Avaliação da biologia e da infecção por Rickettsia rickettsii (Rickettsiales: Rickettsiaceae) em Haemaphysalis leporispalustris (Acari: Ixodidae) utilizando coelho doméstico como hospedeiro

Abstract

With the aim to increase data about the biology of Haemaphysalis leporispalustris in Brazil, two studies were conduced. The first experiment evaluated biological parameters of nymphs of H. leporispalustris during and after the parasitism with the aim to relating those with appearance of males or females. The male parasitism is also evaluated. We tried stipulated the period of minimum and maximum survival of males on the host and the influence of number or longevity of males in the reproductive capacity of females. The second experiment approached the biological acting of the tick front to the infection for Rickettsia rickettsii, causal agent of the Brazilian Spotted Fever. In the first experiment, the engorged nymphs that changed for males were lighter and presented shorter parasitic period (p <0,05) that the ones that changed for females. The sexual ratio (SR) was established in agreement with the parasitic period. Engorged nymphs of shorter parasitic period (5 and 6 days) created a larger proportion of males (1:0 and 1,70: 1, respectively) that the nymphs of longer parasitic period (9 to 10 days, and SR of 1:3,07 and 1: 4,60, respectively). Already the nymphs that engorged in 7 to 8 days, created males and females in proportion of 1: 1,73 and 1:1,67, respectively.Only the larval hatching was influenced by the number of live males. The weight of the engorged females was more influenced by the host resistance than for the number of live males. In the second experiment, alterations in the biological parameters of H. leporispalustris exposed to the R. rickettsii infection were appraised during the parasitic and no parasitic phase of larvae, nymphs and females ticks. Experimental groups were generated by fed on R. rickettsii infected rabbits, during larvae, nymphs and adult phase. Other group was created through co-feeding of R. rickettsii positive males with larvae in healthy rabbits. The tick s group directly fed in inoculated animals suffered larger effect of the infection on the biological parameters, with increase of the parasitic period and mortality, and decrease of the weight and oviposition period. The group infected in the nymph phase generated lighter females, that produced less eggs than didn't developed appropriately (low hatching). The larvae infected by co-feeding with infected males group represents the closest model to the than it happens in the natural condition. This group presented heavier larvae and smaller mortality of larvae and engorged nymphs, in relation to the control group. The efficiency in the ecdisis of nymphs was greater, and even the engorged females presenting smaller weight, they obtained IER upper to the control group.