animals in relation to those obtained in the second infestation
According to Wikel (1996), the degree of host resistance to ixodide infestations can be measured by the following indicators: decrease of body weight after engorgement with consequent reduction of oviposition, increase of feeding period, and reduction of larval hatchability rate and molting rates
Summary
It is a three host ixodide that primaly infests horses (Borges et al, 2002) This tick species presents low host specificity, during its immature stage of development, being found infesting some species of reptiles, birds, and a wide variety of mammals, including man. A. cajennense tick can be considered as one of the main links between domestic and wild animals, and man; it is a potential vector of pathogens transmitted among these hosts. This ixodide is the main vector of Rickettsia ricketsii, the agent of the Rocky Mountain Spotted Fever in the neotropical region (Guimarães et al, 2001). The role of these secondary hosts as tick disseminators might be significantly limited by the development of resistance of infested animals (Mulenga et al, 2000)
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