Community-based surveillance and control of chagas disease vectors in remote rural areas of the Argentine Chaco: A five-year follow-up.

Prevention of Chagas disease vector-borne transmission mostly relies on the residual application of pyrethroid insecticide. Persistent or recurrent house infestation after insecticide spraying remains a serious challenge in remote, resource-poor rural areas where public health services face substantial constraints. Here we use generalized estimating equations and multimodel inference to model the fine-scale, time-lagged effects of a community-based vector surveillance-and-response strategy on house infestation and abundance of Triatoma infestans in four rural communities of the Argentine Chaco over a five-year period. Householders and community leaders were trained to detect triatomines and spray with insecticides their premises if infested. House infestation and vector abundance were consistently higher in peridomestic habitats than in human habitations (domiciles). Householders supplemented with sensor boxes detected infested domiciles (67%) more frequently than timed-manual searches (49%). Of all houses ever found to be infested by timed-manual searches, 76% were sprayed within six months upon detection. Domestic triatomine abundance was significantly related to house-level insecticide spraying during the previous year (inversely) and current peridomestic abundance (positively). Peridomestic triatomine abundance significantly increased with current domestic bug abundance and maximum peridomestic abundance during the previous year, and was unaffected by insecticide spraying. Our study provides new empirical evidence of the interconnection and flow between domestic and peridomestic populations of T. infestans under recurrent insecticide treatments, and supports targeting both habitats with appropriate tactics for longer-lasting, improved vector control. Community-directed efforts succeeded in controlling domestic infestations and interrupting domestic transmission, whereas persistent peridomestic infestations demand sustained control efforts to address domestic reinvasions.

Chagas disease vector control and Taylor's law.

BACKGROUND: Large spatial and temporal fluctuations in the population density of living organisms have profound consequences for biodiversity conservation, food production, pest control and disease control, especially vector-borne disease control. Chagas disease vector control based on insecticide spraying could benefit from improved concepts and methods to deal with spatial variations in vector population density. METHODOLOGY/PRINCIPAL FINDINGS: We show that Taylor's law (TL) of fluctuation scaling describes accurately the mean and variance over space of relative abundance, by habitat, of four insect vectors of Chagas disease (Triatoma infestans, Triatoma guasayana, Triatoma garciabesi and Triatoma sordida) in 33,908 searches of people's dwellings and associated habitats in 79 field surveys in four districts in the Argentine Chaco region, before and after insecticide spraying. As TL predicts, the logarithm of the sample variance of bug relative abundance closely approximates a linear function of the logarithm of the sample mean of abundance in different habitats. Slopes of TL indicate spatial aggregation or variation in habitat suitability. Predictions of new mathematical models of the effect of vector control measures on TL agree overall with field data before and after community-wide spraying of insecticide. CONCLUSIONS/SIGNIFICANCE: A spatial Taylor's law identifies key habitats with high average infestation and spatially highly variable infestation, providing a new instrument for the control and elimination of the vectors of a major human disease.

A prospective study of the effects of sustained vector surveillance following community-wide insecticide application on Trypanosoma cruzi infection of dogs and cats in rural Northwestern Argentina.

Domestic dogs were used as natural sentinels to assess prospectively the long-term impact of selective, community-based spraying with pyrethroid insecticides after community-wide spraying on transmission of Trypanosoma cruzi in rural villages under surveillance between 1992 and 2002. In 2000 and 2002 light infestations by Triatoma infestans were recorded, and 523 dogs and cats were examined serologically or by xenodiagnosis. The prevalence of T. cruzi infection in dogs decreased from 65% at baseline to 8.9% and 4.7% at 7.5 and 10 years after sustained vector surveillance, respectively. The average annual force of infection dropped 260-fold from 72.7 per 100 dog-years at baseline to <0.3% in 2002, as determined prospectively and retrospectively from the age-prevalence curve of native dogs born during surveillance. Multiple logistic regression analysis showed that prevalent cases in dogs in 2000 and 2002 were associated positively and significantly with the peak number of T. infestans caught in domestic areas at the dog's compound during its lifetime. The sustained decline in T. cruzi infections in dogs and cats is the result of selective, community-based insecticide spraying that kept the abundance of infected T. infestans at marginal levels, fast host population turnover, and low immigration rates from areas with active transmission.

Incidence of trypanosoma cruzi infection among children following domestic reinfestation after insecticide spraying in rural northwestern Argentina.

Following increasing reinfestation with Triatoma infestans after insecticide spraying, the household incidence of infection with Trypanosoma cruzi in children was positively related to the domestic abundance of infected T. infestans and the presence or proportion of infected dogs or cats in Amamá, a rural village in northwestern Argentina. Seven (12.1%) children seronegative for antibodies to T. cruzi at baseline, with no history of travel or blood transfusion, seroconverted after three years. Six incident cases lived in houses heavily infested with T. infestans, with high proportions of bugs infected with T. cruzi and having fed on humans or dogs. The remaining incident case occurred under a very light domestic infestation detected only at the endpoint, and most bugs had fed on humans. Dogs had a 17 times greater force of infection than children (4.3% per year). Sustained vector surveillance is crucially needed in high-risk areas for Chagas disease such as the Gran Chaco.

Spatiotemporal patterns of reinfestation by Triatoma guasayana (Hemiptera: Reduviidae) in a rural community of northwestern Argentina.

Triatoma guasayana (Wygodzinsky & Abalos) is a secondary vector of Trypanosoma cruzi (Chagas), the etiologic agent of Chagas disease, in the Chaco region of Argentina, Bolivia, and Paraguay. The spatial distribution of T. guasayana in a rural community in northwestern Argentina is described and analyzed using very high spatial resolution satellite imagery, geographic information systems, and spatial statistics. Since a 1992 residual spraying with insecticides of all houses, site-specific domestic and peridomestic reinfestations by triatomine bugs were monitored using various methods semiannually from 1993 to 2002. The reinfestation by T. guasayana started with finding of only adult bugs in a few sites. Bug abundance was significantly clustered and predominantly peridomestic in the southern and northern extremes of the community. The identified source of reinfestation in the northern cluster was a colonized wood pile, whereas no potential peridomestic source was found for the southern cluster. The spatial distribution of T. guasayana was positively associated with the abundance and spatial distribution of goats. Active dispersal from the hypothesized source and the surrounding sylvatic environment, and passive transport of bugs in wood piles seems to be the most likely mechanisms underlying the observed spatial pattern of T. guasayana. The absence of domestic colonization indicates that, to date, there is no trend toward increased local domiciliation of T. guasayana. The clustering zones can be considered "hot spots" where bug invasion from other sources is expected to be higher and where eventually, introduction of sylvatic T. cruzi to suitable hosts may occur.

Spatio-temporal analysis of reinfestation by Triatoma infestans (Hemiptera: Reduviidae) following insecticide spraying in a rural community in northwestern Argentina.

The spatio-temporal reinfestation patterns by Triatoma infestans following a blanket insecticide spraying in the rural community of Amama in northwestern Argentina were analyzed using a geographic information system, satellite imagery, and spatial statistics. Domestic and peridomestic reinfestation by triatomine bugs was monitored from 1993 to 1997. Triatoma infestans was detected at least once in 75% of 2,110 sites evaluated. The prevalence of sites positive at least once for T. infestans during the study period increased sharply from 1993-1995 (0.6-2.9%) to November 1997 (32%). The initial source of T. infestans was a pig corral in southern Amama one year post-spraying. Subsequent infestations were clustered around this initial focus at a distance of approximately 400 meters starting in 1995. In 1996, clustering was maximized in sites within the same or in neighboring compounds at distances of 25-175 meters. An effective control program on the community level will be based on the spraying of actual epicenters and sites within 450 meters of these epicenters to prevent the propagation of T. infestans.

Domestic animal hosts strongly influence human-feeding rates of the Chagas disease vector Triatoma infestans in Argentina.

BACKGROUND: The host species composition in a household and their relative availability affect the host-feeding choices of blood-sucking insects and parasite transmission risks. We investigated four hypotheses regarding factors that affect blood-feeding rates, proportion of human-fed bugs (human blood index), and daily human-feeding rates of Triatoma infestans, the main vector of Chagas disease. METHODS: A cross-sectional survey collected triatomines in human sleeping quarters (domiciles) of 49 of 270 rural houses in northwestern Argentina. We developed an improved way of estimating the human-feeding rate of domestic T. infestans populations. We fitted generalized linear mixed-effects models to a global model with six explanatory variables (chicken blood index, dog blood index, bug stage, numbers of human residents, bug abundance, and maximum temperature during the night preceding bug catch) and three response variables (daily blood-feeding rate, human blood index, and daily human-feeding rate). Coefficients were estimated via multimodel inference with model averaging. FINDINGS: Median blood-feeding intervals per late-stage bug were 4.1 days, with large variations among households. The main bloodmeal sources were humans (68%), chickens (22%), and dogs (9%). Blood-feeding rates decreased with increases in the chicken blood index. Both the human blood index and daily human-feeding rate decreased substantially with increasing proportions of chicken- or dog-fed bugs, or the presence of chickens indoors. Improved calculations estimated the mean daily human-feeding rate per late-stage bug at 0.231 (95% confidence interval, 0.157-0.305). CONCLUSIONS AND SIGNIFICANCE: Based on the changing availability of chickens in domiciles during spring-summer and the much larger infectivity of dogs compared with humans, we infer that the net effects of chickens in the presence of transmission-competent hosts may be more adequately described by zoopotentiation than by zooprophylaxis. Domestic animals in domiciles profoundly affect the host-feeding choices, human-vector contact rates and parasite transmission predicted by a model based on these estimates.

Key source habitats and potential dispersal of triatoma infestans populations in Northwestern Argentina: implications for vector control.

BACKGROUND: Triatoma infestans -the principal vector of the infection that causes Chagas disease- defies elimination efforts in the Gran Chaco region. This study identifies the types of human-made or -used structures that are key sources of these bugs in the initial stages of house reinfestation after an insecticide spraying campaign. METHODOLOGY AND PRINCIPAL FINDINGS: We measured demographic and blood-feeding parameters at two geographic scales in 11 rural communities in Figueroa, northwest Argentina. Of 1,297 sites searched in spring, 279 (21.5%) were infested. Bug abundance per site and female fecundity differed significantly among habitat types (ecotopes) and were highly aggregated. Domiciles (human sleeping quarters) had maximum infestation prevalence (38.7%), human-feeding bugs and total egg production, with submaximal values for other demographic and blood-feeding attributes. Taken collectively peridomestic sites were three times more often infested than domiciles. Chicken coops had greater bug abundance, blood-feeding rates, engorgement status, and female fecundity than pig and goat corrals. The host-feeding patterns were spatially structured yet there was strong evidence of active dispersal of late-stage bugs between ecotopes. Two flight indices predicted that female fliers were more likely to originate from kitchens and domiciles, rejecting our initial hypothesis that goat and pig corrals would dominate. CONCLUSIONS AND SIGNIFICANCE: Chicken coops and domiciles were key source habitats fueling rapid house reinfestation. Focusing control efforts on ecotopes with human-fed bugs (domiciles, storerooms, goat corrals) would neither eliminate the substantial contributions to bug population growth from kitchens, chicken coops, and pig corrals nor stop dispersal of adult female bugs from kitchens. Rather, comprehensive control of the linked network of ecotopes is required to prevent feeding on humans, bug population growth, and bug dispersal simultaneously. Our study illustrates a demographic approach that may be applied to other regions and triatomine species for the design of innovative, improved vector control strategies.

Spatial re-establishment dynamics of local populations of vectors of Chagas disease.

BACKGROUND: Prevention of Chagas disease depends mainly on control of the insect vectors that transmit infection. Unfortunately, the vectors have been resurgent in some areas. It is important to understand the dynamics of reinfestation where it occurs. Here we show how continuous- and discrete-time models fitted to patch-level infestation states can elucidate different aspects of re-establishment. Triatoma infestans, the main vector of Chagas disease, reinfested sites in three villages in northwest Argentina after community-wide insecticide spraying in October 1992. METHODOLOGY/PRINCIPAL FINDINGS: Different methods of estimating the probabilities of bug establishment on each site were compared. The results confirmed previous results showing a 6-month time lag between detection of a new infestation and dispersal events. The analysis showed that more new bug populations become established from May to November than from November to May. This seasonal increase in bug establishment coincides with a seasonal increase in dispersal distance. In the fitted models, the probability of new bug establishment increases with increasing time since last detected infestation. CONCLUSIONS/SIGNIFICANCE: These effects of season and previous infestation on bug establishment challenge our current understanding of T. infestans ecology and highlight important gaps in knowledge. Experiments necessary to close these gaps are discussed.

Re-establishment of local populations of vectors of Chagas disease after insecticide spraying.

1. Prevention of Chagas disease is mainly dependent on control of the insect vectors that transmit infection. Unfortunately, this control is not wholly successful and the vectors have been resurgent in some areas. Where re-infestation has occurred, it is important to understand the dynamics of the process. We investigated how a metapopulation framework can elucidate key aspects of re-infestation and thereby contribute to more efficient disease control.2.Triatoma infestans, the main vector of Chagas disease, re-infested sites in three villages in north-west Argentina after community-wide insecticide spraying in October 1992. Ten surveys were carried out at 6-monthly intervals from November 1994 to May 1999.3. Comparisons were made of different methods of estimating the sources of dispersal and the number of sites in which bug infestations became established.4. The results indicated that (i) the number of dispersing Triatoma infestans from a given site was proportional to the number of bugs found at the site; (ii) there was a 6-month time lag between detection of a new infestation and dispersal events; (iii) the relationship between infestations and new establishments varied by season.5. Three of 156 sites at which bugs were found were estimated to be the source of more than 50% of establishment events. These three sites were the only ones with large, persistent bug populations.6.Synthesis and applications. To reduce the risk of human Chagas disease, identifying those few sites infested with large, persistent bug populations and targeting control measures at those sites should greatly improve the efficiency of vector control. The appropriate seasonal timing of vector control could also greatly increase its efficiency. Specific recommendations for the timing of insecticide spraying require further research to establish how the observed temporal pattern of bug establishment is associated with the seasonality of bug dispersal.

Reinfestation sources for Chagas disease vector, Triatoma infestans, Argentina.

Reinfestation by Triatoma infestans after insecticide spraying has caused elimination efforts in the dry Chaco region to fail repeatedly. The sources and spatial extent that need to be considered to understand the reinfestation pattern and to plan a comprehensive control program were studied in 2 adjacent rural communities in northwestern Argentina from 1993 to 1997. The effects of external, residual, and primary sources on the reinfestation pattern were evaluated by using geographic information systems, satellite imagery, spatial statistics, and 5-year retrospective data for 1,881 sites. The reinfestation process depended on primary internal sources and on surrounding infested communities. In the dry Chaco, successfully reducing the risk for reinfestation in a community depends on treating all communities and isolated sites within 1,500 m of the target community. In addition, during the surveillance phase, spraying all sites within 500 m of new foci will delay reinfestation.

The role of the peridomiciliary area in the elimination of Triatoma infestants from rural Argentine communities / El papel del peridomicilio en la eliminación de Triatoma infestans de comunidades rurales argentinas

El objetivo del estudio fue identificar el origen y estudiar la dinámica de la reinfestación por Triatoma infestans ocurrida después de rociar con deltametrina el domicilio y peridomicilio de 94 casas de tres comunidades rurales el noroeste argentino. La efectividad del rociamiento se evaluó inmediatamente después y al segundo mes de rociar las viviendas. Además, se detectaron y rociaron 5 focos residuales peridomiciliarios y 3 preexistentes que no habían sido rociados. Para monitorizar la reinfestación, se colocaron biosensores en los domicilios, se solicitó a cada familia que capturase triatominos y los guardara en bolsas de plástico, y se buscaron triatominos en domicilios y peridomicilios usando un aerosol para desalojar a los insectos de sus refugios. Solo se realizaron rociamientos selectivos donde se encontró alguna colonia de T. infestans. Durante 30 meses de seguimiento, el porcentaje de casas donde se capturó algún T. infestans osciló entre 3% y 9%. En 6 casas se capturaron T. infestans en más de una evaluación. El número de peridomicilios infestados (19) fue el doble que el de domicilios (9). Solo se detectaron colonias de T. infestans en peridomicilios. La cifra de T. infestans capturados en peridomicilios fue seis veces más alta que la de los domicilios. Las gallinas fueron el hospedador más frecuentemente asociado con los focos peridomiciliarios. El peridomicilio constituyó el origen y la principal fuente de reinfestación. Para reducir la velocidad de reinfestación y la frecuencia de rociamientos es preciso combinar medidas de manejo ambiental y control químico en los peridomicilios: reducir los refugios para triatominos; restringir la cría de aves a estructuras no colonizables por triatominos; aplicar un insecticida menos degradable por agentes climáticos o realizar un segundo rociamiento de 6 a 12 meses después del primero, y emplear un dispositivo para detectar tempranamente la presencia de T. infestans en peridomicilios

The purpose of this study was to identify the origin of Triatoma infestans reinfestation and study its dynamics following spraying with deltamethrin inside and around 94 houses in three rural communities in northwestern Argentina. The effectiveness of the spraying was evaluated immediately after the houses were sprayed and two months later. In addition, five residual peridomiciliary foci were found and sprayed, as well as three preexisting ones that had not been sprayed. To monitor reinfestation, biosensors were placed in the houses and each family was also asked to capture triatomines and keep them in plastic bags; in addition, triatomines were searched for in and around houses, using an aerosol that dislodged them from their hiding places. Selective sprayings were carried out only where a colony of T. infestans was found. During the 30 months of follow-up, the percentage of houses in which any T. infestans were captured varied between 3% and 9%. In six houses, T. infestans were captured during more than one evaluation. The number of peridomiciliary areas found to be infested (19) was double the number of infested houses (9). Colonies of T. infestans were found only in the peridomiciliary areas, where the number of T. infestans captured was six times higher than in the houses. Chickens were the host most frequently associated with peridomiciliary foci. This area was the origin and principal source of reinfestation. To reduce the speed of reinfestation and the frequency with which sprayings are needed, the following environmental and chemical control methods must be combined in the peridomiciliary area: reduce the number of hiding places of triatomines; restrict the raising of birds to structures that cannot be colonized by triatomines; apply an insecticide that is less likely to be degraded by exposure to the elements, or perform a second spraying 6 to 12 months after the first; and employ a device for early detection of the presence of T. infestans around houses.

Trypanosoma cruzi infection in Triatoma infestans and other triatomines: long-term effects of a control program in rural northwestern Argentina / Infección por Trypanosoma cruzi en Triatoma infestans y otros triatómidos: efectos a largo plazo de un programa de control en una zona rural del noroeste de Argentina

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 1993-1997, the prevalence of T.cruzi was 2.4 per cent in 664 T. infestans, 0,7 per cent in 268 T.guasayana, and 0.2 per cent 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 per cent to 1.5 per cent 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 per cent to 4.6 per cent in bedrooms, as well as a fall from 6 per cent to 1.8 per cent 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 abundat species, but it was strongly associated with chickens and showed little tendency to invade bedrooms

Durante los cinco años posteriores a una fumigación masiva con deltametrina realizada en 1992 y seguida de fumigaciones selectivas, se investigó la prevalencia de la infección por Trypanosoma cruzi en Triatoma infestans, Triatoma guasayana y Triatoma sordida en Amamá y otras poblaciones rurales vecinas del noroeste de Argentina. Los triatómidos fueron recogidos en los domicilios y en el área peridoméstica por los propios residentes y por personal experto. Durante el quinquenio 1993­1997, la prevalencia de T. cruzi fue de 2,4% en 664 T. infestans, de 0,7% en 268 T. guasayana y de 0,2% en 832 T. sordida. La infección por T. cruzi se detectó con mayor frecuencia en las chinches adultas y en los triatómidos recogidos en los domicilios. T. guasayana y T. sordida fueron, respectivamente, ninfas y adultos recogidos en el área peridoméstica. Durante el período de vigilancia, la prevalencia de la infección por T. cruzi en T. infestans disminuyó de 7,7% en 1993 a 1,5% en 1997, aunque este cambio no fue estadísticamente significativo. La comparación de las tasas de infección de T. infestans antes del programa de control (1992) y durante el período de vigilancia (1993­1997) reveló una disminución altamente significativa, de 49% a 4,6%, en los dormitorios y también en las áreas peridomésticas (de 6% a 1,8%). Debido a su infección por T. cruzi y a su frecuente invasión de las áreas domésticas con ataques a los humanos y a los perros, T. guasayana parecía estar implicado como vector secundario de T. cruzi en las áreas domésticas y peridomésticas durante el período de vigilancia. T. sordida fue la especie más abundante, pero estaba estrechamente asociada a los pollos y mostró escasa tendencia a invadir los dormitorios

El papel del peridomicilio en la eliminacion de Triatoma infestants de comunidades rurales argentinas / The role of the peridomiciliary area in the elimination of Triatoma infestans in rural Argentine communities

El objetivo del estudio fue identificar el origen y estudiar la dinamica de la reinfestacion por Triatoma infestans ocurrida despues de rociar con deltametrina el domicilio y peridomicilio de 94 casas de tres comunidades rurales del noroeste argentino. La efectividad del rociamiento se evaluo inmediatamente despues y al segundo mes de rociar las viviendas. Ademas, se detectaron y rociaron 5 focos residuales peridomiciliarios y 3 preexistentes que no habian sido rociados.Para monitorizar la reinfestacion, se colocaron biosensores en los domicilios, se solicito a cada familia que capturase triatominos y los guardara en bolsas de plastico, y se buscaron triatominos en domicilios y peridomicilios usando un aereosol para desalojar a los insectos de sus refugios. Solo se realizaron rociamientos selectivos donde se encontro alguna colonia de T. infestns. Durante 30 meses de seguimiento, el porcentaje de casas donde se capturo algun T. infestans oscilo entre 3 por ciento y 9 por ciento. En 6 casas se capturaron T. infestans en mas de una evaluacion. El numero de peridomicilios infestados (19) fue el doble que el de domicilios (9). Solo se detectaron colonias de T. infestans en peridomicilios. La cifra de T. infestans capturados en peridomicilios fue seis veces mas alta que las de los domicilios. Las gallinas fueron el hospedador mas frecuente asociado con los focos peridomiciliarios. El peridomicilio constituyo el origen y la principal fuente de reinfestacion. Para reducir la velocidad de reinfestacion y la frecuencia de rociamientos es preciso combinar medidas de manejo ambiental y control quimico en los peridomicilios: reducir los refugios para triatominos; restringir la cria de aves a estructuras no colonizables por triatominos; aplicar un insecticida menos desagradable por agentes climaticos o realizar un segundo rociamiento de 6 a 12 meses despues del primero, y emplear un dispositivo para detectar tempranamente la presencia de T. infestans en peridomicilios

Trypanosoma cruzi infection in Triatoma infestans and other triatomines : long-term effects of a control program in rural northwestern Argentina

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 1993-1997, the prevalence of T.cruzi was 2.4 per cent in 664 T. infestans, 0,7 per cent in 268 T.guasayana, and 0.2 per cent 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 per cent to 1.5 per cent 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 per cent to 4.6 per cent in bedrooms, as well as a fall from 6 per cent to 1.8 per cent 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 abundat species, but it was strongly associated with chickens and showed little tendency to invade bedrooms

Lipoproteínas plasmáticas en las hepatopatías alcohólicas / Plasma lipoproteins in alcoholic liver diseases

Con el propósito de valorar las modificaciones que ocurren en las liproteínas plasmáticas en el alcoholismo crónico y su relación con las alteraciones observadas en la histología hepática fueron estudiadas un grupo de 62 alcoholistas crónicos y uno de 36 sujetos normales de similar sexo y edad que fueron empleados como controles. En base a los hallazgos en la punción biopsia hepática los etilistas fueron clasificados como sin lesión a la histología óptica (6 pacientes) hepatitis e hígado graso (18 pacientes) y cirrosis hepáticca (38 pacientes). El grupo de alcoholistas en conjunto mostró aumentos significativos con respecto al grupo control en la gamaglutamiltranspeptidasa, triglicéridos y apoproteína B y una disminución significativa en los valores de C-HDL y de apoproteínas AI. Los etilistas presentaron un descenso gradual y significativo tanto del C-HDL como de la Apo AI a medida que el daño histológico hepático evolucionaba desde "sin lesión histológica" a "cirrosis hepática". Se concluye que los resultados hallados podrían ser debidos a ambos, el efecto metabólico directo del alcohol y el daño estructural hepático irreversible provocado por el mismo