Dynamics of feeding and defecation behavior of Triatoma infestans hybrids.

Triatoma platensis is occasionally found coexisting with Triatoma infestans in chicken coops in Argentina. Some authors have reported the presence of hybrid specimens of both species in chicken coops and other peridomestic habitats. Given the coexistence of T. infestans with T. platensis and the possibility of generating fertile hybrids, it is important to evaluate the vectorial competence of these hybrids. The objective of this study was to record the dynamics of feeding-defecation behavior in fifth-stage nymphs and adults of hybrids between both species and to compare it with T. platensis and T. infestans. Three experimental groups were formed separated by stage and sex: Hybrid group, T. infestans group, and T. platensis group. During feeding, the following variables were recorded for each group: (i) blood meal size, (ii) feeding time, (iii) number of defecations during feeding, and (iv) number of defecations at 10 and 30 min after feeding. The results indicate that adults and fifth-instar nymphs of hybrids have a feeding and defecation behavior similar to T. infestans: they achieve feeding in a short time and first defecation occurs during or just after feeding. Nevertheless, hybrid's ingestion of blood occurs at higher velocity and they require higher blood intake to provoke early defecations. Considering the blood ingestion velocity, the amount of blood ingested, and the short time required for the production of the first defecation, the results of this study suggest that hybrid can be a competent Trypanosoma cruzi vector.

Calliphoridae (Diptera) in Human-Transformed and Wild Habitats: Diversity and Seasonal Fluctuations in the Humid Chaco Ecoregion of South America.

A temporal study of the Calliphoridae fauna was conducted in five different types of habitats in the Humid Chaco ecoregion: an urban settlement, a cattle farm, an alfalfa crop, a savanna, and a forest. Research was carried out to analyze 1) how the species composition of blow fly communities changes across different types of human-modified and wild environments, 2) their seasonal fluctuations, and 3) the influence of climatic factors (relative humidity, temperature, and precipitations) on the temporal dynamics of these communities. In each habitat, five sites were selected for the collection of blow flies using bait traps, and flies were collected for 1 yr. In total, 32,100 blow flies were collected, distributed in five genera and 11 species. The native species Cochliomyia macellaria (Fabricius) (Diptera: Calliphoridae) was the most abundant, followed by the exotic Chrysomya putoria (Wiedemann) (Diptera: Calliphoridae). The abundance of exotic species represented 59.9% of the total sample, showing a reduction toward less disturbed sites. The Calliphorid communities were compared in terms of species richness, composition, and abundance between habitats and seasons. Our results showed that the habitat type and season affect the composition of blow fly communities. The alfalfa crop and the forest showed the highest diversity of species. In general, there was a decrease in blow fly activity during winter in all habitats. The climatic factors did not greatly affect the diversity of these flies. This study provides a first understanding of several ecological aspects of the Calliphoridae assemblages of the previously unsurveyed Humid Chaco ecoregion of South America.

Study of the life cycle of Amblyomma dubitatum (Acari: Ixodidae) based on field and laboratory data.

The life cycle of Amblyomma dubitatum was described based on the seasonal distribution of all parasitic stages and the development periods of engorged ticks under different conditions of photoperiod and temperature. All stages were found active along the entire year in the study area. Larvae peaked from May to July, nymphs peaked from July to October, and females peaked from November to March. This pattern represents a life cycle with one generation per year with most of the ticks reaching adulthood during the warmest months. The analysis of the effect of the photoperiod on the development of A. dubitatum showed no indication of morphogenetic diapause. Exposure of ticks to field conditions indicates a delay in metamorphosis of immature stages, in the oviposition of females and in the incubation of eggs, which were associated with low winter temperatures. The results indicate that though A. dubitatum has a one year life cycle, more than one cohort can co-exist within the same population in a certain interval of time. Finally, the potential role of small rodents as hosts for larvae and nymphs of A. dubitatum is confirmed.

[Epidemiology of American trypanosomiasis in the North of Corrientes province, Argentina]. / Epidemiología de la tripanosomiasis americana en el Norte de Corrientes.

The aim of this investigation was to evaluate triatomine colonization in domestic and extradomestic ecotopes, to determine triatomines infection index and to assess human prevalence of anti Trypanosoma cruzi antibodies at Berón de Astrada and Mburucuyá Departments, Corrientes, Argentina. Samplings were performed in 2007 and 2008 in randomly selected households at rural areas. Diagnosis of Chagas infection in volunteer residents was performed using indirect hemagglutination, indirect immunofluorescence and indirect immunoen-zimatic assay. Thirty human dwellings and 25 peridomestic ecotopes were searched at Berón de Astrada, and 32 houses and 33 peridomiciles at Mburucuyá. A total of 19 nymphs were captured in a chicken coop at Mburucuyá, the infestation rate was 3.0%. At Berón de Astrada 4.0% of the peridomiciles resulted infested by Triatoma sordida, a female and 58 eggs were collected in a hen nest. Trypanosoma cruzi infection was not detected in Triatoma sordida. The prevalence human rate was 5.2% (11/77) at Mburucuyá and 14.3% (4/77) at Berón de Astrada. Presence of triatomines was not confirmed at the human dwellings, and the infestation of the peridomestic structures was low. It is necessary to implement new strategies of vectorial control, especially for those species that prevail in the peridomicile and sylvatic ecotopes. Seroprevalence was lower that the observed in previous investigations in other rural areas of Corrientes. The absence of seroreactives in the 0-10 age group suggests a halt in T. cruzi transmission in the studied area.

Epidemiología de la tripanosomiasis americana en el Norte de Corrientes / Epidemiology of American trypanosomiasis in the North of Corrientes province, Argentina

El objetivo de esta investigación fue evaluar la presencia de triatominos en ecotopos domésticos y extradomésticos, determinar el índice de infección de los triatominos y estimar la prevalencia humana de anticuerpos contra el Trypanosoma cruzi. Los muestreos se llevaron a cabo en viviendas seleccionadas al azar en áreas rurales (departamentos Mburucuyá en otoño 2007 y Berón de Astrada en verano 2008) de Corrientes, Argentina. El diagnóstico de la infección chagásica se realizó a voluntarios mediante las pruebas de hemaglutinación indirecta, inmunofluorescencia indirecta y ensayo inmunoenzimático. Se exploraron 32 viviendas y 33 peridomicilios en Mburucuyá, y 30 viviendas y 25 peridomicilios en Berón de Astrada. En Mburucuyá la infestación del peridomicilio por Triatoma sordida alcanzó un 3.0%, capturándose 19 ninfas en un gallinero. La infestación del peridomicilio en Berón de Astrada fue 4.0%, detectándose una hembra y 58 huevos en un nidal de ave. Tanto la hembra como las ninfas resultaron negativas al T. cruzi. La prevalencia de seropositivos humanos al T. cruzi fue 5.2% (4/77) en Mburucuyá y 14.3% (11/77) en Berón de Astrada. En el domicilio no se confirmó infestación por triatominos y en el peridomicilio el índice de infestación fue bajo. Es necesario implementar nuevas estrategias de control vectorial, especialmente para las especies que habitan en estructuras peridomésticas y biotopos silvestres. La seroprevalencia fue menor a la observada en investigaciones previas en las áreas rurales de Corrientes. La ausencia de seropositivos de 0-10 años indica que la transmisión vectorial está interrumpida.

The aim of this investigation was to evaluate triatomine colonization in domestic and extradomestic ecotopes, to determine triatomines infection index and to assess human prevalence of anti Trypanosoma cruzi antibodies at Berón de Astrada and Mburucuyá Departments, Corrientes, Argentina. Samplings were performed in 2007 and 2008 in randomly selected households at rural areas. Diagnosis of Chagas infection in volunteer residents was performed using indirect hemagglutination, indirect immunofluorescence and indirect immunoenzimatic assay. Thirty human dwellings and 25 peridomestic ecotopes were searched at Berón de Astrada, and 32 houses and 33 peridomiciles at Mburucuyá. A total of 19 nymphs were captured in a chicken coop at Mburucuyá, the infestation rate was 3.0%. At Berón de Astrada 4.0% of the peridomiciles resulted infested by Triatoma sordida, a female and 58 eggs were collected in a hen nest. Trypanosoma cruzi infection was not detected in Triatoma sordida. The prevalence human rate was 5.2% (11/77) at Mburucuyá and 14.3% (4/77) at Berón de Astrada. Presence of triatomines was not confirmed at the human dwellings, and the infestation of the peridomestic structures was low. It is necessary to implement new strategies of vectorial control, especially for those species that prevail in the peridomicile and sylvatic ecotopes. Seroprevalence was lower that the observed in previous investigations in other rural areas of Corrientes. The absence of seroreactives in the 0-10 age group suggests a halt in T. cruzi transmission in the studied area.

[Composition of the Araneae (Arachnida) fauna of the provincial Iberá Reserve, Corrientes, Argentina]. / Composición de la fauna de Araneae (arachnida) de la Reserva provincial Iberá, Corrientes, Argentina.

A survey of the spider community composition and diversity was carried out in grasslands and woods in three localities: Colonia Pellegrini, Paraje Galarza and Estancia Rinc6n (Iberá province Reserve). Pit fall traps, leaf litter sifting, foliage beating, hand collecting and sweep nets were used. Shannon's diversity index, evenness, Berger-Parker's dominance index, beta and gamma diversity were calculated, and a checklist of spider fauna was compiled. Species richness was estimated by Chao 1, Chao 2, first and second order Jack-knife. A total of 4,138 spiders grouped into 150 species from 33 families of Araneomorphae and two species from two families of Mygalomorphae were collected. Five species are new records for Argentina and eleven for Corrientes province. Araneidae was the most abundant family (39.8%), followed by Salticidae (10.9%), Anyphaenidae (7.9%), Tetragnathidae (7.4%), and Lycosidae (5.5%). The other families represented less than 5% of the total catch. The web-builder guild had the highest number of specimens and the highest richness index. The abundance, observed richness, Shannon diversity and evenness indexes were highest in Colonia Pellegrini woodland and Paraje Galarza grassland. Alpha diversity represented 89% of the gamma; the remaining 11% corresponded to beta diversity. According to the indexes, between 67% and 97% of the existing spider fauna was represented in the collected specimens from Iberá.

Composición de la fauna de Araneae (Arachnida) de la Reserva provincial Iberá, Corrientes, Argentina

Composition of the Araneae (Arachnida) fauna of the provincial Iberá Reserve, Corrientes, Argentina. A survey of the spider community composition and diversity was carried out in grasslands and woods in three localities: Colonia Pellegrini, Paraje Galarza and Estancia Rincón (iberá province Reserve). Pit fall traps, leaf litter sifting, foliage beating, hand collecting and sweep nets were used. Shannon’s diversity index, evenness, Berger-Parker’s dominance index, ß and diversity were calculated, and a checklist of spider fauna was compiled. Species richness was estimated by Chao 1, Chao 2, first and second order Jack-knife. A total of 4 138 spiders grouped into 150 species from 33 families of Araneomorphae and two species from two families of Mygalomorphae were collected. Five species are new records for Argentina and eleven for Corrientes province. Araneidae was the most abundant family (39.8%), followed by Salticidae (10.9%), Anyphaenidae (7.9%), Tetragnathidae (7.4%), and Lycosidae (5.5%). The other families represented less than 5% of the total catch. The web-builder guild had the highest number of specimens and the highest richness index. The abundance, observed richness, Shannon diversity and evenness indexes were highest in Colonia Pellegrini woodland and Paraje Galarza grassland. Alpha diversity represented 89% of the gamma; the remaining 11% corresponded to ß diversity. According to the indexes, between 67% and 97% of the existing spider fauna was represented in the collected specimens from iberá. Rev. Biol. Trop. 57 (1-2): 339-351. Epub 2009 June 30.

Se estudió la composición y diversidad de la comunidad de arañas de la Reserva provincial iberá, Corrientes, Argentina. Se realizaron capturas en bosque y pastizal en Colonia Pellegrini, Paraje Galarza y Estancia Rincón por medio de las técnicas de muestreo: trampas "pit-fall", tamizado, golpeteo de follaje, observación directa y red de arrastre. Las arañas se agruparon en gremios y se compiló un inventario. La similitud entre localidades y unidades ambientales se midió con el índice de Jaccard, y se calcularon los índices de diversidad de Shannon, equitabilidad, dominancia de Berger-Parker, y la diversidad beta y gamma. Para estimar la riqueza de especies se utilizó Chao 1, Chao 2, Jackknife 1 y 2. En total se recolectaron 4 138 arañas, se identificaron 33 familias y 150 especies de Araneomorphae, y dos familias y dos especies de Mygalomorphae. Cinco especies son nuevos registros para Argentina y 11 para la provincia de Corrientes. Araneidae fue la familia más abundante (39.8%), seguida por Salticidae (10.9%), Anyphaenidae (7.9%), Tetragnathidae (7.4%), Lycosidae (5.5%), y las restantes familias representaron menos del 5% de la captura total. El gremio de arañas tejedoras de telas orbiculares fue el de mayor abundancia y riqueza de especies. Entre las unidades ambientales, la mayor abundancia, riqueza y diversidad se verificó en el bosque de Colonia Pellegrini y en el pastizal de Paraje Galarza. La diversidad a fue alta, representó el 89% de la diversidad gamma, y la diversidad ß constituyó el 11% restante. Según los diferentes índices se capturó entre el 67% y el 97% de las especies que están presentes en la Reserva.

Amblyomma boeroi n. sp. (Acari: Ixodidae), a parasite of the Chacoan peccary Catagonus wagneri (Rusconi) (Artiodactyla: Tayassuidae) in Argentina.

All parasitic stages of Amblyomma boeroi n. sp. (Acari: Ixodidae) are described here from Catagonus wagneri (Rusconi) in Argentina. The diagnostic characters for the male are a combination of orbited eyes, a 2/2 dental formula, coxa IV considerably larger than coxae I-III and with a long, sickle-shaped, medially directed spur arising from its internal margin, a scutum which is light grey to very pale ivory in colour, and the absence of a postanal groove. The diagnostic characters for the females are a combination of orbited eyes, a central pair and two marginal pairs of short, coarse notal setae, a 2/2 dental formula, and the absence of a postanal groove. The nymph has short palpi and a 2/2 dental formula arranged in 6 rows, its eyes are convex and orbited, and it has no postanal groove. The dorsally rectangular basis capituli of the larva, its bulging eyes and slightly sinuous posterior scutal margin all serve to distinguish it from the larva of other species of the genus. The principal host for all parasitic stages is C. wagneri (Artiodactyla: Tayassuidae). Phylogenetically A. boeroi appears to represent an independent lineage within Amblyomma Koch, 1844.

[Children enteroparasitosis in north east Argentine urban area]. / Enteroparasitosis infantil en un area urbana del nordeste Argentino.

The aim of the present investigation was to evaluate the importance of enteroparasitosis in a young urban population. The relationship between enteroparasitosis in this population and biological and environmental conditions was established for 113 infants between 0 and 14 years. Serial stool samples were analyzed and Graham tests were performed in each infant. The degree of nutrition of each infant was also assessed. Environmental data were collected via semi-structured surveys. Soil samples were tested to determine the degree of soil contamination. The following species were identified: Blastocystis hominis, Enterobius vermicularis, coccidios, Giardia intestinalis, hookworms, Strongyloides stercoralis, Trichuris trichura, Ascaris lumbricoides, Entamoeba coli, Endolimax nana and Taenia sp. Children infection prevalence was 73.5%. The frequency of enteroparasitosis was largest in the population from 3 to 8 years. The homes of the children analyzed were brick houses with tin roof and access to tap water. A 79.5% of these houses had bathrooms. The remaining used outdoors latrines. In 95.5% of these houses, the residents lived with one or more dogs and cats. The soil collected from nine houses was contaminated with infectious forms of Toxocara canis and ancilostomideos. The relationship between parasitosis and latrines and overcrowding was verified. Five cases of malnutrition were detected (4.4%). The relevance of physical and cultural factors in relation to enteric parasitosis suggests that the pharmacological treatment should be accompanied with preventive measures regarding hygiene and proper elimination of human and pet faeces.

Enteroparasitosis infantil en un area urbana del nordeste argentino / Children enteroparasitosis in North East Argentine urban area

El objetivo del presente trabajo fue evaluar las enteroparasitosis en una población infantil urbana y establecer su relación con factores biológicos y condiciones ambientales. Se investigaron 113 niños entre 0 y 14 años de edad. En cada niño se realizaron exámenes coproparasitológicos y test de Graham y se valoró el estado nutricional. Para el registro de datos ambientales se aplicaron encuestas semiestructuradas. Se analizó la contaminación del suelo. Se identificó Blastocystis hominis, Enterobius vermicularis, coccidios, Giardia intestinalis, uncinarias, Strongyloides stercoralis, Trichuris trichura, Ascaris lumbricoides, Entamoeba coli, Endolimax nana y Taenia sp. La prevalencia de parasitados fue 73.5%. Se verificó mayor frecuencia de enteroparasitosis en la franja etaria de 3 a 8 años. Las viviendas analizadas (n=44) eran de material con techo de chapa, contaban con red de agua potable; el 79.5% poseía baño instalado, las restantes poseían letrinas. En el 95.5% de las unidades domésticas había uno o más perros y gatos. El suelo de nueve viviendas estuvo contaminado con formas infectantes de Toxocara canis y ancilostomídeos. Se comprobó asociación entre parasitosis y uso de letrinas y hacinamiento. Se detectaron cinco casos de desnutrición grado I (4.4%). Se pone de manifiesto la trascendencia de los factores físicos y culturales como condicionantes de las parasitosis entéricas lo que sugiere que se debe insistir, simultáneamente al tratamiento farmacológico, en las medidas preventivas relacionadas con la higiene y la adecuada eliminación de las excretas humanas y de los animales domésticos.

The aim of the present investigation was to evaluate the importance of enteroparasitosis in a young urban population. The relationship between enteroparasitosis in this population and biological and environmental conditions was established for 113 infants between 0 and 14 years. Serial stool samples were analyzed and Graham tests were performed in each infant. The degree of nutrition of each infant was also assessed. Environmental data were collected via semi-structured surveys. Soil samples were tested to determine the degree of soil contamination. The following species were identified: Blastocystis hominis, Enterobius vermicularis, coccidios, Giardia intestinalis, hookworms, Strongyloides stercoralis, Trichuris trichura, Ascaris lumbricoides, Entamoeba coli, Endolimax nana and Taenia sp. Children infection prevalence was 73.5%. The frequency of enteroparasitosis was largest in the population from 3 to 8 years. The homes of the children analyzed were brick houses with tin roof and access to tap water. A 79.5% of these houses had bathrooms. The remaining used outdoors latrines. In 95.5% of these houses, theresidents lived with one or more dogs and cats. The soil collected from nine houses was contaminated with infectious forms of Toxocara canis and ancilostomideos. The relationship between parasitosis and latrines and overcrowding was verified. Five cases of malnutrition were detected (4.4%). The relevance of physical and cultural factors in relation to enteric parasitosis suggests that the pharmacological treatment should be accompanied with preventive measures regarding hygiene and proper elimination of human and pet faeces.

Enteroparasitosis infantil en un area urbana del nordeste argentino / Children enteroparasitosis in North East Argentine urban area

El objetivo del presente trabajo fue evaluar las enteroparasitosis en una población infantil urbana y establecer su relación con factores biológicos y condiciones ambientales. Se investigaron 113 niños entre 0 y 14 años de edad. En cada niño se realizaron exámenes coproparasitológicos y test de Graham y se valoró el estado nutricional. Para el registro de datos ambientales se aplicaron encuestas semiestructuradas. Se analizó la contaminación del suelo. Se identificó Blastocystis hominis, Enterobius vermicularis, coccidios, Giardia intestinalis, uncinarias, Strongyloides stercoralis, Trichuris trichura, Ascaris lumbricoides, Entamoeba coli, Endolimax nana y Taenia sp. La prevalencia de parasitados fue 73.5%. Se verificó mayor frecuencia de enteroparasitosis en la franja etaria de 3 a 8 años. Las viviendas analizadas (n=44) eran de material con techo de chapa, contaban con red de agua potable; el 79.5% poseía baño instalado, las restantes poseían letrinas. En el 95.5% de las unidades domésticas había uno o más perros y gatos. El suelo de nueve viviendas estuvo contaminado con formas infectantes de Toxocara canis y ancilostomídeos. Se comprobó asociación entre parasitosis y uso de letrinas y hacinamiento. Se detectaron cinco casos de desnutrición grado I (4.4%). Se pone de manifiesto la trascendencia de los factores físicos y culturales como condicionantes de las parasitosis entéricas lo que sugiere que se debe insistir, simultáneamente al tratamiento farmacológico, en las medidas preventivas relacionadas con la higiene y la adecuada eliminación de las excretas humanas y de los animales domésticos.(AU)

The aim of the present investigation was to evaluate the importance of enteroparasitosis in a young urban population. The relationship between enteroparasitosis in this population and biological and environmental conditions was established for 113 infants between 0 and 14 years. Serial stool samples were analyzed and Graham tests were performed in each infant. The degree of nutrition of each infant was also assessed. Environmental data were collected via semi-structured surveys. Soil samples were tested to determine the degree of soil contamination. The following species were identified: Blastocystis hominis, Enterobius vermicularis, coccidios, Giardia intestinalis, hookworms, Strongyloides stercoralis, Trichuris trichura, Ascaris lumbricoides, Entamoeba coli, Endolimax nana and Taenia sp. Children infection prevalence was 73.5%. The frequency of enteroparasitosis was largest in the population from 3 to 8 years. The homes of the children analyzed were brick houses with tin roof and access to tap water. A 79.5% of these houses had bathrooms. The remaining used outdoors latrines. In 95.5% of these houses, theresidents lived with one or more dogs and cats. The soil collected from nine houses was contaminated with infectious forms of Toxocara canis and ancilostomideos. The relationship between parasitosis and latrines and overcrowding was verified. Five cases of malnutrition were detected (4.4%). The relevance of physical and cultural factors in relation to enteric parasitosis suggests that the pharmacological treatment should be accompanied with preventive measures regarding hygiene and proper elimination of human and pet faeces.(AU)

[Epidemiology of Chagas disease in San Roque, Corrientes. Triatomine infestation and human seroprevalence]. / Epidemiología de la enfermedad de Chagas en San Roque, Corrientes. Infestación por triatominos y seroprevalencia humana.

This investigation was aimed to evaluate triatomine colonization in domestic and extradomestic ecotopes located around a palm community, to determine triatomines infection index and to obtain human seroprevalence rates. Samplings were performed in spring 1998 and summer 1999 in Colonia Laurel, Department San Roque, Corrientes, Argentina. Timed-collection of triatomines (man/hour method) was performed. Trypanosoma cruzi identity was determined by morphological criteria and by PCR. Indirect hemagglutination and indirect immunofluorescence antibody tests were used for detection of T. cruzi infection in human volunteers. Sixteen human dwellings were analized, 11 resulted infested by Triatoma infestans and two by Triatoma sordida. A total of 122 T. infestans of all age classes were collected and T. cruzi infection was recorded in 16.7%. Triatoma infestans was confirmed as the predominant species in the domicile and T. sordida in the peridomicile. Diagnosis of Chagas disease infection was performed in 77.9% (88/113) of the inhabitants and the prevalence was 26.1%. A relatively high infection rate was observed in the 0-10 age group. Seropositives percentages increased with age and reached 66.6% in older than 40 years. Presence of T. infestans, human seroreactivity to T. cruzi, < or = 4 year old seropositives and precarious life conditions prove that this endemic disease is still a problem in the studied area.

[Population statistics of Triatoma rubrovaria in laboratory]. / Estadísticos poblacionales de Triatoma rubrovaria en condiciones de laboratorio.

OBJECTIVE: To obtain T. rubrovaria population parameters in order to describe its demographic characteristics. METHODS: The study was carried out in the laboratory of Arthropods, Corrientes, Argentina, from October 2000 to February 2003. Eggs were grouped to form five 100-egg cohorts. Insects were fed on chickens (Gallus domesticus). The cohorts were monitored weekly and kept under controlled temperature (28 +/- 3 degrees C) and relative humidity (63 +/- 10%). A life table was constructed and other vital statistics were calculated and recorded. RESULTS: Higher mortality was recorded in the first through the fourth nymphal stadium. A constant decrease was seen from the fifth nymphal instar. Life expectancy dropped linearly after overcoming the critical stages. Adults mean survival was 50.2 weeks. The first oviposition was after 40.6 weeks. The fecundity was 859.6 eggs with an average 22.8 eggs per female. The reproductive period was 37.7 weeks. The generation time was 55.3 weeks and the net reproduction rate was 133.7. The intrinsic rate of weekly increment was 0.088. In a stable age distribution the population would be composed of 25.3% eggs, 72.3% nymphs and 2.4% adults. Adults accounted for more than 70% of the total reproductive value. CONCLUSIONS: Triatoma rubrovaria had a long survival as imago, a late first reproduction and a low intrinsic rate of natural increase.

Estadísticos poblacionales de Triatoma rubrovaria en condiciones de laboratorio / Population statistics of Triatoma rubrovaria in laboratory

OBJETIVO: Obtener parámetros poblacionales de T. rubrovaria a fin de caracterizar demográficamente a esta especie. MÉTODOS: La investigación se realizó entre octubre de 2000 y febrero de 2003 en el laboratorio de artrópodos, Corrientes, Argentina. Se conformaron cinco cohortes de 100 huevos cada una. Los insectos se alimentaron sobre gallina (Gallus domesticus). Las cohortes se controlaron semanalmente. La experiencia se llevó a cabo en condiciones controladas de temperatura (28±3ºC) y humedad relativa del aire (63±10 por ciento). Se elaboraron tablas completas de vida y se obtuvieron estadísticos vitales. RESULTADOS: La mayor mortalidad se registró en ninfas de primero a cuarto estadio. A partir del quinto estadio el número de individuos decreció en forma constante. La expectativa de vida, después de superar las edades críticas, disminuyó en forma lineal. La supervivencia media de los adultos fue 50,2 semanas. La primera oviposición ocurrió a las 40,6 semanas. La fecundidad fue 859,6 huevos, con una media de 22,8 huevos. El período reproductivo fue de 37,7 semanas. El tiempo generacional fue de 55,3 semanas y la tasa neta de reproducción 133,7. La tasa intrínseca de incremento natural resultó 0,088. En una distribución estable de edades 25,3 por ciento correspondería al estado de huevo, 72,3 por ciento al estado ninfal y 2,4 por ciento al estado adulto. Los adultos contribuyeron con más del 70 por ciento al valor reproductivo total. CONCLUSIONES: Triatoma rubrovaria se caracterizó por una supervivencia prolongada como imago, una edad de la primera reproducción tardía y una tasa intrínseca de incremento natural baja.

Epidemiología de la enfermedad de Chagas en San Roque, Corrientes. Infestación por triatominos y seroprevalencia humana. / [Epidemiology of Chagas disease in San Roque, Corrientes. Triatomine infestation and human seroprevalence]

This investigation was aimed to evaluate triatomine colonization in domestic and extradomestic ecotopes located around a palm community, to determine triatomines infection index and to obtain human seroprevalence rates. Samplings were performed in spring 1998 and summer 1999 in Colonia Laurel, Department San Roque, Corrientes, Argentina. Timed-collection of triatomines (man/hour method) was performed. Trypanosoma cruzi identity was determined by morphological criteria and by PCR. Indirect hemagglutination and indirect immunofluorescence antibody tests were used for detection of T. cruzi infection in human volunteers. Sixteen human dwellings were analized, 11 resulted infested by Triatoma infestans and two by Triatoma sordida. A total of 122 T. infestans of all age classes were collected and T. cruzi infection was recorded in 16.7

. Triatoma infestans was confirmed as the predominant species in the domicile and T. sordida in the peridomicile. Diagnosis of Chagas disease infection was performed in 77.9

(88/113) of the inhabitants and the prevalence was 26.1

. A relatively high infection rate was observed in the 0-10 age group. Seropositives percentages increased with age and reached 66.6

in older than 40 years. Presence of T. infestans, human seroreactivity to T. cruzi, < or = 4 year old seropositives and precarious life conditions prove that this endemic disease is still a problem in the studied area.

Epidemiología de la enfermedad de Chagas, Departamento General Paz, Argentina / Chagas' disease epidemiology in the province of General Paz, Argentina

OBJETIVO: El objetivo del presente trabajo fue investigar la colonización por triatominos en ambientes domésticos y peridomésticos y evaluar la seroprevalencia de infectados chagásicos en localidades rurales. MÉTODOS: La investigación se realizó en General Paz, Corrientes, Argentina. Las viviendas y peridomicilios se seleccionaron mediante un muestreo simple al azar. La búsqueda de triatominos se efectuó por el método captura/hora/hombre. Los insectos se identificaron taxonómicamente y se clasificaron según sexo y edad. La infección por Trypanosoma cruzi se detectó por observación directa de las heces al microscopio y por la técnica de la reacción en cadena de la polimerasa (PCR). Se evaluaron serológicamente a pobladores voluntarios mediante las técnicas de hemaglutinación indirecta (HAI) y ensayo inmunoenzimático (ELISA). Se hallaron los índices de infestación, densidad, colonización, infección natural y dispersión. RESULTADOS: Se analizaron 42 viviendas y 50 peridomicilios. En el domicilio los índices de infestación e infección de Triatoma infestans fueron 23,8 y 19,4 respectivamente. Los índices de densidad, colonización y dispersión fueron 2,1; 47,0 y 50,0 respectivamente. La infestación del peridomicilio por T. infestans fue 5,9 por ciento y por T. sordida 11,8 por ciento. T. sordida resultó infectada por Trypanosoma cruzi en un 2,0 por ciento. La seroprevalencia al T. cruzi de los 85 pacientes fue del 22,3 por ciento. CONCLUSIONES: Se estima que en el área investigada la transmisión del T. cruzi está interrumpida. Sin embargo, la presencia de infectados humanos y de T. infestans parasitadas posibilitan el reinicio del ciclo de transmisión. Se proponen acciones de rociado con insecticidas con el objeto de eliminar las poblaciones del vector

[Chagas' disease epidemiology in the province of General Paz, Argentina]. / Epidemiología de la enfermedad de Chagas, Departamento General Paz, Argentina.

OBJECTIVE: The aim of this study was to evaluate triatomine colonization in domestic and peridomestic ecotopes and to assess the seroprevalence of Chagas' disease in rural areas. METHODS: The study was carried out in the province of General Paz, Corrientes, Argentina. Human dwellings and peridomestic ecotopes were randomly selected. Triatomines were collected using the man/hour/capture method. The insects were taxonomically determined and classified by age and sex. Trypanosoma cruzi infection was detected through direct microscopy of feces and polymerase chain reaction (PCR). Diagnosis of Chagas infection in volunteer residents was performed using indirect hemagglutination (IHA) and immunoenzimatic assay (ELISA). Infestation, density, colonization, natural infection and dispersion indexes were recorded. RESULTS; A total of 42 households and 50 peridomestic areas were examined. Triatoma infestans domestic infestation and infection indexes were 23.8 and 19.4; respectively. Density, colonization and dispersion indexes were 2.1; 47.0 and 50.0; respectively. Of all, 5.9% of peridomiciles were infested by T. infestans and 11.8% by Triatoma sordida. Trypanosoma cruzi infection was observed in 2.0% of T. sordida. The seroprevalence rate obtained from 85 human sera analyzed was 22.3%. CONCLUSIONS: The results suggest a halt in T. cruzi transmission in the study area. Nevertheless the presence of seroreactive individuals and infected T. infestans vectors might facilitate the resurgence of the transmission cycle. Control actions with the use of insecticides might be considered in order to eliminate vector populations.

Presencia de triatoma sordida Stäl, 1859 en ecotopos urbanos de la cuidad de Corrientes, Argentina / Presence of triatoma sordida Stäl, 1859 in Corrientes city urban ecotopes

Com o objetivo de verificar a presença de T. sordida em ecótopos urbanos da cidade de Corrientes, Argentina, tomaram-se como base um habit extradomiciliário e a domicílio. Em um pombal situado no parque Mitre foi realizado censo da polulaçäo de T. sordida para o qual foram dissecados 400 ninhos de pombas (Columbia livia). Os exemplares detectados no domicílio foram enviados por moradores ao Laboratório de Artrópodos. Os triatomíneos foram determinados sistematicamente e por classe de idade. A matéria fecal dos mesmos foi examinada ao microscópio com 400 aumentos para a identificaçäo do Trypanosoma cruzi. No pombal coletaram-se 1.920 exemplares de T. sordida, populaçäo constituída por ovos, ninfas e adultos. Em 27 domicílios foi constatada a presença desta espécie, capturando-se 13 ovos, 33 ninfas de diferentes estádios, 27 fêmeas e 9 machos. Nenhum triatomíneo resultou infectado por T. cruzi. Os adultos de T. sordida deslocaram-se ao domicílio na primavera e veräo, sendo que 33 por cento do material encontrado nos domicílios correspondeu a fêmeas. Comprovaram-se a adaptaçäo de T. sordida a um habitat extradomiciliário e a sua tendência a invadir domicílio, fatos que se deveriam ter em conta nos programas de controle de vectores