Abstract
BackgroundGhana is affected by regular cholera epidemics and an annual average of 3,066 cases since 2000. In 2014, Ghana experienced one of its largest cholera outbreaks within a decade with more than 20,000 notified infections. In order to attribute this rise in cases to a newly emerging strain or to multiple simultaneous outbreaks involving multi-clonal strains, outbreak isolates were characterized, subtyped and compared to previous epidemics in 2011 and 2012.Methodology/Principal FindingsSerotypes, biotypes, antibiotic susceptibilities were determined for 92 Vibrio cholerae isolates collected in 2011, 2012 and 2014 from Southern Ghana. For a subgroup of 45 isolates pulsed-field gel electrophoresis, multilocus sequence typing and multilocus-variable tandem repeat analysis (MLVA) were performed. Eighty-nine isolates (97%) were identified as ctxB (classical type) positive V. cholerae O1 biotype El Tor and three (3%) isolates were cholera toxin negative non-O1/non-O139 V. cholerae. Among the selected isolates only sulfamethoxazole/trimethoprim resistance was detectable in 2011, while 95% of all 2014 isolates showed resistance towards sulfamethoxazole/trimethoprim, ampicillin and reduced susceptibility to ciprofloxacin. MLVA achieved the highest subtype discrimination, revealing 22 genotypes with one major outbreak cluster in each of the three outbreak years. Apart from those clusters genetically distant genotypes circulate during each annual epidemic.Conclusions/SignificanceThis analysis suggests different endemic reservoirs of V. cholerae in Ghana with distinct annual outbreak clusters accompanied by the occurrence of genetically distant genotypes. Preventive measures for cholera transmission should focus on aquatic reservoirs. Rapidly emerging multidrug resistance must be monitored closely.
Highlights
The World Health Organization (WHO) estimates that 3–5 million annual cases of cholera occur worldwide, resulting in 100,000–120,000 deaths [1]
A case of cholera is defined according to the WHO standard case definition: If cholera is not known to be present in the area, a case of cholera is considered in a patient 5 years with severe dehydration or death from acute watery diarrhea, while during a cholera epidemic every patient aged 5 years with acute watery diarrhea and/or vomiting is considered as a case
Age was reported for 19,863 cases and distributed with a median age of 26 years and an interquartile range (IQR) of 20–35 years
Summary
The World Health Organization (WHO) estimates that 3–5 million annual cases of cholera occur worldwide, resulting in 100,000–120,000 deaths [1]. In 2013 alone, 22 African countries reported 56,329 cholera cases. These numbers are considered to be substantially underestimated due to poorly functioning national epidemiological and laboratory surveillance systems, which are not able to detect the majority of mild disease presentations. With 90% of the population at risk for cholera transmission, Ghana always ranks among the most affected countries on the African continent [4]. In the year 2014, Ghana experienced an exceptionally large cholera outbreak with 28,975 infections notified to the World Health Organization between June and November [6]. Ghana is affected by regular cholera epidemics and an annual average of 3,066 cases since 2000. In order to attribute this rise in cases to a newly emerging strain or to multiple simultaneous outbreaks involving multi-clonal strains, outbreak isolates were characterized, subtyped and compared to previous epidemics in 2011 and 2012
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