Secretory process of salivary glands of female Amblyomma cajennense (Acari: Ixodidae) ticks fed on resistant rabbits

Abstract

Ticks have great economic and health importance since infested animals have reduced milk and meat production, and, besides that, they are expensive ectoparasites to control. While feeding, ticks can transmit to their hosts a large amount of pathogens, including Rickettsia rickettsii responsible for the "spotted fever" or "fever of the mountains." It is known that animals infested with ticks or artificially immunized with their salivary gland extracts develop resistance, which is related to a decrease in engorged female weight, in egg-laying by adults, in egg viability and, in some cases, in the capacity of pathogens transmission. The present study aimed to examine morpho-histochemically the female salivary glands of semi and engorged Amblyomma cajennense fed on resistant rabbits. The results revealed that acinus I had no changes when compared to that of females fed on naive rabbits. The c cells of acinus II showed signs of early degeneration, which may result in feeding efficiency decrease. In acinus III d cells, activity time was longer. Such occurrence was associated with the time of female fixation, which increased in females fed on resistant hosts.

Ticks’ response to feeding on host immunized with glandular extracts of Rhipicephalus sanguineus females fed for 2, 4, and 6 days. I. Inactivity or early degeneration of salivary glands?

“…It is clear that the resistance of the host influenced in the secretory cycle of the infesting females glands, acting both in the secretory activity of the glandular cells (making them inactive) and leading the glands to early degeneration. Nunes et al (2010) and Jittapalapong et al (2008) have reported that the resistance acquired by the hosts studied by them induced the salivary glands of Amblyomma cajennense and R. (Boophilus) microplus females, respectively, to necrosis. On the other hand, the present study showed that the resistance of the host led to the loss of function (inactivity) of some secretory cells as well as to the early degeneration of the salivary glands due to the occurrence of apoptosis.…”

“…On the other hand, the present study showed that the resistance of the host led to the loss of function (inactivity) of some secretory cells as well as to the early degeneration of the salivary glands due to the occurrence of apoptosis. However, it is known that different species of ticks respond differently to the resistance acquired by the host (Nunes et al 2010).…”

“…In the ticks, the salivary glands (Wikel et al 1978;Gill et al 1986;Almeida et al 1994;Ferreira et al 1996;Szabó and Bechara 1997;Jittapalapong et al 2000a;Nunes et al 2010) and the intestine (Szabó and Bechara 1997;Jittapalapong et al 2000a;Caperucci et al 2009Caperucci et al , 2010Veronez et al 2010) are important sites of antigens production. Because of this, after the first contact of these ectoparasites with some hosts, the latter develop resistance (Wikel et al 1978;Gill et al 1986;Jittapalapong et al 2000a;Zhou et al 2006).…”

“…Because of this, after the first contact of these ectoparasites with some hosts, the latter develop resistance (Wikel et al 1978;Gill et al 1986;Jittapalapong et al 2000a;Zhou et al 2006). In this sense, several studies are carried out to verify the acquisition of resistance by the hosts when these are immunized by successive infestations (Nunes et al 2010;Monteiro and Bechara 2008;Monteiro et al 2010;Veronez et al 2010;Caperucci et al 2009Caperucci et al , 2010Jittapalapong et al 2000a, b) or by the inoculation of extracts of whole ticks or part of them (Wikel 1981;Ferreira et al 1996;Szabó and Bechara 1997;Jittapalapong et al 2000aJittapalapong et al , b, 2008.…”

“…The acquisition of resistance by the hosts is measured by the analysis of feeding and reproductive parameters of infesting ticks of previously immunized animals (Wikel 1981;Szabó and Bechara 1997;Jittapalapong et al 2000b), as well as by the analysis of the impact of this resistance in the salivary glands (Sanders et al 1996;Jittapalapong et al 2008;Nunes et al 2010) and intestines (Veronez et al 2010;Caperucci et al 2009Caperucci et al , 2010 of different species.…”