Abstract

PIP: It is hypothesized that geographical regions where cholera is endemic, V. cholerae 01 may be maintained in estuarine environments. Endemic cholera, unlike epedemic cholera, occurs regularly, and sometimes seasonally, in certain geographical areas without evidence of importation. Measures used to control epedemic cholera are not very effective in preventing endemic cholera. Areas of endemic cholera include southeastern US and several African and Asian countries, including Bangladesh. It has previously been suggested that V. cholerae 01 is maintained in these areas between outbreaks by 1) living in nonhuman animals; 2) residing in chronic human carriers, who may not excrete the organism; 3) by continous transmission to individuals who manifest only mild symptoms of the disease; and 4) by living in aquatic environments. The 1st 3 explanations are to supported by available evidence. The 4th explanation, previously thought to be impossible, is now engendering new interest. Recent studies reveal that V. cholerae 01 can survive in warm water with a salinity of 0.25-3.0% and a ph of 8.0 for a considerable length of time. Estuarine environments may be suitable for the organism's survival. It is hypothesized further that outbreaks of primary cases in estuarine environments may be precipatated by eating certain types of raw or inadequately cooked estuarian plants or animals, perhaps on a seasonal basis. In areas where sanitation is poor, the disease will be transmitted to secondary cases, and in areas where sanitation is good, secondary cases will be rare. Primary cases may also develop in areas some distance from the estuarian environment by the importation of estuarian products. Outbreaks of secondary cases in nonestuarian environments may be due to the seasonal movement of estuarian inhabitants through the area. This explanation fits the epidemiological evidence available for the southeastern US and Bangladesh. If this hypothesis is correct, appropriate control measures will include educating people to refrain from eating raw and improperly cooked seafood.