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Chagas disease is one of the most significant systemic parasitosis in Latin America, caused by Trypanosoma cruzi , which is mainly transmitted by hematophagous insects, the triatomines. This research was carried out in both domestic and wild environments throughout a Northeastern rural locality. Triatomines were captured in both peridomicile and wild environments, obtaining 508 specimens of triatomines, of which 99.6% were Triatoma brasiliensis . Insects were captured in 10 (18.5%) peridomiciles with an average of 8.3 triatomines per residence. Triatoma brasiliensis nymphs and adults were found in six peridomiciles, generating a 11.1% colonization. No T. cruzi infection was detected in the 447 peridomestic insects analyzed. On the other hand, of the 55 sylvatic T. brasiliensis molecularly examined for T. cruzi , 12 (21%) were positive, all harboring T. cruzi I. The blood meal analysis by enzyme-linked immunosorbent assay from gut content revealed that both peridomestic and wild triatomine populations fed mainly on birds, refractory to the parasite, which may explain the null rate of natural infection prevalence in the domestic environment. However, infected triatomines for potential home infestation within the radius of insect dispersion capacity were registered in rock outcrops around the dwellings. Anthropogenic environmental influences are able to rapidly alter these scenarios. Therefore, to avoid disease transmission to humans, we recommend constant vector control combined with periodic serological surveillance. The associated methodology presented herein may serve as a model for early detections of risk factors for Chagas disease transmission in the Brazilian Northeast.

The rupestrian Triatoma costalimai species has been found infected by Trypanosoma cruzi in wild, peridomicile, and intradomicile environments in the municipality of Aurora do Tocantins, Tocantins, Brazil. Proximity between rock outcrops increases the risk of vector transmission of Chagas disease via this species. This work describes a focus of colonization by T. costalimai specimens infected by T. cruzi in rock outcrops located in an urban area in this municipality. Parasitological examination of feces from the collected specimens, axenic cultivation of T. cruzi -positive samples, and genetic characterization of the isolates were performed. Nymph and adult specimens were collected with a high infection prevalence (64.5%) for T. cruzi discrete type unit (DTU I). Participation of the T. costalimai species in the wild cycle of T. cruzi in rock outcrops located in an urban area demonstrates the need for entomological surveillance and control of vector transmission of Chagas disease in the municipality of Aurora do Tocantins, Tocantins.

The effect of a parasite on the life history of its vector is important for understanding and predicting disease transmission. Chagas disease agent Trypanosoma cruzi is a generalist parasite that is diverse across scales from its genetic diversity to the 100s of mammal and vector species it infects. Its vertebrate hosts show quite variable responses to infection, however, to date there are no studies looking at how T. cruzi variability might result in variable outcomes in its invertebrate host. Therefore, we investigated the effect of different T. cruzi I strains on Rhodnius prolixus survival and development. We found significant variation between insects infected with different strains, with some strains having no effect, as compared with uninfected insects, and others with significantly lower survival and development. We also found that different variables had varying importance between strains, with the effect of time postinfection and the blood:weight ratio of the infective meal significantly affecting the survival of insects infected with some strains, but not others. Our results suggest that T. cruzi can be pathogenic not only to its vertebrate hosts but also to its invertebrate hosts., (© The American Society of Tropical Medicine and Hygiene.)

In Chile, the main vector of Chagas disease, Triatoma infestans, is under control after insecticide spraying. However, it has been found colonizing wild habitats. This study evaluated Trypanosoma cruzi infection of sylvatic and domiciliary T. infestans and identified their parasite genotypes. The sample studied was composed mainly of T. infestans sylvatic nymphs and domiciliary adults from a semi-urban area with human dwellings under vector control surveillance. Results showed prevalences of 57.7% in nymphs and 68.6% in adults. Hybridization tests showed a major T. cruzi lineage (TcI) circulating in sylvatic (93.3%) and domiciliary (100%) T. infestans. TcII, TcV, and TcVI were also detected, mainly in nymphs, suggesting differential adaptation of T. cruzi lineages among instars. We also discuss the origin of domiciliary individuals of T. infestans and the risk of human infection by triatomines of sylvatic foci that invade houses despite vector control programs.

Mixed infestation of nymphs and adults of Rhodnius prolixus Stal, 1859 and Panstrongylus geniculatus Latreille, 1811 was detected in 3 (15%) of 20 dwellings in El Guamito, an endemic focus of Chagas disease in Lara State, Venezuela. In one of the houses, both species were positive for Trypanosoma cruzi: 14.3% (R. prolixus) and 20% (P. geniculatus ). The overall infection rate in 143 of 352 R. prolixus was 16.1%. Parasites isolated from R. prolixus were identified as T. cruzi I by random amplified polymorphic DNA analysis. Dot-enzyme-linked immunosorbent assays of 36 R. prolixus showed that 58.3% of the R. prolixus had fed on humans. The gut contents of one fifth-instar nymph of P. geniculatus that was positive for T. cruzi also reacted with anti-human serum. A questionnaire was used to gather data on the demographic and socioeconomic characteristics of the population. An indirect immunofluorescent test, an indirect hemaglutination test, and an ELISA were used to detect the presence of antibodies against T. cruzi in 84 of 86 inhabitants and in 15.5% of people more than 20 years old. The relative risk (RR) of infection was greater in men than in women (RR = 1.61, 95% confidence interval = 0.54-4.80). Of the people more than 15 years old, 36.6% had no formal education. All respondents recognized triatomine bugs, but they did not relate them to Chagas disease transmission. A total of 85.7% of the houses were "ranchos" suitable for the colonization of triatomine bugs. The possible domiciliation of P. geniculatus and the implications of competition with R. prolixus for resources are discussed. Since there is no clear separation of food sources, abiotic factors such as microclimatic variation within houses may be critical to predict the outcome of the process of competition and potential domestication of this generally sylvatic species.

Ixodes spinipalpis maintains Borrelia bissettii spirochetes in Colorado in a cycle involving wood rats and deer mice. This tick has been described as nidicolous, remaining either attached to its rodent hosts or in the rodent nest. Nidicolous ticks pose little risk of pathogen transmission to humans if they do not actively quest for hosts. To investigate the questing potential of I. spinipalpis, sentinel mice were placed in an area where I. spinipalpis had been commonly found on wood rats and deer mice. Concurrently, wild rodent populations were trapped and analyzed for Lyme disease spirochetes, the agent of human granulocytic ehrlichiosis (aoHGE), and Babesia microti. A total of 122 I. spinipalpis larvae and 10 nymphs were found on 19% of 244 sentinel mice. In addition, 4 sentinel mice became infested with Malaraeus telchinus or Orchopeas neotomae fleas. Questing I. spinipalpis were positively associated with woody shrubs and negatively associated with sunny and grassy areas. Four sentinel mice became infected with aoHGE after having been fed upon only by I. spinipalpis larvae. One sentinel mouse became infected with B. bissettii after having an I. spinipalpis nymph feed on it, and one sentinel mouse became coinfected with aoHGE and B. bissettii after it was fed upon by a single I. spinipalpis nymph. These sentinel mouse conversions suggest the possibility that the aoHGE is transovarially transmitted by I. spinipalpis, and that I. spinipalpis is capable of simultaneously transmitting B. bissettii and the aoHGE. The findings that I. spinipalpis quest away from rodent nests and will attach to and infect sentinel mice may be of public health importance. It suggests the potential transmission of the agents of human granulocytic ehrlichiosis and Lyme disease to other hosts by I. spinipalpis, in regions of the western United States where Ixodes pacificus is not found.

Four hundred four patients with chronic Chagas' disease were treated with itraconazole (6 mg/kg of body weight/day for 120 days), allopurinol (8.5 mg/kg of body weight/day for 60 days), or with a placebo of pure starch. Patients were monitored over a period of four years by clinical examination, serology, xenodiagnosis, hemoculture, and electrocardiogram. Drug tolerance was good, with only four treatments discontinued due to side effects that subsided after suspension of treatment. Parasitologic cure was evident in 44% of the those treated with allopurinol and 53% of those treated with itraconazole, and the electrocardiographic evaluation showed normalization in 36.5% and 48.2%, respectively, of patients with chronic or recent cardiopathy.

To determine whether protective immunity against the agent of Lyme disease may be expressed mainly within its tick vector prior to transmission, we passively immunized mice at various intervals after infected ticks had attached, and assayed such mice for evidence of spirochetal infection by xenodiagnosis one month after challenge. Groups of CD-1 mice were intraperitoneally infused with 0.5 ml of hyperimmune rabbit or mouse serum, reagents and quantities previously determined to protect against syringe-challenge with 10(6) low-passage JD1 spirochetes 12 hr after passive transfer. Comparison groups received normal rabbit serum or saline. All mice were protected from infection when infused no more than one day after infective ticks were allowed to attach. However, if infused three or five days post-tick attachment, 60-100% of the mice became infected. All mice became persistently infected when infused with saline or normal rabbit serum. We conclude that antibody is protective against tick-transmitted spirochetal infection only when passively administered before the spirochetes are deposited in the skin of the host. Ingested antibody may destroy spirochetes or interfere with activation and replication within the tick gut, or with dissemination to the salivary glands. Lyme disease vaccines may thus be uniquely effective because of the vulnerability of the spirochetal agent within its vector.

To better define the possible role of argasid ticks in the epidemiology of West Nile virus, adult Argas arboreus, A. persicus, and A. hermanni were fed through a membrane on fetal bovine serum containing 10(5.5) 50% tissue culture infective doses (TCID50)/ml of West Nile virus. The virus was detected for three and four days after feeding in A. persicus and A. hermanni, respectively. The virus titers then decreased to undetectable levels in both species. When the infective dose was increased to 10(6.2), virus was detected until days 6 and 8, respectively. In A. arboreus, virus titers in whole tick homogenates reached a peak of 10(4.0) on day 4 postfeeding and remained constant at 10(3.0) after day 6 throughout the 20- or 50-day observation periods. Virus was detected by isolation, indirect fluorescent antibody, and histochemical techniques in the salivary glands, ovaries, synganglia, and coxal fluids. Infected ticks successfully transmitted virus to clean chickens on day 20 postfeeding. No evidence of transstadial transmission from nymph to adult was detected. Larvae from experimentally infected females successfully transmitted virus to clean chicks and virus was recovered from F1 larvae. Venereal transmission was not detected. Virus was present in coxal fluids secreted by infected females after infective meals. This study demonstrates West Nile virus infection in experimentally infected A. arboreus ticks and documents horizontal and vertical transmission in this species.

Crimean-Congo hemorrhagic fever (CCHF) virus was transmitted from infected adult Hyalomma ticks to uninfected larval and nymphal Hyalomma ticks while cofeeding on a guinea pig host that did not have a detectable viremia. When tested after feeding with infected adults, three (0.8%) of 370 H. truncatum larvae contained detectable CCHF virus (mean virus titer 10(1.6) plaque-forming units [PFU]/tick). The virus was transmitted transstadially from infected larvae and was detected in 15 (1.2%) of 1,253 nymphs and 12 (0.1%) of 2,049 adults. Virus was recovered from 18 (1.9%) of 931 H. impeltatum nymphs, which originated from larvae that cofed with infected adults. After H. impeltatum nymphs cofed with infected adults, CCHF virus was detected in 21 (4.3%) of 449 (mean virus titer 10(1.7) PFU/tick) fed nymphs, but none of 886 adults tested after molt. Results of this study indicate that a small proportion of either larvae or nymphs may acquire CCHF infection while cofeeding on a host without a detectable viremia.