New tick records in the western Brazilian Amazon, with notes on rickettsial infection and molecular evidence for Amblyomma crassum in Brazil.

This study evaluated the richness and abundance of ticks collected during two years in forest fragments of the state of Acre, western Brazilian Amazon. Considering all the environmental and host collections, the following 15 tick species were collected: Amblyomma coelebs, Amblyomma crassum, Amblyomma humerale, Amblyomma latepunctatum, Amblyomma longirostre, Amblyomma naponense, Amblyomma nodosum, Amblyomma oblongoguttatum, Amblyomma ovale, Amblyomma pacae, Amblyomma rotundatum, Amblyomma scalpturatum, Haemaphysalis juxtakochi, Ixodes luciae and Rhipicephalus microplus. Data from the most two abundant tick species, A. oblongoguttatum and A. scalpturatum, indicated a tendency for adults of both species to be more abundant during the dry season, and the nymphs at late rainy season of each year. The findings of A. crassum consisted of six nymphs collected from an amphibian (Rhinella marina) and a mammal (Didelphis marsupialis), which were morphologically unique and whose 16S rRNA partial sequences were 100% identity to a GenBank-16S rRNA partial sequence of A. crassum from Colombia. This is the first confirmed record of A. crassum in Brazil. A total of 155 tick specimens were molecularly tested for rickettsial infection, resulting in a 6.5% overall infection rate. Rickettsia amblyommatis was detected in A. coelebs and A. humerale, whereas Rickettsia rhipicephali was detected in H. juxtakochi. With the present records of A. crassum and H. juxtakochi, the tick fauna of Acre increases to 26 species, which represents 48% of the Ixodidae fauna in Brazil. This is undoubtedly an extraordinary representation, considering that the state of Acre represents <2% of the Brazilian territory.