Species richness and seasonal dynamics of ticks with notes on rickettsial infection in a Natural Park of the Cerrado biome in Brazil

Abstract

This study evaluated the species richness and seasonal dynamics of ticks and rickettsial agents infecting ticks in the largest natural Reserve of the Cerrado biome of Brazil, the Grande Sertão Veredas National Park. During 2012–2014, a total of 9531 host-seeking ticks were collected by dry ice traps and dragging, whereas 1563 ticks were collected from small mammals, and 1186 ticks from domestic animals. Overall, the following 12 tick species were identified: Amblyomma auricularium, Amblyomma dubitatum, Amblyomma naponense, Amblyomma ovale, Amblyomma parvum, Amblyomma sculptum, Amblyomma tigrinum, Amblyomma triste, Dermacentor nitens, Rhipicephalus microplus, Rhipicephalus sanguineus sensu lato, and Ornithodoros mimon. The three most abundant tick species, A. sculptum, A. parvum, and A. triste, are likely to develop one generation per year, with adults predominating between spring and autumn, and immature ticks during autumn-winter. Small mammals seem to be important hosts for immature stages of A. parvum, and A. triste, but not for A. sculptum. Molecular analyses revealed the presence of the human pathogen Rickettsia parkeri in 10% of the A. triste ticks, whereas two agents of unknown pathogenicity, Rickettsia bellii and ‘Candidatus Rickettsia andeanae’ were found in 7 and 5%, respectively, of the A. parvum ticks. A fourth rickettsial agent, Rickettsia amblyommatis, was found in a single A. sculptum tick. Several Vero cell-established isolates of R. parkeri and R. bellii were obtained from A. triste and A. parvum, respectively. Serological analyses of small mammals suggest that they have been infected by R. parkeri and R. bellii, possibly via natural infestations by A. triste and A. parvum, respectively. Because the Park has suffered low anthropic alterations, our results should provide baseline data that shall be used for future comparisons with other Cerrado areas with higher degree of anthropic changes.