Effect of methyl gallate on immune response of Biomphalaria alexandrina (Ehrenberg, 1831) snails to infection with Schistosoma mansoni (Sambon, 1907).

Schistosomiasis still affects a lot of people in many developing countries. Reducing the disease dissemination has been the target of various studies. As methyl gallate has antioxidant properties, it is assumed that it can be a good candidate for stimulating the immune response of snails. So, the aim of this work is to investigate the potential of using methyl gallate as an immunostimulant to Biomphalaria alexandrina snails in order to prevent the development of invading miracidia into infective cercariae. The infected snails were exposed to three concentrations of methyl gallate for two periods: 24 and 72 h. The results indicated that the most effective concentration was the lowest one: 125 mg/L of methyl gallate for 72 h, as it reduced both infection rate and mean number of shed cercariae. Also, it increased the total number of snails' hemocytes in hemolymph, which were observed in head-foot region and digestive gland of treated snails surrounding degenerated sporocysts and cercariae. In addition, hydrogen peroxide showed its highest content in tissues of snails exposed to 125 mg/L of methyl gallate for 72 h. In conclusion, methyl gallate can be considered as one of the most promising immunostimulants of B. alexandrina snails against infection with Schistosoma mansoni.

Reprotoxicity of 4-nonylphenol to Biomphalaria alexandrina snails at certain temperatures.

One of the most common compounds in pesticide formulations, plastics, and papers is 4-nonylphenol (4-NP). It is contained in agricultural, industrial, and wastewater effluents, which when discharged into surface waters affect aquatic fauna. Therefore, the present study aimed to use Biomphalaria alexandrina snails to evaluate the chronic toxicity of 4-NP. Its concentrations in collected water samples from Giza Governorate ranged from 400 to 1600 µg/l. Based on these environmentally relevant concentrations, laboratory experiments were carried out using standard 4-NP to investigate the effect of three concentrations; namely 400, 750, and 1600 µg/l. Survival rate of the exposed snails to 4-NP concentrations was affected after 4 weeks. Reproduction of the exposed snails to 4-NP concentrations was lower than that of the control at 30 °C, while the exposed snails to 400 µg/l of 4-NP showed maximum reproduction at 15 °C. The lowest hatchability percentage was recorded with egg masses laid by the exposed snails to 400 and 1600 µg/l of 4-NP at 15 and 30 °C, respectively. Furthermore, the results showed fluctuated levels of progesterone, estradiol, and testosterone depending upon the concentration and the temperature, which played a key role in determining the degree of 4-NP toxicity.

The comparative effect of chlorine and Huwa-san as disinfecting agents on Biomphalaria alexandrina snails and free larval stages of Schistosoma mansoni.

Many chemicals are applied for disinfecting purposes. Although chlorination is the most common procedure, it has many drawbacks. So there becomes an urgent need for new chemicals which are both effective and less harmful to other water fauna. The present work aims at investigating the comparative effects of chlorine and Huwa-san as a new disinfectant on Biomphalaria alexandrina snails which act as bioindicators of toxicity, besides evaluating their miracicidal and cercaricidal activities. The results showed that Huwa-san was more toxic on tested snails than chlorine, where the LC50 values were 21 and 1368.9 ppm, respectively after 24 h. Also, it was found that the activities of catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), and glutathione peroxidase (GPX) in snails' tissues were either induced or inhibited according to the tested disinfectant. Regarding reduced glutathione (GSH) content, it was increased as chlorine concentrations increased, while it reached its minimum content at the highest Huwa-san concentration. Such fluctuations were supported by histopathological examination of digestive and hermaphrodite glands, as prolonged exposure to chlorine led to more detrimental effects than Huwa-san concentrations. Moreover, Huwa-san was more effective on Schistosoma mansoni miracidia than on its cercariae, while the reverse was observed with chlorine. In conclusion, Huwa-san as a newly applied disinfectant can also be used as miracicidal and cercaricidal agent at small concentrations. Despite being more toxic to B. alexandrina snails, the chronic effect of its sublethal concentrations is less harmful than chlorine.