On palms, bugs, and Chagas disease in the Americas.

Palms are ubiquitous across Neotropical landscapes, from pristine forests or savannahs to large cities. Although palms provide useful ecosystem services, they also offer suitable habitat for triatomines and for Trypanosoma cruzi mammalian hosts. Wild triatomines often invade houses by flying from nearby palms, potentially leading to new cases of human Chagas disease. Understanding and predicting triatomine-palm associations and palm infestation probabilities is important for enhancing Chagas disease prevention in areas where palm-associated vectors transmit T. cruzi. We present a comprehensive overview of palm infestation by triatomines in the Americas, combining a thorough reanalysis of our published and unpublished records with an in-depth review of the literature. We use site-occupancy modeling (SOM) to examine infestation in 3590 palms sampled with non-destructive methods, and standard statistics to describe and compare infestation in 2940 palms sampled by felling-and-dissection. Thirty-eight palm species (18 genera) have been reported to be infested by ∼39 triatomine species (10 genera) from the USA to Argentina. Overall infestation varied from 49.1-55.3% (SOM) to 62.6-66.1% (dissection), with important heterogeneities among sub-regions and particularly among palm species. Large palms with complex crowns (e.g., Attalea butyracea, Acrocomia aculeata) and some medium-crowned palms (e.g., Copernicia, Butia) are often infested; in slender, small-crowned palms (e.g., Euterpe) triatomines associate with vertebrate nests. Palm infestation tends to be higher in rural settings, but urban palms can also be infested. Most Rhodnius species are probably true palm specialists, whereas Psammolestes, Eratyrus, Cavernicola, Panstrongylus, Triatoma, Alberprosenia, and some Bolboderini seem to use palms opportunistically. Palms provide extensive habitat for enzootic T. cruzi cycles and a critical link between wild cycles and transmission to humans. Unless effective means to reduce contact between people and palm-living triatomines are devised, palms will contribute to maintaining long-term and widespread, albeit possibly low-intensity, transmission of human Chagas disease.

[Spider diversity in cultures of Citrus sinensis (Rutaceae) in Corrientes province, Argentina]. / Diversidad de Araneae en cultivos de Citrus sinensis (Rutaceae) de la Provincia de Corrientes, Argentina.

Spiders are predators that reduce insect pest populations in agroecosystems. In spite that the presence of spider assemblages has been described in different crop plants, no reports have been done for Citrus species in Argentina. We studied the spider community associated with cultures of Citrus sinensis in the province of Corrientes, Argentina, in two plots (AM1 irrigated and AM2 unirrigated) of 0.82 hectares each. Spiders were collected monthly by using pitfall traps, hand capture, agitation of foliage and sieving of soil litter. A total of 7174 specimens were collected (33 families, 44 genera and 200 species/morphospecies). The AM1 recorded 3811 individuals (33 families, 179 species/morphospecies) and AM2 3363 individuals (31 families, 174 species/morphospecies). November, December and January showed the highest abundance in both plots. A total of 70% of collected spiders were juveniles. Eight families were the most abundant and represented 75% of spiders collected in both plots, the largest being Lycosidae. We identified eight guilds in both plots, for which the ground runners resulted the most abundant (AM1 n = 1341, s=39, n=999 AM2, s = 33), followed by orb weavers (AM1 n = 637, s = 36; AM2 n = 552, s = 33), the stalkers (AM1 n = 471, s = 43, AM2 n = 453, s = 47) and the space web-builders (AM1 n = 446, s = 23; AM2 n = 342, s = 25). The analysis of alpha diversity in both plots (AM1H' = 4.161, J' = 0.802; AM2 H' = 4.184, J' = 0.811) showed no significant differences (t = 1.083 p = 0.279). The linear dependences model was the one with the best fit results, where the species observed were more than estimated. Clench model estimated 90.9% of the spiders observed in the unit with irrigation and 90.6% in the unit without irrigation.

Diversidad de Araneae en cultivos de Citrus sinensis (Rutaceae) de la Provincia de Corrientes, Argentina / Spider diversity in cultures of Citrus sinensis (Rutaceae) in Corrientes province, Argentina

Spiders are predators that reduce insect pest populations in agroecosystems. In spite that the presence of spider assemblages has been described in different crop plants, no reports have been done for Citrus species in Argentina. We studied the spider community associated with cultures of Citrus sinensis in the province of Corrientes, Argentina, in two plots (AM1 irrigated and AM2 unirrigated) of 0.82 hectares each. Spiders were collected monthly by using pitfall traps, hand capture, agitation of foliage and sieving of soil litter. A total of 7 174 specimens were collected (33 families, 44 genera and 200 species/morphospecies). The AM1 recorded 3 811 individuals (33 families, 179 species/morphospecies) and AM2 3 363 individuals (31 families, 174 spe- cies/morphospecies). November, December and January showed the highest abundance in both plots. A total of 70% of collected spiders were juveniles. Eight families were the most abundant and represented 75% of spiders collected in both plots, the largest being Lycosidae. We identified eight guilds in both plots, for which the ground runners resulted the most abundant (AM1 n=1341, s=39, n=999 AM2, s=33), followed by orb weavers (AM1 n=637, s=36; AM2 n=552, s=33), the stalkers (AM1 n=471, s=43, AM2 n=453, s=47) and the space web- builders (AM1 n=446, s=23; AM2 n=342, s=25). The analysis of alpha diversity in both plots (AM1H’=4.161, J’=0.802; AM2 H’=4.184, J’=0.811) showed no significant differences (t=1.083 p=0.279). The linear dependences model was the one with the best fit results, where the species observed were more than estimated. Clench model estimated 90.9% of the spiders observed in the unit with irrigation and 90.6% in the unit without irrigation.

Las arañas son ideales como indicadores de cambios ecológicos por su diversidad y abundancia. En la provincia de Corrientes, Argentina, se estudiaron arañas de Citrus sinensis en parcelas de 0.82 hectáreas, con riego (AM1) y sin riego (AM2). Mediante pitfall, agitación de follaje, captura manual y tamizado de hojarasca se recolectaron 7 174 ejemplares (33 familias, 44 géneros y 200 especies/morfoespecies), el 70% fueron juveniles. AM1 registró 3 811 individuos (33 familias, 179 especies/morfoespecies) y AM2 3 363 (31 familias, 174 especies/morfoespecies). Durante el verano se observó la mayor abundancia. En ambas parcelas, ocho familias representaron el 75% del total, Lycosidae fue la más numerosa y se identificaron ocho gremios; las vagabundas de suelo fueron las más abundantes (AM1 n=1341, s=39; AM2 n=999, s=33) seguida por las constructoras de telas orbiculares (AM1 n=637, s=36; AM2 n=552, s=33), las cazadoras al acecho (AM1 n=471, s=43; AM2 n=453, s=47) y las de telas espaciales (AM1 n=446, s=23; AM2 n=342, s=25. La diversidad alfa en ambas parcelas (AM1 H’=4.161, J’=0.802; AM2 H’=4.184, J’=0.811) no mostró diferencias significativas (t=1.083, p=0.279). El modelo de dependencia lineal fue el que mejor ajustó los resultados. El modelo de Clench estimó el 90.9% de las observadas en AM1 y el 90.6% en la AM2.

Diversidad del orden Lepidoptera (Hesperioidea y Papilionoidea) de la ciudad Corrientes, Argentina

Diversity of the order Lepidoptera (Hesperioidea and Papilionoidea) from Corrientes city, Argentina. Urbanization is one of the most important threats for biodiversity. Among many different organisms, butterflies are useful indicators of environment diversity and quality. The aim of this study was to investigate the Lepidoptera from Corrientes city. Random samplings were performed at two sites: a native forest situated in Santa Catalina district and an urban area, Parque Mitre. The captures were carried out using entomological nets, at four seasons between January to October 2007. A total of 1 114 butterflies, represented by six families: Hesperiidae, Lycaenidae, Nymphalidae, Papilionidae, Pieridae and Riodinidae and 18 subfamilies were recorded. Fifty-nine genera and 75 species were identified; Anartia jatrophae jatrophae was the most abundant species at both localities. This species and Urbanus procne, Phoebis sennae marcellina, Pyrgus orcus and Dryas iulia alcionea were, among other seven, captured at all months. Highest values of abundance were registered during the warmest seasons. Santa Catalina presented the largest abundance (n=701), richness (S=74) and diversity (H’=3.87). A total of 413 individuals and 52 species were identified at Parque Mitre, and Shannon diversity index was 3.58. The obtained data reveals a high species richness and similarity at both sites. Rev. Biol. Trop. 59 (1): 299-308. Epub 2011 March 01.

El proceso de urbanización representa una de las amenazas más importantes a la biodiversidad. Los lepidópteros son uno de los grupos taxonómicos utilizados como indicadores de la diversidad y calidad del ambiente. El objetivo del presente trabajo es conocer los Lepidoptera (Papilionoidea y Hesperioidea) de la ciudad de Corrientes. Se llevaron a cabo muestreos al azar en un parche de bosque nativo situado en el barrio Santa Catalina y en un área antropizada, el Parque Mitre. Las recolectas se realizaron en las cuatro estaciones climáticas entre enero y octubre de 2007 con redes entomológicas. El total de ejemplares capturados asciende a 1 114, los que se distribuyen en seis familias: Hesperiidae, Lycaenidae, Nymphalidae, Papilionidae, Pieridae y Riodinidae y 18 subfamilias. Se identificaron 59 géneros y 75 especies. Anartia jatrophae jatrophae fue la especie más abundante en ambas unidades. Esta especie junto a Urbanus procne, Phoebis sennae marcellina, Pyrgus orcus y Dryas iulia alcionea se capturaron en todas las estaciones. El mayor número de ejemplares se colectó en las estaciones más cálidas. La abundancia (n=701), riqueza (S=74) y diversidad (H’=3.87) fueron superiores en Santa Catalina. Las unidades exploradas exhiben una elevada riqueza de especies y alta similitud.

Estudio transversal de la Enfermedad de Chagas en un área endémica de la Provincia de Corrientes, Argentina / Transversal study on Chagas´ disease in an endemic area of Corrientes Province, Argentina

El objetivo de esta investigación fue evaluar la presencia de triatominos en ecotopos domésticos y extradomésticos, conocer el índice de infección natural de Triatoma infestans y estimar la prevalencia humana de anticuerpos contra el Trypanosoma cruzi. Los muestreos se llevaron a cabo en primavera del 2008 y verano - otoño del 2009 en viviendas seleccionadas al azar de áreas rurales del Departamento San Luis del Palmar, Provincia 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 investigaron 27 domicilios, de los cuales el 29,6% (8/27) estaban infestados por T. infestans. Se colectaron 50 ejemplares de todas las edades y el 7,0% resultaron infectados por T. cruzi. Se exploraron 24 peridomicilios y un 20,8% (5/24) resultaron positivos, capturándose 157 individuos de T. sordida, ninguno de los cuales resultó infectado. La prevalencia global de los 163 voluntarios fue 11,7% (19/163) y en el grupo 0 -10 años fue 4,8%. La realidad de San Luis del Palmar no responde a exitosas condiciones de control y si bien la infestación doméstica por T. infestans fue moderada, la transmisión del T. cruzi sigue activa, por lo que se concluye que este departamento no reúne las condiciones de baja endemicidad.

The aim of this investigation was to evaluate triatomine presence in domestic and extradomestic ecotopes, to determine the Triatoma infestans natural infection index and to estimate human seroprevalence to Trypanosoma cruzi. Samplings were performed in spring 2008 and summer- autumm 2009 in randomly selected households in rural areas of Department San Luis del Palmar, Corrientes Province, Argentina. Diagnosis of Chagas infection was performed combining Indirect Hemagglutination Test; Indirect Immunofluorescence Test and Indirect Immunoenzimatic assay on voluntary residents.Twenty seven human dwellings were analyzed and 29.6% (8/27) were infested by T. infestans. A total of 50 T. infestans of all age classes were collected and T. cruzi infection was confirmed in 7.0%. Only 20.8% (5/24) of the twenty four extradomestic ecotopes were positive and 157 T. sordida were captured, none of them were infected. Serological study of 163 human volunteers showed that 11.7% (19/163) were seroreactive, the prevalence observed in the 0 - 10 age group was 4.8%. At San Luis del Palmar the control actions are not successful, and although the T. infestans domestic infestation is mild, there is an active T. cruzi transmission of Chagas. These results show that the endemicity at this department is not low.

[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.

Culicidae (Diptera) de la reserva provincial Iberá Corrientes Argentina / Culicidae (Diptera) of Iberá Corrientes province reserve Argentina

El objetivo de este trabajo fue conocer la composición taxonómica, abundancia y diversidad de los Culicidae de la Reserva Provincial Iberá. La investigación se llevó a cabo en Estancia Rincón, Colonia Carlos Pellegrini y Paraje Galarza, provincia de Corrientes, Argentina. En el área de estudio los muestreos se realizaron en tres transectas de 200m de longitud y 2m de ancho en bosque y pastizal. Los ejemplares se capturaron en forma manual con aspiradores sobre cebo humano y trampa de luz. Se colectaron 1694 mosquitos pertenecientes a nueve géneros y 21 especies. En la unidad de paisaje correspondiente al bosque se observó mayor diversidad que en el pastizal. El 13,5% de los culícidos fue atraído por las trampas de luz y el 86,5% por cebo humano. Se capturaron especies importantes como vectoras de virus. La distribución, abundancia y composición específica de la culicidofauna fueron distintas en las localidades y unidades ambientales estudiadas. En Estancia Rincón la degradación del bosque producida por el ganado podría explicar el reducido número de especies. En Colonia Carlos Pellegrini y Paraje Galarza Aedes (Ochlerotatus) scapularis (Rondani, 1848) fue abundante, pero la presencia de numerosos ejemplares de Limatus durhami Theobald, 1901 y pocos individuos de las tribus Mansonini y Culicini indican una reducida influencia antrópica.

Estructura y dinámica poblacional de Triatoma sordida Stål 1859 en una comunidad de Butia yatay en Argentina / Population structure of Triatoma sordida Stål 1859 collected in a comunity of Butia yatay in Argentina

Se estudió la estructura poblacional de Triatoma sordida que infesta Butia yatay y su abundancia relativa durante un año, en Colonia Laurel, Departamento San Roque, Corrientes, Argentina (28 °28 ’ S;58 °26 ’ W). Los muestreos se realizaron en primavera de 1998, verano, otoño e invierno de 1999. Se disecaron 55 ejemplares de palmas y se con firmó el predominio de T. sordida (N=423) en relación al reducido número de Triatoma platensis y de Psammolestes coreodes capturados. Es la primera cita para Argentina sobre la presencia de T. sordida en esta especie de palma. La abundancia relativa de T. sordida mostró una marcada estacionalidad. En primavera el total de individuos colectados triplicó al hallado en las restantes estaciones y las abundancias relativas oscilaron entre 57 y 88 individuos por mes, coincidiendo con el período reproductivo de la especie. Todos los estadios ninfales estuvieron presentes, con predominio de NIII, NIV y NV. En forma global, las ninfas representaron el 91,7%, los huevos el 4,3% y los adultos el 4,0% de la población total colectada. La menor abundancia se verificó en Enero y podría interpretarse como una inhibición del desarrollo causado por las temperaturas elevadas. Algo semejante ocurrió en Junio, alregistrarse la temperatura ambiental más baja, en invierno se produciría la mayor mortalidad de ninfas menores, conduciendo a la presencia de pocos ejemplares y aún a la extinción. Las fluctuaciones en la densidad de esta especie se atribuyen a factores bioclimáticos y a la disponibilidad de fuentes de alimentación.

Triatomines involved in domestic and wild Trypanosoma cruzi transmission in Concepción, Corrientes, Argentina.

An entomological and serological survey was performed in three localities of the Department of Concepción, Province of Corrientes, Argentina in 1998 and 1999, to identify triatomines species involved in domestic and wild transmission of Chagas disease. Triatomines were collected by man/hour capture in 32 houses randomly selected and 44 nearby outdoor ecotopes. Trypanosoma cruzi infection in triatomines was assessed by direct microscopic observation (400x) of feces and polymerase chain reaction. Serological techniques used for people were Indirect Hemagglutination Test and Indirect Fluorescent Test. Triatomines were collected in 28.1% of the houses and 31.8% of the wild biotopes. Triatoma infestans (Klug 1834) was exclusively found indoors and T. cruzi infected 60% of them. Triatoma sordida (Stål 1859) was mainly found in extradomestic ecotopes where trypanosome infection rate reached 12.7%. Serological study of 98 local people showed that 29.6% were seroreactive; most of their houses were closed to wild biotopes colonized by T. sordida. Results indicate that there is an active T. infestans mediated transmission of Chagas disease in this zone that yields important human prevalence and that the populations of T. sordida in wild biotopes not only sustain the wild T. cruzi cycle but also represent an actual risk for people living in the area.

Triatomines involved in domestic and wild Trypanosoma cruzi transmission in Concepción, Corrientes, Argentina

An entomological and serological survey was performed in three localities of the Department of Concepción, Province of Corrientes, Argentina in 1998 and 1999, to identify triatomines species involved in domestic and wild transmission of Chagas disease. Triatomines were collected by man/hour capture in 32 houses randomly selected and 44 nearby outdoor ecotopes. Trypanosoma cruzi infection in triatomines was assessed by direct microscopic observation (400x) of feces and polymerase chain reaction. Serological techniques used for people were Indirect Hemagglutination Test and Indirect Fluorescent Test. Triatomines were collected in 28.1 percent of the houses and 31.8 percent of the wild biotopes. Triatoma infestans (Klug 1834) was exclusively found indoors and T. cruzi infected 60 percent of them. Triatoma sordida (StÕl 1859) was mainly found in extradomestic ecotopes where trypanosome infection rate reached 12.7 percent. Serological study of 98 local people showed that 29.6 percent were seroreactive; most of their houses were closed to wild biotopes colonized by T. sordida. Results indicate that there is an active T. infestans mediated transmission of Chagas disease in this zone that yields important human prevalence and that the populations of T. sordida in wild biotopes not only sustain the wild T. cruzi cycle but also represent an actual risk for people living in the area

Triatoma sordida StÕl 1859 (Hemiptera, Reduviidae: Triatominae) in palms of northeastern Argentina

Several palms species provide an important habitat for triatomines and associate vertebrates in tropical America. The objective of this work is to identify the triatomine species living in the palms of rural areas in the Province of Corrientes, and to estimate the potential epidemiological risk they represent for the residents of nearby houses. The survey was carried out in a palm community in Colonia Laurel, Department San Roque, Province of Corrientes, Argentina. Samplings were performed in October, November and December 1998; January, February and March 1999; May and June 1999. Thirty palms: 27 (90 percent) Butia yatay (Mart.) Becc. and 3 Acrocomia aculeata (Jacq.) Lodd ex Mart. were dissected. Triatoma sordida StÕl 1859 was found in 96.2 percent of B. yatay and in all the A. aculeata palms. A total of 272 live T. sordida was collected; 36 of them (13.2 percent) were found in bird nests in the frond and the remainder in other locations of the tree. The mean number of triatomines per palm was 9.6 (range 1-60, mode 2). T. sordida was collected during all the sampling months and all stages were present at all seasons. The highest population density was reached in spring and the lowest in autumn. Trypanosoma cruzi was detected in 38.5 percent in feces of 174 examined insects and identified as such, both by microscopical examination and PCR. This is the first finding of T. sordida populations in B. yatay, an endemic palm of South America distributed in southern Brazil, Uruguay and northeastern Argentina. The high infection prevalence found in this work suggests that T. sordida plays an essential role in the maintenance of the wild T. cruzi transmission cycle in northeastern Argentina

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

Esta investigación tiene como objetivo identificar los triatominos que predominan en ambientes domésticos y extradomésticos de diferentes departamentos de la Provincia de Corrientes mediante muestreos llevados a cabo dese 1985 hasta 1995. En los ecótopos domiciliarios se detectaron Triatoma infestans (Klug, 1834), Triatoma sordida (Stal, 1859), Panstrongylus geniculatus (Latreille, 1811) y Panstrongylus megistrus (Burmeister, 1835). T. infestans y T. sordida se hallaron también en ambientes peridomésticos. Triatoma platensis (Neiva, 1913), Psammolestes coreodes (Bergroth, 1911), T. sordida y Triatoma rubrovaria (Blanchard, 1843) se colectaron en biótopos silvestres. En los domicilios, se confirmó el predominio de T. infestans. Esta especie fue la única parasitada por tripanosomas cruziformes. Si bien T.sordida fue más frecuente en los ecótopos extradomésticos, se demostró su tendencia a colonizar los ambientes domésticos.

Contribución al conocimiento de los reservorios del Trypanosoma cruzi (Chagas, 1909) en la Provincia de Corrientes, Argentina / Contribution to knowledge of reservoirs of Trypanosoma cruzi (Chagas, 1909) in Corrientes Province, Argentina

Con el propósito de identificar a reservorios del Trypanosoma cruzi se investigaron 60 mamíferos en los Departamentos Capital y San Luis del Palmar. Se examinaron. primates, roedores, marsupiales, carnívoros y edentados; 40 vivían en cautiverio y 20 fueron capturados mediante trampas en una comunidad rural florestal. Los mamíferos fueron analizados por xenodiagnóstico, empleándose ninfas de 3§ o 4§ estadío de Triatoma infestans ayunadas durante 2 semanas. Las heces de los triatominos fueron observadas al microscopio (400x) a los 30, 60 y 90 días post-alimentación. En 2 Saimiri sciureus y en 1 Cebus apella se constató infección por tripanosomas cruziformes. Se concluye que la parasitemia detectada fue baja. La presencia de Didelphis albiventris, reservorio potencial del Trypanosoma cruzi, en una zona de transmisión activa del parásito representa un factor de riesgo, por lo que son necesarias futuras investigaciones epidemiológicas para determinar la real diagnosis de esta parasitosis en la provincia de Corrientes, Argentina

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

Para saber se algum tipo de interaçäo se produzia entre populaçöes de Triatoma infestans e T. sordida que conviviam em uma unidade experimental e compartilharam o mesmo recurso alimentar (ave), foi realizado estudo que abrangeu o período de setembro de 1988 a abril de 1989. A composiçäo etária inicial para cada espécie foi: 27 N1, 7 N2, 11 N3, 3 N4, 8 N5, 4 machos e 10 fêmeas. A dinâmica da populaçäo, o estado nutricional, a predaçäo e a conduta gregária foram estimados mediante censos mensais. T. infestans obteve maior êxito colonizador que T. sordida dado os valores alcançados em: fecundidade (146 ovos/fêmea), longevidade (157,8 dias) e mortalidade (39,4 por cento), em comparaçäo aos obtidos por T. sordida: 118 ovos/fêmeas, 81,1 dias e 54,0 por cento respectivamente. A populaçäo de T. infestans teve crescimento do tipo exponencial, com alta taxa de renovaçäo ninfal; em contraposiçäo, a populaçäo de T. sordida se extinguiu mais cedo. Em geral, o peso médio dos exemplares de T. infestans manteve-se em valores próximos ao inicial, enquanto que em T. sordida se reduziu. Os grupos gregários se formaram sobretudo no setor inferior da parede 1 (próximo ao hospedeiro), observando-se maior nível de contágio em T. infestans. A partir dos resultados obtidos, formulou-se a hipótese da superioridade competitiva de T. infestans