Los caracoles de la familia Lymneidae, como Pseudosuccinea columella, actúan como hospedadores intermediarios de Fasciola hepatica, el agente etiológico de la fasciolosis, zoonosis que afecta al ganado y al hombre en todo el mundo. Conocer profundamente las características biológicas de estos caracoles resulta esencial para describir la dinámica de transmisión y controlar esta parasitosis. La calidad del alimento afecta significativamente el crecimiento, la fecundidad y la fertilidad de estos caracoles. En este estudio, evaluamos la utilización de la espirulina (Arthrospira platensis) como fuente de alimento para la cría artificial de P. columella, una especie invasora que actúa como el principal hospedero intermediario de F. hepatica en el Noreste Argentino. El objetivo principal de este trabajo fue medir el efecto de la espirulina en parámetros del fitness tales como: tasa de supervivencia, tasa de crecimiento, tamaño que alcanzan a la madurez sexual, duración del período fértil, fecundidad y viabilidad de la descendencia. Se utilizaron 20 767 huevos F2 recién puestos; la mitad de ellos fue alimentado con lechuga (tratamiento L) y la otra mitad con lechuga mas espirulina (tratamiento L+S). En comparación con las P. columella alimentadas solamente con lechuga, las P. columella alimentadas con lechuga mas espirulina: 1) presentaron mayores tasas de supervivencia, 2) alcanzaron mayores tamaños y en menor tiempo, 3) alcanzaron la madurez sexual antes de tiempo (L+S:60 días vs. L:120 días) y a menor tamaño (L+S:4.8mm vs. L:8.2mm), 4) tuvieron un período reproductivo más largo (L+S:150 días vs. L:90 días), 5) produjeron mayor cantidad de huevos/caracol (L+S:29.6 vs. L:13.3) y 6) su descendencia tuvo una mayor tasa de eclosión (L+S:70% vs. L:40%). La incorporación de espirulina como suplemento alimenticio mejoró significativamente los parámetros biológicos de P. columella y maximizó la cría artificial de esta especie en laboratorio. La espirulina podría tener un efecto positivo directo sobre el desarrollo de P. columella mediante su consumo, pero también podría tener un efecto positivo indirecto al mejorar la calidad del agua. Con la técnica de cría desarrollada en este trabajo se obtiene una gran cantidad de caracoles adultos reproductores y una continua producción de huevos que son esenciales para desarrollar futuros estudios que permitan aumentar nuestro conocimiento sobre la biología de P. columella.

Snails of the family Lymnaeidae, as Pseudosuccinea columella, are the intermediate hosts of Fasciola hepatica, the causative agent of fasciolosis in human and livestock all over the world. A thorough knowledge of snail biology is essential for describing the transmission dynamics and for controlling this disease. Since food quality has had a significant effect on snail growth, fecundity and fertility, in this study we evaluated the use of spirulina (Arthrospira platensis) as a food resource for the artificial breeding of P. columella, an invasive snail and the main intermediate host of F. hepatica in Northeastern Argentina. The main purpose was to measure the effect of spirulina on fitness parameters such as survival rate, growth rate, size at first reproduction, lifetime fecundity and viable offspring. A total of 20 676 newly-laid F2 eggs were used; half of them were fed with lettuce (treatment L) and the other half with lettuce plus spirulina (treatment L+S). In comparison with P. columella snails fed only with lettuce, we found that P. columella fed with lettuce plus spirulina: 1) showed higher survival rates, 2) grew faster and showed higher growth increments, 3) attained sexual maturity earlier in time (L+S:60 days vs. L:120 days) and at a smaller size (L+S:4.8mm vs. L:8.2mm), 4) had a longer reproductive period (L+S:150 days vs. L:90 days), 5) produced a higher number of eggs/snail (L+S:29.6 vs. L:13.3), and 6) showed a higher offspring hatching rate (L+S:70% vs. L:40%). The supplementation of P. columella diet with commercial spirulina enhances it fitness and improved the artificial breeding of this species. Spirulina may have a direct positive effect on P. columella development by consuming it, along with an indirect positive effect by improving the water quality. This rearing technique provided large number of reproducing adults and a continuous production of offspring, which are essential for developing future experimental studies in order to improve our knowledge on P. columella biology.

An epidemiological focal study was performed in Loncopué, Neuquén, Argentina, in November 2002 to detect the origin of the infection in a human case of fascioliasis confirmed by an indirect-ELISA test, six months before the study. Thirty five individual fecal samples were taken from domestic livestock, and watercress plants and snails were collected from the irrigation ditches connected to a main canal in the surroundings of the patient’s house. A new blood sample was taken from the already recovered patient. The patient was still seropositive to Fasciola hepatica antigens. No metacercariae were found in the 222 watercress leaves checked. All the snails collected (n=130) were identified as Lymnaea viatrix and two out of 101 (2%) were infected with F. hepatica larvae. Coprological analysis showed F. hepatica eggs in 100% of goats (10/10), 82% of sheep (9/11) and 86% of bovines (6/7). The number of eggs per gram shed by positive goats (median=20.7, Q1=6.2, Q3=34.5) and sheep (4, 1.8, 13) was significantly higher than in cows (0.3, 0.3, 1.7) (p<0.01). Local veterinary control programs were apparently not effective in this case. Anthelmintics used and treatment schedule should be revised and small herds raised at households should also be included and treated.

El objetivo del trabajo fue realizar un estudio de foco relacionado con un caso de fasciolosis humana ocurrido en abril de 2002 en Loncopué, Neuquén, Argentina. La confirmación diagnóstica se efectuó en mayo de 2002 por el test de ELISA. En noviembre de 2002 se realizó un muestreo en el área rural donde se ubicaba la vivienda de la paciente, ya restablecida, y se le tomó una nueva muestra de sangre. El suero de la paciente continuó reactivo para antígenos de Fasciola hepatica. Se muestrearon plantas de berro para detectar metacercarias. Se recolectaron caracoles en cuatro canales de riego conectados a un canal principal. Los caracoles fueron trasladados vivos para su identificación, medición y examen de infección. Se recolectaron 35 muestras fecales de ganado de cría. No se observaron metacercarias en las hojas de berro examinadas (n=222). Se recolectaron 130 caracoles identificados como Lymnaea viatrix y 2 de 101 ejemplares (2%) estaban infectados con larvas de F. hepatica. Las prevalencias en el ganado adulto fueron: 100% (10/10) para caprinos, 82% (9/11) para ovinos y 86% (6/7) para bovinos. El número de huevos eliminados por las cabras (mediana = 20.7; Q1=6.2; Q3=34.5) y ovejas (4, 18, 13) infectadas, resultó mayor que el eliminado por vacas (0.3; 0.3; 1.7) (p<0.01). La práctica de control local no tuvo efecto aparente en este caso, por lo que deberían revisarse los calendarios de tratamiento y los antiparasitarios utilizados. Los resultados muestran que el ganado criado a pequeña escala por los pobladores debe incluirse en los programas de control. Se discute la posible importancia de la fasciolosis humana en Argentina.

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, < 4 year old seropositives and precarious life conditions prove that this endemic disease is still a problem in the studied area.

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.

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

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

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

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.

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%) Butia yatay (Mart.) Becc. and 3 Acrocomia aculeata (Jacq.) Lodd ex Mart. were dissected. Triatoma sordida Stål 1859 was found in 96.2% of B. yatay and in all the A. aculeata palms. A total of 272 live T. sordida was collected; 36 of them (13.2%) 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% 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.

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

Canine-borne helminthiases constitute a worldwide problem. Some of these parasites can originate serious pathologies in humans. Given the potential existence of these zoonoses in Argentina, horizontal surveys on contamination degree evaluated as faeces per hectare and on parasite prevelence in faeces were carried out in six localities of the Province of Chubut. The behaviour of people visiting public places was also analyzed qualitatively. All of the survey sites were contaminated with faeces and with some parasitic forms. Contamination degrees ranged from 32 to 147 faeces/ha. Toxocara sp. (17.4%), Strongyloides sp. (5.1%), and Ancylostoma. sp (5.6%) were the main genera among other parasites detected. As a whole, the analysis revealed that contamintion degree, prevalence and human behaviuor in relation to the exposure to the parasite would be the main factors to be taken into account in formulating control measures. Transmission risk patterns in Chubut were not homogenous; therefore, studies and control strategies should be devised and implemented at the local scale.

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

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

Triatoma guasayana and two putative cryptic species pertaining to T. sordida complex (named groups 1 and 2) occur in sympatry in the Bolivian Chaco. Using multilocus enzyme electrophoresis and subsequent genetic analysis, our work assesses their population distribution and dispersal capacity in domestic, peridomestic, and silvatic environments. Our collections by light trap in the silvatic environment indicated a predominance of T. guasayana and T. sordida group 2 and a lesser abundance of T. sordida group 1 (£ 10% of the total of captures). Their similar distribution in two silvatic areas 80 km apart supports the hypothesis of their homogeneous dispersal through the Bolivian Chaco. The distribution of T. guasayana and T. sordida groups 1 and 2 was similar between silvatic environment and peridomestic ecotopes where 25% of positive places was occupied by two or three species. Bromeliads were confirmed as favorable shelter for T. guasayana but were free of T. sordida. T. sordida group 1 and to a lesser extent T. guasayana would be more invasive vectors for houses than T. sordida group 2. The spatial partition in the three species sampled in two distant sites suggested a reduced dispersive capacity.

We determined the seroprevalence of leptospirosis in a suburban canine population for the purpose of analyzing the association between different individual and environmental variables and seropositivity for leptospirosis. The study, which was cross-sectional, was performed in July 1992 in a neighborhood of Greater Buenos Aires with approximately 9 500 inhabitants and a canine population of around 2 000 animals. We studied a random sample of 223 dogs and obtained a blood sample from each. Each animal’s epidemiologic history was obtained by interviewing the housewife. Serologic measurements were performed by the microagglutination technique with the use of 10 different serotypes of Leptospira interrogans. Of the 223 dogs that were tested, 57% showed seropositivity; 82% of the positive sera coagglutinated with two or more serotypes. The most frequently detected serotypes were canicola and pyrogenes. Seroprevalence in females was less common than in males (P <0,05) and in puppies less than 1 year old it was less common than in older animals (P <0,01). Street behavior in the dog and the presence of stagnant water in front of the owner’s dwelling were the most important of the risk factors examined. The associations between seropositivity on the one hand and contact with trash deposits, hunting behavior and the presence of rodents inside the dwelling on the other were not statistically significant. Different control measures are discussed.

Se determinó la seroprevalencia de leptospirosis en una población canina suburbana con el objeto de analizar la asociación entre distintas variables individuales y ambientales y la seropositividad a leptospirosis. El estudio, de diseño transversal, se llevó a cabo durante julio de 1992 en un barrio del Gran Buenos Aires en el que viven unos 9 500 habitantes y una población canina de unos 2 000 animales. Se estudió una muestra aleatoria de 223 perros, de cada uno de los cuales se obtuvo una muestra de sangre. La ficha epidemiológica del animal se obtuvo por encuesta al ama de casa. Las determinaciones serológicas se realizaron por microaglutinación frente a 10 serotipos de Leptospira interrogans. Se halló seropositividad en 57% de los 223 perros examinados; 82% de los sueros positivos coaglutinaron con dos o más serotipos. Los serotipos detectados con mayor frecuencia fueron canicola y pyrogenes. La seroprevalencia en hembras fue menor que en machos (P <0,05) y entre los cachorros de menos de 1 año de edad, menor que en los animales de mayor edad (P <0,01). El callejeo del perro y la presencia de agua estancada frente a la vivienda del propietario fueron los factores de riesgo más importantes entre los que se estudiaron. Las asociaciones de la seropositividad con el contacto con un basural, con el comportamiento de caza del perro y con la presencia de roedores en la vivienda no fueron estadísticamente significativas. Se discuten distintas medidas de control.

This study was performed in an urban neighborhood of the capital city of the province of San Juan, Argentina. Erected as a housing complex, the place consists of 768 flats distributed in buildings of three and seven floors each. A survey was carried out in 33% of the dwellings, enquiring about the number of Triatoma infestans found indoors, stage of the bug development - nymph or adult - and how these insects had entered their homes. Adult T.infestans were found on all floors; 163 people (64%) had found them at least once, and 130 (51%) several times. Dispersal flight seems to have been the main mechanism of infestation by adult bugs in this area, and a total of 51% of the surveyed inhabitants reported that the insects had flown into their flats.