Evaluation of pot-chlorination of wells during a cholera outbreak, Bissau, Guinea-Bissau, 2008.

We evaluated the ability of UNICEF-designed pot-chlorinators to achieve recommended free residual chlorine (FRC) levels in well water in Bissau, Guinea-Bissau, during a cholera outbreak. Thirty wells were randomly selected from six neighbourhoods. Pot-chlorinators--perforated plastic bottles filled with gravel, sand and calcium hypochlorite granules--were placed in each well. FRC was measured before and 24, 48 and 72 h after placement and compared with World Health Organization (WHO)-recommended levels of 21 mg L(-1) for well water during cholera outbreaks and 0.2-5 mg L 1 in non-outbreak settings. Presence of well covers, distance from wells to latrines, and rainfall were noted. Complete post-chlorination data were collected from 26 wells. At baseline, no wells had FRC>0.09 mg L(-1). At 24, 48 and 72 h post-chlorination, 4 (15%), 1 (4%) and 0 wells had FRC>or=1 mg L(-1) and 16 (62%), 4 (15%) and 1 (4%) wells had FRC between 0.2 and 5 mg L(-1), respectively. Several families reported discontinuing household water chlorination after wells were treated with pot-chlorinators. Pot-chlorinators failed to achieve WHO-recommended FRC levels in well water during a cholera outbreak, and conveyed a false sense of security to local residents. Pot-chlorination should be discouraged and alternative approaches to well-water disinfection promoted.

Field evaluation of crystal VC Rapid Dipstick test for cholera during a cholera outbreak in Guinea-Bissau.

OBJECTIVES: To evaluate performance characteristics and ease of use of the new commercially available Crystal VC Rapid Dipstick (VC) test (Span Diagnostics, India) for Vibrio cholerae O1 and O139. METHODS: Whole stool was collected from patients presenting to a hospital cholera ward during a 2008 epidemic in Guinea-Bissau. The VC test on stool samples was conducted on-site; samples were subsequently stored in Cary-Blair transport media and sent to the Centers for Disease Control and Prevention for diagnostic testing by culture and polymerase chain reaction (PCR). In addition, four local laboratory technicians who were unfamiliar with the test were provided with stool samples, the VC test kit, and simple written instructions and asked to perform the test and interpret results. RESULTS: A total of 101 stool specimens were collected and tested. Compared with PCR, the test was 97% sensitive and 71-76% specific. Laboratory technicians in Bissau performed the test and interpreted results correctly using only simple written instructions. CONCLUSIONS: The VC test may be useful for cholera diagnosis in outbreak situations where laboratory capacity is limited.