water has only recently become a problem: because of pollution in the former, and in the latter because of falling water tables arising from forest clearance.
The tidal areas of the Brackish and Fresh-water ecozones are particularly susceptible to pollution in the dry season when the rivers are slow moving, so that pollutants are inefficiently flushed out as incoming tides tend to push them back upstream. This is graphically illustrated on the New Calabar River at Alu, North of Port Harcourt, where sump-oil from the Wills Brothers depot and spills from the bunkering operations at the Nigerian Institute of Oceanography, accumulate and merely move up and down the river with the tides.
In human terms much of the water in the Niger Delta is so polluted that illness and death from water-borne diseases are part of life. The most common water-borne illnesses are Diarrhoea, Dysentery and Cholera, and there is the ever-present danger of Typhoid and Guinea worm infection. Moreover parts of the Niger Delta are suitable environments for Bilharzia and River Blindness.
Details of the various water-borne diseases are as follows.
Diarrhoea: watery faeces which is often caused by water-borne bacteria in the gut.
Dysentery: caused by water-borne bacteria causing acute Diarrhoea in which blood is present.
Cholera: caused by water-borne bacteria causing chronic Diarrhoea and vomiting leading to death.
Typhoid: caused by water-borne bacteria which infect the gut causing symptoms similar to those of Malaria.
Guinea Worm - Dracunculatus dedinesis: the worm is taken into the system by drinking water contaminated with the water cyclops (tiny one-eyed crustaceans) that are infected with the Guinea Worm larvae. The cyclops is digested releasing the larvae that migrate into the abdominal tissues where they grow and mate. The males die but the females migrate to various parts of the body, most often the legs, and after about a year emerge in a painful blister. On contact with water the female releases eggs that thrive in still, shallow waters, but that die within three days if they do not find a water cyclops.
River Blindness - Onchocerciasis: caused by the parasitic filarial nematode, Onchocerca volvulus, it is transmitted to humans by the black fly (genus Simulium) which lives alongside rivers. The disease is endemic in much of Nigeria. The adult nematodes enter the skin of humans (the host) through the bite of the black fly (the intermediate host) as it makes a blood meal. A fibrous nodule develops in the skin which houses the adult nematodes that mate producing millions of microfilariae which migrate around the body (even to the eyes). When the black fly takes its next meal it ingests the microfilariae which develop into adults in the stomach wall, migrate to the head and proboscis (the feeding organ of the fly) ready to re-infect the human again. River Blindness is debilitating disease because after numerous infections, not only do the accumulated nodules cause ugly skin disorders and breakdown of the lymph glands but also insensitivity to light, loss of vision and eventually blindness.
Bilharzia - Schistosomiasis: caused by the liver fluke, Schistosoma haematobium, which thrives in still shallow waters. It is transmitted to humans, its