Molluscicidal activity of crude water and hexane extracts of Hypericum species to snails (Radix peregra)

Biocontrol of snail-borne parasites with the glossiphoniid leech, Helobdella austinensis

Parasites in which freshwater snails are intermediate hosts pose a serious threat to human health worldwide. We show here that freshwater snails can potentially be controlled by leech predation; in principle, this approach could significantly reduce snail-borne parasitic diseases (SBPDs). Specifically, glossiphoniid leeches, Helobdella austinensis and congener species, consume freshwater snails indiscriminately, while other common leeches do not. A single adult H. austenensis, for example, can consume up to its weight in snails, e.g. Physella acuta, per day. Our predator-prey models suggest that snail populations could be eliminated in relatively short time periods (approximately six months) using a leech biocontrol approach. This could have considerable impact on global SBPDs by breaking the intermediate host life cycle.

Snail-borne parasitic diseases: an update on global epidemiological distribution, transmission interruption and control methods

Background

Snail-borne parasitic diseases, such as angiostrongyliasis, clonorchiasis, fascioliasis, fasciolopsiasis, opisthorchiasis, paragonimiasis and schistosomiasis, pose risks to human health and cause major socioeconomic problems in many tropical and sub-tropical countries. In this review we summarize the core roles of snails in the life cycles of the parasites they host, their clinical manifestations and disease distributions, as well as snail control methods.

Main body

Snails have four roles in the life cycles of the parasites they host: as an intermediate host infected by the first-stage larvae, as the only intermediate host infected by miracidia, as the first intermediate host that ingests the parasite eggs are ingested, and as the first intermediate host penetrated by miracidia with or without the second intermediate host being an aquatic animal. Snail-borne parasitic diseases target many organs, such as the lungs, liver, biliary tract, intestines, brain and kidneys, leading to overactive immune responses, cancers, organ failure, infertility and even death. Developing countries in Africa, Asia and Latin America have the highest incidences of these diseases, while some endemic parasites have developed into worldwide epidemics through the global spread of snails. Physical, chemical and biological methods have been introduced to control the host snail populations to prevent disease.

Conclusions

In this review, we summarize the roles of snails in the life cycles of the parasites they host, the worldwide distribution of parasite-transmitting snails, the epidemiology and pathogenesis of snail-transmitted parasitic diseases, and the existing snail control measures, which will contribute to further understanding the snail-parasite relationship and new strategies for controlling snail-borne parasitic diseases.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0414-7) contains supplementary material, which is available to authorized users.

Molluscicidal activity of Manilkara subsericea (Mart.) dubard on Biomphalaria glabrata (Say, 1818)

Schistosomiasis is promoted for species from Schistosoma genus affecting over 200 million people worldwide. Molluscicides are an efficient method to control this disease, being able to reduce intermediate host snail Biomphalaria glabrata number. In function of resistance cases using niclosamide, natural products are promisors to discover new drugs. Manilkara subsericea is endemic to Brazilian sandbanks of Rio de Janeiro State and wide ranges of biological activities. However, there is no studies evaluating its effects as molluscicidal agent. We tested crude extract from leaves of M. subsericea molluscicidal action, as well it ethyl-acetate fraction and isolated substances against B. glabrata. M. subsericea leaves crude extract and ethyl acetate fraction induced 80±4.13% and 86.66±4.59% mortality of adult snails at concentrations of 250ppm after 96h, and their LD₅₀ values were 118.7±1.62 and 23.41±1.15ppm respectively. Isolated substances from M. subsericea were also considered active. Quercetin, myricetin and ursolic acid, at concentration of 100ppm (96h), were able to induce mortality levels of 100%, 80% and 53.33%, respectively. Our results suggest that M. subsericea can be considered promising as a molluscicide agent.

A host–guest complexation based fluorescent probe for the detection of paraquat and diquat herbicides in aqueous solutions

A new method based on fluorescence quenching of host–guest complexation was proposed for the determination of the two herbicides in river water and cabbages. The method is rapid, direct and simple.