Molluscicidal activity of polyhexamethylene biguanide hydrochloride on the early-life stages and adults of the Biomphalaria glabrata (Say, 1818).

Schistosomiasis is a disease that affects tropical and subtropical areas and is considered the second most prevalent parasitic disease in the world. One of the ways of combating this disease is the use of molluscicidal agents to eliminate or reduce the population of intermediate host snails. Polyhexamethylene biguanide hydrochloride (PHMB) is a chemical biocide commonly used as a disinfectant and antiseptic in the food industry and very successfully for the disinfection of swimming pools. The US Environmental Protection Agency (USEPA) indicated the PHMB as low environmental risk. The present study aimed to evaluate the molluscicidal activity of the PHMB in freshwater snail (Biomphalaria glabrata), intermediate host of Schistosoma mansoni. The PHMB showed high toxicity against all stages of the snail B. glabrata: embryos, new-borns and adults. The LC50 estimated was 0.98 mg L-1; 1.43 mg L-1 and 1.49 mg L-1, respectively, after exposure of 144 h for embryos and 96 h for new-borns and adults. PHMB did not prevent the development of embryos within the egg mass, since at all concentrations evaluated 80% of the embryos managed to develop until the hypo-stage, which is the last stage of development before hatching. However, PHMB inhibited the hatching of embryos by 100% at all concentrations above 1.6 mg L-1. PHMB proved to be a promising substance in the fight against schistosomiasis by eliminating the intermediate host (B. glabrata). This was the first study that makes an experimental observation of the molluscicidal activity of PHMB.