Potential for Transmission of Schistosomiasis in Kayonza District

Introduction: Schistosomiasis; also known as bilharzia or snail fever; is a tropical parasitic disease caused by a trematode platyhelminthes called Schistosoma check for this species in other resources sp. Schistosoma species are transmitted by cercariae penetrating the skin when a person is bathing; washing clothes; fishing or engaged in agricultural activities; involving contact with fresh water that has fecal or urinary contamination; and contains the parasites' snail host. The present study aimed to survey freshwater snails in Kayonza District (Rwanda) especially Lake Muhazi and surrounding water bodies; stream and swamps to assess the potential for transmission of two species of Schistosoma: S. mansoni check for this species in other resources and S. haematobium check for this species in other resources. Methods: Six sites were selected to assess the potential for transmission of schistosomiasis. The intermediate hosts of schistosomes; namely the snails Biomphalaria check for this species in other resources ; Bulinus check for this species in other resources sp. and Lymnaea check for this species in other resources sp.; were collected and brought to the laboratory and investigated to see if trematode cercaria responsible for the disease were present. Results: Snails dissected were not only infected with trematode cercaria but also with annelids and flatworms (Platyhelminths). Cercaria found therein were of two types: furcocercous; probably responsible for schistosomiasis; and gymnocephalous cercaria for fasciolasis: an infection of cattle; goats and sheep. Conclusion: Biomphalaria sp were the major hosts for schistosome cercaria; and most snails collected of this species were infected. Moreover; they were found in large number from all sites. Lymnaea sp; hosts snails for Fasciola cercaria check for this species in other resources ; were also found in a considerable number compared to the low number of Bulinus sp in the region. District and national authorities may wish to further investigate this infestation and identify potential interventions to disrupt the disease transmission

Aspects of the ecology and public health importance of snails in the Weija lake

A survey was undertaken in water-contact sites of communities on the Weija lake over a 12-month period to update information on the snails in the lake. The study involved the collection of snails with scoop-net from the sediments; floating; marginal and submerged aquatic vegetation and other objects in the lake. All snails collected were identified. Bulinus truncatus; B.(Physopsis) globosus and Biomphalaria pfeifferi were examined for trematode infection. Nine species of snails were encountered. They were either autochthonous fauna of the River Densu basin or possibly introduced. Four of the snail species encountered: Biomphalaria pfeifferi; Bulinus trucatus; B.(Physopsis) globosus and Lymnaea natalensis were of medical and veterinary importance. B.(Physopsis) globosus however; has been unsuccessful in colonising the lake though it was the dominant bulinid snail transmitting S. haematobium before the impoundment. The previously rather rare B. truncatus has become the dominant S. haematobium transmitting snail in the lake. Biomphalaria pfeifferi has also established itself in the lake with the possibility of the introduction and increased transmission of intestinal schistosomiasis. This species succession is likely to heighten schistosomiasis transmission in the lake

A preliminary study on intermediate snail hosts of schistosomes in Reiver enyau; Arua District; Uganda

A total of 1260 snail intermediate hosts of both Schistosoma mansoni and Schistosoma haemotobium were collected along the non-seasonal river enyau which lies half a kilometre west of Arya; north-western Uganda town. The snails collected were Biomphalaria pfeireri 709: Biomphalaria choanomphala 457; Bulinus tropicus 94. These were screened for cercariae shedding and 25 B. pfeifferi and 12 B. choabomphalal shed mammalian cercaricae while none of the Bulinus) tropicus shed any cercae. River enyau Biomphalaria snails were susceptible to a Schistosoma mansoni strain from Entebbe. Cercariae derived from these snails and also those found infected in the River Enyau were confirmed to be S. mansoni using laboratory mice

Preliminary study on Intermediate snail hosts of schistosomes in River Enyau; Arua District; Uganda

A total of 1260 snail intermediate hosts of both Schistosoma mansoni and Schistosoma haemotobium were collected along the non-seasonal River enyau which lies half a kilometre west of Arua; a north-western Uganda town. The snails collected were Biomphalaria pfeifferi 709: Biomphalaria choanomphala 457; Bulinus Bulinus tropicus 94. These were screened for cercarieae while none of the Bulinus (Bulinus) tropicus shed any cercariae. River Enyau Biomphalaria snails were susceptible to a Schistosoma mansoni strain from Entebbe. Cercariae derived from these snails and also those found infected in the river enyau were confirmed to be S. mansoni using laboratory mice

The intensity of Schistosoma mansoni in the fishing villages of Bugonga and Kitubulu in Entebbe peninsula; Uganda

The intensity of Schistosoma mansoni infection in the fishing villages of Bugonga and Kitubulu; and the occurrence of snail intermediate host population in the two villages are described and compared. A total of five hundred and six faecal samples from both villages were examined by modified Kato's technique and the prevalence infection rate at Kitubulu was 40.3with mean egg count of 187 eggs per gram (epg) while in Bugonga it was 32.4and 126 egg respectively. The snail intermediate host for S. mansoni in the two villages was 2;750 Biomphalaria choanomphala at Kitubulu and 1;268 at Bugonga. But at Kitubulu in the vicinity of the village 185 Biomphalaria peifferi occurred in small localized population. The cercarial screening test conducted on 4;018 B. choanomphala and 185 B. peifferi from the two villages revealed higher snail infection rate for both mammalian and non-mammalian cercariae at Kitubulu than Bugonga. Variations in infection rates both among the inhabitants and host snail populations in the two villages are discussed

Schistosomiasis control measures for small irrigation schemes in Zimbabwe

A pilot study was initiated in 1984 on the 600 ha Mushandike Irrigation Project near Masvingo; Zimbabwe; with the objective of developing and field-testing practical guidelines to reduce the risk of schistosomiasis transmission foruse by those involved in planning designing; constructing and operating small-holder irrigation projects in Zimbabwe. Schistosomiasis is a parasitic disease which is particularly prevalent on irrigated land because of high levels of human contact with water and because colonisation by the aquatic snails; which actas its intermediate hosts; is generally favoured by the aquatic environments created within irrigation and drainage systems. A number of important phases of the project are complete. These include formulating citeria for schistosomiasis control; implementing these criteria within the design and construction precesses; establishing regular monitoring of the human and snail populations and introducing micro-computer assisted irringation scheduling to reduce the likelihood of snailcolonisation in parts of the system. [abstract terminated]

Schistosomiasis control measures for small irrigation schemes in Zimbabwe : results from three years of monitoring at Mushandike Irrigation Scheme

A pilot study was initiated in 1984 on the 600 ha Mushandike Irrigation Project near Masvingo; Zimbabwe; with the objective of developing and field-testing practical guidelines to reduce the risk of schistosomiasis transmission for use by those involved in planning; designing; constructing and operating small-holder irrigation projects in Zimbabwe. Schistosomisasis is a parasitic disease which is particularly pravalent on irrigation land because of high levels of human contact with water and because colonisation by the aquatic snails; which act as its intermediate hosts; is generally favoured by the equatic enviornments created within irrigation and drainage systems. A number of important phases of the project are complete. These include formulating criteria for schistosomiasis control; implementing these criteria with the design and construction processes; establishing regular monitoring of the human and snail populations and introducing micro-computer assisted irrigation scheduling to reduce the likelihood of smail colonisation in parts of the system. Interim results form the monitoring exercise are now available which enable comparisons to be drawn between different zones of the project and with irrigated land nearby on which control measures have not been introduced. These results indicate that a combination of concrete lining; irrigation scheduling and using innovative control structures on the infield works has had a major impact on the snail hosts. Some disease transmission is; however; occuring in the pilot areas. This is apparently associated with some unsuitable village lacations; inadequate access to safe domestic water supplies and enhanced flows in some natural drainage channels; This report reviews the monitoring to date and discusses what further studies are needed to establish the effectiveness of the control measures

Schistosomiasis research at the Blair Research Institute - Annual report - 1991

Genetic studies on some schistosome intermediate host snails in Zimbabwe were carried out. The variation in enzyme; electrophoresis patterns and chromosome numbers of snails from different geographical areas were examined. From the data collected and partial analysis of the electrophoresis data; there was no evidence suggesting the existence of more than one species (Balinus globosus) in the studied areas. The chromosome preparations observed did not show any variations in chromosome numbers (n = 18); although eliminating the existence of polyploidy it does not clarify which members of the B. tropicus/truncatus exists in Matabeleland (B. tropicus and/or B. tropicus) hence further research is needed; possibly using Biotechnological techniques