We report the first finding of Lymnaea viatrix south of parallel 41ºS, in rural and urban areas from Argentina. Ninety snails were collected during year 2000, from a concrete pond at a Public Square in El Bolsón Village, Río Negro province, and 811 snails in November 1999, and during 2000 from waterbodies within a farm at Cholila locality, Chubut province. Fasciola hepatica infection was detected in 0.9% snails from the rural area. We discuss the potential risk of L. viatrix to public health in urban areas and its epidemiological importance in rural areas of the Andean Patagonian region.

This study aimed at identifying the ecological characteristics of Triatoma patagonica Del Ponte 1929 (Hemiptera: Reduviidae) and evaluating the epidemiological importance of this species at its southernmost distribution limit. We carried out two surveys in the Province of Chubut, in summer and in spring, 1998. In each survey, we interviewed local health care agents for triatomine recognition and reports of the bugs, followed by entomological searches in houses and peridomestic and silvatic biotopes. The presence of T. patagonica was confirmed in two of the five localities indicated by interview. In agreement with previous studies, all these positive localities were east of the 11°C isotherm, within the Monte phytogeographic province. Triatomine abundance and infestation levels (in peridomiciles and peridomestic biotopes) were higher in summer than in spring, possibly reflecting adverse environmental conditions such as flood and cold winter weather. In the silvatic environment, we found three adult bugs under rocks in summer. In peridomestic sites bugs were only found associated with chickens, which were also the only blood meal source identified. Infection by Trypanosoma cruzi was not detected. We conclude that T. patagonica at its southernmost distribution limit does not represent a risk to public health due to its low abundance, lack of association with humans, and absence of T. cruzi infection.

We report the first evidence of natural infection of Lymnaea columella with Fasciola hepatica in Argentina. A sample of 601 snails was collected in May 2003 in northeastern Corrientes, a province bounded on the north by Paraguay, on the east by Brazil and on the southeast by Uruguay. Among 500 examined snails, 44 (8.8%) were exclusively infected with F. hepatica. Parasite identification was based on morphological features of cercariae from snails, and of eggs and adult flukes from Wistar rats. We discuss the events suggesting that an enzootic transmission cycle of F. hepatica has been recently established in northeastern Corrientes.

Triatoma guasayana is a silvatic triatomine species distributed in Argentina, Bolivia and Paraguay. The study was performed in a secondary forest of Santiago del Estero, Argentina. The abundance of T. guasayana was evaluated by census in the following wild biotopes: quimiles (Opuntia quimilo), chaguares (dry bromeliads), logs and underground burrows. Ten biotopes of each type were dismantled in winter (August) and another 40 in summer (January); all fauna was recorded. The biotopes most infested by T. guasayana were quimiles (65%), followed by chaguares (55%), and logs (25%). Quimiles and chaguares were infested in both seasons, whereas logs were positive only in summer and burrows were never infested. Infestation and abundance were higher in summer than in winter. The biotope structure is a key factor for T. guasayana colonization. The larger number of refuges, the constant presence of blood sources and suitable inner microclimatic conditions offered by quimiles may favour the persistence of T. guasayana colonies. The richness of invertebrate fauna per type of biotope was ranked in the same order as that of T. guasayana, suggesting similar microhabitat requirements for all studied arthropods.

The opossum of the genus Didelphis is one of the principal wild reservoirs of Trypanosoma cruzi and is widely distributed in the Western Hemisphere. Didelphis albiventris is the most common marsupial in Amamá and Trinidad, two communities in the province of Santiago del Estero, Argentina. The D. albiventris population is replaced every year, and the opossum normally has two reproductive periods, one at the beginning of the spring and another at the beginning of the summer. The two litters are weaned, and they leave the mother's marsupial pouch to join the population, the first (G1) at the beginning of the summer and the second (G2) at the beginning of the fall. Between 1988 and 1991 409 D. albiventris opossums were studied, and xenodiagnoses showed that 35% of them were infected with T. cruzi. Annual cycles of renewed infection were observed, with prevalences that ranged between 22% and 43%. The acquisition of the parasite occurred over the entire year, from the summer through the spring. The prevalence of infection increased with age. The G1 individuals tended to present higher prevalences than the G2 individuals, probably from being exposed to transmission for a longer period of time. In the first two (younger) age categories for the opossums, G2 individuals showed higher prevalences than did the G1 individuals. This indicates a significant increase in transmission intensity during the fall. Opossums should be regarded as a potential source of T. cruzi entry to the domestic transmission cycle.

Entre los principales reservorios silvestres de Trypanosoma cruzi se encuentran las zarigüeyas del género Didelphis, ampliamente distribuidas por el continente americano. En Amamá y Trinidad, Provincia de Santiago del Estero, Argentina, Didelphis albiventris es el marsupial más frecuente. Su población se renueva cada año y normalmente hay dos períodos reproductivos: uno a principios de la primavera y otro a principios del verano. Estas dos camadas son destetadas y abandonan la bolsa marsupial para incorporarse a la población, la primera (G1) a principios del verano y la segunda (G2) a principios del otoño. Entre 1988 y 1991 se estudiaron 409 individuos distintos de D. albiventris y los xenodiagnósticos revelaron que 35% de ellos estaban infectados por T. cruzi. Se observaron ciclos de renovación anual de la infección con prevalencias que oscilaron entre 22 y 43%. La adquisición del parásito ocurría a lo largo de todo el año, desde el verano hasta la primavera. La prevalencia de la infección aumentó con la edad. Los individuos G1 tuvieron tendencia a presentar mayores prevalencias que los G2, probablemente debido a un mayor tiempo de exposición a la transmisión. En las dos primeras categorías de edad, los individuos G2 mostraron mayores prevalencias que los G1, lo cual indica un aumento significativo de la intensidad de la transmisión durante el otoño. Las zarigüeyas deberían considerarse como una fuente potencial de ingreso de T. cruzi al ciclo doméstico.

This paper attempts to prove if a high Trypanosoma cruzi prevalence of opossums might be reached with few potential infective contacts. One non-infected Didelphis albiventris to T. cruzi and 10 infected nymphs of Triatoma infestans were left together during 23 hr in a device that simulated a natural opossum burrow. Twenty-six replicates were perfomed using marsupials and triatomines only once. Potentially infective contacts occurred in all the trials. From the 26 opossums used in trials, 54% did not eat any bug. Of the 260 bugs used, 21% were predated. In the 25 trials involving 205 surving bugs, 36 % of them did not feed. In 15/25 cases, maior ou igual a 60% of the triatomines were able to feed. The parasitological follow-up of 24 opossums showed that among 10 that had eaten bugs, 4 turned out infected and among the 14 that had not predate, 3 (21%) became positive. In sum, 7/24 (29%) of the marsupials acquired the infection after the experiment. This infection rate was similar to the prevalences found for the opossum population of Santiago del Estero, Argentina, suggesting that the prevalences observed in the field might be reached if each marsupial would encounter infected bugs just once in its lifetime.

This paper compares the predation pressure that ducks and chickens exert on triatomines. For the tests, these birds were placed in individual boxes together with a known number of Triatoma infestans and left to interact from 6 p.m. till the next morning, involving a long lasting period of complete darkness limited by two short-term periods of semi-darkness. There was a shelter which could prevent the bugs from being predated. The number of live and dead triatomines was recorded, considering missing bugs as predated by the birds. Ducks exhibited a greater predatory activity than chickens, that could be due to a long term active period at night while chickens sleep motionless from sunset to dawn. Surviving triatomines that had fed on chickens outnumbered those fed on ducks suggesting that these were less accessible to the triatomine biting. If ducks are better than chickens to detect and eat bugs and to interfere with their feeding in the field, an increase in duck number might help to diminish triatomine density. Further research is needed to determine the feasibility of application of these experimental results.

Determinou-se a associação entre Triatoma infestans, aves domésticas e o homem no povoado de Trinidad, Santiago del Estero, Argentina. Para coletar triatomíneos foram realizadas quatro amostragens no peridomicílio de seis casas, utilizando-se o método de captura hora/homem (dezembro de 1991 a outubro de 1992). Os anexos foram classificados em antrópicos (onde o homem realiza atividades cotidianas) e não-antrópicos. Além disso, determinou-se o perfil alimentar dos barbeiros. De um total de 134 ecótopos investigados, 21% tinham T. infestans; 22% possuíam aves domésticas; e 54% eram antrópicos. Em 25% destes ecótopos foram encontradas aves e T. infestans simultaneamente. As aves foram os únicos animais domésticos associados com o T. infestans, sendo que esta relação só ocorreu nos ecótopos antrópicos. A proporção de ingestas em aves (61/146) foi altamente significativa. Em Trinidad não há galinheiros, utilizando-se, assim, os anexos entrópicos do peridomicílio como local para se construir os ninhos para as aves. tanto pelos elementos usados na preparação dos ninhos como pelo uso posterior dos mesmos, poder-se-ia estabelecer um fluxo periódico de barbeiros do intradomicílio para o peridomicílio, e vice-versa, através do transporte passivo. Esta relação estreita entre Triatoma infestans, aves domésticas e o homem, encontrada nos ecótopos antrópicos, onde também existem outros reservatórios de T. cruzi, como os cães, favorece a manutenção de colônias de barbeiros domiciliares e a transmissão da doença de Chagas ao homem.

An association was determined between Triatona infestans, poultry, and humans in Trinidad, in the Province of Santiago del Estero, Argentina. To collect triatomines, four samples were taken at the area immediately surrounding six houses by the one hour/man capture method (December 1991 - October 1992). Peridomiciliary ecotopes were classified as arthropic (where humans carry out daily activities) or non-anthropic. Tratomine feeding habits were also determined. Of 134 biotopes, 21% had T. infestans, 22% had poultry, and 54% were anthropic. Some 25% of the latter harboured both poultry and T. infestans. Poultry were the only domestic animals associated with T. infestans, a finding that was exclusive to anthropic ecotopes. The proportion of feedings on individual fowl (61/146) was highly significant. Chicken coops are not used in Trinidad, and poultry brood in anthropic structures. Due to the materials used for making their nests and their repeated use, a periodic bug flow can be established from the intra- to the peridomiciliary area and vice versa, through passive transport. The close relationship among T, infestans, poultry, and humans in anthropic biotopes where other T. cruzi reservoirs such as dogs are also present contributes to the maintenance of domestic triatomine colonies and transmission of Chagas' disease to humans.

Determinou-se a associação entre Triatoma infestans, aves domésticas e o homem no povoado de Trinidad, Santiago del Estero, Argentina. Para coletar triatomíneos foram realizadas quatro amostragens no peridomicílio de seis casas, utilizando-se o método de captura hora/homem (dezembro de 1991 a outubro de 1992). Os anexos foram classificados em antrópicos (onde o homem realiza atividades cotidianas) e não-antrópicos. Além disso, determinou-se o perfil alimentar dos barbeiros. De um total de 134 ecótopos investigados, 21% tinham T. infestans; 22% possuíam aves domésticas; e 54% eram antrópicos. Em 25% destes ecótopos foram encontradas aves e T. infestans simultaneamente. As aves foram os únicos animais domésticos associados com o T. infestans, sendo que esta relação só ocorreu nos ecótopos antrópicos. A proporção de ingestas em aves (61/146) foi altamente significativa. Em Trinidad não há galinheiros, utilizando-se, assim, os anexos entrópicos do peridomicílio como local para se construir os ninhos para as aves. tanto pelos elementos usados na preparação dos ninhos como pelo uso posterior dos mesmos, poder-se-ia estabelecer um fluxo periódico de barbeiros do intradomicílio para o peridomicílio, e vice-versa, através do transporte passivo. Esta relação estreita entre Triatoma infestans, aves domésticas e o homem, encontrada nos ecótopos antrópicos, onde também existem outros reservatórios de T. cruzi, como os cães, favorece a manutenção de colônias de barbeiros domiciliares e a transmissão da doença de Chagas ao homem.

An association was determined between Triatona infestans, poultry, and humans in Trinidad, in the Province of Santiago del Estero, Argentina. To collect triatomines, four samples were taken at the area immediately surrounding six houses by the one hour/man capture method (December 1991 - October 1992). Peridomiciliary ecotopes were classified as arthropic (where humans carry out daily activities) or non-anthropic. Tratomine feeding habits were also determined. Of 134 biotopes, 21% had T. infestans, 22% had poultry, and 54% were anthropic. Some 25% of the latter harboured both poultry and T. infestans. Poultry were the only domestic animals associated with T. infestans, a finding that was exclusive to anthropic ecotopes. The proportion of feedings on individual fowl (61/146) was highly significant. Chicken coops are not used in Trinidad, and poultry brood in anthropic structures. Due to the materials used for making their nests and their repeated use, a periodic bug flow can be established from the intra- to the peridomiciliary area and vice versa, through passive transport. The close relationship among T, infestans, poultry, and humans in anthropic biotopes where other T. cruzi reservoirs such as dogs are also present contributes to the maintenance of domestic triatomine colonies and transmission of Chagas' disease to humans.

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.

To identify wild hosts of Trypanosoma cruzi, surveys were conducted in the subandean valleys of Jujuy Province, Argentina, between June 1986 and March 1987. Seventy two mammals from 13 different species were examined by xenodiagnosis. Fifty two of them were mostly roedents trapped at the localities of Maimará, León and Tilcara, and the remainder had been kept in captivity at the Estación Biológica Experimental, in Jujuy. Trypanosoma cruzi infection was detected only in 2 Octodontomys gliroides (2 pos./8 exam. 25%) from all 72 examined mammals. Isolates were called Octodontomys Argentina 1 and 2 (OA1 and OA2). Both infected animals were caught at the archaelogical ruin of Pucará, at Tilcara. Repeated searches for triatomines in the ruin itself and in neighbour houses rendered negative results. Groups of mice inoculated with either OA1 or OA2 isolates became infected between 7 (OA1) to 12 days (OA2) postinoculation PI. Parasitemia peaks were observed between day 12th - 14th PI. Scarce amastigote nests were found in myocardium and skeletal muscle. Mortality was observed only for mice inoculated with OA1. Isoenzyme patterns of OA1 and OA2 were identical to one found in dogs and slightly different from that of human parasites in Argentina. Bones from Octodontomys sp., were recently found in a cave, dated 10200-8600 BC, in Pumamarca, near Tilcara, Jujuy. There are evidences that O. gliroides cohabited with man in ancient times and was associated to the domestic cycle of T. cruzi transmission, playing a role like that of domestic cavies. in Bolivia.