Rhodnius spp. infestation in palm trees and natural infection by Trypanosoma cruzi and Trypanosoma rangeli in periurban and rural areas of state of the Rondônia, in the Brazilian Amazon.

The state of Rondônia in the Brazilian Amazon is prone to diseases transmitted by insect vectors because of the environmental and population changes resulting from large hydroelectric projects and the expansion of agricultural and livestock industries. The first case of Chagas disease by vectorial transmission was recorded in 2019 in a rural area in Rondônia, reinforcing the need for entomological surveillance. Hence, our goal was to estimate the abundance of Rhodnius spp. in palm trees located in rural and periurban areas and in Brazil-Bolivia border regions, perform domiciliary searches, and check for possible associations between triatomines and the presence/absence of palm-inhabiting fauna and outdoor farming, domestic animals, and buildings. The sampling took place in five municipalities of Rondônia in 2014 (June to August) and 2015 (April to June). Triatomines were collected by active searches during the selective pruning of palm tree crowns. Domiciliary inspections lasted from 30 to 60 min. A set of captured triatomines was analyzed for Trypanosoma cruzi and T. rangeli infection by PCR. Overall, 496 insects were captured during sampling of 150 palms in rural areas and 150 in periurban areas. No triatomine was found during active searches of 59 dwelling either indoors or outdoors. The majority of triatomines caught in the palm trees were identified as Rhodnius robustus (98.6%), and seven specimens were R. pictipes. Triatomine infestation was observed in only 20% of the sampled palms (61/300) in the vicinity of 26/59 households. Nearly half of the infested palm trees had only one or two triatomines, and few palms presented more than 15 triatomines. The municipality of Buritis had the highest triatomine abundance and percentage of infested palms; however, the highest triatomine density per infested palm was observed in Alvorada D'Oeste, where a quarter of the palms were infested. Ants, arachnids, termites, reptiles, and rodents were frequently found in palm trees. Dogs were the predominant domestic animals in households, whereas hens and cattle were the main farming animals. Model estimates showed that the number of triatomines was affected by the presence of henhouses and varied strongly between localities. No relationships were detected between the average number of triatomines and palm fauna and/or palm height. Overall, approximately half of the triatomines were infected with T. cruzi (51.4%) and/or T. rangeli (47.2%), reinforcing the need for continuous entomological surveillance and implementation of community-based approaches because the Brazilian state of Rondônia borders areas experiencing reinfestation by domiciled species and potential colonization of animal shelters by triatomines.

Distribution of the CCR5delta32 allele (gene variant CCR5) in Rondônia, Western Amazonian region, Brazil.

Since around 1723, on the occasion of its initial colonization by Europeans, Rondonia has received successive waves of immigrants. This has been further swelled by individuals from northeastern Brazil, who began entering at the beginning of the twentieth century. The ethnic composition varies across the state according to the various sites of settlement of each wave of immigrants. We analyzed the frequency of the CCR5Δ32 allele of the CCR5 chemokine receptor, which is considered a Caucasian marker, in five sample sets from the population. Four were collected in Porto Velho, the state capital and the site of several waves of migration. Of these, two, from the Hospital de Base were comprised of HB Mothers and HB Newborns presenting allele frequencies of 3.5% and 3.1%, respectively, a third from the peri-urban neighborhoods of Candelária/Bate-Estaca (1.8%), whereas a fourth, from the Research Center on Tropical Medicine/CEPEM (0.6%), was composed of malaria patients under treament. The fifth sample (3.4%) came from the inland Quilombola village of Pedras Negras. Two homozygous individuals (CCR5Δ32/CCR5Δ32) were detected among the HB Mother samples. The frequency of this allele was heterogeneous and higher where the European inflow was more pronounced. The presence of the allele in Pedras Negras revealed European miscegenation in a community largely comprising Quilombolas.