effect of the trematode Echinostoma liei and certain non-vector snails as biocontrol agents against infectivity of Schistosoma mansoni larval stages to their hosts under laboratory conditions

ABSTRACT

The present investigation was carried out to study the effect of the non-medically important parasite Echinostoma liei in the presence of three non-vector snails [Planorbis planorbis, Melanoides tuberculata and Helisoma duryi] on the infectivity of the larval stages of Schistosoma mansoni to Biomphalaria alexandrina and to albino mice [Mus Musculus].The infection rates of Biomphalaria alexandrina exposed to Schistosoma mansoni miracidia in the presence of Planorbis, Melanoides and Helisoma snails at ratios of 1B 5 non-vector snails were significantly lower being 62.9%, 46.9% and 44.4% versus to 83.7% in control group. Also, there are reduction in mean total numbers of cercariae/snail and duration of shedding specially in the presence of Planorbis and Helisoma snails, while the prepatent periods were elongated by the presence of Planorbis and Melanoides snails. Snails exposed to Echinostoma liei miracidia showed reduction in infection rates in the presence of the three studied non-vector snails and in duration of shedding by the presence of Melanoides and Helisomd snails. Snails exposed to both parasites showed reduction in the infection rate especially in the presence of Melanoides and Helisoma snails. No Biomphalaria snails were infected with both parasites in the groups maintained with H. duryi at ratios of 1B 3H and 1B 5H. The lowest total number of schistosome and echinostome cercariae was in the group of 1B 3M. The presence of non-vector snails with infected Biomphalaria suppressed the infectivity of schistosome cercariae to the experimental mice