Water Related Diseases

Cholera

Cholera is probably the best known of the diarrheal diseases. These cause infected people serious discomfort, dehydration, the loss of important electrolytes from the body and can, if left untreated result in death. All diarrheal diseases are transmitted via the "faeco-oral route". Simply put, this means that the faeces of one person is ingested by another person. The ways in which this can happen are illustrated in what is commonly called the F-diagram, as F is the first letter of each of the transmission routes:

Fluids (typically water)
Fingers
Food
Flies
and from Fields

These diseases therefore thrive in areas where both sanitation and hygiene is poor. They are considered as being waterborne (carried by water) or water washed (that the lack of sufficient water for washing results in poor hygiene and thus infection).

Cholera was the first disease to be shown as being waterborne. It is caused by the bacteria Vibrio cholerae. This bacteria causes large volumes of acute and extremely watery diarrhea, followed by vomiting and muscle cramps. In untreated cases around 60 % of untreated victims die. The large volumes of diarrhea result in the immediate environment being full of viable Vibrio cholerae bacteria, which if not contained, will infect further people. Treatment is however relatively simple and can result in deaths falling to below 1 % of those infected (World Bank 1983).

Bilharzia (Schistosomiasis)

Bilharzia, or schistosomiasis, is a water based helminthic (worm) infection. Over 250 million people are infected with schistosomiasis around the world, mainly in developing countries. Infection occurs through the skin by bathing in contaminated water.

The parasitic worm develops to maturity in the human body, inhabiting the veins around the bladder or between the intestines and the liver. Here the worms multiply and lay hundreds of eggs. It is the eggs that cause the disease. Some escape into the bowel or bladder and leave the body in urine and excreta, causing bleeding and tissue damage. When the eggs enter water, they infect aquatic snails and spend a part of their life cycle there. They eventually leave the snail and swim free in the water, ready to infect a new human host. The eggs that remain in the body become stuck in the blood vessels, lungs, the brain or even the spinal cord. They cause chronic inflammation, are painful and can lead to cancer and death (World Bank 1983). Open defecation, allowing eggs to enter new water bodies, ensures continued infections (see the figure below). Schistosomiasis has a serious detrimental impact on children's mental and physical development.

Malaria

Malaria is an insect vector disease with the disease-spreading insect, the anopheles mosquito, breeding in water. It is common in most tropical and sub-tropical regions, with up to 500 million cases worldwide every year and 3 million deaths, the majority of which are among young children. 90 % of all malaria deaths occur in Sub-Saharan Africa.

A mosquito becomes infected when it takes a blood meal from an infected human. Once ingested, the parasitic cell taken up in the blood will further differentiate into male or female cells and fuse within the mosquito gut. This fertilised cell penetrates the gut lining and forms a cyst in the gut wall. When the cyst ruptures, it releases "sporozoites" that migrate through the mosquito's body to the salivary glands, where they are then ready to infect a new human host. The sporozoites are injected into the skin, alongside saliva, when the mosquito takes a subsequent blood meal. As the mosquitoes breed and lay their eggs in standing water, poor drainage and pools of water encourage breeding and thus increase the possibility of malaria spreading.