Thiago F. Martins , Amália R. M. Barbieri , Francisco B. Costa , Flávio A. Terassini , Luís M. A. Camargo , Cássio R. L. Peterka , Richard de C. Pacheco , Ricardo A. Dias , Pablo H. Nunes , Arlei Marcili , Alessandra Scofield , Artur K. Campos , Mauricio C. Horta , Aline G. A. Guilloux , Hector R. Benatti , Diego G. Ramirez , Darci M. Barros-Battesti , Marcelo B. Labruna
31 March 2016
Until recently, Amblyomma cajennense (Fabricius, 1787) was considered to represent a single tick species in the New World. Recent studies have split this taxon into six species. While the A. cajennense species complex or A. cajennense ( sensu lato) ( s.l.) is currently represented by two species in Brazil, A. cajennense ( sensu stricto) ( s.s.) and Amblyomma sculptum Berlese, 1888 , their geographical distribution is poorly known .
The distribution of the A. cajennense ( s.l.) in Brazil was determined by morphological examination of all lots of A. cajennense ( s.l.) in two large tick collections of Brazil, and by collecting new material during three field expeditions in the possible transition areas between the distribution ranges of A. cajennense ( s.s.) and A. sculptum. Phylogenetic analysis inferred from the ITS2 rRNA gene was used to validate morphological results. Morphological description of the nymphal stage of A. cajennense ( s.s.) is provided based on laboratory-reared specimens.
From the tick collections, a total 12,512 adult ticks were examined and identified as 312 A. cajennense ( s.s.), 6,252 A. sculptum and 5,948 A. cajennense ( s.l.). A total of 1,746 ticks from 77 localities were collected during field expeditions, and were identified as 249 A. cajennense ( s.s.), 443 A. sculptum, and 1,054 A. cajennense ( s.l.) [these A. cajennense ( s.l.) ticks were considered to be males of either A. cajennense ( s.s.) or A. sculptum]. At least 23 localities contained the presence of both A. cajennense ( s.s.) and A. sculptum in sympatry. DNA sequences of the ITS2 gene of 50 ticks from 30 localities confirmed the results of the morphological analyses. The nymph of A. cajennense ( s.s.) is morphologically very similar to A. sculptum.
Our results confirmed that A. cajennense ( s.l.) is currently represented in Brazil by only two species, A. cajennense ( s.s.) and A. sculptum. While these species have distinct distribution areas in the country, they are found in sympatry in some transition areas. The current distribution of A. cajennense ( s.l.) has important implications to public health, since in Brazil A. sculptum is the most important vector of the bacterium Rickettsia rickettsii, the etiological agent of Brazilian spotted fever.