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(2000). The transmission status of Bulinus on Zanzibar Island (Unguja), with implications for control of urinary schistosomiasis. Annals of Tropical Medicine & Parasitology: Vol. 94, No. 1, pp. 87-94.

The planorbid snail, Helisoma duryi, has been proposed as a possible biocontrol agent against the intermediate host snails of schistosomiasis. In an attempt to evaluate the possible effect of interference between H. duryi and Biomphalaria pfeifferi, life-tables were compiled for these two snail species maintained both in the presence of each other and separately. The calculated population parameters indicated that H. duryi had a higher innate capacity of increase, net reproduction rate and finite rate of increase as well as a longer lifespan than the target species. However, the biological potential of B. pfeifferi was not influenced by the presence of H. duryi, and the latter appears to be unable to act as competitor against B. pfeifferi under similar prevailing conditions. It is possible that the situation might change under conditions of crowding and starvation.

(1976). Geology and geomorphology in relation to the distribution of snail intermediate hosts of bilharzia in South Africa. Annals of Tropical Medicine & Parasitology: Vol. 70, No. 2, pp. 189-198.

Studies were carried out from April 1977 to November 1978 on the transmission of Schistosoma haematobium and on the bionomics of its intermediate snail host, Bulinus abyssinicus, in Koryole and Merca Districts, Somalia. In Koryole, snail populations and the numbers of infected snails on the east side of the Shebelli River exceeded those on the west side. The overall snail infection rate for Koryole was 1·;7% (69/4103). In Merca, snail populations and the numbers of infected snails were higher than in Koryole. The overall snail infection rate for Merca was 1·6% (152/9509).Snails and S. haematobium infections were found mainly in standing-water. Snails were unable to establish themselves in irrigation canals because the water in the canals was fast-flowing, there were no plants to provide food and substrate and the canals were allowed to dry out and to be dug out frequently, rendering them unsuitable as snail habitats. Also, snails were unable to aestivate and survive in dry mud for long periods.

Thiara granifera is a melaniid snail capable of maintaining very high densities in a variety of habitats. It has been introduced into the New World from the Far East and is now spreading rapidly throughout the Caribbean. In Puerto Rico and Dominica casual observations following natural invasion by T. granifera suggest that it may exert a powerful restraining influence on populations of Biomphalaria glabrata, the major intermediate host of Schistosoma mansoni in the Caribbean. The potential of T. granifera in biological control is being investigated in St. Lucia. In four field trials, B. glabrata was apparently eliminated from marshes and streams six to 22 months after the introduction of T. granifera. Thiara granifera shows promise as a major factor in the suppression of schistosomiasis in the Caribbean, but it is unsuitable for universal use as it is an intermediate host of the lung fluke, Paragonimus westermani.

The growth of Biomphalaria glabrata, B. schrammi, Drepanotrema lucidum and D. kermatoides was studied in three habitatis on Guadeloupe. Theortical growth curves were calculated for each species by applying the Walford method and the von Bertalanffy equation. On Guadeloupe, the growth of B. glabrata was faster in the ponds of Grand Terre than in the small high altitude streams of Basse Terre. There is good correlation between the observations made in Guadeloupe and previous data obtained on Pureto Rico and St Lucia.

The intensity and prevalence of Schistosoma haematobium infection has been measured in a community in the laterite plateau area of the McCarthy Island Division, The Gambia. The prevalence reaches 100% by the age of 10 years and counts of over 1000 ova in 10 ml of noon urine are common. During the second and third decade prevalence and intensity of infection decline and the mean egg output of a cohort falls by approximately 50% every three years. In subjects aged over 30 sex differences in exposure to infection and egg output suggest the possible effect of protective immunity.

(1978). Malumfashi Endemic Diseases Research Project, IV. Changes in snail population following the construction of a small dam. Annals of Tropical Medicine & Parasitology: Vol. 72, No. 5, pp. 483-487.

Both intestinal and urinary schistosomiasis occur widely in Saudi Arabia. The rate of snail infection with schistosome cercariae was highest in Gizan. The intermediate host for Schistosoma mansoni is Biomphalaria arabica and for S. haematobium, Bulinus beccarii (and possibly Physa acuta, which was recorded for the first time in the central region of Saudi Arabia). The examination of different types of water bodies did not show any apparent overlap between the different snail vectors of Schistosoma.

Prevalence surveys of Schistosoma haematobium were carried out in the Koryole and Merca Districts of the Somali Democratic Republic. The examination of urine samples from farmers from many parts of...

(1970). On the resistance of the snail, Lymnaea catascopium pallida (Adams) to concurrent infection with sporocysts of the strigeid trematodes, Cotylurus flabelliformis (Faust) and Diplostomum flexicaudum (Cort and Brooks) Annals of Tropical Medicine & Parasitology: Vol. 64, No. 1, pp. 101-107.

(1967). The survival time and fecundity of Bulinus truncatus after desiccation in mud. Annals of Tropical Medicine & Parasitology: Vol. 61, No. 2, pp. 139-143.

(1967). The effect of infection with Schistosoma haematobium on the growth and reproduction rates of Bulinus (Physopsis) nasutus productus. Annals of Tropical Medicine & Parasitology: Vol. 61, No. 3, pp. 321-325.

(1969). Cercarial shedding patterns of various schistosome species under outdoor conditions in the Transvaal. Annals of Tropical Medicine & Parasitology: Vol. 63, No. 3, pp. 359-371.

(1966). Studies on the ecology of snails transmitting urinary schistosomiasis in Western Nigeria. Annals of Tropical Medicine & Parasitology: Vol. 60, No. 2, pp. 198-211.

(1963). Electrophoretic Studies of Blood and Egg Proteins in Australorbis Glabratus (Gastropoda, Planorbidae) Annals of Tropical Medicine & Parasitology: Vol. 57, No. 1, pp. 47-51.

(1966). The influence of temperature on the biology of Biomphalaria pfeifferi (Krauss), an intermediate host of Schistosoma mansoni. Annals of Tropical Medicine & Parasitology: Vol. 60, No. 1, pp. 100-105.