Field trials of low dose Bayluscide on snail hosts of schistosome and selected non-target organisms in sahelian Cameroon

More than 85 percent of all cases of schistosomiasis in Cameroon occur in the northern sahelian half of the country representing 20 percent of the population. Several workers have advocated the integrated approach to schistosomiasis control, including snail control, but the death and decay of aquatic organisms, and fish kill that often follows Bayluscide application at the dose of 1g/m³ decrease its acceptability. The present study was designed to assess the effect of lower Bayluscide doses on snail host and non-target fish, frog, the tadpole kill. Bayluscide was applied to study ponds at concentrations of 0, 0.25, 0.5, and 1 g/m³ (ppm). Pre and post application assessment of snails hosts of schistosomes, fish, frog, and tadpole kill were carried out. All 0.25, 0.5, and 1 g/m³ Bayluscide concentrations reduced snail population significantly. Bayluscide concentration of 0.50 g/m³ applied in two rounds of 0.25 g/m³ resulted in high snail mortality and low lethality to fish, frogs, and tadpoles. Further studies are needed to assess the cost-effectiveness of Bayluscide in the control of schistosomiasis following the simplified approach.

Impact of desiccation on biology of Biomphalaria alexandrina and Bulinus truncatus snails

Biomphalaria alexandrina and Bulinus truncates snails were exposed to either complete or partial desiccation. Complete desiccation was carried out in dried plastic jars, while in partial one, the snails were exposed on filter paper saturated with dechlorinated and chlorinated water. Desiccation periods were 1 or 3 days, followed by recovery [1, 4, 6 and 8 days]. This technique was continued throughout 6 weeks for B. truncates and 18 weeks for B. alexandrina. Also, the hatchability of eggs laid by desiccated B. alexandrina eggs was evaluated. All treatments of both partial and complete desiccation decreased the survival and net reproductive rates of B. alexandrina and B. truncates snails. The net reproductive rates for snails partially desiccated for 24hr, followed by 6 days of recovery were reduced by 72.3% and 57.9% for B. alexandrina and B. truncates, respectively. Moreover, elongation of partial desiccation to 3 days, followed by 4 days of recovery highly suppressed this parameter for B. truncates to be 1.68 compared to 13.29 for control groups as well the life span of desiccated snails was shortened. In addition, B. truncates could not survive after 3 days of complete desiccation followed by 4 days of recovery, while only 7% of B. alexandrina survived at the 6th week of the test. Data also indicated that hatchability of B. alexandrina eggs obtained from snails exposed to both types of desiccation was not approximately affected, but the hatchability period was elongated in some treatments

Studies on the biology of schistosomiasis with emphasis on the Senegal river basin

The construction of the Diama dam on the Senegal river, the Manantali dam on the Bafing river, Mali and the ensuing ecological changes have led to a massive outbreak of Schistosoma mansoni in Northern Senegal, associated with high intensity of infections, due to intense transmission, and the creation of new foci of S. haematobium. Data on the vectorial capacity of Biomphalaria pfeifferi from Ndombo, near Richard Toll, Senegal are presented with sympatric and allopatric (Cameroon) S. mansoni. Comparisons are made on infectivity, cercarial production, chronobiology of cercarial emergence and longevity of infected snails. Recent data on the intermediate host specificity of different isolates of S. haematobium from the Lower and Middle Valley of the Senegal river basin (SRB) demonstrate the existence of at least two strains of S. haematobium. The role of Bulinus truncatus in the transmission of S. haematobium in the Lower and Middle Valleys of the SRB is reviewed. Both S. haematobium and S. mansoni are transmitted in the same foci in some areas of the SRB

Impact des effluents d'un complexe agro-industriel sucrier sur la distribution des mollusques dulcaquicoles a Mbandjock (Cameroun)

Des prospections malacologiques ont ete entreprises dans la zone sucriere de Mbandjock (Cameroun). La discussion des mollusques est discutee suivant les types d'habitat. L'incidence des effluents du complexe agro-industriel (SOSUCAM) sur la faune malacogique est evaluee. En general; un faible degre de pollution est favorable a la faune malacologique alors qu'une forte pollution lui est nuisible. La presence de bulinus globosus est mise en evidence. Ce mollusque; hote intermediaire de schistosoma haematobium; etait absent lors des prospections anterieures. L'extension de bulinus globosus dans la localite devrait faire l'objet d'une surveillance a long terme