A preliminary study on biological control of the snail intermediate hosts of schistosomiasis in U.A.R. by Helisoma duryi snails

Further laboratory studies on the interspecific competition between Helisoma duryi (Wetherby) and the intermediate hosts of schistosoma mansoni sambon: Biomphalaria alexandrina (Ehrenberg) and B. camerunensis (Boettger)

“…Growth inhibiting factors could act by binding calcium or interfering with the mechanism of calcium uptake. Food competition has probably been involved in earlier studies on the competition between H. duryi and different intermediate hosts of schistosomiasis (Ayad et al, 1970;Abdallah & Nasr, 1973 ;Frandsen, 1976 ;and Malek & Malek, 1978) as there has not been paid much attention to this possibility . However alternative food sources do exist in the aquaria (i .e.…”

“…As a possible method of biological control of schistosomiasis the introduction of the North American planorb Helisoma duryi as a competitor of the intermediate host snails has been proposed (Mandahl-Barth, 1965 ;Ayad et al, 1970 ;Abdallah & Nasr, 1973 ;Frandsen, 1976 ;Malek & Malek, 1978) . H. duryi cannot be infected by schistosomes and seems not to be the intermediate host of other medically or veterinary important trematodes (Frandsen & Madsen, 1978) .…”

Preliminary observation on the role of conditioning and mechanical Interference with egg masses and Juveniles in the competitive relationships Between Helisoma Durvi (Wetherby) and the Intermediate host of Schistosoma Mansoni Sambon: Biomphalaria Camerunensis (Boettger).

“…207-214, 1979 (1979) found that despite continuous presence of food in the aquaria, food competition was involved, while it was realized that the role chemical interactions between the two snail species could not be conclusively evaluated from experiments in balanced aquaria . Ayad et al (1970), Mandahl-Barth (1970), Abdallah & Nasr (1973) and Malek & Malek (1978) have proposed that the action of H. duryi on the intermediate hosts was due to chemical factors inhibiting the hatching of egg masses and the development of juveniles of the intermediate host species .…”