| dc.description.abstract | Introduction. Cholera is a preventable and treatable disease that is a major cause of morbidity and mortality in Uganda resulting in serious socioeconomic consequences. The aims of this study were to genotype the V. cholerae organisms in Uganda, establish the physicochemical characteristics of surface water sources in cholera affected areas of Uganda and to evaluate the modified cholera Rapid Diagnostic Test (RDT), Crystal VC® for detection and monitoring of cholera outbreaks so as to guide cholera prevention and control in Uganda.
Methodology. This study consisted of four sub-studies that were conducted at the Central Public Health Laboratories, Kampala and in cholera endemic/prone districts of Kampala, Nebbi, Kasese, Buliisa, Busia and Kayunga. The first sub-study was a cross-section study that involved genotyping of 63 V. cholerae isolates from the districts that reported cholera outbreaks for the period 2014 – 2016 by use of the three molecular tests namely; Polymerase Chain Reaction (PCR), Multi locus Variable number repeat Analysis (MLVA) and Whole Genome Sequencing (WGS). The second sub-study was a longitudinal study conducted on the surface water to detect and genotypes of the V. cholerae present in aquatic environment (surface water) by use of the RDT and PCR tests. The third sub-study was also a longitudinal study conducted on the surplus water collected in the second sub-study to establish the physiochemical water characteristics. The second and the third sub-studies involved testing the surface water collected from the six cholera prone or endemic districts of Kasese, Buliisa, Kampala, Nebbi, Kayunga and Busia between February 2015 – January 2016. Monthly water testing to detect V. cholerae and to establish water physicochemical characteristics (temperature, dissolved oxygen, turbidity, pH and electric conductivity) were carried out using RDT, multiplex PCR and digital meters (Hach and turbidity). One Way ANOVA test was used to determine variation in the physicochemical parameters of water. The fourth sub-study was a comparative study in which a modified cholera RDT, Crystal VC® was evaluated against the culture method for detection and monitoring of cholera outbreaks. Fresh stool samples from suspected cholera patients were tested by both RDT and culture tests. The test results were interpreted in form of sensitivity, specificity positive and negative predictive values and accuracy.
Results. Three genetically closely related MLVA clonal complexes (CC): CC1, 32% (20/63); CC2, 40% (25/63) and CC3, 28% (18/63) were identified in Uganda. Each CC contained isolates from a different whole genome sequencing clade. One clade was contained in the transmission event (T13) lineage. Vibrio cholerae genetic lineages spread between districts within Uganda and across the national borders.
Of 322 surface water samples tested, 35 (10.8%) were positive for V. cholerae non O1/non O139; 2 samples tested positive for non-toxigenic atypical V. cholerae O139. None of the samples tested had toxigenic V. cholerae O1 or O139 that are responsible for cholera epidemics.
The mean physicochemical water characteristics varied within the test sites and were statistically significantly different between the test sites or water bodies. The majority of water samples had mean physicochemical parameters in acceptable World Health Organization (WHO) water safety limits except for water turbidity where all (100%) of the tested samples had unacceptable level of above 5 Nephlometric Turbidity Units.
The majority, 91/102 (89%) of the fresh stool samples tested positive by both Crystal VC® RDT and culture test. Nine stool samples were negative by Crystal VC® RDT and culture test. Sensitivity of 99%, Specificity of 90%, Positive Predictive Value of 99%, Negative Predictive Value of 90% and Accuracy of 98% were documented.
Conclusion. Vibrio cholerae responsible for cholera epidemics in Uganda consisted of three genetically closely related bacteria stains that spread within Uganda, East Africa and Central Africa regions. Cross-border spread into and out of Uganda played an important role in the propagation and spread of cholera epidemics. There were no epidemic V. cholerae species in the surface water sources in Uganda, though the surface water sources were natural habitats for V. cholerae, non O1/non O139 and atypical non toxigenic O139. The physicochemical parameter of the tested water sources varied within the sites overtime. There were statistically significant differences in the physicochemical parameters between the test sites. All surface water tested had turbidity outside the WHO recommended safety levels. The modified Crystal VC® dipsticks had high level of accuracy and is a quick alternative cholera outbreak detection and monitoring tool.
Recommendations. To prevent, control and eliminate cholera in Uganda the stakeholders should support targeted provision of social services (safe water, hygiene, sanitation, education and healthcare services) in cholera prone communities in Uganda. Cross-border collaboration and coordination of cholera prevention and control between countries in the region should be promoted. Affirmative action for cholera prone communities in Uganda to access safe water and additional water studies to generate information on the non O1/non O139 and other physicochemical characteristics not covered in this study are required. In addition, cholera RDT should be used whenever an outbreak of cholera is suspected to ease early case detection and to monitor outbreak progression | en_US |
