In vitro assessment of the acaricidal activity of a carvacrol shampoo on tick larvae.

Ticks are a widely distributed arthropod of veterinary importance. Resistance of ticks to synthetic acaricides has become widespread, warranting the development of new drugs for tick management. Carvacrol is a volatile monoterpene, with promising results against various species of ticks; however, to be used for therapeutic purposes, carvacrol must be included in a formulation that makes its application feasible. This study aims to develop a formulation of a carvacrol-containing shampoo that is effective against two species of ticks: Rhipicephalus sanguineus and R. microplus. Shampoo sensory characteristics and pH were evaluated at 37, 25 and 5 °C, for a maximum of 15 days. The shampoo remained stable at 25 and 5 °C. The efficacy of the carvacrol-containing formulation against two species of ticks was assessed by the larval immersion test. Mortality of both tick species was significantly higher for the carvacrol shampoo than for a carvacrol hydroalcoholic solution. In conclusion, the carvacrol-containing shampoo showed larvicidal efficacy on ticks.

Feeding and respiratory gas exchange of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae).

Ticks are subject to various environmental constrains, such as dehydration, desiccation and long-waiting for hosts to attach. These factors are crucial for tick survival in the environment. Ticks have developed physiological mechanisms and/or strategies that allow adaptability and survival in the environment in which they live, such as spiracle control and cyclical or discontinuous gas exchanges. However, details of gas exchange profile have been reported only in a few tick species in the past. The present study aims to identify and describe respiratory gas exchange patterns in a tropical population of the brown dog tick Rhipicephalus sanguineus sensu lato and effects of blood feeding. Adult female ticks were fed on rabbit hosts. Partially fed (4 to 6 days) and completely fed (> 9 days) ticks were collected daily during feeding, weighed and subjected to CO2 emission measurement at 25 °C using flow-through respirometry. Unfed adult females showed a well-defined periodical burst of CO2 emissions, followed by short periods of low-emission intercepts. The fed groups had drastic changes in respiratory profiles with semi-engorged females showing a high-intensity respiratory pattern alternating between continuous and discontinuous and the engorged females showing a continuous respiratory pattern with high frequency and intensity. The findings from this study contribute to a better understanding of the respiratory physiological process of a tropical population of the dog tick, which may help future investigations on other biological aspects of this ectoparasite and development of control measures.