Assessment of the Abundance and Diversity of Calliphoridae and Sarcophagidae (Diptera) in Sites With Different Degrees of Human Impact in the Iberá Wetlands (Argentina).

The aim of the present study was to explore the diversity and describe the spatial distribution of Calliphoridae and Sarcophagidae along an urbanization gradient in the Iberá Wetlands. The flies were collected at 18 sampling points, three per site. In total, 3,318 flies were collected (3,077 blow flies and 241 flesh flies), distributed in 13 genera and 33 species. Calliphoridae was the most abundant, comprised 92.74% of all adult flies. Chrysomya albiceps (Wiedemann), Cochliomyia macellaria (F.), Chrysomya megacephala (F.), and Chrysomya putoria (Wiedemann) were the most abundant species, representing 82.21% of the total sample. The genus Oxysarcodexia Townsend was the most diverse with 10 species represented. The abundance of exotic species represents 62.85% of the total sample, showing a reduction toward less disturbed sites. The results of this study indicated that sites with intermediate impact had higher diversity than those where the disturbances are high or absent. Our findings provide the first assessment of Calliphoridae and Sarcophagidae diversity in the area of the Iberá Wetlands.

Spatial and temporal variation of dung beetle assemblages in a fragmented landscape at eastern humid Chaco.

The aims of this study were to characterize the fauna of dung beetles and analyze their spatial and temporal diversity in a cattle ranch in the province of Chaco. Seven surveys were conducted in three environmental units: a forest fragment, a cattle pasture, and an open grassland. The efficiency of the sampling was assessed with non-parametric richness estimators, and attributes of the assemblage were evaluated. The species composition and the abundance distribution in each of the environmental units studied were compared using rank-abundance curves. The indicator value of each species was measured with the IndVal method. The relationship between richness, abundance, and environmental variables (temperature, precipitation, and relative humidity) was calculated by multivariate multiple regression analysis. A total of 3,356 adult individuals belonging to 29 species of the subfamily Scarabaeinae and to five species of Aphodiinae were captured. Dichotomius nisus (Olivier), Trichillum externepunctatum (Preudhomme), Canthon podagricus (Harold), Onthophagus hirculus (Mannerheim), Pseudocanthon aff. perplexus, Ontherus sulcator (Fabricius), and Ataenius platensis (Blanchard) were the most abundant. Diversity, species richness, and abundance were highest in the forest fragment and in spring and summer captures. Between 94% and 97% of the species present in the entire landscape were recorded. According to the analysis of similarity, the composition of the assemblage was different among habitats. Eurysternus caribaeus (Herbst), Eurysternus aeneus (Génier), and O. sulcator were indicators of the forest. In the three units, the coprophagous species represented more than 60% of the total species number. The rainfall regime, the temperature, and the heterogeneous use of the environmental units influenced the structure of dung beetle assemblages.

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

El objetivo fue evaluar la presencia de triatominos en ecotopos domésticos y extradomésticos localizados en el área circundante a una comunidad de palmas, determinar el índice de infección de los triatominos y estimar la prevalencia humana de individuos serorreactivos al Trypanosoma cruzi. Los muestreos se efectuaron en primavera de 1998 y en verano de 1999 en Colonia Laurel, Departamento San Roque, Corrientes, Argentina. La colección de triatominos se realizó por el método de captura/ hora/ hombre. La identificación del T. cruzi se efectuó según criterios morfológicos y por PCR. El diagnóstico de la infección chagásica se llevó a cabo en pobladores voluntarios mediante las pruebas de hemaglutinación indirecta e inmunofluorescencia indirecta. Se analizaron 16 viviendas, 11 resultaron infestadas por Triatoma infestans y dos por Triatoma sordida. Se colectaron 122 ejemplares de T. infestans de todas las edades. La infección por T. cruzi fue 16.7%. Triatoma infestans fue la especie predominante en el domicilio y T. sordida en el peridomicilio. El 77.9% (88/113) de los pobladores se analizaron serológicamente y la prevalencia fue 26.1%. La tasa de infección fue relativamente alta en el grupo etario de 0-10 años. El porcentaje de seropositividad se incrementó con la edad y ascendió al 66.6% en los pobladores de más de 40 años. La presencia de T. infestans, de pobladores serorreactivos y de niños seropositivos ≤4 años, así como las condiciones precarias de vida, indican que la endemia chagásica continúa siendo un problema en el área de estudio. (AU)

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

El objetivo fue evaluar la presencia de triatominos en ecotopos domésticos y extradomésticos localizados en el área circundante a una comunidad de palmas, determinar el índice de infección de los triatominos y estimar la prevalencia humana de individuos serorreactivos al Trypanosoma cruzi. Los muestreos se efectuaron en primavera de 1998 y en verano de 1999 en Colonia Laurel, Departamento San Roque, Corrientes, Argentina. La colección de triatominos se realizó por el método de captura/ hora/ hombre. La identificación del T. cruzi se efectuó según criterios morfológicos y por PCR. El diagnóstico de la infección chagásica se llevó a cabo en pobladores voluntarios mediante las pruebas de hemaglutinación indirecta e inmunofluorescencia indirecta. Se analizaron 16 viviendas, 11 resultaron infestadas por Triatoma infestans y dos por Triatoma sordida. Se colectaron 122 ejemplares de T. infestans de todas las edades. La infección por T. cruzi fue 16.7%. Triatoma infestans fue la especie predominante en el domicilio y T. sordida en el peridomicilio. El 77.9% (88/113) de los pobladores se analizaron serológicamente y la prevalencia fue 26.1%. La tasa de infección fue relativamente alta en el grupo etario de 0-10 años. El porcentaje de seropositividad se incrementó con la edad y ascendió al 66.6% en los pobladores de más de 40 años. La presencia de T. infestans, de pobladores serorreactivos y de niños seropositivos ≤4 años, así como las condiciones precarias de vida, indican que la endemia chagásica continúa siendo un problema en el área de estudio.

Competition between vectors of Chagas disease, Triatoma infestans and T. sordida: effects on fecundity and mortality.

Interspecific competition between two species of triatomine bugs (Hemiptera: Reduviidae), vectors of Chagas disease, was assessed for 16 months through comparative fecundity and mortality of experimental populations in chicken nests, maintained indoors with ambient conditions. Triatoma sordida (Stål), the secondary vector in north-eastern Argentina, was compared with Triatoma infestans (Klug) the more widespread domestic vector in the southern cone of South America. Both species populations originated from females collected in 1995 from the community of Empedrado, Corrientes, Argentina. Three population units were monitored: T. infestans alone, T. sordida alone and both species together in equal proportions. Each population started with six male and six female adults, 116 eggs, and nymphal instars I to V numbering 82, 48, 16, 11 and 19, respectively. Numbers and weight of individual bugs were recorded monthly (August 1995 to December 1996). The pure populations of T. infestans and T. sordida showed temporal changes in abundance, rising in summer and falling in winter, similar to the typical trends under normal field conditions. In the mixed population, however, T. sordida fell to extinction after 6 months, whereas T. infestans reached similar abundance to the pure (control) population. For each nymphal instar of T. sordida, the mean body weight was significantly less and mortality rate was higher in the mixed population compared to the pure population, but there were no significant differences of adult longevity or fecundity between the pure and mixed populations of T. sordida. The apparent competitive displacement of T. sordida by T. infestans was attributed to the latter species having better ability to obtain bloodmeals. This might explain the rarity of mixed populations where these two species occur in sympatry.

[Detection of triatomines (Hemiptera: Reduviidae) in domiciliary and extra-domiciliary ecotopes. Corrientes, Argentina. ]. / Detección de triatominos (Hemiptera: Reduviidae) en ambientes domésticos y extradomésticos. Corrientes, Argentina.

In order to identify intra- and extra-domiciliary triatomines, a study in different counties of Corrientes Province, Argentina, was conducted from 1985 to 1995. Triatoma infestans (Klug, 1834), Triatoma sordida (Stål, 1859), Panstrongylus geniculatus (Latreille, 1811), and Panstrongylus megistus (Burmeister, 1835) were detected in domestic ecotopes. T. infestans and T. sordida were also found in the peridomicile. Triatoma platensis (Neiva, 1913), Psammolestes coreodes (Bergroth, 1911), T. sordida, and Triatoma rubrovaria (Blanchard, 1843) were collected in sylvatic biotopes. T. infestans was confirmed as the predominant species in the domestic environment and was the only species infected with Trypanosoma cruzi-like parasites. T. sordida was most frequent in extra-domiciliary ecotopes, but could be considered capable of colonizing human dwellings.

Interactions between Triatoma infestans and Triatoma sordida (Hemiptera: Reduviidae) in artificial ecotopes: population growth and age structure.

Interaction characteristics between Triatoma infestans Klug, 1834 and Triatoma sordida Stal, 1859 populations were studied in artificial ecotopes for 16 mo. The experimental design involved simultaneous treatments with T. infestans and T. sordida together in the same experimental unit (EU) and each separately in two control units (CU) made of adobe bricks. Chickens were used as host animals. Each unit was dismantled monthly to estimate triatomine population size and age structure, rebuilt, and repopulated with the same insects. In both units, T. infestans population growth followed a logistic model, whereas T. sordida did not show this pattern. T. infestans completed a generation in 24 wk (EU) and 32 wk (CU1), whereas T. sordida did not complete one generation during this period. We concluded that T infestans showed a better colonizing success than T. sordida. After living together for 1 yr, an interference process took place that resulted in the extinction of T. sordida.

Infestacion domestica por Triatoma infestans y prevalencia de seropositivos al Trypanosoma cruzi en un area rural del nordeste argentino / Domestic infestation by Triatoma infestans and prevalence of seropositives to Trypanosoma cruzi in a rural population of the Northeast of Argentina

An epidemiological study was carried out from April 1991 to December 1993 to obtain a general view of T. cruzi domestic transmission in rural areas of San Miguei Department, Corrientes. From 100 analyzed households, 50.0 per cent was infested by T infestans (Klug, 1834) and 1.0 per cent by T. sordida (Stal, 1859). Domiciliary colonization by T. sordida is reported for first time in Corrientes province. T. cruzi infection of T. infestans was 23.1 per cent. Indirect hemagglutination and indirect immunofluorescence antibody tests were used for detection of anti T. cruzi antibodies in 388 human sera, 23.4 per cent showed serological reactivity. An important high rate (12.9 per cent) was observed in the age group of higher transmission risk. Seropositives percentages increased with age and reached 50.0 per cent in 31-40 years old group. Domestic infestation by T. infestans, seropositive human prevalence to T. cruzi and householders precarious life conditions prove that this endemic disease is still a problem in the studied area.

[Domestic infestation by Triatoma infestans and prevalence of Trypanosoma cruzi seropositives in a rural area of the Argentinian northeast]. / Infestacion domestica por Triatoma infestans y prevalencia de seropositivos al Trypanosoma cruzi en un area rural del nordeste argentino.

An epidemiological study was carried out from April 1991 to December 1993 to obtain a general view of T. cruzi domestic transmission in rural areas of San Miguei Department, Corrientes. From 100 analyzed households, 50.0% was infested by T infestans (Klug, 1834) and 1.0% by T. sordida (Stal, 1859). Domiciliary colonization by T. sordida is reported for first time in Corrientes province. T. cruzi infection of T. infestans was 23.1%. Indirect hemagglutination and indirect immunofluorescence antibody tests were used for detection of anti T. cruzi antibodies in 388 human sera, 23.4% showed serological reactivity. An important high rate (12.9%) was observed in the age group of higher transmission risk. Seropositives percentages increased with age and reached 50.0% in 31-40 years old group. Domestic infestation by T. infestans, seropositive human prevalence to T. cruzi and householders precarious life conditions prove that this endemic disease is still a problem in the studied area.

[Population statistics of Triatoma sordida Stäl 1859 (Hemiptera:Reduviidae) in experimental conditions]. / Estadísticos poblacionales de Triatoma sordida Stäl 1859 (Hemiptera:Reduviidae) en condiciones experimentales.

Four cohorts of 100 Triatoma sordida eggs were reared under standard laboratory conditions (28 degrees C, 63% R.H.) and fed weekly on hens during 40 minutes. The numbers of dead insects, moults and eggs laid were recorded weekly. A constant survival value was observed without any important peaks in the four cohorts. Life expectancy was 37.4 weeks for males and 36.8 weeks for females. The average generation time was 61.7 weeks. The average net reproduction rate suggests that this population would increase 143.2 times during each generation. The average intrinsic rate of natural increase was 0.082 per individual per week. The highest reproductive value was observed 3 weeks after entering the adult stage. The age structure, assuming stable age distribution, would be 32% eggs, 26% of first instar nymphs, 19% of second instar nymphs, 13% of third instar nymphs, 6% of fourth instar nymphs, 3% of fifth instar nymphs and 1% of adults. Our results suggest that this species behaves as a k-strategist under experimental conditions.

[Population interactions between Triatoma infestans and Triatoma sordida]. / Interacción entre poblaciones de Triatoma infestans y Triatoma sordida.

Populations of T. infestans and T. sordida were studied between September 1988 and April 1989 with a view to discovering if any kind of interaction took place between them while they lives together in the same experimental unit and exploited the same food resource (chicken). The initial age structure for each species was: 27 N1, 7 N2, 11 N3, 3 N4, 8 N5, 4 males and 10 females. The population dynamics nutritional status, predation and gregarious behavior were estimated by means of a monthly census. The colonizing success of T. infestans was greater than that of T. sordida in view of the values obtained: fecundity (146 eggs/female), longevity (157.8 days) and mortality (39.4) compared with the values recorded for T. sordida: 118 eggs/female, 81.1 days and 54.0% respectively. The population growth of T. insfestans followed an exponential model, with a high nymphal recruitment rate, while the T. sordida population was early extinguished. In general, the average weight of T. infestans remained close to the initial values while that of T. sordida declined. Gregarious groups were formed principally in the inferior sector of wall 1 (near the host) with a higher aggregation in T. infestans. These results make it possible to propose the hypothesis of the competitive superiority of T. infestans.

[Presence of Triatoma sordida Stäl, 1859 in urban ecotopes, of the city of Corrientes, Argentina]. / Presencia de Triatoma sordida Stäl, 1859 en ecotopos urbanos de la ciudad de Corrientes, Argentina.

With the intention of verifying the presence of T. sordida Stál 1859 in urban ecotopes in Corrientes city, Argentina, both, human dwellings and an extradomiciliary habitat were taken as a basis. A complete T. sordida population census was carried on in Mitre Park pigeon house and 400 pigeon nests (Columbia livia) were dissected. The triatomineos samples that had been detected in human dwellings were sent to the Arthropods Laboratory by their inhabitants. These triatomineos were classified systematically and according to their age class. Their feces were examined under a microscope 400 x, so as to identify Trypanosoma cruzi. Six eggs, 45 first-instar nymphs, 110 second-instar nymphs, 226 third-instar nymphs, 303 fourth-instar nymphs, 1.103 fifth-instar nymphs, 12 females and 11 males were collected from the pigeon house. The presence of this species was verified in the 27 houses, situated in 8 different neighborhoods in the city; 13 eggs, 33 different instar nymphs, 27 females and 9 males were captured, 82 samples altogether. No triatomineo was infected by T. cruzi. T. sordida adults moved towards the houses in Spring and Summer. Of the material found in human dwellings 33% was female. The adaptation of T. sordida to extra-domestic habitats and their tendency to invade human houses has thus been verified. This fact should be taken into account in vector control programs.

[Triatoma infestation in the San Luis del Palmar Department of Corrientes Province, Argentina]. / Triatomismo del Departamento San Luis del Palmar de la provincia de Corrientes, Argentina.

The purpose of this study was to determine domestic and peridomestic infestation of Triatominae, Trypanosoma cruzi infection rates, and the prevalence of human seroreactivity in rural areas of the Department of San Luis del Palmar, Corrientes, Argentina (Fig. 1). The study took place from April 1986 to May 1989. The Department of San Luis del Palmar covers an area of 2551 km2 and is part of the Neotropical biogeographic region, Chacoan Dominion and Province. The climate is of the subhumid type. The mean annual temperature is 21.6 degrees C. Some localities were chosen because of the presence of triatominae. Households were carefully examined and classified according to their building materials. A 0.2% solution of tetrametrine was sprayed in all possible hiding places to dislodge bugs, which were collected by capture/hour/man methods. A survey to determine the socioeconomical, sanitary, and cultural conditions of house-dwellers was carried out. The same method was used to examine peridomiciles and total demolition was carried out in the positive ones. Fecal examination was carried out to verify the presence of T. cruzi in collected insects and observed at 400X. Human blood was obtained through venipuncture. The serum was kept in a freezer until examined. Serologic studies included indirect hemagglutination test (IHAT) and indirect immunofluorescence antibody test (IFAT). Positive titer for IHAT and IFAT was 1/64. Seroreactives were those that had two positive assays. The whole data obtained was analyzed by chi 2 tests. From one hundred households studied, 80% belonged to huts and 20% to houses. Mud walls were predominant in huts while brick walls were predominant in houses.(ABSTRACT TRUNCATED AT 250 WORDS)

Triatomismo del Departamento San Luis del Palmar de la provincia de Corrientes, Argentina. / [Triatoma infestation in the San Luis del Palmar Department of Corrientes Province, Argentina]

The purpose of this study was to determine domestic and peridomestic infestation of Triatominae, Trypanosoma cruzi infection rates, and the prevalence of human seroreactivity in rural areas of the Department of San Luis del Palmar, Corrientes, Argentina (Fig. 1). The study took place from April 1986 to May 1989. The Department of San Luis del Palmar covers an area of 2551 km2 and is part of the Neotropical biogeographic region, Chacoan Dominion and Province. The climate is of the subhumid type. The mean annual temperature is 21.6 degrees C. Some localities were chosen because of the presence of triatominae. Households were carefully examined and classified according to their building materials. A 0.2

solution of tetrametrine was sprayed in all possible hiding places to dislodge bugs, which were collected by capture/hour/man methods. A survey to determine the socioeconomical, sanitary, and cultural conditions of house-dwellers was carried out. The same method was used to examine peridomiciles and total demolition was carried out in the positive ones. Fecal examination was carried out to verify the presence of T. cruzi in collected insects and observed at 400X. Human blood was obtained through venipuncture. The serum was kept in a freezer until examined. Serologic studies included indirect hemagglutination test (IHAT) and indirect immunofluorescence antibody test (IFAT). Positive titer for IHAT and IFAT was 1/64. Seroreactives were those that had two positive assays. The whole data obtained was analyzed by chi 2 tests. From one hundred households studied, 80

belonged to huts and 20

to houses. Mud walls were predominant in huts while brick walls were predominant in houses.(ABSTRACT TRUNCATED AT 250 WORDS)

Triatomismo del Departamento San Luis del Palmar de la provincia de Corrientes, Argentina. / [Triatoma infestation in the San Luis del Palmar Department of Corrientes Province, Argentina]

The purpose of this study was to determine domestic and peridomestic infestation of Triatominae, Trypanosoma cruzi infection rates, and the prevalence of human seroreactivity in rural areas of the Department of San Luis del Palmar, Corrientes, Argentina (Fig. 1). The study took place from April 1986 to May 1989. The Department of San Luis del Palmar covers an area of 2551 km2 and is part of the Neotropical biogeographic region, Chacoan Dominion and Province. The climate is of the subhumid type. The mean annual temperature is 21.6 degrees C. Some localities were chosen because of the presence of triatominae. Households were carefully examined and classified according to their building materials. A 0.2

solution of tetrametrine was sprayed in all possible hiding places to dislodge bugs, which were collected by capture/hour/man methods. A survey to determine the socioeconomical, sanitary, and cultural conditions of house-dwellers was carried out. The same method was used to examine peridomiciles and total demolition was carried out in the positive ones. Fecal examination was carried out to verify the presence of T. cruzi in collected insects and observed at 400X. Human blood was obtained through venipuncture. The serum was kept in a freezer until examined. Serologic studies included indirect hemagglutination test (IHAT) and indirect immunofluorescence antibody test (IFAT). Positive titer for IHAT and IFAT was 1/64. Seroreactives were those that had two positive assays. The whole data obtained was analyzed by chi 2 tests. From one hundred households studied, 80

belonged to huts and 20

to houses. Mud walls were predominant in huts while brick walls were predominant in houses.(ABSTRACT TRUNCATED AT 250 WORDS)