ABSTRACT
Ornithodoros brasiliensis: Aragao is an endemic tick restricted to the highlands of the state of Rio Grande do Sul, Brazil. This species is very aggressive toward humans, causing fever, great pain and intense inflammatory response at the bite site. It is also very aggressive toward dogs, and tick toxicosis syndrome has been reported in this host. In order to elucidate the biology of this tick, the present study describes its life cycle under laboratory conditions, using guinea pigs as hosts for two generations. In the nonparasitic phase, the ticks were maintained in sand, in an incubator under controlled conditions. The larvae molted to the nymphal stage without feeding, and five nymphal stages (N1, N2, N3, N4 and N5) were observed in both generations. In both generations emergence of adults started from N3 when sex ratio was 0.85:1 (23 males and 27 females) in F1 and 0.63:1 (34 males and 54 females) in F2. For both generations, N4 generated more females, while N5 only produced females. The pre-ecdysis period of the nymphs ranged from 31.1 to 38.6 days. Two gonotrophic cycles were observed, and the first one presented a higher average number of eggs deposited (N=139) than the second (N=73.8). The mean duration of the life cycle (egg to egg) of O. brasiliensis was 215.4 days for the first generation and 195 days for the second
Subject(s)
ParasitologyABSTRACT
In this study, Amblyomma ovale Koch ticks were collected from domestic dogs in two localities of the Atlantic rainforest biome of Brazil: 1) the Paty Valley of the Chapada Diamantina National Park, Bahia state (northeastern Brazil), and 2) Adrianopolis, Parana state (southern Brazil). Ticks were screened for the presence of Rickettsia-like structures by the hemolymph test with Gimenez staining, and then processed for isolation of rickettsiae in Vero cell culture by the shell-vial technique. Rickettsiae were isolated from one A. ovale tick of each of the two localities. The two isolates were successfully established in the laboratory with several passages, each one reaching >90% infection of the cells. The two isolates were identified as the spotted fever group (SFG) agent Rickettsia sp. strain Atlantic rainforest, as their gltA (350 bp), ompB (781 bp), and ompA (567 bp) gene fragments were 100% equal to GenBank corresponding sequences of the original strain Atlantic rainforest, reported to be infecting a human in southeastern Brazil, and also 100% equal to the available ompA sequence of strain Bahia, reported to be infecting a human in Paty Valley, the same area of the present study in Bahia state. Ten dogs from Paty Valley were serologically tested against rickettsial antigens by the indirect immunofluorescence antibody test. At least 60% of them were seroreactive to SFG rickettsiae. The role of A. ovale as vector of Rickettsia sp. strain Atlantic rainforest in the Paty Valley area, as well as in other parts of Latin America, is discussed.
Subject(s)
Parasitology , BacteriologyABSTRACT
Background: 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. Methods: 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. Results: 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. Conclusion: 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
