Rickettsiae-infected Ticks in an Endemic Area of Spotted Fever in the State of Minas Gerais, Brazil

First identification of natural infection of Rickettsia rickettsii in the Rhipicephalus sanguineus tick, in the State of Rio de Janeiro

“…Hemolymph samples of specimens collected from R. sanguineus were analyzed by Giemsa stain and immunofluorescence assay and microorganisms with similar morphology to (SFGR) were detected (Lemos et al 1996, Lemos et al 1997a, Rozental et al 2002.…”

“…On the other hand, recently R. sanguineus has been identified as reservoir of Rickettsia felis in Brazil (Cardoso et al 2006, Oliveira et al 2008), although previous studies had shown evidence of infected R. sanguineus in endemic areas in Brazilian states of Minas Gerais and Rio de Janeiro (Lemos et al 1997a, Rozental et al 2002 The increasing number of cases of human parasitism by R. sanguineus ticks reported in the literature indicates that the interaction between human beings and R. sanguineus may be more common than it is recognized in the American continent.…”

More about the role of 2,6-dichlorophenol in tick courtship: identification and olfactometer bioassay in Amblyomma cajennense and Rhipicephalus sanguineus

“…A. cajennense especially parasitizes equids, but it may infest other mammals such as bovids, cervids, wild and domestic canids, birds and even man. In Brazil, A. cajennense is considered the main vector of R. rickettsii, the agent of Rocky Mountain spotted fever (Dias & Martins 1939, Lemos et al 1997, Horta et al 2004, Guedes et al 2005 Mate-finding and courtship behavior in ticks are largely regulated by pheromones. According to Sonenshine (1991), the hypothetical behavioral stages that occur during Dermacentor variabilis (Say) courtship can be described as follows.…”

Occurrence of ticks (Acari: Ixodidae) on human hosts, in three municipalities in the State of Pará, Brazil

“…Considering that these two species are acknowledged as rickettsia vectors, with an emphasis on Brazilian Spotted Fever (SERRA-FREIRE; PINTO, 2008); that ticks of the Ixodes genus keep the R. rickettsii in circulation among sylvatic synanthrope animals like opossums; that R. sanguineus keeps FMB enzootic among dogs in an urban environment (LEMOS et al, 1997); that A. cajennense is responsible for FMB enzootics in rural and peri-urban environments (PEREZ et al, 2008), influenced by its seasonal activity (LEMOS et al, 1997); that A. dubitatum was found keeping those rickettsias in circulation in fields and sylvatic environments (LEMOS et al, 1996); and that all those species parasitize humans in Pará; they are an indication of risk for the establishment of these diseases in humans in the state.…”

“…However, according to Hoogstraal and Aeschlimann (1982), the discriminatory sense of ticks is weakened or even lost when they are dislodged during the feeding process, which might explain why the people in the study group observed the presence of ticks after contact with dogs and horses. R. sanguineus is referred to as a human parasite in many countries, such as: the United States (CLARK et al, 1996;FELZ et al, 1996) Most studies on the prevalence of ixodides in humans in Brazil were carried out in rural or periurban regions and the only species found was Amblyomma cajennense (LEMOS et al, 1997;LABRUNA;PEREIRA, 2001). But parasitism by R. sanguineus in humans assumed special importance when it was considered that the results of Rozental et al (2002) identified by direct immunofluorescence the presence of the spotted fever agent, R. rickettsii, in this species of tick, which may imply on the maintance of that rickettsia in nature, and even its transmission to man.…”