Monitoring Water Sources for Environmental Reservoirs of Toxigenic Vibrio cholerae O1, Haiti

Meer T. Alam, Thomas A. Weppelmann, Chad D. Weber, Judith A. Johnson, Mohammad H. Rashid, Catherine S. Birch, Babette A. Brumback, Valery E. Madsen Beau de Rochars, J. Glenn, and Afsar Ali

Author affiliations: University of Florida College of Public Health and Health Professions, Gainesville, Florida, USA (M.T. Alam, T.A. Weppelmann, V.E. Madsen Beau de Rochars, A. Ali); University of Florida Emerging Pathogens Institute, Gainesville (M.T. Alam, T.A. Weppelmann, C.D. Weber, J.A. Johnson, M.H. Rashid, C.S. Birch, B.A. Brumback, V.E. Madsen Beau de Rochars, J.G. Morris, Jr., A. Ali); University of Florida College of Medicine, Gainesville (M.H. Rashid, V.E. Madsen Beau de Rochars, A. Ali)

Abstract

An epidemic of cholera infections was documented in Haiti for the first time in more than 100 years during October 2010. Cases have continued to occur, raising the question of whether the microorganism has established environmental reservoirs in Haiti. We monitored 14 environmental sites near the towns of Gressier and Leogane during April 2012–March 2013. Toxigenic Vibrio cholerae O1 El Tor biotype strains were isolated from 3 (1.7%) of 179 water samples; nontoxigenic O1 V. cholerae was isolated from an additional 3 samples. All samples containing V. cholerae O1 also contained non-O1 V. cholerae. V. cholerae O1 was isolated only when water temperatures were ≥31°C. Our data substantiate the presence of toxigenic V. cholerae O1 in the aquatic environment in Haiti. These isolations may reflect establishment of long-term environmental reservoirs in Haiti, which may complicate eradication of cholera from this coastal country.

Epidemic cholera was identified during October 2010 in Haiti; initial cases were concentrated along the Artibonite River (1,2). The clonal nature of isolates during this initial period of the epidemic has been described (3–6). Because cholera had not been reported in Haiti for at least 100 years, there is a high likelihood that the responsible toxigenic Vibrio cholerae strain was introduced into Haiti, possibly through Nepalese peacekeeping troops garrisoned at a camp along the Artibonite River (4,7). In the months after October 2010, cholera spread quickly through the rest of Haiti: 604,634 cases and 7,436 deaths were reported in the first year of the epidemic (1). In the intervening years, cases and epidemics have been reported, and it has been suggested that onset of the rainy season serves as a trigger for disease occurrences (2,8).

V. cholerae is well recognized as an autochthonous aquatic microorganism species with the ability to survive indefinitely in aquatic reservoirs and is possibly in a “persister” phenotype (9).V. cholerae strains can also persist in aquatic reservoirs as a rugose variant that promotes formation of a biofilm that confers resistance to chlorine and to oxidative and osmotic stresses (10–13) and also persists in a viable but nonculturable form (14). Work by our group and others suggests that cholera epidemics among humans are preceded by an environmental bloom of the microorganism and subsequent spillover into human populations (15–17). In our studies in Peru (16), water temperature was found to be the primary trigger for these environmental blooms and could be correlated with subsequent increases in environmental counts and occurrence of human illness.

To understand patterns of ongoing cholera transmission and seasonality of cholera in Haiti, and to assess the likelihood of future epidemics, it is essential to know whether environmental reservoirs of toxigenic V. cholerae O1 have been established, where these reservoirs are located, and what factors affect the occurrence and growth of the microorganism in the environment. We report the results of an initial year of monitoring of environmental sites in the Ouest Department of Haiti, near the towns of Leogane and Gressier, where the University of Florida (Gainesville, FL, USA) has established a research laboratory and field area.