Factors associated with the presence of triatomines in rural areas of south Argentine Chaco

Abstract INTRODUCTION: The domestic and peridomestic presence of Triatoma infestans depends on several factors, such as human behavior, vector behavior, ecology, and the environment. METHODS: This work was conducted in 139 domiciliary units, where triatomines were captured and risk factors in domiciles and peridomicilies were recorded. Household dwellers were interviewed to obtain information about practices regarding this disease and entomological indicators were calculated. RESULTS: Infestation indices were 59.7% for house compounds, 4.3% for domestic areas and 58.3% for the peridomestic areas. Intradomicile infestation was significantly associated with housing characteristics. The presence of chicken coops in peridomicilies was associated with an increased risk of infestation. Of the respondents, 80% did not recognize the importance of the peridomiciliary structures for triatomine control and had infested peridomicilies. CONCLUSIONS: The results show the importance of peridomiciles as refuge sites for Triatominae bugs; however, household dwellers do not perceive peridomiciles as areas that favor the presence of vectors. Actions for raising awareness about factors that favor the presence of triatomines are needed to improve the conditions of peridomiciliary environments.

Effect of feeding frequency on the reproductive efficiency of two species of Triatoma with different epidemiological importance

Introduction In Triatominae, reproductive efficiency is an important factor influencing population dynamics, and a useful parameter in measuring a species' epidemiological significance as a vector of Trypanosoma cruzi (Chagas, 1909). The reproductive efficiency of triatomines is affected by food availability; hence, we measured and compared the effects of feeding frequency on the reproductive parameters of Triatoma patagonica (Del Ponte, 1929) and Triatoma infestans (Klug, 1934), and the effects of starvation on T. patagonica. Methods Couples from both species were fed weekly, or every 3 weeks; in addition, females in couples of T. patagonica were not fed. Each couple was observed weekly and reproductive efficiency was assessed on the following parameters: fecundity (eggs/female), fertility (eggs hatched/eggs laid), initiation and end of oviposition, initiation of mating, number of matings/week, and number of reproductive weeks. Relative meal size index (RMS), blood consumption index (CI), and E values (eggs/mg blood) were also calculated. Results Changes in feeding frequency affected the reproductive parameters of T. patagonica only, with a decrease in fecundity and number of reproductive weeks for those fed every 3 weeks, or not fed. The reproductive period, RMS index, and CI were lower for T. patagonica than T. infestans. However, despite the lower fecundity of T. patagonica, this species required less blood to produce eggs, with an E values of 2 compared to 2.94 for T. infestans. Conclusions Our results suggest that the differences in fecundity observed between species reflect the availability of food in their natural ecotopes. .

Comparison of feeding and defecation patterns between fifth-instar nymphs of Triatoma patagonica (Del Ponte, 1929) and Triatoma infestans (Klug, 1934) under laboratory conditions / Comparação dos padrões alimentar e de defecação em ninfas de quinto estádio de Triatoma patagonica (Del Ponte, 1929) e Triatoma infestans (Klug, 1934), em condições de laboratório

Among the vectors of Chagas disease, Triatoma patagonica is a species in the process of adaptation to the human environment. However, its vector competence is not well known. This study had the aim of evaluating and comparing feeding and defecation patterns among fifth-instar nymphs of Triatoma patagonica and Triatoma infestans that were fed ad libitum. The results showed that nymphs of Triatoma patagonica had a feeding pattern similar to that of Triatoma infestans. Sixty nine percent and 58 percent of nymphs of Triatoma patagonica and Triatoma infestans, respectively, produced their first defecation within five minutes after being fed. Triatoma patagonica defecated during feeding, with an average time until first defecation that was shorter than that of Triatoma infestans (3.4 and 6.2 min, respectively). The nymphs of Triatoma patagonica were capable of defecating during or immediately after feeding.

Entre os vetores da doença de Chagas, Triatoma patagonica é uma espécie que se encontra em processo de adaptação ao ambiente humano; embora sua competência vetorial não seja bem conhecida. O estudo teve como objetivo avaliar e comparar padrões de alimentação e defecação em ninfas de quinto estádio de Triatoma patagonica e Triatoma infestans ad libitum. Os resultados mostraram que as ninfas de Triatoma patagonica apresentou padrõe de alimentação semelhante a Triatoma infestans. Sessenta e nove por cento e 58 por cento das ninfas de Triatoma patagonica e Triatoma infestans respectivamente, realizaram a primeira defecação cinco minutos após de serem alimentadas; sendo que a primeira defecou durante a alimentação, com um tempo médio de dejeção menor do que para Triatoma infestans (3,4 vs 6,2 respectivamente). As ninfas de Triatoma patagonica foram capazes de defecar durante ou imediatamente após de se alimentarem.

Enfermedad de Chagas en Argentina: herramientas para que los escolares vigilen y determinen la presencia de factores de riesgo en sus viviendas / Chagas disease in Argentina: tools for schoolchildren to exercise vector surveillance and identify household risk factors

El objetivo de este trabajo fue validar herramientas para que escolares puedan vigilar sus viviendas. Se desarrollaron dos tipos de planillas, una sobre la presencia de factores de riesgos y otra para registrar la presencia de vinchucas en las viviendas. Estas planillas fueron puestas a prueba en campo por 100 escolares de escuelas de áreas endémicas de Argentina y validadas en campo por personal técnico. Los resultados obtenidos por los escolares sobre porcentajes de viviendas que presentan factores de riesgos y viviendas positivas fueron similares a los obtenidos por el personal técnico. La información recabada permitió a los docentes caracterizar las viviendas como "con mucho riesgo", "de riesgo" o "sin riesgo". Esta información sobre nivel de riesgo de las viviendas puede ser una importante ayuda para los agentes primarios de salud. Por lo tanto, se recomienda incluir estas estrategias educativas en los programas de control, en especial para la fase de vigilancia.

Feeding and defaecation behaviour of Triatoma patagonica (Del Ponte, 1929) (Hemiptera: Reduviidae)

Among the vectors of Chagas disease, Triatoma patagonica is a species in the process of adaptation to the human environment being recently registered in urban and suburban zones. However, its importance as a vector of Chagas disease is unknown. The aim of this work was to evaluate two aspects of vectorial competence: the feeding behaviour and the defaecation pattern. These processes were studied in females of T. patagonica fed ad libitum on a restrained pigeon. The results showed that the blood meal size was negatively correlated with the time of first defaecation (r = -0.42). The first defaecation was emitted before the first 10 min and defaecations during feeding were frequent. A total of 73 percent of females, defaecated during the first 30 min post-feeding. These results suggest that if this species subsequently colonizes the domicile, it would be capable of transmitting Trypanosoma cruzi

Conocimientos sobre la enfermedad de Chagas y factores de riesgo en comunidades epidemiologicamente diferentes de Argentina / Extent of knowledge of Chagas' disease and its risk factors in Argentine communities showing different epidemiologic trends

Actualmente, el control de la enfermedad de Chagas se basa en acciones químicas contra la vinchuca. Sin embargo, existen factores de riesgo como la falta de higiene y el desorden que serían responsables de la persistencia de focos de triatominos. Teniendo en cuenta que las comunidades expuestas al riesgo de contraer la enfermedad poseen escasos conocimientos sobre ella, se definió el nivel óptimo de conocimientos y se determinó el nivel medio de conocimientos de los habitantes de dos zonas epidemiológicamente diferentes de Argentina y se identificaron los factores de riesgo presentes en ambas. El nivel óptimo de conocimientos se definió por 25 "nociones elementales" sobre la enfermedad, a partir de las cuales se elaboraron los cuestionarios para evaluar el nivel medio de conocimientos. Los resultados obtenidos reflejaron un predominio de los factores de riesgo relacionados con la construcción de las viviendas y el desorden, y un limitado nivel de conocimientos sobre la enfermedad. Resultó deficiente el conocimiento de información básica sobre la enfermedad, relacionada, por ejemplo, con el reconocimiento de las ninfas y el mecanismo de transmisión. Un mejor conocimiento del tema supondría un importante avance en la lucha contra la enfermedad de Chagas, conduciendo a los habitantes de áreas endémicas a una mejor comprensión de su realidad y a la adquisición de hábitos que les permitan ser los protagonistas de su propio bienestar

Currently, Chagas' disease control consists mainly of chemical warfare against the insect vector. However, a number of risk factors, such as poor hygiene and clutter, can facilitate the persistence of triatomine breeding sites. Relying on the premise that communities at risk of Chagas have little knowledge about the disease, the authors defined the extent of knowledge that is considered optimal and determined how much is known, on average, by the inhabitants of two areas in Argentina showing different epidemiologic trends. Risk factors in both areas were identified. The optimal extent of knowledge was defined in accordance with 25 "basic concepts" surrounding the disease, and from these questionnaires were constructed for evaluating average knowledge about the disease. Results obtained showed that risk factors were linked primarily with the type of dwelling construction and with clutter, as well as with limited knowledge about the disease. There was little basic knowledge about Chagas, with an inability, for example, to identify the vector and describe the mode of transmission. Increasing people's knowledge about the disease would be an important step in the fight against Chagas and would give the inhabitants of endemic areas a better understanding of their situation as well as the chance to develop behaviors that would allow them to assume responsibility for their own welfare.

Temperature effect upon blood consumption in Triatoma infestans

Different blood consumption speed was observed in Triatoma infestans - nymphs and adults - exposed to 12 degrees C and 28 degrees C. Exposure to optimal temperature (28 degrees C) allows the insects to consume blood at a rate of 9% per day. Significative relationship between blood amount present in the promesenteron and consumed blood was found at 28 degrees. Consumption of blood was drastically reduced at the lowest temperature. Accordingly, lack of ovaric development, oviposition and mating behaviour was observed in insects kept at 12 degrees C. Relationship between laboratory and field observations are discussed