Developmental profiles in tick water balance with a focus on the new Rocky Mountain spotted fever vector, Rhipicephalus sanguineus

Abstract

Recent reports indicate that the common brown dog tick, or kennel tick, Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) is a competent vector of Rocky Mountain spotted fever in the U.S.A. This tick is of concern to public health because of its high frequency of contact, as it has a unique ability to thrive within human homes. To assess the moisture requirements necessary for survival, water balance characteristics were determined for each developmental stage, from egg to adult. This is the first time that water relations in ticks have been assessed throughout the complete lifecycle. Notably, R. sanguineus is differentially adapted for life in a dry environment, as characterized by a suppressed water loss rate distinctive for each stage that distinguishes it from other ticks. Analysis of its dehydration tolerance limit and percentage body water content provides no evidence to suggest that the various stages of this tick can function more effectively containing less water, indicating that this species is modified for water conservation, not desiccation hardiness. All stages, eggs excepted, absorb water vapour from the air and can drink free water to replenish water stores. Developmentally, a shift in water balance strategies occurs in the transition from the larva, where the emphasis is on water gain (water vapour absorption from drier air), to the adult, where the emphasis is on water retention (low water loss rate). These results on the xerophilic-nature of R. sanguineus identify overhydration as the primary water stress, indicating that this tick is less dependent upon a moisture-rich habitat for survival, which matches its preference for a dry environment. We suggest that the controlled, host-confined conditions of homes and kennels have played a key role in promoting the ubiquitous distribution of R. sanguineus by creating isolated arid environments that enable this tick to establish within regions that are unfavourable for maintaining water balance.

Survey of Ehrlichia canis, Babesia spp. and Hepatozoon spp. in dogs from a semiarid region of Brazil

“…According to Tanikawa et al (2013), the warm weather that occurs in the city of Patos, Paraiba State, which is located in the semiarid region of Northeastern Brazil, is an important factor contributing to the dissemination of this tick species, while at the same time precluding the establishment of many other tick species, which usually require higher moisture during their off-host developmental stages. R. sanguineus ticks are considered less dependent for survival upon moisture-rich habitats, allowing for their establishment in regions with unfavorable water balances (YODER et al, 2006). This characteristic contributes to the establishment of these ticks in semi-arid regions, such as that of the present study.…”

Ticks on domestic animals in Pernambuco, Northeastern Brazil

“…They are common anywhere, from Recife (far east) to Petrolina (far west). This is expected due to the fact that R. sanguineus is differentially adapted to live in both humid and dry environments (YODER et al, 2006). Interestingly, the intensity of parasitism by R. sanguineus on dogs living in rural areas is lower than in urban areas (F.D.-T, personal observations).…”

Parâmetros da fase de vida livre de Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae): adaptado ao clima subtropical

“…Por outro lado, Dantas-Torres et al (2011), na Itália, ao estudarem os efeitos do clima na biologia de R. sanguineus, adaptado às condições de climas quente e seco, encontraram um período de pré-postura de 2,5 dias. Correlações referentes à influência da água no ciclo de vida de R. sanguineus, realizadas por Yoder et al (2006) Nos primeiros sete dias, foram ovipostos 99,0 e 98,0% da massa total de ovos provenientes de fêmeas pré e pós-desprendimento, sendo que Bellato; Daemon (1997) avaliaram que, nas mesmas condições, (temperatura 27 ± 1°C e umidade relativa superior a 70,0%) foram ovipostos 91,55% da massa total de ovos. Coelho (1993) observou em infestações subsequentes que, nos sete primeiros dias, foram ovipostos 89,54% do total da massa de ovos na primeira geração, 81,33% para a segunda e 89,43% para a terceira.…”