Seasonal changes in infectivity of domestic populations of Triatoma infestans (original) (raw)
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Revista Panamericana de Salud Pública, 1999
The prevalence of Trypanosoma cruzi infection in Triatoma infestans, Triatoma guasayana, and Triatoma sordida was evaluated in Amamá and other neighboring rural villages in northwestern Argentina for five years after massive spraying with deltamethrin in 1992 and selective sprays thereafter. Local residents and expert staff collected triatomines in domiciliary and peridomestic sites. During 1993During -1997, the prevalence of T. cruzi was 2.4% in 664 T. infestans, 0.7% in 268 T. guasayana, and 0.2% in 832 T. sordida. T. cruzi infection was more frequently detected in adult bugs and in triatomines collected at domiciliary sites. The infected T. guasayana and T. sordida were nymphs and adults, respectively, captured at peridomestic sites. The prevalence of T. cruzi infection in T. infestans decreased from 7.7% to 1.5% during the surveillance period, although that change was not statistically significant. Comparison of T. infestans infection rates before the control program and during surveillance showed a highly significant decrease from 49% to 4.6% in bedrooms, as well as a fall from 6% to 1.8% in peridomestic sites. Because of its infection with T. cruzi and frequent invasion of domiciliary areas and attacks on humans and dogs, T. guasayana appeared implicated as a putative secondary vector of T. cruzi in domestic and peridomestic sites during the surveillance period. T. sordida was the most abundant species, but it was strongly associated with chickens and showed little tendency to invade bedrooms.
The American journal of tropical medicine and hygiene, 1998
In three rural villages of northwest Argentina, the overall proportion of domiciliary Triatoma infestans infected with Trypanosoma cruzi was 49% among 1,316 bugs individually examined for infection in March and October 1992). Most of the variation among individual households in the proportion of infected triatomines was explained by variations among houses in the proportion of bugs that fed on dogs or cats, the prevalence of infected dogs or cats, and the proportion of bugs that fed on humans, according to a logistic multiple regression analysis. The effects of human infection rates on bug infection rates were not statistically significant. After adjusting for the effects of other predictors, the presence of chickens in bedroom areas had negative and significant effects on the proportion of infected Triatoma infestans, and positive and significant effects on the number of T. cruzi-infected triatomines collected per person-hr per house. Dog or cat infection rates and the proportion o...
American Journal of Epidemiology, 1991
The reduction of domiciliary infestation by insect vectors, the key to controlling Chagas' disease, depends on identification of housing features associated with infestation. In this study, log-linear modeling was used to reanalyze data collected in 1964-1968 from 371 houses on characteristics potentially associated with infestation by the vector Triatoma dimidiata in a Costa Rican town with endemic Chagas' disease. A possible increased risk of infestation was observed for houses with a dirt floor (as compared with houses with another floor type) and for houses in poor sanitary condition (as compared with houses in good sanitary condition). A new risk factor for house infestation, the presence of roof tiles, was identified; the odds of infestation for houses with a tile roof were 2.4 times greater than the odds for houses with a galvanized metal roof. This significantly increased risk is probably due to the harboring of T. dimidiata in stacks of spare tiles next to house walls rather than to the tile roofs themselves. Am J Epidemiol 1991 ;133:740-7. epidemiologic methods; housing; insect vectors; risk factors; socioeconomic factors; Triatomidae; Trypanosoma cruzi; trypanosomiasis, South American Chagas' disease (American trypanosomiasis) has been reported from every country in Central and South America, as well as from Mexico, and sporadically from the United States. It adversely affects the health, welfare, and productivity of large groups of people, especially those of low socioeconomic status in agricultural regions (1-3). Recent studies estimate that 19-24 million people are infected with the etiologic agent Trypanosoma cruzi and that about 65 million people are currently exposed (1,4, 5). These represent substantial increases from the 1960 World Health Organization estimates of 7 million and 35 million, respectively (3). This corresponds to a current prevalence of 6-8 percent in Latin America, although prevalence may exceed 40 percent in endemic areas (6, 7). The parasitic protozoan T. cruzi has a
Chagas disease represents a major public health concern in most of Latin America, and its control is currently based on vector control and blood bank screening. We investigated the geographic distribution and seasonal variations in triatomine populations in the Yucatan peninsula of Mexico to obtain entomologic data for the optimization of potential control programs. We collected domiciliated and peri-domiciliated Triatoma dimidiata from 115 houses in 23 villages distributed throughout most of the peninsula. A high abundance of bugs was observed in the northern part of the peninsula, indicating a prioritary area for vector control. Part of this distribution could be attributed to the type of vegetation. We also documented strong seasonal variations in T. dimidiata populations, with a higher abundance during the hot and dry season in April-June. These variations, associated with reduced year-round colonization of houses and the analysis of developmental stage structure, suggest that flying adults seasonally invading houses may play a larger role than domiciliated bugs in transmission of Trypanosoma cruzi to humans. The importance of this transmission dynamics may not be limited to the Yucatan peninsula, but may be a general mechanism contributing to natural transmission that should be taken into account in other regions for the design and optimization of control strategies.
The American journal of tropical medicine and hygiene, 2012
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.
Epidemiological profile of Chagas disease in the southern coast of Ecuador: pilot study of Trypanosoma cruzi infection in the vector Triatoma dimidiata., 2014
Chagas disease is a prevalent and potentially fatal parasitic infection that affects millions of people, especially in Latin America. The causative agent of the disease is the protozoan Trypanosoma cruzi, transmitted mainly by blood-sucking insect vectors of the subfamily Triatominae. The objective of this study was to analyze the infection by Trypanosoma cruzi in the vector Triatoma dimidiata in a rural area of Southern coastal Ecuador. Triatominae searches were carried out in peridomestic habitats of households located in Bajada de Chanduy, a rural village in the border between Santa Elena and Guayas provinces. Feces and intestinal contents were extracted from the insects and observed in the microscope for the presence of mobile trypanosomes. Approximately 72% of the insects analyzed were infected with trypanosomes. This percentage reflects the occurrence of active foci of T. cruzi and the potential risk that this poses for people living in rural villages in the study area. The trypanosomes that were found infecting the triatomine bugs will be molecularly identified and a study of the genetic variability of the population of T. dimidiata collected at the study site will be carried out in the future. The results of all these analyses will provide a better understanding of the epidemiology of Chagas disease in rural Ecuador, which is an essential step in the development of control and prevention strategies for the transmission of this pathogenic parasite.
Avances en Ciencias e Ingeniería, 2014
Chagas disease is a prevalent and potentially fatal parasitic infection that affects millions of people, especially in Latin America. The causative agent of the disease is the protozoan Trypanosoma cruzi, transmitted mainly by blood-sucking insect vectors of the subfamily Triatominae. The objective of this study was to analyze the infection by Trypanosoma cruzi in the vector Triatoma dimidiata in a rural area of Southern coastal Ecuador. Triatominae searches were carried out in peridomestic habitats of households located in Bajada de Chanduy, a rural village in the border between Santa Elena and Guayas provinces. Feces and intestinal contents were extracted from the insects and observed in the microscope for the presence of mobile trypanosomes. Approximately 72% of the insects analyzed were infected with trypanosomes. This percentage reflects the occurrence of active foci of T. cruzi and the potential risk that this poses for people living in rural villages in the study area. The trypanosomes that were found infecting the triatomine bugs will be molecularly identified and a study of the genetic variability of the population of T. dimidiata collected at the study site will be carried out in the future. The results of all these analyses will provide a better understanding of the epidemiology of Chagas disease in rural Ecuador, which is an essential step in the development of control and prevention strategies for the transmission of this pathogenic parasite.
PloS one, 2014
Chagas disease transmission by Triatoma dimidiata persists in Guatemala and elsewhere in Central America under undefined ecological, biological and social (eco-bio-social) conditions. Eco-bio-social risk factors associated with persistent domiciliary infestation were identified by a cross-sectional survey and qualitative participatory methods. Quantitative and qualitative data were generated regarding Trypanosoma cruzi reservoirs and triatomine hosts. Blood meal analysis and infection of insects, dogs and rodents were determined. Based on these data, multimodel inference was used to identify risk factors for domestic infestation with the greatest relative importance (>0.75). Blood meal analysis showed that 64% of 36 bugs fed on chickens, 50% on humans, 17% on dogs; 24% of 34 bugs fed on Rattus rattus and 21% on Mus musculus. Seroprevalence among 80 dogs was 37%. Eight (17%) of 46 M. musculus and three (43%) of seven R. rattus from households with infected triatomines were infecte...
Memorias Do Instituto Oswaldo Cruz, 2002
An entomological and serological survey was performed in three localities of the Department of Concepción, Province of Corrientes, Argentina in 1998 and identify triatomines species involved in domestic and wild transmission of Chagas disease. Triatomines were collected by man/hour capture in 32 houses randomly selected and 44 nearby outdoor ecotopes. Trypanosoma cruzi infection in triatomines was assessed by direct microscopic observation (400x) of feces and polymerase chain reaction. Serological techniques used for people were Indirect Hemagglutination Test and Indirect Fluorescent Test. Triatomines were collected in 28.1% of the houses and 31.8% of the wild biotopes. Triatoma infestans (Klug 1834) was exclusively found indoors and T. cruzi infected 60% of them. Triatoma sordida (Stål 1859) was mainly found in extradomestic ecotopes where trypanosome infection rate reached 12.7%. Serological study of 98 local people showed that 29.6% were seroreactive; most of their houses were closed to wild biotopes colonized by T. sordida.
Acta Tropica, 2007
The relative impact of two community-based vector control strategies on house infestation by Triatoma infestans and Trypanosoma cruzi infection in bugs, domestic dogs and cats was assessed in two neighboring rural areas comprising 40 small villages and 323 houses in one of the regions most endemic for Chagas disease in northern Argentina. The prevalence and abundance of domestic infestation were 1.5-and 6.5-fold higher, respectively, in the area under pulsed, non-supervised control actions operating under the guidelines of the National Vector Control Program (NCVP) than in the area under sustained, supervised surveillance carried out jointly by the UBA research team and NCVP. The prevalence of infestation and infection varied widely among village groups within each area. In the pulsed control area, the prevalence of infection in bugs, dogs and cats was two-to three-fold higher than in the area under sustained surveillance, most of the infected animals qualified as autochthonous cases, and evidence of recent transmission was observed. Infection was highly aggregated at the household level and fell close to the 80/20 rule. Using multiple logistic regression analysis clustered by household, infection in dogs was associated positively and significantly with variables reflecting local exposure to infected T. infestans, thus demonstrating weak performance of the vector surveillance system. For high-risk areas in the Gran Chaco region, interruption of vectormediated domestic transmission of T. cruzi requires residual insecticide spraying that is more intense, of a higher quality and sustained in time, combined with community participation and environmental management measures.