Abstract
Cholera is a major public health problem in the African Great Lakes basin. Two hypotheses might explain this observation, namely the lakes are reservoirs of toxigenic Vibrio cholerae O1 and O139 bacteria, or cholera outbreaks are a result of repeated pathogen introduction from the neighboring communities/countries but the lakes facilitate the introductions. A prospective study was conducted in Uganda between February 2015 and January 2016 in which 28 selected surface water sources were tested for the presence of V. cholerae species using cholera rapid test and multiplex polymerase chain reaction. Of 322 water samples tested, 35 (10.8%) were positive for V. cholerae non O1/non O139 and two 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 Lake Albert region registered the highest number of positive tests for V. cholerae non O1/non O139 at 47% (9/19). The peak period for V. cholerae non O1/non O139 positive tests was in March–July 2015 which coincided with the first rainy season in Uganda. This study showed that the surface water sources, including the African Great Lakes in Uganda, are less likely to be reservoirs for the observed V. cholerae O1 or O139 epidemics, though they are natural habitats for V. cholerae non O1/non O139 and atypical non-toxigenic V. cholerae O139. Further studies by WGS tests of non-toxigenic atypical V. cholerae O139 and physicochemical tests of surface water sources that supports V. cholerae should be done to provide more information. Since V. cholerae non O1/non O139 may cause other human infections, their continued surveillance is needed to understand their potential pathogenicity.
Highlights
Cholera, a preventable and treatable infectious disease, is a major contributor to morbidity and mortality in many countries in the world (Mengel et al, 2014; Ali et al, 2015)
The type of V. cholerae present was identified through polymerase chain reaction (PCR) amplification of specific genes namely: outer membrane protein (OmpW), cholera enterotoxin sub-unit A, and rfb genes according to previously described methods (Nandi et al, 2000)
35 samples were positive for V. cholerae non O1/non O139, as determined by a positive band for OmpW
Summary
A preventable and treatable infectious disease, is a major contributor to morbidity and mortality in many countries in the world (Mengel et al, 2014; Ali et al, 2015). There are >200 serotypes of V. cholerae but only serotypes O1 and O139 are responsible for cholera epidemics (Cabral, 2010). Cholera appeared in Africa in the early 1970s, and spread to 30 out of, the 46 countries in the continent (Glass et al, 1991). In recent years, over 41% of all cholera cases and deaths reported to the World Health Organization (WHO) were from African countries (World Health Organization, 2016b). The top 10 African countries reporting cholera cases and deaths annually to WHO were in sub-Saharan Africa and included Uganda (World Health Organization, 2004, 2015, 2016a). The consequences of cholera epidemics may be severe and lead to national crises in some African countries (Mason, 2009; Morof et al, 2013)
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