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Water and Sanitation Related Diseases  

The people of  the Kunene River basin are exposed to a range of diseases best described as being related to contaminated water or the lack of sanitation. The three most significant of these are presented below and are:

  • Cholera
  • Bilharzia (Schistosomiasis)
  • Malaria

Cholera

Cholera is probably the best known of the diarrhoeal diseases. These cause  serious discomfort, dehydration, the loss of important electrolytes from the body and can, if left untreated, result in death. All diarrhoeal 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).

The faeco-oral disease transmission routes - the F diagram.
Source: Davis and Lambert 1995
( click to enlarge )

Cholera was the first disease to be shown as being waterborne. It is caused by the bacteria Vibrio cholerae. This bacterium causes large volumes of acute and extremely watery diarrhoea, followed by vomiting and muscle cramps. In untreated cases around 60 % of 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 other people Treatment is however relatively simple and can result in deaths falling to below 1 % of those infected (World Bank 1983).

Cholera outbreaks have been a frequent occurrence in the Kunene River basin in recent years. In 2006 Angola was hit by one of Africa's biggest cholera epidemics in the last 10 years, with over 43 000 people infected and 1 600 dead. In the Kunene basin, the provinces of Huambo, Huíla and Namibe were all affected. 2009 however saw a dramatic reduction in cholera cases in the first seven months of the year with only 681 cases and three deaths. Although not as dramatic as the Angola 2006 outbreak, Namibia was also struck by cholera following floods in 2008.

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 inside the snail. 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, the 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.

Schistosomiasis is endemic throughout Angola. In Namibia, which is considerably drier, the risk of infection is limited mainly to the north and north east of the country, leaving the basin unaffected (IAMAT 2010).

The life cycle of the schistosomiasis parasite.
Source: www.cdc.gov
( click to enlarge )
The life cycle of the malaria parasite.
Source: www.cdc.gov
( click to enlarge )

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.

Click on the following link to view an animated presentation of the Lifecycle of a Malaria Parasite.

Malaria is a major problem within the Angolan part of the Kunene River basin. Angola has a high malaria burden, with 3.1 million registered malaria cases and 8 000 deaths in 2009. Transmission occurs all year round but has a more seasonal trend in the south, with the Upper and Middle Kunene being a malaria endemic zone (MARA 2005).

The drier climate of Namibia makes it generally much less suitable for the spread of malaria. In the basin, the area south of the river from Ruacana to around the Epupa Falls is a zone where epidemics can occur, however malaria is not endemic in this region (MARA 2005).  Government statistics in 2010 show that deaths due to malaria dropped by 90 % between 2001 and 2008 (from 1728 to 171) whilst the number of malaria cases treated at hospitals fell by 77 %, from 41 100 to 5 200, during the same period.

 

 



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