To further evaluate the risk for cholera transfer through ballast water under existing management approaches, we applied the IMO ballast water exchange depth and distance criteria to the Caribbean region. Buffers of 50 and 200 nautical miles were generated on the basis of the Global Self-Consistent, Hierarchical, High-Resolution Shoreline Database (version 2.1; www.ngdc.noaa.gov/mgg/shorelines/gshhs.html) and overlaid on bathymetric data from the ETOPO1 Global Relief Model (www.ngdc.noaa.gov/mgg/global/global.html) (10,11). We acquired these datasets through the National Oceanic and Atmospheric Administration’s National Geophysical Data Center (www.ngdc.noaa.gov).

Figure

Figure. . . Zones in the Caribbean region where distance from shore and water depth meet International Maritime Organization guidelines for ballast exchange. To exchange ballast >200 nautical miles from shore...

Mapping indicates that waters around Haiti where the IMO guidelines can be followed are extremely limited (Figure). To exchange ballast >200 nautical miles from shore in water 200 m deep, ships must travel 280 nautical miles northeast of Haiti (Figure, A) or to the Gulf of Mexico (Figure, B). To exchange ballast at the minimum 50 nautical miles from shore in water >200 m deep, ships must travel >90 nautical miles northeast (Figure, C) or 50 nautical miles south (Figure, D) of Haiti or conduct the exchange in an area <45 nautical miles wide approximately equidistant from Haiti, Cuba, and Jamaica (Figure, E).

After discussions with staff at CDC and the Pan American Health Organization, the Director General of the Haitian Ministry of Health and Population issued 2 memoranda addressing ballast water management. The first, issued November 10, 2011, asked ship captains not to exchange ballast water in Haitian harbors. The second, issued November 15, 2011, reminded ship captains to adhere to IMO guidelines for ballast water exchange. However, ships operating in the Caribbean Sea face practical difficulties in conducting ballast water exchange at the recommended distances without making large deviations from usual routes. The BWM Convention recommends that designated ballast water exchange areas should be on or close to existing maritime routes and does not require that ships deviate course or delay voyages to comply with ballast water exchange guidelines (6). Ballast water exchange at sea also presents operational and safety challenges to ships and might not be completely effective in preventing spread of aquatic organisms (12).

As an alternative management measure, ballast water treatment systems are being developed to meet the BWM Convention’s numeric discharge standards, and several systems are available (13). These systems combine filtration with nonchemical (e.g., UV light, shear, heat) and chemical biocides to remove or kill organisms (14). Ballast water treatment systems are designed to achieve the BWM Convention efficacy levels, and their future use in the Caribbean region would likely be a more effective management approach than ballast water exchange.

The Haiti cholera outbreak spread to the neighboring Dominican Republic, and cholera cases associated with travel to Haiti were recognized in the United States (7), but there is no evidence that V. cholerae was transferred by ship ballast water in these instances. The Wider Caribbean Region comprises 28 island and continental countries with coasts on the Caribbean Sea, the Gulf of Mexico, and adjacent waters of the Atlantic Ocean. This area is at elevated risk for transfer of contaminated ballast water because of the high volume of cargo trade in the region and has been prioritized by the Global Ballast Water Management Program (http://globallast.imo.org/index.asp), a program administered by IMO, the Global Environment Facility, and the United Nations Development Program to assist developing countries implement ballast water management measures (15).

A comprehensive regional strategic plan has been developed to promote ratification of the BWM Convention and to facilitate its implementation within the Wider Caribbean Region through regional cooperation, training, communication, compliance monitoring and enforcement, and promotion of national-level legislation, task forces, action plans, and sustainable resources to support activities (15). Implementation of this plan will help protect public health by reducing the likelihood that V. cholerae and other pathogens will be transferred by ballast water.