Potential schistosome-vector snails and associated trematodes in ricefields of Corrients province, Argentina: preliminary results

Abstract

Considering the possibility of introduction of schistosomiasis mansoni into Argentina as a consequence of dam construction on the Rio De La Plata basin, preliminary studies have been carried out on agrosystems such as ricefields in Corrientes province with the following purposes: 1) to survey and estimate the relative abundance of planorbids and identify potential vector species; 2) to identify environmental factors capable of influencing Biomphalaria population dynamics; and 3) to find out snail-parasite associations and estimate snail infection rates in order to detect possible competitive interactions between larval stages of native trematodes that could be used in biological control of Schistosoma mansoni. Three potential schistosome vectors were detected in ricefields, namely Biomphalaria straminea, B. tenagophila and B. peregrina, although B. orbignyi, a species refractory to infection with S. mansoni, proved the most frequent and abundant. Positive correlations (P less than 0.05) were found between Biomphalaria abundance and some environmental parameters: conductivity, hardness, calcium, nitrites plus nitrates, ammonium and bicarbonates. Water temperature correlation was negative (P less than 0.05). No correlation (P less than 0.05) was found in total iron, phosphates (SRP), pH and soil granulometry.

Susceptibility of Argentinean Biomphalaria tenagophila and Biomphalaria straminea to infection by Schistosoma mansoni and the possibility of geographic expansion of mansoni schistosomiasis

“…The signifi cance of B. straminea as a vector of S. mansoni is associated with greater endemicity in northeastern Brazil. Furthermore, an extended geographical distribution of B. straminea in South America has been noticed in recent years 6,10 . Michelson & Dubois 31 defi ned B. straminea as a species of competitive superiority due to its capacity to invade territory occupied by other species.…”

“…This species was reported 6 in a pisciculture aquarium in Porto Alegre (RS, Brazil). B. straminea and B. tenagophila have been identifi ed in rice fi elds in Corrientes (Argentina); B. straminea was more abundant than B. tenagophila 10 .…”

“…Among the species described in Rio Grande do Sul (Brazil), the primary vector of S. mansoni in the South American continent, B. glabrata, is responsible for the occurrence of the disease in the municipality of Esteio 4 . In Uruguay, Paraguay, and Argentina, numerous planorbid breeders have been described in association with B. tenagophila and B. straminea [8][9][10][11][12] , which are known to be natural vectors of S. mansoni. Breeding conditions are favorable for these mollusks in the fl ooded fi elds used for plantations and in irrigation canals and reservoir dams.…”

Diversity and distribution of mollusks along the Contas River in a tropical semiarid region (Caatinga), Northeastern Brazil

“…These mollusks have a high capacity to tolerate oxygen scarcity, and they are also more tolerant to extreme variations of temperature than are most prosobranchs (McMahon 1983, Brown et al 1998). The pulmonates P. acuta and B. straminea have been recorded in lentic environments with low oxygen concentration in many parts of Brazil (Martins-Silva & Barros 2001, Vidigal et al 2005, Tibiriçá 2006) and in nearby countries (Rumi & Hamann 1990, De Francesco & Hassan 2009). Among the Brazilian species of Biomphalaria, B. straminea is the best adapted to dry climates (Paraense 1977).…”

Estudios morfoanatómicos y tendencias poblacionales en especies de la familia <i>Chilinidae</i> Dall, 1870 (Mollusca: Gastropoda) en la Cuenca del Plata

“…Además de la identificación específica, la determinación de áreas de distribución y el grado de susceptibilidad, los estudios para establecer las épocas de reclutamiento y la velocidad del crecimiento, permiten elaborar estrategias de control indirecto del parásito. En la Argentina, y sobre gasterópodos pulmonados dulceacuícolas se pueden mencionar los trabajos realizados por Rumi & Hamann (1990, 1992, Rumi (1993), Borda & Rea (1997) y Rumi et al (2004b).…”