Protozoan and helminths infestation of Nile tilapia Oreochromis niloticus and its correlation with certain water quality variables along river Nile in the area of Greater Cairo.

Pollutants and parasites represent stressors for fish at the individual, population, or community levels. The current study outlines the seasonal infestation pattern of Oreochromis niloticus by protozoan and helminths parasites linked to some physicochemical parameters (pH, dissolved oxygen, total dissolved solids, and electrical conductivity), and metals (Cd, Pb, Fe, Zn, and Ca), at nine selected sites in River Nile (Greater Cairo area) from summer 2019 till spring 2020. Most of the studied criteria in Nile water samples showed normal levels during all seasons compared to the recommended limits of EPA. The parasitological examinations recorded three protozoan categories: Myxobolus (8 species), hemoflagellates (Trypanosoma mukasi) and Ciliates (Trichodina compacta), and three helminths; Clinostomum sp., Acanthocephala sp. and Euclinostomum ardeola. The highest incidence of infection was determined for Clinostomum sp., followed in descending order by Myxobolus sp., Acanthocephala sp., T. mukasi, E. ardeolathen, and T. compacta. Notably, this study introduces the novel identification of new species of Myxobolus in the blood of Oreochromis niloticus. The histopathological examination of gills, muscles, and kidneys reveals serious changes and the presence of encysted trematodes, metacercariae, and cysts of protozoan parasites. Additionally, the study employs cluster analysis based on site similarity in water variables and canonical correspondence analysis, explaining 98.7 % of the variables and indicating correlations between parasite infestation and environmental factors. These analytical approaches reveal the impact of land use activities on water variables and the influence of adjacent activities on fish parasite infestation patterns. In conclusion, this study provides a comprehensive perspective by considering various factors to enhance our understanding of pollutants and parasites affecting fish in the River Nile.

Comparative study on Lake Manzala in Egypt after and before development and purifications: Ecosystem and biomarkers; biochemical, histopathological and immunohistochemical.

The present work aims to evaluate the impact of Lake Manzala development, started in 2017, on lake water quality and biomarkers of Lake Oreochromis niloticus and Biomphalaria alexandrina samples from Dakahlia and Port Said during 2021 and compare it with the results of a series of studies concerning the same criteria in Lake Manzala during 2015. Results showed a remarkable increase in water EC, indicating a higher water exchange with the sea, a significant decrease in Pb, Cd, Cu, and Zn levels in water samples, and a remarkable decline in Cd and Pb bioaccumulation in all fish and snail samples. Macroinvertebrate samples showed higher taxa richness than in 2015, indicating biologically improved lake water quality. Results showed no trematode transmission, while there were natural infections in B. alexandrina snails during 2015. Biochemically, liver enzymes and hematological criteria in fish and snail samples during 2021 showed levels nearer to control at Port Said, indicating a less stressed liver and more healthy specimens than in 2015. Histopathological examination of fish organs (except spleen) and snail tissues pointed to their improved tissue architecture in Port Said than that of Dakahlia (2021). However, the 2021 samples were better than those of 2015. The immunohistochemical study showed higher expression of IL-6 in Dakahlia samples than the other samples, denoting higher tissue inflammation and humoral immune response. So, all the examined criteria indicated that Manzala Lake is positively impacted by the developmental and purification process, especially in Port Said.

Assessment of schistosomiasis transmission in the River Nile at Greater Cairo using malacological surveys and cercariometry.

Continuous field studies on the abundance and distribution of freshwater snails and cercarial populations are important for schistosomiasis control programs. In the present work, snail surveys and cercariometry were conducted for four successive seasons at 12 sites on the Nile River banks in the area of Greater Cairo to identify potential transmission foci for schistosomiasis. In addition, water physicochemical parameters were recorded. The results showed that the electrical conductivity, total dissolved solids, dissolved oxygen, and pH were within the permissible levels, except that the water temperature increased, especially in the spring season. Malacological surveys identified 10 native snail species at the studied sites of the Nile River, namely Bulinus truncatus, Biomphalaria alexandrina, Lymnaea natalensis, Lanistes carinatus, Cleopatra bulimoides, Melanoides tuberculata, Helisoma duryi, Bellamya unicolor, Physa acuta, Thedoxus niloticus, and one invasive snail species, Thiara scabra. The calculated diversity index indicated that the structure of snails' habitats was poor, while Evenness index indicated that the individuals were not distributed equally. Natural infection results identified no schistosome cercariae in B. truncatus and B. alexandrina. However, the cercariometry recovered Schistosoma cercariae in all the surveyed sites during all seasons with variable distribution. The preceding data suggest that there are still some active transmission foci for schistosomiasis infection in the Nile River. Moreover, the present finding highlights the importance of cercariomety as a complementary approach to snail samplings for identifying the transmission foci for schistosomiasis.

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.

Toxicological assessment of lambda-cyhalothrin and acetamiprid insecticides formulated mixture on hatchability rate, histological aspects, and protein electrophoretic pattern of Biomphalaria alexandrina (Ehrenberg, 1831) snails.

Several formulated mixtures of pesticides are widely used in modern agriculture. Nevertheless, the agriculture runoff causes a serious damage to the aquatic ecosystem. Therefore, the present study aims to use B. alexandrina snails as bioindicators for 30 g/l lambda-cyhalothrin and 17 g/l acetamiprid as a formulated mixture insecticide. Results showed that it has a molluscicidal activity against snails at LC50 7.9 mg/l. The hatchability percent of both treated 1-day-aged and/or 3-day-aged groups were less than that of the control group. The sublethal concentrations of the tested insecticide caused a remarkable abnormal necrosis in male and female gametogenic cells, besides a severe damage in both secretory and digestive cells. The results of SDS-PAGE protein profiles of treated snails showed that the least number of protein bands was noticed in snail groups that subjected to LC10 (6.6 mg/l) and LC25 (7.2 mg/l) concentrations when compared to control protein fractions.

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.