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Schistosomiasis is a disease endemic in several states of Brazil. The population control of the transmitter mollusks is done with Bayluscide WP 70®, in the control programs. OMS preconize molluscicidal assays using Becker with 500 mL of final volume, restringing the number of natural products and synthetic drugs to be tested in function of high quantity of material necessary. A new technique to assess the toxic effects for Biomphalaria sp. is the purpose of this work, for developing adaptation for this aquatic organism, using a low volume of test solution in 24-well plates. We used Biomphalaria glabrata (10–12 mm size) in a static system, consisting of the following components: Becker containing 10 snails or 24-well plates where snails were individualized for a volume of 2 mL per well for 24 and 48 hours. For the assays, we added aqueous solutions of Bayluscide WP 70, at a concentration of 1–5 mg/L, distilled water, and 1% dimethyl sulfoxide. Data were evaluated using Kappa's coefficient, Z factor validation, and comparison study. This technique to assess the toxic effect has proven to be a useful tool to detect lethal and sublethal effects, which could be used as a new evaluation protocol.

BACKGROUND This work describes a chemical study of the essential oil from leaves of Xylopia ochrantha , an endemic Annonaceae species from Brazil, and its activity against Biomphalaria species. Considering its poor solubility in aqueous medium, the essential oil was nanoemulsified to evaluate its action on controlling some mollusc species of genus Biomphalaria , snail hosts of Schistosoma mansoni that causes schistosomiasis, which mainly affects tropical and subtropical countries. OBJECTIVES The main aims of this work were to analyse the chemical composition of essential oil from X. ochrantha , and to evaluate the effect of its nanoemulsion on molluscs of genus Biomphalaria and their oviposition. METHODS Chemical analysis was performed by gas chromatography coupled to mass spectrometry. Nanoemulsions were prepared by a low energy method and characterised by particle size and polydispersity index. Biological assays evaluating the mortality of adult species of B. glabrata , B. straminea and B. tenagophila and their ovipositions upon contact with the most stable nanoemulsion during 24 and 48 h were performed. FINDINGS Chemical analysis by mass spectrometry revealed the majority presence of bicyclogermacrene and germacrene D in the essential oil. The formulation with a hydrophilic-lipophilic balance (HLB) of 9.26 was the most suitable for the oil delivery system. This nanoemulsion caused the mortality in B. tenagophila , B. straminea and B. glabarata of different sizes at levels ranging from 50 to 100% in 48 h. Additionally, the formulation could inhibit the development of deposited eggs. CONCLUSION Thus, these results suggest the use of nanoemulsified essential oil from X. ochrantha as a possible alternative in controlling some Biomphalaria species involved in the schistosomiasis cycle.

Ocotea pulchella as an alternative against schistosomiasis: chemical analysis, development of nanoemulsion and biological control activity [Ocotea pulchella como una alternativa ante esquistosomiasis: análisis químico, desarrollo de una nanoemulsión y actividad en control biológico]

Schistosomiasis is caused by the intestinal parasite Schistosoma mansoni. Individuals are affected by schistosomiasis when they are exposed to aquatic environments contaminated with Schistosoma cercariae that emerged from the infected intermediate host mollusk of the genus Biomphalaria. The WHO recommends using molluscicidal products to reduce the snail population and disease transmission. The WHO encourages the search for alternative substances in schistosomiasis control. Natural products are seen as a promising alternative because they are abundant in countries where schistosomiasis is endemic and have many different substances in their extracts, impairing cases of resistance. Therefore, the nanoemulsion effect of a butanol-soluble fraction of Sideroxylon obtusifolium leaves was evaluated against three study points in the biological cycle of the disease, that is, adults and young Biomphalaria glabrata, spawning by the host mollusk, and infectious larvae of the parasite. Extract-SOB (butanol fraction) and nano-SOB (nanoemulsion) demonstrated promising activity in adult B. glabrata population control with an LC50 of 125.4 mg/L, an LC90 of 178.1 mg/L, an LC50 of 75.2 mg/L, and an LC90 of 97 mg/L. Nano-SOB presented greater potency against young B. glabrata, with an LC90 of 72.1 mg/L and an LC50 of 58.3 mg/L. Still, relevant activity against S. mansoni cercariae was eliminated in 4 h (LC90: 34.6 mg/L). Nano-SOB reduced viable spawning by approximately 30% at 178.1 and 97 mg/L. Referring to most substances in this extract, quercetin-3-rhamnosyl-(1-6)-galactoside and hyperoside may cause low environmental toxicity and human toxicity according to in silico analysis. Thus, nano-SOB is a promising agent to combat B. glabrata population growth and schistosomiasis transmission.

Schistosomiasis is caused by the parasite Schistosoma mansoni, which uses mollusks of the Biomphalaria genus as intermediate hosts. In 2020, approximately 241 million people worldwide underwent treatment for schistosomiasis. For this reason, the World Health Organization encourages research on alternative molluskicides based on plant species. The objective of this work was to investigate Neomitranthes obscura essential oil from leaf chemical composition and its essential oil nanoemulsion activity on intermediate hosts of schistosomiasis Biomphalaria glabrata control. The major chemical components of the Neomitranthes obscura essential oil were zonarene, seline-3,7(11)-diene, β-selinene, and α-selinene. The nanoemulsion tested using 24-well plate methodology showed lethality and juvenile mollusks with LC90 values of 53.9 and 25.0 ppm after 48 h, respectively, and on their spawning with an LC90 of 66.2 ppm after 48 h. Additionally, the nanoemulsion exhibited an LC90 value against the infective form of the parasite Schistosoma mansoni of 11.5 ppm after 4 h. This pharmaceutical formulation acted inhibiting the acetylcholinesterase activity and was not toxic for Mellanoides sp. This result suggests the use of this nanoformulation as a promising alternative in the control of Biomphalaria glabrata and the transmission of schistosomiasis.

No abstract

Introdução: A esquistossomose é uma doença parasitária causada pelo schistosoma mansoni. Segundo a Organização Mundial da Saúde (OMS) esta doença infecta mais de 200 milhões de pessoas, resultando em aproximadamente 200.000 mortes por ano. Objetivo: O objetivo deste estudo foi testar e comparar a atividade moluscicida do extrato bruto e do extrato fracionado em diclorometano das folhas de Plectranthus grandis sobre Biomphalaria glabrata. Material e métodos: O extrato bruto em diclorometano foi realizado no extrator soxhlet. A fração em diclorometano foi obtida através da cromatografia tipo “flash”. Os bioensaios foram realizados com moluscos de 10-12 mm, onde foram alocados em placas de 24 poços. Foram utilizados controles negativos (água destilada e DMSO 1%) e controle positivo (Niclosamida). Neste bioensaio, os caramujos foram expostos, por 24h e 48h. Os experimentos foram realizados em triplicata. Resultados: No ensaio moluscicida com o extrato bruto em diclorometano das folhas de Plectranthus grandis, foi possível observar uma taxa de mortalidade de 100 %, na concentração de 600 mg/L. Após o período de 48 h foi possível calcular as concentrações letais 50 e 90 sendo, 150 mg/L e 318 mg/L, respectivamente. No ensaio moluscicida com a fração em diclorometano, na concentração de 300 mg/L a taxa de mortalidade foi de 100 %. As concentrações letais das frações em diclorometano foram de CL50 = 134,71 mg/L e CL90 = 239, 97 mg/L. Conclusão: Pode-se observar que o extrato bruto e a fração em diclorometano apresentaram atividade moluscicida sobre Biomphalaria glabrata. Foi possível calcular as concentrações letais do extrato bruto e da fração em diclorometano e pode-se observar que a concentração letal 90 da fração em diclorometano está mais próximo do valor recomendado pela OMS. De acordo com estes dados, sugerem-se mais estudos utilizando a fração sobre embriões de B. glabrata e cercárias de Schistosoma mansoni.