The nonparasitic phase of Dermacentor nitens under field conditions in southeastern Brazil

Ticks (Acari: Ixodidae) and tick-borne agents associated with domestic dogs in an environmental protection area in Brazil, with molecular evidence of Rhipicephalus linnaei (Audouin, 1826)

Wild animals and domestic dogs living in human dwellings near forested areas can share ectoparasites, including ticks. In this study, we surveyed ticks associated with dogs which tutors living in the Palmares Environmental Protection Area (EPA Palmares). Dogs were classified into three categories, domiciled, semi-domiciled and wandering dogs according to dog care/ type of dwelling. Ticks were collected monthly from January to December, 2020. Overall, 60 (33.9%) out of 177 examined dogs were infested by ticks. Six species of ticks were identified: Rhipicephalus linnaei, Amblyomma aureolatum, Amblyomma sculptum, Amblyomma ovale, Amblyomma dubitatum and Rhipicephalus microplus. The overall prevalence and presence in semi-domicilied+wandering dogs was higher for A. aureolatum than for R. linnaei by the Chi-square statistic tests. A random sample of 50 ticks, collected from 22 different dogs, were processed through molecular analyses. Ticks were submitted to DNA extraction and also by PCR, using specific primers in order to pathogens monitoring. Four males of A. aureolatum yielded DNA sequences (350 bp) that were 100% identical to the type strain of Rickettsia bellii in GenBank (CP000087).

Biology of the non-parasitic phase of the cattle tick Rhipicephalus (Boophilus) microplus in an area of Amazon influence

BACKGROUND

Rhipicephalus (Boophilus) microplus is the most important tick species affecting cattle in the world. Under field conditions, the non-parasitic phase of R. (B.) microplus is unknown in the Amazon biome, including Brazil. The present study aimed to evaluate the non-parasitic phase of R. (B.) microplus in field (grass plots) and laboratory conditions.

METHODS

The study was conducted from September 2020 to April 2022 in an Amazonian region (Maranhão State, Brazil). We evaluated the biological parameters of R. (B.) microplus under laboratory and field conditions. Engorged females were exposed to experimental conditions every 14 days, totaling 20 months of study. The following biological parameters were observed: pre-oviposition period, egg mass incubation period, and maximum larval survival period.

RESULTS

Abiotic data (e.g., temperature and humidity) varied little throughout the year. Precipitation was the factor that varied the most throughout the year (dry ~ 30 mm3 and rain 400 mm3), and the parameters of pre-oviposition and pre-hatching are longer during the rainy season. A possible negative effect of the dry season on the percentage of hatched eggs was observed. Larval longevity in the plots of both control and free females was short (mean ~ 50-60 days), below that recorded for larvae under controlled conditions (mean ~ 95 days).

CONCLUSIONS

Rhipicephalus (Boophilus) microplus was able to complete its non-parasitic phase by producing host-seeking larvae in the pasture during all months of the study. The results indicate that R. (B.) microplus can complete up to six generations per year in biome Amazon. To our knowledge, this is the highest number of annual generations for R. (B.) microplus in Latin America.

Serosurvey of spotted fever group Rickettsia in equids from western Pará, Amazon, Brazil

From a previous large epidemiological survey, we randomly selected 474 serum samples (463 horses and 11 mules) distributed among four municipalities of Pará state, Amazon region, Brazil, and from three types: farm animal, urban carthorse, and sport horse. Samples were tested by indirect fluorescence antibody test (IFAT ≥ 64) for antibodies reactive to spotted fever group (SFG) rickettsiae using Rickettsia rickettsii as crude antigens. From the 474 equids tested, 149 (31.4%) had ticks attached during sampling, belonging mostly to the species Dermacentor nitens. The overall seroprevalence for SFG rickettsiae was 31.4% (95% confidence interval: 27.3-35.9%) with 149 seropositive animals out of 474 screened. Notably, 77 equids (16.2%) had high endpoint titers ranging from 512 to 16,384, indicating that they had been exposed to SFG rickettsiae not long before sampling. Animal type affected rickettsial seroprevalence, with significantly higher values among farm horses when compared with urban and sport animals. Presence of dogs and tick infestation were negatively associated with equid seropositivity to R. rickettsii. This is the first report of SFG rickettsiae-reactive antibodies in equids from Pará state, Brazilian Amazon.