A Comparative Study of Haemocytes from Resistant and Susceptible Lymnaea Natalensis Snails Exposed to Fasciola Gigantica Miracidia

Effect of infection with Fasciola gigantica on total and differential haemocytes count of resistant and susceptible Lymnaea natalensis snails were studied. Exposure of L. natalensis resistant and susceptible strains to F. gigantica on miracidia caused gradual increase in the number of circulating haemocytes at the same time of exposure. In susceptible strain, the increase in the number of circulating haemocytes became significant at the second week post exposure being 2560 cell / ml (p < 0.05) in comparison with control group being 1760 cell / ml. While in resistant strains, the increase became significant at second, third and sixth weeks post exposure being 2660 cell/ml, 2500 cell/ml and 2360 cell/ml respectively,then a gradual decrease occurred. Examination of haemocytes obtained from L. natalensis snails revealed that haemolymph contained three morphological types of haemocytes, designated as round small, round large (hyalinoctyes) and granulocytes spreading. Their average percentage was 12.3±5.5 %, 81.0 ± 4.6 % and 6.7 ± 2.1 % of total cells respectively. Data indicated that by the second day post exposure infected snails had significantly higher percentage of granulocytes than controls.