Infestação domiciliária em grau extremo por Triatoma infestans

Abstract

Uma pequena cafua com 4 dependências e sòmente um quarto de dormir, com uma área de 60 [metros quadrados] de paredes internas, construída em 1949, foi reconhecida desde 1951 como uma das mais infestadas por triatomas, no Município de Bambuí. De outrubro a dezembro de 1951 foram nela capturados, por meio de 26 expurgos com pós de pirêtro, 2 505 exemplares de T. infestans e 3 de P. megistus. Em dezembro de 1951 foram recolhidos pelo mesmo processo, em 5 dias seguidos, mais de 4 645 T. infestans e 1 P. megistus. A cafua foi demolida em janeiro de 1955, tendo sido capturados ainda 1 398 T. infestans, perfazendo-se assim, um total de 8 552 barbeiros apanhados em uma única cafua! Observou-se uma baixa das percentagens de infecção de T. infestans por S. cruzi, que de 37,7% em 1951, caiu para 6,5% em 154. Nos indivíduos adultos ela baixou de 61,5% para 9,4%, nas ninfas de 33,3% para 3,5%, diferenças essas que se mostraram estatisticamente significativas. Todos os 6 moradores eram portadores de doença de Chagas; a reação de fixação do complemento foi positiva em todos e o xenodiagnóstico em 4 dêles. O hemograma, feito em 5 dêsses indivíduos, revelou graus variáveis de anemia. Sòmente o chefe da família, um homem de 49 anos, era caso de cardiopatia chagásica crônica, apresentando bloqueio completo de ramo direito. O último filho do casal faleceu aos 14 meses com edema generalizado, sendo possìvelmente um caso de esquizotripanose aguda, embora um único exame a fresco tenha sido negativo, pouco antes da morte.<br>A small mud hut, which was built by its owners in 1949, was known, since 1951, to be one of the houses most heavily populated by triatomid or cone-nosed bugs in Bambuí. A total of 2 505 individuals, belonging to the species Triatoma infestans, were collected there from October to December, 1951, in 26 applications of pyrethrum powders into the holes of the walls. Three years later, in December, 1954 no less than 4 645 bugs were collected the same way, in five consecutive days. The hut was destroyed in January 13, 1955 when 1 398 additional insects were collected. Then, a total of 8 548 specimens of Triatoma infestans were captured in this single house, while only 4 P. megistus were captured. It has been observed that the proportion of bugs naturally infected with S. cruzi decreased from 37,7 per cent in 1951 to 6,5 per cent in 1954. The percentage of infected adult individuals dropped from 61,5 to 9,4 and "nymphs" it dropped from 33,3 to 3,5 in respectively 1951 and 1954. These differences were found to be statistically significant. All the six people inhabiting this hut exhibited a positive complement-fixation test (S. cruzi culture antigen) and xenodiagnosis was positive in 4 of them. Haemograms taken from 5 of them showed varying degrees of anaemia. The head of the family, 49 years old, was a Chagas' disease case with right bundle-branch block, while the electrocardiogram was normal in the other people. The las-born child of the couple died at the age of 14 months with fever and oedema, so it was possibly a case ...

Effects of refuge availability on the population dynamics of Triatoma infestans in central Argentina

“…The population abundance of T. infestans fluctuated seasonally, with only one annual peak in summer closely correlated with temperature fluctuations. This pattern, also observed in rural houses (table 3 in Dias & Zeledón 1955; Schofield 1980; Schofield & Marsden 1982) and experimental chicken houses under natural climatic conditions (Gorla & Schofield 1985, 1989; Gorla 1991), differs from predictions of a mathematical model of T. infestans population dynamics showing two peaks per year (Rabinovich & Himschoot 1990). Our data also show two peaks of adult emergence of differing intensity, and peak numbers of eggs per female lagging by 1 month in maximum and intermediate refuge huts.…”

“…Nearly 16 000 live bugs were recorded in the maximum refuge control hut after 2 years, which sets a record for the bug carrying capacity of a single chicken in a small closed hut or of any triatomine‐infested house (Dias & Zeledón 1955; Zeledón & Rabinovich 1981). This also suggests that the replicate huts were far from any equilibrium abundance.…”

Differences in competitive ability for the occupancy of shelters in triatomines

“…During the past century, T. infestans seems to have progressively displaced P. megistus , which was formerly the most abundant species in human dwellings in central and eastern Brazil (Pereira et al ., ). There have been reports of the coexistence of T. infestans and P. megistus in Brazil (Dias, ; Dias & Zeledon, ), but in all cases T. infestans presented higher densities. As T. infestans continued its spread to northern Brazil, it managed to displace other triatomine species from human dwellings, such as T. sordida (Schofield, ), Triatoma brasiliensis (Neiva 1911) and Triatoma pseudomaculata (Correa & Espínola 1964) (Silveira et al ., ).…”

“…Fifth instar nymphs and adults of T. infestans have been found mostly around different materials near roofs, whereas less developed nymphal stages occupy shelters around the beds and belongings of human residents (Gürtler et al ., ). Inside dwellings in which roofs were made of thatch, tile or other materials that offer less adequate spaces for triatomines, all developmental instars of T. infestans were found mainly inside wall cracks (Dias & Zeledon, ), demonstrating that all five nymphal stages and adults can be found inside the same restricted area and may share the same shelter. Furthermore, this species also shows preferences for wall shelters located near the floor, even in experimental environments, which indicates the importance of proximity to the food source (Bar et al ., ).…”

Dynamics of transmission of Trypanosoma cruzi in a rural area of Argentina: III. Persistence of T. cruzi parasitemia among canine reservoirs in a two-year follow-up

“…While this study and a pioneering one of PREI-TAS 4 have shown overwhelmingly similar percentages of infected bugs fed upon parasitemic dogs (65 vs 71%), wider cross-sectional surveys of human populations have shown that people with parasitemia infect on the average from 20-30% of T. infestans 5th instar nymps 7 -9 to 60% 4 . Interestingly enough, during a parasitological follow-up of a seroreactive family, only 5% of infected xenodiagnosis bugs were obtained 3 . On the other hand, presumably chronic human subjects selected for xenodiagnosis trials have been informed to infect variable percentages of T. infestans nymphs, ranging from 3% (3rd instar) 2 to 26-44% (5th instar) ».…”