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Chagas disease was investigated in four periurban areas of Ceará state, northeastern Brazil, through serological, parasitological and molecular methods in humans, reservoirs and vectors. A cross-sectional survey revealed a seroprevalence rate of 1.2% (13/1076 residents, six also proving positive through PCR). Trypanosoma cruzi infection was not detected in children under 10 years old. Triatoma pseudomaculata prevailed in the peridomiciles: 63 specimens, 69% (34/49) infected with trypanosomatids. Rhodnius nasutus was captured in Copernicia prunifera palm trees (n=280; 25.0% infected with trypanosomatids) and inside dwellings (n=8, all uninfected). Trypanosoma cruzi seropositive reservoirs, represented by Didelphis albiventris (n=27), Rattus rattus (n=24), Thrichomys laurentius (n=2), Mus musculus (n=1) and Monodelphis domestica (n=1), were identified. Among domestic dogs (n=96) seroprevalence reached 21.9%. Miniexon multiplex PCR assays characterized TcI in triatomines. Both TcI and TcII were detected in wild mammal hosts. We conclude that Trypanosoma cruzi circulates within a domestic zoonotic cycle, requiring continuous surveillance. Insecticide application to domiciles does not appear to prevent continuous reintroduction of wild triatomine specimens, presenting a challenge to authorities involved in Chagas disease control.

We assessed some ecological parameters of Triatoma brasiliensis in rock piles in the state of Ceará during the rainy and dry seasons. The greatest density was in April (median = 12.5 triatomines/site). The greatest abundance was in December, when the insects were more dispersed and the density per site was lower (6 triatomines/site). The nutritional status of females and 5 th instar nymphs was increased in July. The rate of T. cruzi infection reached its highest peak in July (10.9%). ELISA revealed that the principal food sources were birds (33.1%), followed by armadillos (18.8%). Food sources were more frequently identified during the rainy season. T. brasiliensis specimens collected in the drought tended to: i) present lower rates of T. cruzi infection and gut content reactivity to tested antisera, ii) have a poorer nutritional status, iii) exhibit lower fecundity, iv) be more dispersed among the studied collection sites, and v) be more abundant and easily collected in the surface of the rocks, possibly reflecting an increased searching for blood meals. Such findings underscore epidemiological concerns and allow inferences about the season when triatomines can more frequently invade the peridomestic environment in search of food and recolonize artificial structures. Journal of Vector Ecology 35 (2): 385-394. 2010.

With the aid of live-bait traps, we studied the risk that Copernicia prunifera palm trees, present in both periurban and rural localities of an endemic Brazilian northeast Chagas disease region, represent to domestic infestation by Rhodnius nasutus. In this area, this important vector has been encountered harboring and transmitting Trypanosoma cruzi, the etiologic agent of the American trypanosomiasis, to mammals, possibly including humans. Results indicate that this bug colonizes C. prunifera palm trees of both regions, mainly in dry seasons, and is infected with high levels of T. cruzi. Although more triatomines were captured in rural areas, proportionally the number of infected bugs from peri-urban regions was much higher. Herein we address the epidemiologic implications and challenge for the Brazilian health authorities to control the disease in this region, where the native palm trees have been largely destroyed causing a severe disturbance in the environmental equilibrium.

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Chagas disease was investigated in two new settlements of landless rural workers inhabiting prefabricated, triatomine-proof houses and in four neighboring older communities where mud huts were still well suitable for vectors. Through a cross-sectional survey and entomological assessment, we surveyed 148 houses/families in the two new settlements and in 47 houses/families in the four older localities. We determined seroprevalence of Chagas disease through IFI and Elisa (eluates) assays and searched for vectors in the domestic and peridomestic environments. Seroprevalence reached 0.6% (3/466) in the new settlements and 0.8% (1/115) in the older communities. Triatomines were not found in the new settlements, while 7 Triatoma brasiliensis, 4 T. pseudomaculata, 1 Panstrongylus lutzi, and 145 Rhodnius nasutus were collected in the older localities. In addition, a colony of T. brasiliensis (n = 55) was encountered inside a school attended by children of the region. Parasite strains isolated from the insects were characterized as T. cruzi I. Despite the low prevalence of Chagas disease in both scenarios, entomological surveillance must be strengthened and housing improvement reinforced in order to control vector transmission. The risk of infection by the vectors was lower in the settlements of improved homes, where conditions for colonization of the peridomestic environment by transmitting insects were not observed.

Abstract. The importance of Rhodnius nasutus in the transmission of Chagas disease in northeastern Brazil was investigated regarding feeding and defecation patterns of this triatomine under laboratory conditions. An average of 30 samples were studied for each instar, from fourth-instar nymphs onward. On average, 86.4% started feeding after less than 10 minutes. In terms of the duration of feeding, 53.3% of fourth instar nymphs, 81.9% of fifth-instar nymphs, 21.9% of males, and 36.7% of females fed for more than 15 minutes. In all groups, there were insects that defecated and urinated during feeding; adult males defecated the most and fourth instar nymphs defecated the least. The results demonstrate that R. nasutus may be considered an efficient T. cruzi vector because it avidly searches for a food source, has a lengthy feeding time with low probability of interruption during feeding, and achieves a high percentage of engorgement.