Intestinal schistosomiasis in Ugandan schoolchildren: A rapid mapping assessment around Lake Victoria,

supplemented by questionnairesClaire J. Standley1,2, Moses Adriko3, Moses Alinaitwe3, Francis Kazibwe3, Narcis B. Kabatereine3 and J. Russell Stothard1

1Department of Zoology, Natural History Museum, London, SW7 5BD, UK; 2Institute of Genetics, School of Biology, University of Nottingham, University Park, Nottingham, NG7 2RD, UK; 3Vector Control Division, Ministry of Health, 15 Bombo Road, PO Box 1661, Kampala, Uganda

The data presented here were submitted for publication in the journal Geospatial Health in June 2009. I would like to thank the Natural History Museum and the EU-CONTRAST consortium (www.eu-contrast.eu) for supprot and funding

• Rapid mapping is a valuable exercise for monitoring on-going control initiatives• Patterns of abundance of snails and prevalence/intensity of infection similar

• Demographic variables should be integrated into surveillance protocols• Treatment coverage low given on-going control: need for rigorous monitoring

CONCLUSIONS

Study site: Lake Victoria

KeyNo Biomphalaria

<10

10-30>30

Shedding cercariae

Study site: Lake Victoria

KeyNo Biomphalaria

<10

10 - - 30>30

Shedding cercariae

Figure 1: Distribution and abundance of Biomphalaria snails across 54 sites

INTRODUCTIONIntestinal schistosomiasis, caused by Schistosoma mansoni, is a scourge to communities in highly endemic areas, such as Lake Victoria. Snails of the genus Biomphalaria act as the intermediate host, and thus presence of these snails may be important in determining levels of local transmission risk. Despite an on-going national control programme, prevalence of the disease remains high, and some areas are infrequently monitored. Here, we test a rapid mapping protocol for surveying snail and parasite prevalence in remote parts of the Ugandan shoreline of Lake Victoria, and also investigate demographic variables as risk factors for infection in schoolchildren.

METHODSSnail surveys:- Semi-quantitative sampling at 54 sites- Collected snails shed for infection status- Water chemistry data recorded and specimens preserved for molecular analysis

Parasitological surveys:- Attempted to survey 15 children from around 25 schools (based on WHO rapid assessment protocols) - Stool samples taken for Kato-Katz slides, read twice for presence and number of eggs- Each child answered short questionnaire on their place of birth, length of time of residence in district, treatment history and knowledge of schistosomiasis

RESULTSSnail surveys:- Average abundance of snails shown to be higher in eastern districts- Naturally-infected snails found at four sites, all located in eastern districts (Figure 1)Parasitolocal surveys:- 456 stool samples collected from 478 schoolchildren surveyed in 27 schools across six disctricts- Average prevalence 41.7% and mean intensity of infection was 634.4 eggs per gram of faeces (Figure 2)- Both prevalence and intensity of infection were statistically higher in the eastern districts- Almost 50% of children reported being born in districts other than that where they currently attend school (Figure 3)-Only 60% reported ever having received treatment with praziquantel

0%

20%

40%

60%

80%

100%

Busia (36) Kalangala(189)

Masaka (14) Mayuge (105) Mukono (92) Rakai (18)

District (number of children surveyed)

Pe

rce

nta

ge

Born outside of Uganda(Kenya/Tanzania)

Born in non-Lake Victoria district inUgandaBorn in Lake Victoria district other thanwhere currently living

Born in same district as currentlyattending school

Figure 2: Prevalence and intensity of S. mansoni in 27 Ugandan schools

Figure 3 (below): ‘Place of birth’ survey responses