Increased Isolation Frequency of Toxigenic Vibrio cholerae O1 from Environmental Monitoring Sites in Haiti

Abstract

Since the identification of the first cholera case in 2010, the disease has spread in epidemic form throughout the island nation of Haiti; as of 2014, about 700,000 cholera cases have been reported, with over 8,000 deaths. While case numbers have declined, the more fundamental question of whether the causative bacterium, Vibrio cholerae has established an environmental reservoir in the surface waters of Haiti remains to be elucidated. In a previous study conducted between April 2012 and March 2013, we reported the isolation of toxigenic V. cholerae O1 from surface waters in the Ouest Department. After a second year of surveillance (April 2013 to March 2014) using identical methodology, we observed a more than five-fold increase in the number of water samples containing culturable V. cholerae O1 compared to the previous year (1.7% vs 8.6%), with double the number of sites having at least one positive sample (58% vs 20%). Both seasonal water temperatures and precipitation were significantly related to the frequency of isolation. Our data suggest that toxigenic V. cholerae O1 are becoming more common in surface waters in Haiti; while the basis for this increase is uncertain, our findings raise concerns that environmental reservoirs are being established.

Deadly River: Cholera and Cover-Up in Post-Earthquake Haiti

“…Although initial epidemic spikes were followed by a rapid decline in case numbers, cholera remains a critical public health problem for Haiti. Of immediate concern, the number of cases in the first 4 months of 2016 (close to 14,000 reported cases) exceeds the reported case numbers for the same period in 2014 and 2015 ( 1 ), consistent with the hypothesis that cholera in Haiti is becoming endemic, potentially with the establishment of environmental reservoirs ( 2 , 3 ). …”

Cholera Transmission in Ouest Department of Haiti: Dynamic Modeling and the Future of the Epidemic

“…Almost four years after the identification of the first cholera cases, the transmission appears to have temporarily slowed, however the future of the cholera epidemic in Haiti remains uncertain [ 4 ]. After the initial isolation of toxigenic V. cholerae O1 from surface water monitoring sites in the Ouest Department of Haiti in 2012 and 2013, there is evidence that the frequency of isolation from the environment has actually increased between 2013 and 2014 [ 5 ] [ 6 ]. In the absence of ongoing transmission, the presence of toxigenic V. cholerae O1 in the aquatic environment has left the international scientific community divided on the possibility that the causative bacterium has established environmental reservoirs in the surface waters of Haiti [ 7 ] [ 8 ] [ 9 ].…”

“…[ 11 ]. However, despite empirical evidence that V. cholerae O1 is increasingly present in the surface water as reported cases continue to decline, none of the previous models have considered the role of environmental reservoirs in cholera transmission [ 6 ]. Though the environmental compartment has been included in the models, it is assumed that V. cholerae O1 occupy a transient state where after being shed from the human host they will eventually become removed from the environment at a constant rate of decay [ 12 ].…”

Toxigenic Vibrio cholerae evolution and establishment of reservoirs in aquatic ecosystems

“…1A). The prevalence of toxigenic aquatic V. cholerae O1 correlated with increased temperature and rainfall but not with fecal coliform counts, suggesting that the presence was not due to fecal contamination alone (10). Monthly case counts in Ouest, oscillating yearly but decreasing during the dry season and increasing during the rainy season (April to October), correlated with increased temperature and rainfall (Fig.…”

“…Environmental survey resulted in the isolation of 27 toxigenic V. cholerae O1 strains between 2012 and 2015. Both clinical and environmental V. cholerae O1 isolates were confirmed by standard microbiological, biochemical, serological, and genetic analysis as described previously (10,30). Of 800 clinical isolates, 205 strains (116 from the Ouest Department) as well as all 27 environmental O1 strains were analyzed in this study.…”