Studies On The Chemoreception Profile Of Bulinus Truncatus {Avdouin) As An Aid To The Development Of Controlled Release Molluscicides.

GENERAL INTRODUCTION. 1.1 Epidemiology and geographical distribution of Schistosomiasis: Schistosomiasis is the second most prevalent parasitic infection apart from malaria. Unlike the latter, whose prevalence tends to fluctuate with the rains in many areas of high endemicity for the year, schistosome infection prevalence may be usually high throughout the year in areas where the disease is endemic. Available WHO(1991) document indicates that the disease afflicts more than 200million people while 500-600million are considered to be at risk of infection in 76 countries. Furthermore, mortality rate is estimated to be in excess of 200,000 per year and 20million people are known to suffer from various forms of clinical morbidity and disability due to the infection each year (TDR, 1995; Hodasi, 1995). Essentially, schistosomiasis is a tropical disease . It affects people of all countries in Africa, except Lesotho, especially those south of the Sahara where the disease is endemic. In South America it is endemic in Brazil, Surinam and Venezuela. In the middle-east it occurs in Yemen, Saudi Arabia, Israel and UAR. Some countries in the Caribbean such as St Lucia, Puerto Rico and Antigua and also the West Indies, parts of China and India have considerable numbers of schistosome infections (Rollinson and Southgate, 1987; Correa and Paraense, 1973). Out of the 76 countries affected by the disease more than 50 occur in Africa and it is estimated that 90% of all cases of schistosomiasis occur in Africa. In addition, every 3 out of 4 children may be infected (TDR, 12th Program report, 1995). One of the most important causes of the increase in prevalence of the disease in most areas has been the rapid increases in the development of freshwater resources . These developments sought to 1 provide sufficient freshwater for agriculture, hydroelectric power and also for domestic use. Unfortunately, the health implications of these developments were not given any serious attention before such programs were undertaken.