Schistosomiasis is a neglected tropical disease and affects over 200 million people worldwide. The snail Biomphalaria glabrata is one of the intermediate hosts of S. mansoni. The aim of this work was to verify the action of Euphorbia milii var. hislopii latex in the hemocytes profile and histopathology of B. glabrata infected by S. mansoni. Uninfected and infected snails were exposed to sublethal concentration of E. milii latex for 24 hours (1.0 mg/L). The survival rate was 88.5% for the uninfected snails and 66.6% for the infected and exposed snails. In the snails infected by S. mansoni, the exposure to E. milii latex promoted proliferation of hemocytes in the tentacles, mantle, digestive gland and kidney. In the digestive gland and the kidney, granulomatous reactions occurred around the sporocysts and caused their destruction. The number of circulating hemocytes from the group infected and exposed to E. milii latex was significantly higher than in the other groups. Three types of hemocytes were found: hyalinocytes, granulocytes and blast-like cells. We conclude that the E. milii latex influenced the cellular immune response of the susceptible B. glabrata strain to infection by S. mansoni, promoting the destruction of parasites.

Angiostrongylus cantonensis is a nematode parasite that resides in the pulmonary arteries of rodents, serving as its definitive hosts. The life cycle involves several species of non-marine gastropods as intermediate hosts, and the African giant snail Achatina fulica is considered one of the most important around the world. Experimental data concerning A. cantonensis infection in the African giant snail remains notably limited. This helminth causes eosinophilic meningitis or meningoencephalitis in humans, representing an emergent zoonosis in Brazil. Understanding the host–parasite relationship through the application of new tools is crucial, given the complex interaction between zoonosis and the intricate mechanisms involving wild/human hosts, parasite adaptation, and dispersion. The objective of this study was to employ SEM as a novel methodology to understand the structural organization of the host tissue, particularly the granuloma formation. This sheds light on the complex balance between A. fulica and A. cantonensis. Nine three-month-old snails were randomly selected and exposed for 24 h to a concentration of 2000 L1/dose of A. cantonensis. A necropsy was performed 37 days after the infection, and the samples were examined using light and scanning electron microscopy (SEM). The histopathological results revealed third-stage larvae of A. cantonensis associated with granulomas distributed throughout the head-foot mass, mantle, and kidney. Scanning electron microscopy of the histological section surface showed that the granuloma is surrounded by a cluster of spherical particles, which are distributed in the region bordering the larvae. This reveal details of the nematode structure, demonstrating how this methodology can enhance our understanding of the role of granulomas in molluscan tissue. The structural characteristics of granuloma formation in A. fulica suggest it as an excellent invertebrate host for A. cantonensis. This relationship appears to provide protection to the parasite against the host’s immune defense system while isolating the snail’s tissue from potential exposure to nematode antigens.

The natural phytochemical latex of Euphorbia milii var. hislopii is one of the most promising natural molluscicides for the control of Biomphalaria glabrata, and has been widely studied under laboratory conditions for selective control of schistosomiasis transmission. However, the effect of this product on B. glabrata infected by other helminths had not yet been investigated. The present study reports evaluation of the effect of E. milii var. hislopii latex on the survival and reproductive activity of B. glabrata infected by Angiostrongylus cantonensis. For this purpose, the following groups were formed: control (C), exposed (E), infected (I) and infected and exposed for different time intervals (1 day - I+E-1D, 7 days - I+E-7D, 14 days - I+E-14D, 21 days - I+E-21D and 28 days - I+E-28D). The experimental infection was performed with L1 larvae of A. cantonensis and exposure to 0.08 mg/L (LC50) of E. milii latex for a period of 24 hours. We analyzed the effects of E. milii latex on the survival of snails during four weeks, reproductive parameters and possible histophysiopathological changes in the gonad and albumen gland of the snails. Regarding survival, there was reduction of more than 50% in the groups exposed to latex (E and I + E) compared to the control group. As for the number of ovigerous masses, eggs, and average number of hatched snails, significant increases were observed in the I+E-1D group at the 4th week compared to the control group and the other weeks in the same group. Angiostrongylus cantonensis larvae were observed in the gonad and albumen gland from day 21 and 28 of infection in groups I and I+E, respectively, with granuloma-like formation. At these observation periods and in these groups, an increase in galactogen was observed in the albumen gland, which influenced egg laying, suggesting the existence of a fecundity compensation mechanism phenomenon. It was possible to conclude that both stressors – A. cantonensis infection and exposure to E. milii latex – directly influenced the survival and reproductive parameters of B. glabrata.

Background/objectives: Schistosomiasis is a parasitic disease that represents a serious public health problem. An alternative for the control of snails, intermediate hosts of schistosomiasis, is the use of molluskicides. Niclosamide, recommended by the WHO, has limitations, such as environmental toxicity, which has driven the search for safer and biodegradable alternatives, especially of plant origin. In this context, this study investigated the biological activity of Cymbopogon winterianus essential oil on embryos, juveniles, and adults of Biomphalaria glabrata and cercariae of Schistosoma mansoni. Methods: Essential oils (EOs) were extracted from fresh leaves via the Clevenger system and characterized via gas chromatography (GC/MS and GC/FID), revealing geraniol (25.0%), citronellal (29.2%), citronellol (10.5%) and elemol (9.6%) as the main components. Results: The results revealed lethal concentrations 90 (LC₉₀) for young and adult snails of 60.72 mg/L, 74.21 mg/L and 115.35 mg/L, respectively. In the histological analysis, no changes were observed in the tissues of the mollusks exposed to the lethal concentration 25 (LC₂₅). However, the lethal concentrations 50 (LC₅₀) and 75 (LC₇₅) caused crystalline concretions in proximity to the renal saccular portion. At a concentration of 60 mg/L, the oil resulted in 100% lethality in embryos and cercaricidal activity greater than 90% in 3 h. Acute toxicity tests in mice via the intraperitoneal or oral route did not reveal toxic effects, with hematological and biochemical parameters within the reference values. Furthermore, the oil did not inhibit acetylcholinesterase (AChE), indicating low toxicity to fish, and caused a slight reduction in human butyrylcholinesterase (hBChE) activity without affecting human AChE, which suggests low toxicity to mammalian tissues. In terms of environmental impact, the oil was not toxic to algae until the 75th day, with mortality observed thereafter. Conclusions: These results indicate that essential oils have great potential as biodegradable and safe alternatives for controlling mollusks and interrupting the schistosomiasis cycle.