Silvia Pietrokovsky

Feeding Patterns of Triatoma longipennis Usinger (Hemiptera, Reduviidae) in Peridomestic Habitats of a Rural Community in Jalisco State, Mexico

Abstract We analyzed triatomine blood feeding patterns to evaluate the role of peridomiciles in Trypanosoma cruzi transmission at the rural village of Tepehuaje de Morelos at Jalisco State, Mexico (1999). A total of 206 bugs were collected in 11 out of 26 households (42.3%). Nymphs predominated in the collections (64.9% of the total). Except for one Triatoma barberi female, a species that belongs to the protracta species complex, all adults were Triatoma longipennis, a species of the phyllosoma complex. Triatomines were exclusively present in peridomestic sites mainly piles of tiles and bricks, and none were found indoors. Overall infection rate was 56.6% and no significant differences (P > 0.05) were observed between nymphs and adults or males and females. Identified blood meals were chicken (29.4%), opossum (20.9%), pig (24.5%), murid (20.9%), dog (3.5%), and armadillo (0.7%). No gut content reacted against anti-human, anti-bovine, anti-rabbit, and anti-cat sera. In contrast to fifth nymphs and adults, 87% of the small nymphs fed on one host, indicating that they are less mobile than other stages. Most fifth nymphs and adults fed on domestic hosts, while small nymphs mainly fed on opossum and murid. Infection blood-meal indexes were around 50% for single meals on opossum and murid, stressing their importance as trypanosome donors. Peridomiciles in Tepehuaje could be regarded as interaction sites among domestic and wild and synanthropic mammals and triatomines, which would facilitate circulation of the same T. cruzi strains between domestic and sylvatic cycles. Stone-made walls and building materials, which hold synanthropic rodents and opossums, should be considered as targets for vector control measures.

Fasciola hepatica infections in livestock flock, guanacos and coypus in two wildlife reserves in Argentina

Between autumn and spring 2006, a coprological survey was performed in two wildlife reserves located in the north of Argentine Patagonia to determine the prevalence of Fasciola hepatica and the number of parasite eggs per gram (epg) of feces in wild guanacos (Lama guanicoe), coypus (Myocastor coypus), and locally born and raised goats and sheep. Snails of the Family Lymnaeidae were collected in freshwater habitats, identified taxonomically and analyzed parasitologically. Prevalence of patent infection was 100% in sheep (n=69) and coypus (n=9), 84% in goats (n=20) and 0.5% in guanacos (n=224). No significant differences in epg were found among animals, but the median epg of coypus (160) and sheep (160) was higher than that of goats (80). For guanacos and goats, a negative binomial model estimating the population egg-count frequency could be fitted, while for coypus and sheep parasite egg-count frequencies trended toward a normal distribution, indicative of a more even, and much less aggregated distribution across sampled hosts. All snails (n=175) were Lymnaea truncatula and none of them was found infected. This is the first report of fascioliasis in free-ranging guanacos in Argentina. Coypu appears to be a major wildlife reservoir of F. hepatica, which was presumably introduced locally by livestock.

Real-time PCR strategy for rapid discrimination among main lymnaeid species from Argentina.

Snails of the Family Lymnaeidae act as an intermediate hosts of Fasciola hepatica worldwide. The taxonomy of lymnaeid species is relevant for epidemiological studies and molecular strategies are increasingly used for that purpose. This work presents the first report of a real-time PCR approach used to identify the most important lymnaeid species in the Southern Cone of South America. Species discrimination is based on the sequence polymorphism located within the helix E10-1 of the variable region V2 of the 18S rRNA genes, which yields amplicons with clearly different melting temperatures. This procedure minimises the risk of carry-over contamination because it does not require post-PCR manipulations, and the whole protocol can be completed in less than 4h with a single snail foot as starting material. This method was successfully carried out in a blind study that included a panel of 20 Galba truncatula, 5 Lymnaea viatrix, 5 Lymnaea diaphana and 5 Pseudosuccinea columella specimens from different endemic areas for fasciolosis. This molecular approach constitutes a key laboratory tool complementing ecological studies that ultimately will promote more efficient control strategies.

Comparative Meiotic Studies in Triatoma sordida (Stål) and T. guasayana Wygodzinsky & Abalos (Reduviidae, Heteroptera)

Triatoma sordida and T. guasayana are competent Trypanosoma cruzi vectors, with overlapping distribution areas in Argentina. Both species are morphologically similar, and their immature stages are hard to discriminate. Cytogenetic studies in the genus Triatoma reveal scarce karyotypic variations, being 2n = 20 + XY the most frequent diploid number in males. In the present work the meiotic behaviour of different Argentinian populations of T. sordida and T. guasayana has been analyzed; the meiotic karyotype of both species has also been compared. The species differ in total chromosome area and in the relative area of the sex chromosomes. These meiotic karyotypic differences constitute an additional tool for the taxonomic characterization of T. sordida and T. guasayana. The analysis of an interpopulation hybrid of T. sordida (Brazil x Argentina) reveals a regular meiotic behaviour; despite the presence of heteromorphic bivalents. Our observations support the hypothesis that karyotype variations through the gain or loss of heterochromatin can not be considered as a primary mechanism of reproductive isolation in Triatoma.

Molecular characterization of cryptic and sympatric lymnaeid species from the Galba/ Fossaria group in Mendoza Province, Northern Patagonia, Argentina

BackgroundFreshwater lymnaeid snails can act as the intermediate hosts for trematode parasites such as the liver fluke Fasciola hepatica, that cause significant economic and biomedical burden worldwide, particularly through bovine fascioliasis. Transmission potential is tightly coupled to local compatibility with snail hosts, so accurate identification of lymnaeid species is crucial for understanding disease risk, especially when invasive species are encountered. Mendoza Province, in Argentina, is a center of livestock production and also an area of endemic fascioliasis transmission. However, the distribution of lymnaeid species in the region is not well known.MethodsThis study examined lymnaeid snails from seven localities in the Department of Malarguë, Mendoza Province, using morphological and molecular analyses and also describing ecological variables associated with snail presence.ResultsWhile morphological characters identified two species of lymnaeid, Galba truncatula and G. viatrix, molecular data revealed a third, cryptic species, G. neotropica, which was sympatric with G. viatrix. G. truncatula was exclusively found in high altitude (>1900 meters above sea level [masl]) sites, whereas mixed G. neotropica/G. viatrix localities were at middle elevations (1300–1900 masl), and G. viatrix was found alone at the lowest altitude sites (<1300 masl). Phylogenetic analysis using two mitochondrial markers revealed G. neotropica and G. viatrix to be closely related, and given their morphological similarities, their validities as separate taxonomic entities should be questioned.ConclusionsThis study highlights the need of a robust taxonomic framework for the identification of lymnaeid snails, incorporating molecular, morphological and ecological variables while avoiding nomenclature redundancy. As the three species observed here, including one alien invasive species, are considered hosts of varying susceptibility to Fasciola parasites, and given the economic importance of fascioliasis for livestock production, this research has critical importance for the ultimate aim of controlling disease transmission.

Temperature and development rate of Triatoma guasayana (Hemiptera: Reduviidae) eggs under laboratory conditions: physiological and adaptive aspects

Abstract Eggs laid in the laboratory by T. guasayana (Wygodzinsky & Abalos 1949) adults collected from wild biotopes in Santiago del Estero (Argentina) were exposed to fluctuating temperatures, and 172 egg batches, involving 1574 eggs, completed development. Their development times were fitted to the linear degree‐day model and three nonlinear models (devar, Lactin, and Rueda). Parameter values and 95% CL were estimated. The lower development threshold is estimated to be 15 °C (linear devar model) and 17.5 °C (Lactin model), and the temperature resulting in the shortest development time is estimated to be between 26 °C (Lactin model) and 37 °C (nonlinear devar model). The thermal death point by the Lactin model is 34.4 °C, and conforms well with other studies. Differences between the present results and those of other studies for T. guasayana are discussed in terms of the maternal effects, the influence of experimental conditions, and the rate summation effect. Using the climatic conditions of the natural environment of T. guasayana, the results are interpreted in terms of physiological adaptation. A generalized development rate response of T. guasayana eggs to increasing temperature is proposed, with three ranges: between 10 and 14.8 °C development rate increases in an accelerating way; between 14.8 and 29.2 °C development rate increases more or less linearly, and between 29.2 and 34 °C development rate decreases.

Unraveling the diversification history of grasshoppers belonging to the “Trimerotropis pallidipennis” (Oedipodinae: Acrididae) species group: a hotspot of biodiversity in the Central Andes

The Andean Mountain range has been recognized as one of the biodiversity hotspots of the world. The proposed mechanisms for such species diversification, among others, are due to the elevation processes occurring during the Miocene and the intensive glacial action during the Pleistocene. In this study we investigated the diversification history of the grasshopper Trimerotropis pallidipennis species complex which shows a particularly wide latitudinal and altitudinal distribution range across the northern, central and southern Andes in South America. Many genetic lineages of this complex have been so far discovered, making it an excellent model to investigate the role of the central Andes Mountains together with climatic fluctuations as drivers of speciation. Phylogenetics, biogeographic and molecular clock analyses using a multi-locus dataset revealed that in Peru there are at least two, and possibly four genetic lineages. Two different stocks originated from a common ancestor from North/Central America—would have dispersed toward southern latitudes favored by the closure of the Panama Isthmus giving rise to two lineages, the coastal and mountain lineages, which still coexist in Peru (i.e., T. pallidipennis and T. andeana). Subsequent vicariant and dispersal events continued the differentiation process, giving rise to three to six genetic lineages (i.e., clades) detected in this study, which were geographically restricted to locations dispersed over the central Andes Mountains in South America. Our results provide another interesting example of “island diversification” motored by the topography plus unstable climatic conditions during the Pleistocene, pointing out the presence of a hotspot of diversification in the Andean region of Peru.