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Biomedical subjects

R Chuit

Publications and source records attributed to R Chuit.

14 recordsLinked to original sources
PubMed1996

Host-feeding patterns of domiciliary Triatoma infestans (Hemiptera: Reduviidae) in Northwest Argentina: seasonal and instar variation.

Blood meal sources of 1,964 Triatoma infestans Klug collected in bedrooms in 3 rural villages in northwest Argentina were identified by agar double-diffusion tests. Bugs were collected in September (1988, end of winter), October (1992), December (1988, spring), and March (1989, 1992, summer), and tested for human, dog, cat, chicken-duck, and goat-sheep serum antigens. From late winter to late summer, the percentage of domiciliary T. infestans that fed on humans decreased from 81 to 50-51%, whereas the percentage of bugs that fed on dogs rose from 39 to 45-57%, on chickens from 8 to 40-54%, and on cats from 7 to 12-23%. Bugs that fed on goat-sheep (2%) were collected mostly from 1 house. In winter, most bugs fed on humans only (48%), followed by dogs only (13%), cats only, or chickens only (approximately 1%). In spring-summer, the percentages of bugs that fed exclusively on humans (19%), dogs (16%), or chickens (17%) were similar. The seasonal shift was associated closely with changes in the sleeping places of people from indoors in winter to verandahs in summer, and with the presence of brooding hens or ducks in or close to bedrooms in spring-summer. In spring-summer, at each instar, bugs had more identified blood meals, switched hosts from earlier instars, fed on a larger number of different host types, and took mixed meals more frequently than in winter. Bugs collected from walls, roofs and household goods showed similar blood-feeding patterns, whereas bugs from beds showed the highest frequency of human meals. The increased anthropophagy of domiciliary T. infestans populations at the end of winter and during spring precedes or coincides with the spring peak incidence of acute cases of Chagas disease in the region. This is the 1st report documenting seasonal variation in host selection of any triatomine species.

Animals↗
PubMed1996

Probability of infection with Trypanosoma cruzi of the vector Triatoma infestans fed on infected humans and dogs in northwest Argentina.

The probability that an uninfected Triatoma infestans would become infected with Trypanosoma cruzi after a single feed on people or dogs seropositive for T. cruzi was estimated in Amama, a rural village in northwest Argentina where transmission had resurged four years earlier. The prevalence of seropositivity for T. cruzi was 34.2% among 225 people tested, and 65.1% among 83 dogs tested. Parasitemia was detected by xenodiagnosis in 29.3% of 41 seropositive persons and in 85.3% of 34 seropositive dogs. Parasitemia decreased with age more sharply in seropositive people than in seropositive dogs. Seropositive humans infected 2.6% (95% confidence interval = 1.6%-3.6%) of 963 third or fourth instar nymphs fed once on them, whereas dogs infected 48.7% (44.7%-52.7%) of 610 nymphs. The probability of bug infection increased significantly with instar and was positively related to molting success. The infectivity to bugs of seropositive dogs was 12 times higher than that of seropositive children, and 100 times higher than that of seropositive adults. The weighted probability of infection of an uninfected bug fed randomly on any dog (0.3082) was about 50 times higher than that of bugs fed on any human (0.0062). Such differences in relative infectivity, combined with the relative host-feeding preference of domiciliary Triatoma infestans for dogs, reinforces the important role of domestic dogs as a risk factor for the domestic transmission of T. cruzi.

Adolescent↗
PubMed1995

Detecting domestic vectors of Chagas disease: a comparative trial of six methods in north-west Argentina.

Six methods for detecting domestic infestations by triatomine bugs were compared in the rural community of Amamá, north-west Argentina. An average of three pairs (range, 2-5 pairs) of sensor boxes and sheets of pink typing-paper were tacked to the walls of human sleeping areas in 45 houses for 30 days and then inspected by a two-man team. Triatoma infestans bugs were collected in bedrooms by a different two-man team aided by a flushing-out agent both before and after application of sensing devices. Finally, knockdown collections of bugs after application of one insecticide fumigant canister per bedroom were also made. The proportion of houses with evidence of current domestic bug infestations that were detected by the various methods were as follows: sensor boxes (95.3%), reports of householders (88.4%), knockdown (87.8%), paper-sheets (86.0%), and flushing-out (69.8-76.7%). The detectability of infestations, irrespective of the method used, increased with the density of the bugs. At low or intermediate bug densities, individual sensor boxes were more sensitive than their matched paper-sheets, but at any bug density there were no significant differences between the pooled results for all the boxes and for all the paper-sheets in the house. On average, each sensor box recorded 2.25 times more triatomine faecal smears than its matched paper-sheet, and this relation increased with the density of bugs in the house. Both sensing devices were effective at monitoring unsuccessful attempts of peridomestic triatomine populations to colonize houses.

Animals↗
PubMed1993

Comparison of two sampling methods for domestic populations of Triatoma infestans in north-west Argentina.

In mud-and-thatch houses of Santiago del Estero Province, north-west Argentina, where no insecticides had been sprayed officially to control domestic infestations of the Chagas disease vector Triatoma infestans (Klug) (Hemiptera: Reduviidae), two knockdown (KD) insecticidal collection procedures were compared with the standard flush-out (FO) method for sampling T. infestans. Bugs were collected by FO using 0.2% tetramethrin in bedrooms of (1) 41 houses of Amamá village employing 1 man-hour of capture effort per house, and (2) 19 houses of Trinidad and Mercedes villages employing 4 man-hours/house. From the same houses, 2-5 days after the manual FO collection, bugs were collected by KD indoor-spraying of deltamethrin 25 mg a.i./m2 in Amamá, or burning of one gamma-HCH (= gamma-BHC) fumigant tablet 3.1 g of gamma-isomer) per bedroom in Trinidad and Mercedes. The majority of infestations were detected by both methods, the proportion of positive houses being 81% at Amamá and 95% at the other villages. Although the FO method was more sensitive, at least because it was applied first, the KD method detected infestations in 25% of houses where bugs were not found by FO. Bug densities estimated by FO or by subsequent KD in each house were significantly correlated: r = 0.795 for deltamethrin; r = 0.882 for gamma-HCH. Compared with FO collections of T. infestans large stages, i.e. adults plus fourth and fifth instar nymphs, the KD catch averaged 0.88 x with deltamethrin and 0.57 x with gamma-HCH, regardless of the apparent population density of bugs per house. However, the KD method has practical advantages of speed and standardization.

Animals↗
PubMed1992

Result of a first step toward community-based surveillance of transmission of Chagas' disease with appropriate technology in rural areas.

The objective of this work was to develop an effective methodology for the surveillance of Chagas' disease vectors in rural areas. It was based on the use of sensor boxes and portable mini-pumps to be integrated into the regular health promotion activities of the Primary Health Care (PHC) agents. The proposed methodology involves a continuous passive intradomiciliary detection of triatomines by sensor boxes that are monitored quarterly by PHC agents. Insecticidal treatment of the houses was performed immediately after the detection of triatomines. The more conventional method of vertical surveillance involves a direct entomologic evaluation conducted by trained professionals. The entire house is searched and there is a mandated treatment of the positive houses. The results of the followups obtained in the county of Rio Hondo in Santiago del Estero Province during a 36-month evaluation period immediately following attack phase application of insecticides were analyzed. The initial high domiciliary and peridomiciliary infestations decreased abruptly after the insecticidal treatment in both areas. When the performances of both types of surveillance were compared, the PHC agent method showed a lower percentage of houses reinfested, with fewer triatomines in the former, and a decrease in their rate of Trypanosoma cruzi infection. Evaluations of reinfestations using the man/hour method and the senor box method showed the same sensitivity. A higher sensitivity for detection of low densities of vector populations was achieved using the sensor boxes. The cost of PHC agent/sensor boxes surveillance was five times lower than the classic one. The proposed strategy for the continuous surveillance of Chagas' disease vectors has demonstrated effectiveness, allows community participation, and seems suitable for large scale application.

Animals↗
PubMed1991

The status of transmission of Trypanosoma cruzi in an endemic area of Argentina prior to control attempts, 1985.

A field survey of transmission of Trypanosoma cruzi was carried out in an area which had never been sprayed with insecticide. A population census, mapping and house classification, examination of insects in houses, and a human serological survey were performed. The entomological examination showed that 97% of the houses (433/445) were infested by Triatoma infestans and that 31% of the bugs examined were infected with T. cruzi. The level of infection, as well as the number of insects captured, had no apparent relationship with the type of house. Trypanosoma cruzi was found in 30% of the human population, and in 10% of children up to four years old. The rates of infection were significantly lower for inhabitants, especially children, living in 'urban' houses. The prevalence rate for the children did not correlate with the number of insects collected in the houses. The improvement of houses, outside the framework of an integrated control programme, had no obvious impact on the level of transmission. Nevertheless, the replacement of the original houses by houses with plastered walls and roofs of metal or cement resulted in a decrease in the prevalence of infection in children younger than four years of age. The community showed little confidence in sanitary precautions against Chagas' disease prior to the start of the survey.

Age Factors↗
PubMedDate not supplied

Chagas disease in north-west Argentina: risk of domestic reinfestation by Triatoma infestans after a single community-wide application of deltamethrin.

The risk of domestic reinfestation by Triatoma infestans after a single community-wide application of delta-methrin (2.5% suspension concentrate at 25 mg active ingredient/m2) was studied in Amamá, north-west Argentina, where no insecticide spraying had been done by official control services. The percentage of infested houses fell from 88% before spraying in 1985 to nil during the 6 months after spraying, and thereafter increased from 5% in 1986 to 96% before a second treatment in 1992, fitting closely to a logistic model (r2 = 0.997). Significant risk factors associated with domestic reinfestation determined from stepwise logistic regression and one-factor analysis were the density of T. infestans in bedrooms just before spraying and the surface structure of indoor walls. Peak densities of bugs in 1988-1989 significantly differed between levels of both risk factors. Our study suggests the existence of stable determinants of infestation linked to the household which, in the absence of effective control measures, would also determine the speed of house recolonization and the ensuing bug densities. Plastering of mud walls before application of insecticides to all domestic and peridomestic structures is supported by the study.

Animals↗
PubMedDate not supplied

Usefulness of serology for the evaluation of Trypanosoma cruzi transmission in endemic areas of Chagas' disease.

Thirteen communities from 7 Argentinian provinces were selected for the evaluation of serology as an indicator of transmission of Chagas disease. Of the communities appraised, 6 did not have a history of previous treatment with insecticides and 7 had received sporadic or continuous insecticide treatment. The inhabitants of 20% of the houses of each locality were studied by serology. The samples were obtained by finger pricking and 50 microliters of blood were mixed with 15 microliter of 50% glycerine solution in tissue culture media to be assayed by Indirect Hemagglutination and Indirect Immunofluorescence tests. In untreated areas, the prevalence of infection in infants 0-4 years old was 17.5%, reaching to over 22% for the 5-9 year old group, and to 33.3% in 10-14 year old individuals. The prevalence in treated and surveyed areas was 2.6% in 0-4 year old children, 5.4% in 5-9 year old and 6.2% in 10-14 year old youngsters. The differences between both areas were statistically significant (p less than 0.005). This study favors serology as a valid indicator for the evaluation of transmission of Chagas disease in rural areas.

Adolescent↗