An epidemiological assessment of Ambrosia maritima on the transmission of schistosomiasis in the Egyptian Nile Delta.

Ambrosia maritima (Damsissa), a proven molluscicide, was investigated in a seven year epidemiological trial in four villages in the northern Egyptian Nile Delta. Schistosoma mansoni prevalence and other measures of infection were initially high in the four villages before the trial began. Two villages were used to test the impact of A. maritima application both on snail populations and on infection in the village population. Two villages were held as controls and not treated with A. maritima. The entire population of all four villages was included in the study. Prevalence and other measures of infection fell dramatically following treatment with praziquantel 40 mg kg-1 body weight. On annual follow ups, the prevalence of infection and geometric mean egg counts began to increase back to original levels in both test and control villages; age adjusted incidence rates were lower in one test village, but higher in the other when compared to the control villages. Snail populations were destroyed in the treated canals and drains located near the test villages. The lack of a clear epidemiologic impact is discussed.