Amer H. AHMED1, Reda
M.R. RAMZY2, Andreas RUPPEL3, Abdel Rahman
H. ELl-REFAIR4, Fouad A. FAHMY4 and Mohamed
A. EL-ALAMY5
1 Institute of
Research for Tropical Medicine, General Organization of Teaching
Hospitals and Institutes, Cairo, Egypt.
2 Research and Training Center on Vector of
Diseases, Faculty of Science Building, Ain Shams University, Abassia,
Cairo, 11566, Egypt.
3 Institute of Tropical Hygiene, University
Of Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany.
4 Plant Protection Department, Faculty of Agriculture,
Al-Azhar University, Cairo, Egypt.
5 Egyptian Ministry of Health.
Seasonal variation of Biomphalaria alexandrina and Bulinus truncatus populations and their infection rates with schistosome and other trematode cercariae were studied in four water courses located in Giza and Faiyoum Governorates. The abundance of both species varied from year to year and according to the type of habitat. The prevalence of Schistosoma mansoni in Biomphalaria snails was 0.29%, while the prevalence of S. haematobium in Bulinus snails was 1.36%. Seasonal variations of age structure of the two vector snails were monitored throughout the survey period. The infection rates with schistosome and other trematodes among Bulinus and Biomphalaria snails increased with the increase in their size. The antagonistic interaction between schistosome and non-human cercariae, specially echinostome, will be discussed.
A survey of B. alexandrina and B. truncatus was also executed at five watercourses in Qalyoub region. An attempt was made to correlate snail distribution with the concentrations of four metals of ecotoxicological importance (i. e. copper, zinc, lead and manganese). The results showed that there was a correlation between heavy metals concentrations, particularly copper, and the distribution of the vector snails.
In recent years, several molluscicides of plant origin have been studied as source for biological reagents to control snail-transmitted parasitic diseases. Previous studies showed that an Egyptian weed, Solanum nigrum has molluscicidal activties. Now we present data on the optimum time for plant collection and the characteristics of the collected plant specimens. Our results revealed that the toxicity of Solanum nigrum increased during warm seasons but decreased dramatically during winter. Toxicity of S. nigrum fruits gradually decreased with increase in fruit size. S. nigrum (black fruits) was more toxic than the other two types, S. nigrum v. vellosum (yellow fruits) and S. nigrum v. juidaicum (red fruits).
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created 21/12/00
