Morphology and kinetics of susceptible and resistant Biomphalaria alexandrina hemocytes during the first week of exposure to Schistosoma mansoni miracidia

Abstract

Background: Few studies concerning Biomphalaria alexandrina (B. alexandrina) snail hemocytes' subpopulations, and their relation to the compatibility with Schistosoma mansoni (S. mansoni)' miracidia were performed. Manipulation of parasite development inside these snails could be applied as a control measure against schistosomiasis. Objectives: Knowing that the snail hemocytes temporarily bind to the parasites, allowing the development of cercariae that are infective to the definitive host. This study aimed at studying the morphology and kinetics of diverse hemocytes of susceptible and resistant B. alexandrina and their participation in the snail early immune response after challenge by S. mansoni. Material and Methods: Giemsa stained hemocytes were characterized using light microscopy. Total and differential hemocyte counts (THC and DHC) were calculated in the hemolymph of two groups composed of 60 susceptible and 60 resistant snails. Each group was further subdivided as 12 control pre-exposure snails (PE) and 48 post-exposure snails (PO) to S. mansoni at different time points (6 h, 1, 3 and 7 days). THC and DHC counts were recorded by a snail hemogram. Results: Results revealed that granulocytes constituted the most common population all through the experiment with the large dense-granulated granulocytes subpopulation being the largest-sized cells detected. The highly reactive subpopulations that increased in number upon exposure to S. mansoni were the few-granulated and the large-granulated granulocytes, suggesting their possible participation in early parasite destruction. Conclusion:The resulting hemograms helped determine the participation of hemocyte populations and subpopulations in the defense against S. mansoni, aiding in understanding snail compatibility patterns. Further studies to propagate transgenic B. alexandrina snails abundant in large granular granulocytes utilizing (gene editing) CRISPR-Cas9 technique are recommended. This would be required to spread schistosome resistance traits in snail populations, thus, contributing to reduced schistosomiasis transmission in the long run.

Assessment of Amphora coffeaeformis and Scenedesmus dimorphus algae as immunostimulant agents on Biomphlaria alexandrina snails against Schistosoma mansoni

“…The hematological study of hemolymph of infected B. alexandrina snails previously exposed to A. coffeaeformis showed several vacuoles within hemocytes, the appearance of many pseudopodia, and the formation of coarse granules in granulocytes. The hemocytes that contain coarse granules were occasionally detected and known (s) between digestive glands contained few germinal cells and the size of the vacant space was wider than normal to transport metabolic substances from the digestive glands or may be involved in the aggregation process (Nakayama et al 1997;Kheder 2020). The present findings match those introduced by Ibrahim and Abdel-Tawab (2020) who estimated that snails treated with LC 50 of algal extract (Cystosiera barbata) caused the formation of pseudopodia in hemocytes.…”