title: High prevalence of schistosomiasis in Mbita and its adjacent islands of Lake Victoria, western Kenya.
abstract: BACKGROUND
  Intestinal schistosomiasis continues to be a significant cause of morbidity among communities located around Lake Victoria and on its islands. Although epidemiological surveys have been conducted in other areas bordering the lake in western Kenya, Mbita district and its adjacent islands have never been surveyed, largely due to logistical challenges in accessing these areas. Consequently, there is a paucity of data on prevalence of schistosomiasis and soil-transmitted helminth (STH) infections that are endemic in this region.
  
  
  METHODS
  This cross-sectional study determined the prevalence, intensity of infection and geographical distribution of schistosome and STH infections among 4,065 children aged 5-19 years in 84 primary schools in Mbita and nearby islands of Lake Victoria (Mfangano, Ringiti, Rusinga and Takawiri), in western Kenya. Single stool samples were collected and examined for eggs of Schistosoma mansoni and STHs (Hookworms, Ascaris lumbricoides and Trichuris trichiura) using the Kato-Katz technique. Primary schools were mapped using geographical information system data on PDAs and prevalence maps generated using ArcView GIS software.
  
  
  RESULTS
  Overall, 65.6% (95% CI = 64.2-67.1%) of children were infected with one or more helminth species; 12.4% (95% CI = 11.4-13.4%) of children were infected with one or more STH species. Mean school prevalence of S. mansoni infection was 60.5% (95% CI = 59.0-62.0%), hookworms 8.4% (95% CI = 7.6-9.3%), A. lumbricoides 3.3% (95% CI = 2.7-3.8%), and T. trichiura 1.6% (95% CI = 1.2-2.0%). Interestingly, the mean S. mansoni prevalence was 2-fold higher on the islands (82%) compared to the mainland (41%) (z = 5.8755, P < 0.0001). Similarly, intensity of infection was 54% higher on the islands (217.2 ± 99.3) compared to the mainland (141.3 ± 123.7) (z = 3.9374, P < 0.0001). Schools in closest proximity to Lake Victoria had the highest S. mansoni prevalence while prevalence of STHs was more homogenously distributed.
  
  
  CONCLUSIONS
  The very high prevalence of schistosomiasis in Mbita and the 4 islands is quite alarming, and indicates an urgent and critical need for control interventions. Findings from this survey indicate the need to implement treatment in remote areas not previously covered by mass drug administration programs.
authors.affiliation: Neglected Tropical Diseases Branch, Centre for Global Health Research, Kenya Medical Research Institute, P, O, Box 1578-40100, Kisumu, Kenya. modiere@kemricdc.org
authors.forename: Maurice R
authors.initials: MR
authors.lastname: Odiere
authors.forename: Fredrick O
authors.initials: FO
authors.lastname: Rawago
authors.forename: Maurice
authors.initials: M
authors.lastname: Ombok
authors.forename: William Evan
authors.initials: WE
authors.lastname: Secor
authors.forename: Diana M S
authors.initials: DM
authors.lastname: Karanja
authors.forename: Pauline N M
authors.initials: PN
authors.lastname: Mwinzi
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Lammie
authors.forename: Kimberly
authors.initials: K
authors.lastname: Won
mesh_terms: D000293:Adolescent; D000723:Ancylostomatoidea / Q000302:isolation & purification; D000818:Animals; D017164:Ascaris lumbricoides / Q000302:isolation & purification; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005243:Feces / Q000469:parasitology; D005260:Female; D006801:Humans; D007630:Kenya / Q000453:epidemiology; D008297:Male; D015995:Prevalence; D012550:Schistosoma mansoni / Q000302:isolation & purification*; D012555:Schistosomiasis mansoni / Q000453:epidemiology*; D014258:Trichuris / Q000302:isolation & purification; D055815:Young Adult