Tropical Diseases

Best known in the United States as a benign but unpleasant condition, diarrhea is one of the leading causes of death in developing countries. Indeed, diarrhea causes about 4.3 million deaths each year, more than malaria or many of the other serious tropical illnesses. Though most of the approximately 28 billion individuals who develop diarrhea survive, the health consequences of diarrhea are great in tropical areas.

Infants and small children are most likely to die of diarrhea. This is because loss of even a small amount of water can be life-threatening to small children. Death due to diarrhea stems from loss of fluid, loss of plasma, and the collapse of the cardiovascular system. Infants being weaned from the mother's breast are particularly susceptible to malnutrition and dehydration. Diarrhea can be caused by bacteria or viruses.

Residents of tropical disease areas are less likely than residents of developed areas to have access to emergency treatment for extreme diarrhea. They are also more likely to be exposed to pathogens that cause intense diarrhea in contaminated food or water. Cholera, a life-threatening condition whose major symptom is watery diarrhea, is spread through dirty water.

Oral rehydration therapy, an approach which uses a solution of glucose or sucrose and salt to hydrate the body, is an effective treatment for life-threatening diarrhea. One problem with the approach is that it must be made available immediately after a child gets sick, as diarrhea can cause enough fluid loss within the first 12 to 24 hours to cause death. Many individuals in tropical disease areas live many hours by foot from medical care. Therefore, health experts are working to make oral rehydration therapy, along with education about the therapy, available at home to residents of tropical-disease areas.

The most infamous type of diarrheal disease is cholera, which is also marked by vomiting, intense thirst, and abdominal cramping. Cholera is so common it is endemic in some parts of the world, such as India. In other parts of the world, it occurs as an epidemic or a pandemic.

The disease is caused by the Vibrio cholerae bacteria, which typically spreads through dirty water, food, or seafood from areas with contamination. The bacteria that causes cholera multiplies in the human intestinal tract, but has also been known to multiply in water.

Symptoms of cholera are a direct result of the cholera enterotoxin, the toxic substance elaborated by cholera bacteria that affects the cells of the small intestine. The substance forces the mucosal cells to secrete large quantities of fluid, resulting in diarrhea.

Control of cholera calls for good sanitation measures, specifically clean water and good food hygiene. Boiling water eliminates the bacteria. A vaccine that offers limited effectiveness—30-80% protection for up to six months—is available.

While treatment is effective, involving antibiotics, nutritional support, and treatment for dehydration, the death rate in epidemics may reach 30%.