title: Environmental epidemiology of intestinal schistosomiasis in Uganda: population dynamics of biomphalaria (gastropoda: planorbidae) in Lake Albert and Lake Victoria with observations on natural infections with digenetic trematodes.
abstract: This study documented the population dynamics of Biomphalaria and associated natural infections with digenetic trematodes, along the shores of Lake Albert and Lake Victoria, recording local physicochemical factors. Over a two-and-a-half-year study period with monthly sampling, physicochemical factors were measured at 12 survey sites and all freshwater snails were collected. Retained Biomphalaria were subsequently monitored in laboratory aquaria for shedding trematode cercariae, which were classified as either human infective (Schistosoma mansoni) or nonhuman infective. The population dynamics of Biomphalaria differed by location and by lake and had positive relationship with pH (P < 0.001) in both lakes and negative relationship with conductivity (P = 0.04) in Lake Albert. Of the Biomphalaria collected in Lake Albert (N = 6,183), 8.9% were infected with digenetic trematodes of which 15.8% were shedding S. mansoni cercariae and 84.2% with nonhuman infective cercariae. In Lake Victoria, 2.1% of collected Biomphalaria (N = 13,172) were infected with digenetic trematodes with 13.9% shedding S. mansoni cercariae, 85.7% shedding nonhuman infective cercariae, and 0.4% of infected snails shedding both types of cercariae. Upon morphological identification, species of Biomphalaria infected included B. sudanica, B. pfeifferi, and B. stanleyi in Lake Albert and B. sudanica, B. pfeifferi, and B. choanomphala in Lake Victoria. The study found the physicochemical factors that influenced Biomphalaria population and infections. The number and extent of snails shedding S. mansoni cercariae illustrate the high risk of transmission within these lake settings. For better control of this disease, greater effort should be placed on reducing environmental contamination by improvement of local water sanitation and hygiene.
authors.affiliation: Vector Control Division, Ministry of Health, 15 Bombo Road, P.O. Box 1661, Kampala, Uganda.
authors.forename: Candia
authors.initials: C
authors.lastname: Rowel
authors.affiliation: Vector Control Division, Ministry of Health, 15 Bombo Road, P.O. Box 1661, Kampala, Uganda.
authors.forename: Besigye
authors.initials: B
authors.lastname: Fred
authors.affiliation: Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Hertfordshire AL9 7TA, UK.
authors.forename: Martha
authors.identifier: 0000-0002-4220-3290
authors.initials: M
authors.lastname: Betson
authors.affiliation: Centro de Investigação em Saúde de Angola, Hospital Provincial, Rua Direita do Caxito, Bengo, Angola ; Department of Life Sciences, Natural History Museum, Wolfson Wellcome Biomedical Laboratories, Cromwell Road, London SW7 5BD, UK.
authors.forename: Jose C
authors.initials: JC
authors.lastname: Sousa-Figueiredo
authors.affiliation: Vector Control Division, Ministry of Health, 15 Bombo Road, P.O. Box 1661, Kampala, Uganda.
authors.forename: Narcis B
authors.initials: NB
authors.lastname: Kabatereine
authors.affiliation: Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
authors.forename: J Russell
authors.initials: JR
authors.lastname: Stothard
mesh_terms: D000818:Animals; D001700:Biomphalaria / Q000235:genetics* / Q000472:pathogenicity; D006801:Humans; D060106:Lakes / Q000469:parasitology; D011157:Population Dynamics; D012550:Schistosoma mansoni / Q000235:genetics / Q000472:pathogenicity*; D012555:Schistosomiasis mansoni / Q000453:epidemiology* / Q000235:genetics / Q000469:parasitology; D014454:Uganda / Q000453:epidemiology