All water that is to be used for drinking or cooking must be potable (free from
disease-producing organisms). Some of the intestinal diseases that may be transmitted
by contaminated water are cholera, shigellosis, and infectious hepatitis (hepatitis A).
These diseases were discussed in Lesson 1. The following diseases are also
transmitted by water.
a. Typhoid Fever. Typhoid fever is a serious disease caused by Salmonella
typhi, a bacillus of the same genus as those causing salmonellosis (bacterial food
poisoning). Signs and symptoms of typhoid fever include fever, headache, rose spots
on the body, loss of appetite, and a generalized ill feeling. Diarrhea is sometimes
present, but constipation is more common. The death rate is about two percent with
antibiotics and around 10 percent without antibiotics. Fortunately, the disease is very
rare among military personnel since immunization against typhoid is a standard
b. Amebiasis (Amebic Dysentery). Amebiasis is a parasitic disease caused
by ingesting the cysts of the protozoan Entamoeba hystolitica. Signs and symptoms of
the disease may vary from mild abdominal discomfort to acute dysentery with fever,
chills, and blood or mucus in the stools. Individuals may harbor the cysts in their
intestinal tracts--with or without symptoms--for years. The disease occurs worldwide,
but it is most prevalent in areas with poor sanitation in the developing countries of
Africa, the Far East, and the Tropics.
c. Schistosomiasis (Bilharziasis). Schistosomiasis is a parasitic disease
caused by the invasion of the body by microscopic-sized larvae of several species of
parasitic worms known as schistosomes (blood flukes). These larvae spend a part of
their life cycle in the bodies of certain fresh water snails. These snails are found
principally in Africa, South America, the Caribbean, and the Far East (including Japan
and the Philippines). The larvae are capable of penetrating the skin of persons bathing
or wading in infested waters. They will also penetrate the stomach lining if infested
water is drunk without being disinfected. Once in the body, the larvae migrate to the
blood vessels where they mature. The adult is about one-half inch long. The adult
schistosomes migrate to the liver, bladder, or lungs and cause obstructions of the blood
vessels in those organs. Symptoms of the disease may include an upper digestive
discomfort, flatulence, nausea, and intolerance to muscular effort. Continued infection
may lead to loss of weight, malnutrition, intolerance of food, abdominal distension, easy
fatigue, and lack of resistance to infections. Such late complications as liver failure,
cancer of the bladder, and obstruction of the blood vessels of the lungs may be fatal.
An important aspect of this disease is that it poses a hazard not only to those who drink
water contaminated with the parasites, but also to those who wade, swim, or bathe in it.