RESUMEN
Tests of a slow-release molluscicide containing 50% copper sulfate were under-taken in laboratory and field situations in St. Lucia. In laboratory trials, a granule form of the molluscicide produced 100% mortality of Biomphalaria glabrata down to 4 mg/liter active ingredient (a.i), while the pellet form produced 100% mortality down to 8 mg/liter a.i. In field trials, a dose of 100 mg/liter a.i. in granule form caused mortality of B. glabrata in banana drains but had no effect on B. glabrata populations in a marsh habitat. In both habitats, the dose of 100 mg/liter produced mortality of other molluscan fauna which caused changes in the molluscan diversity indices. This failure in field trials may have been due to dilution of copper levels caused by flooding and also by uptake of copper by mud and algae.
Asunto(s)
Cobre , Moluscocidas , Animales , Biomphalaria , Eucariontes , Población , Sulfatos , Factores de Tiempo , Indias OccidentalesRESUMEN
Individual households in five settlements were provided with piped water in a pilot scheme to investigate the effect on transmission of S. mansoni in St Lucia. Nearby comparison settlements, in the same valley, were provided with water through a public standpipe system. The incidence of S. mansoni infection among children decreased in the experimental area, leading to lower prevalence rates and lower intensity of infection in all age groups. Over the study period, indices of infection increased in the comparison settlements, but by the end of the period development was making those settlements less suitable for comparison purposes and some reduction in transmission was occurring.The changes in human infection rates were reflected in the results of studies with sentinel snails. In the experimental area, infection rates gradually fell owing to reduced water contact and consequently less contamination of the river and its banks, and possibly to the gradual reduction in contamination potential of the community with reduced prevalence and intensity of infection. It is suggested that a piped water supply be considered as a method of schistosomiasis control, but that the cost should not be debited only to the control of this disease since a clean water supply has other medical and social benefits.
Asunto(s)
Esquistosomiasis/prevención & control , Abastecimiento de Agua , Adolescente , Adulto , Niño , Preescolar , Humanos , Lactante , Persona de Mediana Edad , Schistosoma mansoni , Esquistosomiasis/transmisión , Indias OccidentalesRESUMEN
Chemotherapy of all persons infected with Schistosoma mansoni was begun in Marquis Valley, St. Lucia, in March 1974. From January 1972 to the start of chemotherapy, the infection rate in field Biomphalaria glabrata collected in the valley was 1.09% (117/10,736) and the rate in sentinel B. glabrata was 1.48% (56/3,790). From March 1974 through December 1975, no infections were detected in either field snails (11,742 collected) or sentinel snails (3,230 exposed). The accumulated date suggest that, because of differences in topography and average annual rainfall, S. mansoni transmission occurs in this valley during the rainy season, whereas in other St. Lucian valleys under study it occurs during the dry season.
Asunto(s)
Biomphalaria/parasitología , Schistosoma mansoni , Esquistosomiasis/tratamiento farmacológico , Animales , Lluvia , Esquistosomiasis/prevención & control , Estaciones del Año , Indias OccidentalesRESUMEN
A relatively simple, standardized hatching test was devised, tested and used to estimate the Schistosoma mansoni hatching rate for 88 St Lucian subjects selected by age, sex and intensity of infection. The hatching rate was dependent on the intensity of infection and rose proportionately with it. The rate also decreased with increasing age of the subject. Sex alone had no direct effect but there was a suggestion of an interaction between sex and age. These results suggest that several hatching tests are necessary, before and after treatment in schistosomicidal drug trials, to permit valid conclusions to be drawn. The hatching data are used in conjunction with survey results to calculate the contamination potential of different age groups in a population. School children (5-14 years old) are about twice as important as young adults (15-29 years old) who, nevertheless, contribute over a quarter of the total contamination potential. However, whereas school children are fairly accessible for mass chemotherapy control programmes, young adults often are not and, furthermore, involve problems associated with the treatment of women of child-bearing age.