Monitoramento da população de Biomphalaria tenagophila (Gastropoda, Planorbidae) em Bananal-SP no período de 2013 – 2015, após a introdução da linhagem do Taim-RS

Abstract

In the present study, the efficacy of the new model of biological control in the transmission of schistosomiasis was evaluated in a stream in the city of Bananal-SP. This model consists of the large-scale introduction of specimens of the Taim strain B. tenagophila (resistant) with the purpose of transmitting their dominant resistance to B. tenagophila (susceptible) populations of the Herivelto Martins stream. To evaluate the effect of this introduction on the levels of susceptibility of the Bananal population, a study was conducted during the period from 2013 to 2015. The parameters analyzed were the susceptibility rates and the presence of the typical molecular marker of the Taim lineage (350 bp). The results showed that the offspring of the molluscs collected 40 and 64 months after the introduction, that were submitted to the tests of infection with S. mansoni SJ strain, presented susceptibility rates of 17.3% and 40.54% respectively. These data indicate significant differences in molluscs susceptibility when compared to the control group rates, 34.6% and 68.08%, respectively. An increase in susceptibility in the group of molluscs analyzed after 64 months, as well as in their control group was observed. In this study it was not possible to evaluate the infection rates of the mollusc descendants collected at 52 months. Only the molecular tests were performed, being all specimes negative for the presence of the 350 bp marker. On the other hand, this marker was present in 26.92% and 11.76% of the analyzed samples, after 40 and 64 months of intervention, respectively. The reduction in the volume of the Herivelto Martins stream, between the years 2014 and 2015, caused by low annual precipitation, reduced the population density of molluscs. However, the presence of genetic patrimony of the Taim lineage indicates the success of the introduction, showing the efficacy of this form of schistosomiasis control.