Causal Agents of Urinary Schistosomiasis
Urinary schistosomiasis is caused by digenetic blood trematode known as schistosoma flukes that have complex lifecycle involving specific fresh water snail species as intermediate hosts. Infected snails release large number of minute, free swimming larval (Cercaria) that are capable of penetrating unbroken skin of the human host. Even brief exposure to contaminated fresh water such as wading swimming of bathing can acquired by contact with salt water such as oceans or seas. However the cercaria of birds and aquatic mammals can penetrate the skin of human being who enter infected fresh or salt water in many parts of the world including cool temperate areas. These cercaria die in the skin but may elicit a pruritic rash known as “Swimmers” itch or calmdigger’s itch (CDC, 2006).
The three main species of schistosomes infecting human are schistosoma haematobuim, S. japonicum and S. manconi. Two other species more geographically seen are S. mekongi and S. ntercalatum. In addition, other species of schistosomes which parasitize birds and mammals can cause cercarial dermatitis in Humans (Cdc, 2004).
The disease is found in the tropical countries in Africa Caribbean, Eastern south America, East Asia and in the middle East. S-mansom occur with S. haematabium in 41 countries of Africa and Eastern Mediterranean. Water development project for water conservation, irrigation and hydroelectric power have contributed to the spread of S. mansom and change in its distribution (cheese brough, 2004). Schistosoma haematobium is found in Africa, Middle East and is endemic in 54 countries mainly Africa and Earthen Mediterranean. It is found in several Indian Ocean Island and small Island off the coast of East and West Africa. In some areas of distribution of S. haematobium overlaps with S. mansoni causing double infection. It is important to note that natural hybrids of S. haematobium and S. ntercalatum occur in Cameron (Cheesbrough 2004).
An estimated 207 million people have the disease 120 million symptomatic and 600 million are at risk of infection and is endemic in 74 developing countries (SWAPHER, 2004). Estimate suggests that 85% of as schistosomiasis cases are now in sub Sahara Africa.
The disease have been reported to be the second to malaria as a source of human morbidity (Ukoli; 1992). The disease in common in the Niger basin and every country within the West Africa region. A few countries have eradicated the disease and many as working towards it.
The WHO is promoting efforts working towards this goal. The most common way of getting schistosomiasis in developing countries is by wading or swimming in lakes, ponds and other bodies or water which are infected with the snail (usually of the Biomphalaira bulinus) that are the natural reservoir of the schistosoma pathogen (Ukoli, 1992). In Nigerian studies have been carried out to show the prevalence and incidence of the disease among school children and adults in Osun, Ogun, Imo, Anambra, Ebonyi, Logos etc. prevalence of urinary schistosomiasis in Northern States is attributable to mobility of the nomads and labourers and water development projects undertaken in different parts of the Northern states.
Urinary schistosomiasis is endemic throughout the Northern region and some are marked by particular heavy infection. In most studies the disease is prevalent in males than in females. (Ukoli, 1992).
Urinary schisotosomiasis is also wide spread in the western region of Nigeria with high incidence in three areas. The 1st extends at the coast of Badagary and Epe with high prevalence in and near Ibadan, Abeokua, Epe, IJebude. A 2nd heavy infected areas centers around Ondo and extended North to Addo Ekiti. The 3rd area in the western region in the creeks and Delta region as well as further inland.
In some areas boys were more infected while girls were more infected in others. High prevalence among girls indicates that they perform domestic function such as washing of clothes, cooking utensils etc more than their male counterparts. Also the traditional role of females helping their mothers in domestic and social needs further suggests such high prevalence in female than male.
Acute schistosomiasis, most clinical manifestation are benign, some severe and may repair hospitalization. If acute schistosomiasis is not suspected clinically and treated appropriately, it can result in severe morbidity or death.
In chromic schistosomiasis, most patients are asymptomatic or mildly symptomatic and do not require medical attention only a small proportion of the endemic population harbours a heavy worn burden that later leads to clinical complication.