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Schistosoma mansoni is the main factor of human schistosomiasis which is responsible for high rates of mortality. Recently, the use of alternative biological control agents has gained importance in disease control because the intensive use of molluscicides is very harmful to human health and poses risks to the environment. In the present work, the potential effect of two freshwater algae, Amphora coffeaeformis and Scenedesmus obtusus, on the immune response of Biomphalaria alexandrina snails against infection with S. mansoni was investigated. Two different concentrations 1 and 2 g L− 1 from each dried algal material were tested on snails before exposure to miracidial infection by one day. The use of Amphora coffeaeformis has a greater immunostimulatory effect than Scendesmus obtusus at a low concentration of 1.0 g L− 1. The tested algae affected the snail’s hemocytes and its immune response to S. mansoni as evidenced by a significant decrease in infection rate and cercariae production. In addition, increasing in total hemocyte count, the formation of vacuoles, the appearance of several pseudopodia, and the formation of coarse granules in hemocytes of infected snails treated with A. coffeaeformis. Intense tissue reactions were also observed. In conclusion, it was confirmed that these algae can be used as an immunostimulant in the prevention and control of S. mansoni.

Keywords: Propofol fresensius Nervous system Biomphalaria alexandrina Bioindicator Golgi bodiesThis study was aimed to evaluate the effect of propofol fresensius 1% on the nervous system of Biomphalaria alexandrina snails, which represent the intermediate host of schistosoma mansoni after acute exposure (5ml/L) for 24 hours and chronic exposure (1ml/L) for 72 h, using scanning and transmission electron microscope. After chronic exposure, visceral ganglion was observed compressed and elongated, not paired with pedal ganglia and its nerves did not contact with it. 1ml/L propofol completely blocked synaptogenesis between visceral and pedal neurons. After acute exposure, the varicosities have few granular vesicles, whereas in the chronic exposure, the varicosities were empty and no granular vesicles were found inside it. Poorly developed endoplasmic reticulum, few Golgi bodies, elongated mitochondria, and more intercellular connective space were observed.

In this study, the distribution pattern of Schistosoma haematobium miracidia level to host susceptibility/resistance and the basic cellular responses during the parasite development was investigated. Several snail stocks showed a wide spectrum of host reaction to the parasite. A vigorous "resistant-type" cellular response to invading miracidia was seen in the histological sections of non-susceptible snails. In this respect, they were classified as "resistant snails". Bulinus truncatus infected with S. haematobium exhibited a wide range of histopathological change, suggesting the presence of endogenous factors preventing the immune system of susceptible snails from destroying the developed parasite larvae. Therefore, the mechanism underlying the susceptibility of the snails should be investigated by studying the host-parasite interactions by light and electron microscopy.

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