title: Role of phytoplankton in maintaining endemicity and seasonality of cholera in Bangladesh.
abstract: BACKGROUND
  In Bangladesh, cholera is endemic and maintains a regular seasonal pattern. The role of phytoplankton in maintaining endemicity and seasonality of cholera was monitored in Matlab, Bangladesh.
  
  
  METHODS
  Phytoplankton and water samples were collected from two ponds bi-weekly for 1 year. The association of Vibrio cholerae O1 with phytoplankton was studied by culture and direct fluorescent antibody techniques. The bio-physicochemical parameters of water were measured and data for cases of cholera were collected from the records of Matlab hospital. The correlation of cholera cases with levels of phytoplankton, V. cholerae and bio-physicochemical parameters of water was carried out using Pearson's correlation coefficients.
  
  
  RESULTS
  V. cholerae O1 survived for 48 days in association with Anabaena variabilis in a culturable state, but survived for a year in a viable but non-culturable (VBNC) state. V. cholerae survived for 12 and 32 days in a culturable state in control water (without algae) and water with algae, respectively. There was a significant correlation between changing levels of cholera cases in the community and the blue green algae and total phytoplankton in the aquatic environment. A significant correlation was also found between the cholera cases and chlorophyll-a and VBNC V. cholerae O1 in the aquatic environment.
  
  
  CONCLUSIONS
  This study demonstrated the role of phytoplankton in maintaining endemicity and seasonality of cholera in Bangladesh.
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, 68 Shahid Tajuddin Ahmed Sarani, Mohakhali, Dhaka 1212, Bangladesh sislam@icddrb.org.
authors.forename: M Sirajul
authors.initials: MS
authors.lastname: Islam
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, 68 Shahid Tajuddin Ahmed Sarani, Mohakhali, Dhaka 1212, Bangladesh.
authors.forename: M Shafiqul
authors.initials: MS
authors.lastname: Islam
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, 68 Shahid Tajuddin Ahmed Sarani, Mohakhali, Dhaka 1212, Bangladesh.
authors.forename: Zahid H
authors.initials: ZH
authors.lastname: Mahmud
authors.affiliation: London School of Hygiene & Tropical Medicine, Keppel St, London, WC1E 7HT, UK.
authors.forename: Sandy
authors.initials: S
authors.lastname: Cairncross
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, 68 Shahid Tajuddin Ahmed Sarani, Mohakhali, Dhaka 1212, Bangladesh.
authors.forename: John D
authors.initials: JD
authors.lastname: Clemens
authors.affiliation: Northumbria University, Newcastle Upon Tyne, UK.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Collins
mesh_terms: D001459:Bangladesh / Q000453:epidemiology; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D002771:Cholera / Q000453:epidemiology*; D019353:Endemic Diseases / Q000706:statistics & numerical data*; D006801:Humans; D010839:Phytoplankton / Q000382:microbiology*; D012621:Seasons; D016019:Survival Analysis; D041241:Vibrio cholerae O1 / Q000302:isolation & purification; D014871:Water Microbiology
chemical_list: D002734:Chlorophyll; D000077194:Chlorophyll A
keywords: Bangladesh; Cholera; Endemicity; Phytoplankton; Seasonality