Analyses of drinking water quality during a protracted cholera epidemic in Malawi - a cross-sectional study of key physicochemical and microbiological parameters

Anecdotal evidence and available literature indicated that contaminated water played a major role in spreading the prolonged cholera epidemic in Malawi from 2022 to 2023. This study assessed drinking water quality in 17 cholera-affected Malawi districts from February to April 2023. Six hundred and thirty-three records were analysed. The median counts/100 ml for thermotolerant coliform was 98 (interquartile range (IQR): 4-100) and that for Escherichia coli was 0 (IQR: 0-9). The drinking water in all (except one) districts was contaminated by thermotolerant coliform, while six districts had their drinking water sources contaminated by E. coli. The percentage of contaminated drinking water sources was significantly higher in shallow unprotected wells (80.0% for E. coli and 95.0% for thermotolerant coliform) and in households (55.8% for E. coli and 86.0% for thermotolerant coliform). Logistic regression showed that household water has three times more risk of being contaminated by E. coli and two and a half times more risk of being contaminated by thermotolerant coliform compared to other water sources. This study demonstrated widespread contamination of drinking water sources during a cholera epidemic in Malawi, which may be the plausible reason for the protracted nature of the epidemic.

Évolution de la sensibilité de Vibrio cholerae 01 après utilisation prolongée d'antibiotiques en traitement et en prophylaxie au cours de l'épidémie de choléra de Douala (Cameroun) 2004

Antibiotics were extensively used, both for curative as for prophylactic purposes, to prevent an explosive spread of the 2004 cholera epidemic in Douala. It was thus necessary to control the antibiotic susceptibility of Vibrio cholerae.

OBJECTIVE

The authors had for aim to describe the epidemic, the use of antibiotics, and to follow the susceptibility of V. cholerae.

DESIGN

The 14 hospitals in the study all used the same diagnostic, treatment, and preventive protocols, as well as in community practice with home visits. All cases were clinically confirmed and reported. Samples were systematically taken at the beginning and at the end of the epidemic, and randomly during the epidemic. Each identified strain was tested by the disk method for antibiotic susceptibility.

RESULTS

Between January and September 2004, 5013 patients and 177,353 people in contact with the patients were given a single dose of doxycycline or amoxicillin for 3 days. Sixty-nine deaths were recorded (lethality 1.37%). One hundred (and) eleven strains of V. cholerae were identified in 187 samples. All of them were resistant to sulfamides and colistin, but susceptible to cyclins, betalactams, and fluoroquinolones, without any modification during the 8 months of follow-up.

CONCLUSION

Despite the risk of a massive and prolonged use of antibiotics, strictly prescribed and controlled, no resistance developed in the identified strain. Chemoprophylaxis must follow rigorous protocols and be continuously monitored.

[Factors contributing to endemic cholera in Douala, Cameroon]

Cholera has been endemic in Douala, Cameroon since 1971. A number of environmental factors favourize the survival of the Vibrio in Douala including location at the mouth of Wouri delta on the Atlantic Ocean, sandy clay soil, shallow dirty polluted foul-smelling groundwater, presence of vast expanses of swamp, streams/drainage ditches infested with algae, and high temperatures with low rainfall and drought during certain periods of the year. Most outbreaks have started in Bepanda, a slum area built on a garbage dump in a swampy zone fed by drainage ditches carrying the faecal pollution from neighbouring upstream districts. It is a densely overcrowded area of uncontrolled urbanization generated by the influx of poor city new-comers who live without adequate access to clean water or basic sanitary facilities. The most affected areas are those resulting from recent unregulated urban sprawl in polluted swamp zones or garbage dumps. Since access to the public water system is inadequate with only 65000 persons connected for 3 million inhabitants, dwellers in most areas must take water from the 70000 urban wells (estimated in 2004) that are often not more than 1.5 m deep. Sewage facilities are insufficient to provide complete evacuation of solid and liquid waste. The network of rivers, streams and man-made ditches waste are poorly maintained and often overflow during the rainy season. The contents of latrines are often discharged directly into the environment. Social factors such as the reformation of urban tribes and persistence of traditional attitudes toward waste disposal and water use have not only led to high-risk behaviour but also created barriers to sanitation and hygiene education. With an inadequate sanitation inspection system, a large but purely accessible public health system and a highly disorganized private health sector exists, effective preventive measures are difficult to implement. The combination of these factors probably account for the endemicity of cholera in Douala.