Mollusks and larvae of trematodes in a non-endemic area for schistosomiasis mansoni

Abstract

Schistosomiasis is a relevant disease for public health in Brazil and Alagoas, and it is important to investigate the presence of the disease in endemic and non-endemic areas for the progress of eradicating this disease. Thus, the objective of the study was to carry out an investigation of mollusks and larvae of trematodes in an area not endemic for schistosomiasis mansoni. The study was carried out in Santana do Ipanema, Alagoas, by capturing snails in the Camoxinga stream and analyzing positivity for trematode larvae, including Schistosoma mansoni larvae, the etiological agent of schistosomiasis mansoni.  In addition, an analysis of the species' constancy of capture and the influence of periods of drought and rain and the average monthly precipitation on the abundance of snail species for the period from August 2018 to July 2019 was carried out. period, 2,431 snails were captured, with 443 (18.2%) dead. The animals captured alive (1,988) belonged to the species Biomphalaria straminea (Dunker, 1848) (Planorbidae) (989; 40%), Melanoides tuberculatus (Müller, 1774) (Thiaridae) (792; 32%), Pomacea lineata (Spix, 1827 ) (Ampullariidae) (133; 5.4%), Drepanotrema depressissimun (Moricand, 1839) (53; 2.18%), Physa marmorata (Guilding, 1828) (19; 0.78%) and Cyanocyclas brasiliana (Deshayes, 1854) (2; 0.03%) . In addition, B. glabrata and M. Tuberculatus were the species that were constantly collected and had abundant status for the study area. Regarding the two species of greatest constancy and abundance in the study area, B. straminea and M. Tuberculatus, it was not possible to establish a relationship between the abundance of animals and the period of collection (rainy or dry, p = 0.2336). The largest number of animals of both species was captured in the months of June and July 2019 for M. tuberculatus and B. straminea, respectively. The increase in the number of animals collected began to occur with the increase in rainfall indexes (January to April 2019) with a reduction in rainfall and animal abundance (May 2019), followed by a subsequent increase in both parameters, until the end of the year. end of the period studied. There was a linear relationship between rainfall and the abundance of B. straminea snails. The analysis of the infection of animals collected by larvae of trematodes showed that no animal of the species B. straminea was infected with larvae of Schistosoma mansoni. On the other hand, snails of the species B. straminea, D. depressissimun and M. tuberculatus were diagnosed eliminating cercariae of the species Longifurcate pharyngeate distome - Estregeocercária, Echinocercaria sp. and Xiphidiocercaria that were released from the mollusc M. tuberculatus, D. depressissimum and B. straminea. This research notifies the distribution of different species of snails being the first report of the presence of mollusks M. tuberculatus, D. depressissimum, Physa marmorata, Pomacea insularum, Cyanocyclas brasiliana in the Riacho Camoxinga, demonstrating the importance of studies of malacofauna in non-endemic areas for schistosomiasis to promote the prevention and control of these animals of medical importance, since these invertebrates can act as intermediate hosts of trematodes.