title: Urogenital schistosomiasis transmission on Unguja Island, Zanzibar: characterisation of persistent hot-spots.
abstract: Elimination of urogenital schistosomiasis transmission is a priority for the Zanzibar Ministry of Health. Preventative chemotherapy together with additional control interventions have successfully alleviated much of the disease burden. However, a persistently high Schistosoma haematobium prevalence is found in certain areas. Our aim was to characterise and evaluate these persistent "hot-spots" of transmission and reinfection in comparison with low-prevalence areas, to support the intervention planning for schistosomiasis elimination in Zanzibar.
  
  
  
  Prevalences of S. haematobium were annually determined by a single urine filtration in schoolchildren from 45 administrative areas (shehias) in Unguja in 2012, 2013 and 2014. Coverage data for biannual treatment with praziquantel were available from ministerial databases and internal surveys. Among the 45 shehias, five hot-spot (≥ 15 % prevalence) and two low-prevalence (≤ 5 %) shehias were identified and surveyed in mid-2014. Human-water contact sites (HWCSs) and the presence of S. haematobium-infected and uninfected Bulinus globosus, as well as safe water sources (SWSs) and their reliability in terms of water availability were determined and mapped.
  
  
  
  We found no major difference in the treatment coverage between persistent hot-spot and low-prevalence shehias. On average, there were considerably more HWCSs containing B. globosus in hot-spot than in low-prevalence shehias (n = 8 vs n = 2) and also more HWCSs containing infected B. globosus (n = 2 vs n = 0). There was no striking difference in the average abundance of SWSs in hot-spot and low-prevalence shehias (n = 45 vs n = 38) and also no difference when considering SWSs with a constant water supply (average: 62 % vs 62 %). The average number of taps with a constant water supply, however, was lower in hot-spot shehias (n = 7 vs n = 14). Average distances from schools to the nearest HWCS were considerably shorter in hot-spot shehias (n = 229 m vs n = 722 m).
  
  
  
  The number of HWCSs, their infestation with B. globosus and their distance to schools seem to play a major role for a persistently high S. haematobium prevalence in children. In addition to treatment, increasing access to reliably working taps, targeted snail control at HWCSs near schools and enhanced behaviour change measures are needed to reduce prevalences in hot-spot areas and to finally reach elimination.
  
  
  
  ISRCTN48837681 .
authors.affiliation: Wolfson Wellcome Biomedical Laboratories, Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK.|Department of Pathology and Pathogen Biology, Centre for Emerging, Endemic and Exotic Diseases, Royal Veterinary College, University of London, Hawkshead Lane, Hatfield, Hertfordshire, AL9 7TA, UK.
authors.forename: Tom
authors.initials: T
authors.lastname: Pennance
authors.affiliation: Independent Consultant, Schistosomiasis Consortium for Operational Research and Evaluation, University of Georgia, Athens, GA, USA.
authors.forename: Bobbie
authors.initials: B
authors.lastname: Person
authors.affiliation: Zanzibar Neglected Tropical Diseases Programme, Ministry of Health, P.O. Box 236, Zanzibar Town, Unguja, United Republic of Tanzania.
authors.forename: Mtumweni Ali
authors.initials: MA
authors.lastname: Muhsin
authors.affiliation: Zanzibar Neglected Tropical Diseases Programme, Ministry of Health, P.O. Box 236, Zanzibar Town, Unguja, United Republic of Tanzania.
authors.forename: Alipo Naim
authors.initials: AN
authors.lastname: Khamis
authors.affiliation: Zanzibar Neglected Tropical Diseases Programme, Ministry of Health, P.O. Box 236, Zanzibar Town, Unguja, United Republic of Tanzania.
authors.forename: Juma
authors.initials: J
authors.lastname: Muhsin
authors.affiliation: Zanzibar Neglected Tropical Diseases Programme, Ministry of Health, P.O. Box 236, Zanzibar Town, Unguja, United Republic of Tanzania.
authors.forename: Iddi Simba
authors.initials: IS
authors.lastname: Khamis
authors.affiliation: Zanzibar Neglected Tropical Diseases Programme, Ministry of Health, P.O. Box 236, Zanzibar Town, Unguja, United Republic of Tanzania.
authors.forename: Khalfan Abdallah
authors.initials: KA
authors.lastname: Mohammed
authors.affiliation: Zanzibar Neglected Tropical Diseases Programme, Ministry of Health, P.O. Box 236, Zanzibar Town, Unguja, United Republic of Tanzania.
authors.forename: Fatma
authors.initials: F
authors.lastname: Kabole
authors.affiliation: Wolfson Wellcome Biomedical Laboratories, Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK.
authors.forename: David
authors.initials: D
authors.lastname: Rollinson
authors.affiliation: Wolfson Wellcome Biomedical Laboratories, Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK. s.knopp@unibas.ch.|Swiss Tropical and Public Health Institute, Socinstrasse 57, P.O. Box, CH-4002, Basel, Switzerland. s.knopp@unibas.ch.|University of Basel, Petersplatz 1, CH-4003, Basel, Switzerland. s.knopp@unibas.ch.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Knopp
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use; D002648:Child; D060740:Disease Eradication / Q000379:methods; D060766:Drinking Water / Q000469:parasitology; D005260:Female; D006801:Humans; D017053:Infection Control / Q000379:methods; D008297:Male; D011223:Praziquantel / Q000627:therapeutic use; D015995:Prevalence; D012548:Schistosoma haematobium / Q000302:isolation & purification*; D012553:Schistosomiasis haematobia / Q000453:epidemiology* / Q000469:parasitology / Q000635:transmission*; D012574:Schools; D012908:Snails / Q000469:parasitology*; D011795:Surveys and Questionnaires; D013636:Tanzania / Q000453:epidemiology; D014556:Urine / Q000469:parasitology
chemical_list: D000871:Anthelmintics; D060766:Drinking Water; D011223:Praziquantel
keywords: Bulinus globosus; Cercariae; Control; Elimination; Hot-spot; Safe water; Schistosoma haematobium; Snail; Urogenital schistosomiasis; Zanzibar