Eficiência da alimentação in vitro de fêmeas de Rhipicephalus microplus (Acari: Ixodidae)

Abstract

The technique of artificial feeding is an important tool for enabling the analysis of biological and evaluating the efficiency of ticks as vectors of bio-agents. The objective was to evaluate the effect of weight range, the interval between collection and beginning of artificial feeding, as well as the influence of different forms of presentation of bovine blood, temperatures and adapted devices for artificial feeding of partially engorged females of Rhipicephalus microplus. Preliminarily, the females were washed in distilled water and evaluated for integrity gnatossoma, weighed and fixed in trays with the ventral surface facing up. Five experiments were carried out by adopting a completely randomized design. At the first was verified the effect of the weight range on the in vitro feeding of partially engorged females. In the second, we measured the interval between the collection of ticks and the beginning of artificial feeding. The third was to determine the effect of different forms of presentation of bovine blood on the effectiveness of artificial feeding of females. In the first three experiments, ticks were fed with bovine blood through capillary tubes for 24 hours. During this period, the capillaries were changed every 60 minutes and the groups kept in greenhouse at 27 ± 1°C and humidity of 80 ± 5%. In the fourth experiment, we evaluated the influence of different temperatures on the feeding of females. Ticks were kept at temperatures between 32 and 37°C and humidity 80 ± 5%, being evaluated, in each temperature, the feeding with bovine blood through capillary tubes for 12 and 24 hours. In the fifth and last experiment was evaluated the use of capillary tubes and plastic pipette tips, in the artificial feeding of female R. microplus with bovine blood. Ticks were kept in a greenhouse at a controlled temperature of 37°C and humidity of 80 ± 5% and fed in periods of 12 and seven hours through capillary tubes and plastic pipette tips, respectively. At the end of the last three experiments, ticks were fixed in Petri dishes and incubated at a temperature of 27 ± 1ºC and humidity of 80 ± 5% for biological monitoring. It was found that females with an initial weight of 40 to 69mg were more likely to gain weight being able to resume their feeding process, after an interval of 12 hours. In addition, was found that regardless of how the bovine blood was presented, the degree of tick engorgement achieved was equivalent. When fed at a temperature of 37°C, there was no statistical difference between the weight of females fed for 12 and 24 hours. The use of plastic pipet allowed the continuous intake of blood, without the need of exchange, so the females with average initial weight of 48.9 mg had an average weight of 200.17 mg. The technique didn´t showed deleterious effects on the biological aspects of non-parasitic phase of R. microplus.