Flight activity and invasion of houses by Triatoma sordida and T. guasayana were studied in the Province of Santiago del Estero, Argentina. Spontaneous findings of both species in houses were recorded from 1982 to 1989. Light trap collections were performed in 1982, 1983 and 1984, at the woods surrounding the settlements of Amamá (43 houses) and Trinidad (19 houses). Most of the 101 triatomines collected, were unfed and negative for Trypanosoma cruzi. T. guasayana predominated over T. sordida, and both appeared on the lighted screens between 19-31 min (mean 24) after dusk and the catch time was 30-45 min. Although entomological evaluation of 41 houses at Amamá performed in September 1985, just before insecticidal spraying, showed that Triatoma infestans predominated, adults of T. guasayana were collected in sleeping places, in 7 houses (17%). Most triatomines invading houses from then up to 1990 were flying T. guasayana (20/27) and females outnumbered males. Three non infected T. guasayana females were fed on man and two T. guasayana males positive for "T. cruzi like" trypanosomes were unfed. Therefore, visiting hungry adults could transmit T. cruzi to people and introduce wild parasites to the domestic cycle. T. guasayana stands as the main potential substitute of T. infestans in the studied area, and it might play there the same role as T. sordida in Brazil.

Entomological aspects of an ecological study on domestic T. cruzi transmission carried out in a rural community of Argentina are described. T. cruzi infection rates an d the feeding profiles of domiciliary T. infestans were determined, and bug density was related to house construction. Six of 18 houses studied were new and reformed while 16 households hexachlorocyclohexane (HCH) had been used by the inmates. The lowest bug densities were found in new houses or those receiving good, insecticide treatment. Insecticide treated units had an a verage number of bugs 10 times lower(3.1 bugs/man-hour) than thosefound in a non treated ones indicating the effectiveness of selfp romoted control. A ll bedrooms but only 53% o f peridomestic structures harboured bugs. T. cruzi infection was detected in 39% of domiciliary. T. infestans 96% of the domiciliary bugs (9 6% ) f e d on man, dog, chicken and cat. The affinity index fo r dog was 13 times higher than that for man. The importance of the high density of T. infestans bugs in bedrooms and their close association with "roommate ” dogs is discussed in relation to transmission as well as the need to combine house improvement and health education programmes.

Se describen los resultados entomológicos de un estúdio sobre transmiswn del Tripanosoma cruzi realizado en un caserío rural de Argentina. Se determino la prevalencia de infección elperfil alimentario de los Triatoma infestans domiciliados, relacionándose su densidad con el tipo de vivienda. Seis de las 18 viviendas estudiadas eran nuevas o mejoradas y en 16 los habitantes aplicaban hexaclorociclohexano. La menor densidad de vinchucas correspondió a las casas higiénicas o mejoradas con tratamiento químico, Los ranchos tratados presentaron un número de insectos 10 veces menor que un rancho no tratado, indicando la efectividad del control autogestado. Se hallaron T. infestans en el 100% de los dormitorios pero en sólo el 53% de los localesperidomiciliarios. Un 39% de las vinchucas intradomiciliarias estaban infectadas. El 96% de los insectos de dormitorios se alimentaron sobre hombre, perro, polloygato, siendo el índice afinidad para el perro 13 veces superior al correspondiente al hombre. Se discute la importancia epidemiológica de la concentración de vectores dentro de los dormitorios y su asociación trófica con los perros convivientes, nsí como la necessidad de combinar la mejora de vivienda con educación sanitaria.

Foi determinada a prevalência da infecção por T. cruzi nos humanos, cães e gatos, pertencentes a 47 rancherías em três povoados rurais; Guanaco Muerto (Córdoba), La Invernada e Amamás (Santiago del Estero), mediante reações seroldgicas e xenodiagnóstico. Poram examinadas 245 pessoas, 123 cães e 14 gatos. A taxa de prevalência na população foi entre 58,7% (GM) e 49,6% (LI). Foram detectados 76% de cães infectados, o que resultou significativamente superior aos 51% encontrados nos humanos. As porcentagens de cães (64,2%) e gatos (63,6%) com parasitemia foram significativamente superiores à correspondente aos humanos (12,5%). Se bem que 79% dos gatos estavam infectados, sua pequena quantidade e seus hábitos de perambulação determinam que sua participação na transmissão doméstica do T. cruzi seja restrita. Não obstante existir em média um maior número de humanos que de cães em cada lar, tanto de sujeitos sãos como infectados (6,5 vs. 3,3 e 3,4 vs. 2,4, respectivamente), foram detectados — também na média — mais cães que humanos com parasitemia em cada casa (2,1 vs. 1,0). As altas porcentagens de cães infectados e com parasitemia, além do hábito de repouso intra-domiciliário — o qual ocasiona estreito contacto entre eles e os barbeiros — determinam que os cães sejam os principais provedores de parásitos à disposição para a transmissão, e os hospedeiros mais importantes para /nanutenção da doença de Chagas na Região do Chaco Argentino.

Trypanosoma cruzi prevalence rates of human, dog and cat populations from 47 households of 3 rural localities of the phytogeographical Chaqueña area of Argentina were determined both by serological and xenodiagnostic procedures. Human prevalence rates were uniform and ranged from 49.6 to 58.7%. Overall prevalence rate in dogs (75.0%) was significantly higher than in humans (51.0%). The overall proportion of parasitemic individuals assessed by xenodiagnosis was significantly higher in either dog (64.2%) or cat (63.6%) populations than among humans (12.5%). Although both the average number of resident as well as infected individuals per household was higher for people than for dogs (6.5 vs. 3.3, and 3.4 vs. 2.4, respectively), the reverse was recorded when parasitemic individuals were considered (1.0 vs. 2.1). Results are discussed in relation to dog between dogs and people, and dogs and bugs. In the light of present data, dogs must be considered as the major donors of parasites to vector bugs and thus, principal contributors to transmission in this region of Argentina.