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Laboratorio de Biomoleculas, Universidad Simуn Rodrнguez, Nъcleo Canoabo, Municipio Canoabo, Carretera Nacional Bejuma-Urama, Estado Carabobo, Republica Bolivariana de Venezuela 1
Laboratorio BioMolp, Universidad de Carabobo, Naguanagua, Estado Carabobo, Republica Bolivariana de Venezuela 2
Эта статья опубликована в сборнике по материалы первой Международной юбилейной конференции «Актуальные проблемы инфектологии и паразитологии», посвященной 110-летию со дня открытия проф. К.Н.Виноградовым сибирской двуустки у человека (2-5 апреля 2001, г. Томск)
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Изменение величины Biomphalaria glabrata при заражении Schistosoma mansoni
S. mansoni проходит часть своего жизненного цикла в промежуточном хозяине улитках семейства Planorbidae. Biomphalaria glabrata один из наиболее важных промежуточных хозяев шистосом. В этой статье приводятся данные об изменении размеров B. glabrata (Barbula, Венесуэла), заражённых мирацидиями S. mansoni (SM паразитами, обитающими в штате Carabobo, Венесуэла). Улиток группировали по трём размерам: 1 класс (5-8 мм), 2 класс (>8-11 мм) и 3 класс (> 11-14 мм). Каждая улитка заражалась 5 мирацидиями индивидуально. Процент восприимчивости составил: 1 класс - 88,89%, 2 класс - 11,54% и 3 класс - 8,33%. Корреляционный анализ показал отсутствие связи между величиной промежуточного хозяина и продукцией церкариев.
ABSTRACT. Schistosoma mansoni develops part of its life cycle in intermediate host snails of the family Planorbidae. Biomphalaria glabrata is one of the most important intermediate host species. This paper reports the influence of size of Biomphalaria glabrata (Bбrbula, Carabobo estate, Venezuela) were exposed to miracidia of Schistosoma mansoni (SM parasite, origin of Carabobo state, Venezuela). Snails batches (20, B. glabrata in duplicate) of three different diameter: class I (5-8 mm), class II (>8-11 mm) and class III (>11-14 mm) were exposed individually with five miracidia. The susceptibility percentage present were: class I 88.89%, class II 11.54% and class III 8.33%. The correlation analysis indicated a not relation between the size of host-intermediary and cercarial production.
Key Words: Biomphalaria glabrata, Schistosoma mansoni, susceptibility, size, Venezuela.
INTRODUCTION
Schistosoma mansoni perform part of its biological cycle on Planorbid snails of the genus Biomphalaria. Such a association is restricted by ecological, biochemical, geographical and population .1,2,3,5,11,12
It has been described that genetic and nutritional factors modulate the good or bad association between snails and parasitic. Other trials have showed that the age of the intermediary host is a very important factor in the infectious dynamic, due to the younger host snails are more susceptible than the others. 8,9,10,13 Richards et al in 199213 determinated four category of hospedere-intermediate in relation to response differences of susceptibily: Type I, not-susceptibility of snails in whole life. Type II, juvenile susceptibility/ not-susceptibility when adults. Type III, susceptibily of snails in whole life. Type IV, young susceptibility/ variable adults.
Researches have evidenced the roll of ontogenic in relation to cellular responses of host-intermediate snails, demonstrating that juvenile moluscs present a high valor of positive. The dynamic of immulogical relation between intermediate-host and parasitic involves different strategies: cellular defense and humoral response by snails, encapsulation and destruction of primary sporocyst and phagocytosis of the miracidia.1,4,11
In this work, it is described the influence of size of Biomphalaria glabrata on the values of infectivity and the cercarial liberation dynamic when they are experimentally confronted with isolated of Schistosoma mansoni, proceeding from common geographical area (Carabobo state, Venezuela).
MATERIALS AND METHODS
Protocols experimental. Groups (20 in duplicated) of Biomphalaria glabrata snails of three different shell diameter: class I (5-8 mm), class II (>8-11 mm) and class III (>11-14 mm) were exposed individually with five miracidia of Schistosoma mansoni, which maintained on NMRI mice. The feces was clarified by washing procedures using isotonic saline solution, helping the capture of miracidia13 . The eclosion of the eggs was stimulated during 30 minutes by exposing them to artificial light fountain. Experimental conditions about the infection, evaluation, maintenance of the parasited-snails and controls-snails meet detail described in anterior researches.12,13 Survival reports were carried out weekly, for both controls and parasitized molluscs. They were marked with color code up one to five, using different colors of nail paint.
Statistical analysis. Data was submitted to one-way analysis of variance (p<0.05). Whenever significance was found, the Tunkey test was applied at the same level of significance (p<0.05).
Geographic origin of isolated and molluscs. The insulating SM was obtained of patient native of Guacara, Carabobo state, Venezuela.4 The molluscs Barbula are breeding stablishished in Naguanagua, Carabobo state, Universidad de Carabobo, Venezuela 8. The all studied snails were created in the laboratory besides three generations.
Total number of emissions cercarial. Were carried through registers of the total numbers of eliminate cercariae for each snails 8,9.
RESULTS
In Table 1, the susceptibility percentage obtained to the different shell diameter (mm) of the molluscs Bбrbula, exposed with five miracidia are observed. It observed that 88.89% (size I); 11.54% (size II) and 8.33% (size III) respectively. Statistical analysis reveleated significantive differences between groups (p*0.05). The comparison of mean (Tukey, p *0.05), confirm that the class I is more susceptible to the experimental infection than the rest of studied size (there are not significant differences between II and III). In relation to the prepatencia, it was observed that to the class I was positive beginning the fourth week post-exposition; unlike the class II and III had emissions of cercariae after five weeks (figure 2, 3 and 4).
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