Schistosomiasis is a disease caused by parasites. Schistosoma is the genus of the several species of flatworms that are responsible for causing this disease. Schistosomiasis is popularly known as snail fever. Theodor Bilharz was the first to describe the cause of urinary schistosomiasis in 1851, and this disease is also called Bilharzia or Bilharziosis in many countries after him.
Causes of Bilharzia
This disease mostly affects the tropical countries like Africa , the Caribbean islands, and eastern part of South America , East Asia , and the Middle East . Estimation shows that about 207 million people are suffering from this disease, and about another 120 million are displaying the symptoms. Different types of Schistosomiasis are found in different areas as follows:
Schistosoma mansoni—parts of South America and the Caribbean , Africa , and the Middle East
Schistosoma haematobium— Africa and the Middle East
Schistosoma japonicum— Far East . S. Mekongi and S. intercalatum are found focally in Southeast Asia and central West Africa , respectively
Schistosomiasis is one of the most commonly picked up disease in developing countries which is acquired by swimming in such water bodies that are infested with snails, usually the biomphlaria, bulinus, or the oncomelania types, or which are the carriers of the schistosoma pathogens.
Types of Bilharzia
Depending on their clinical presentation, different species of schistosomiasis affect different organs of the body. The five species of flatworms causing schistosomiasis and the area they affect are as follows:
Schistosoma mansoni (ICD-10 B65.1)— intestinal schistosomiasis
Schistosoma intercalatum (B65.8)—intestinal schistosomiasis
Schistosoma haematobium (B65.0)—urinary schistosomiasis
Schistosoma japonicum (B65.2)—intestinal schistosomiasis
Schistosoma mekongi (B65.8)—intestinal schistosomiasis
Symptoms of Bilharzia
Since schistosomiasis is chronic in nature, symptoms like mild anemia and malnutrition are common in affected areas. Katayama's fever or acute schistosomiasis has been seen to occur weeks after the patient is infected. This is most true for patients infected with schistosoma mansoni and schistosoma japonicum. The major symptoms are:
Abdominal pain
Diarrhea
Cough
Extremely high Eosinophil count
Fever
Fatigue
Enlargement of liver and spleen
Central nervous system lesions can also occur sometimes
Granulomatous reactions and fibrosis in the affected organs can lead to
Colonic polyposis with bloody diarrhea mostly in Schistosoma mansoni;
Portal hypertension with hematemesis and splenomegaly in Schistosoma mansoni, Schistosoma japonicum;
Cystitis and ureteritis with hematuria leading to bladder cancer in Schistosoma haematobium; Pulmonary hypertension in Schistosoma mansoni, Schistosoma japonicum, and even Schistosoma haematobium;
Glomerulonephritis; and central nervous system lesions.
How is the disease diagnosed?
Eggs of the infecting parasite can be identified in the stool or urine of the patient under a microscope. Examination of stool for the identification of the parasites is more common. An egg per gram (epg) is the scientific unit used to measure the eggs in the feces of the affected patient. Stool examination is recommended to patients affected with schistosoma mansoni or schistosoma japonicum; and urine examination for schistosoma haematobium.
Sometimes the Kato-Katz technique (20 to 50 mg of fecal material) or the Ritchie technique is also used for field surveys and investigational purposes.
A team led by Dr. Russell Stothard, head of the Schistosomiasis Control Initiative at the Natural History Museum , London , recently conducted a field evaluation, which reported that even if stool or urine examinations are negative, a tissue biopsy might reveal eggs. Detection of antibody might as well be useful for epidemiological surveys as well as clinical research and management.
Treatment of Bilharzia
Schistosomiasis can be successfully treated using an oral drug Praziquantel. Though a single dose of this drug can cure the infection, it is not effective in preventing re-infection of the patient, which is highly probable in an affected area. Researches are presently being carried on to develop a vaccine for this disease.
The toxic metalloid, antimony was initially used in low doses to treat schistosomiasis, but this is not used in present days. Another drug called Oxamniquine is used outside the U.S to treat Schistosoma mansoni.
Investigations are being carried on a new Egyptian drug, Mirazid for the treatment of this disease.
Other forms of oral medication that are being experimented with are medicinal castor oil, Gopo Berry (by Dr Chidzere of Zimbabwe in 1980s), etc.
Prevention of Bilharzia
A few countries have eradicated the disease, and many more are working towards it. The World Health Organization is promoting efforts working towards this goal. In some cases, urbanization, pollution, and/or consequent destruction of snail habitat has reduced exposure, with a subsequent decrease in new infections.
Avoiding snails
Acrolein, copper sulfate, and niclosamide can be used to eliminate the fresh-water snails that cause the disease.
Crayfish breeding can also be helpful for the purpose though it must be done with caution.
Avoiding water bodies previously detected with snails.
Use of sapindus plant(Phytolacca dodecandra) to prevent the disease by controlling snails. Aklilu Lemma and Legesse Wolde-Yohannes received the Right Livelihood Award in 1989 for their research.
Proper civic designs
Better plans and designs while creating dams and irrigation schemes can prevent this disease from spreading among the nearby population.
Properly designed Campaigns
Egypt is an example of how a wrongly designed campaign can give rise to further complications. Since Egypt had the highest rate of schistosomiasis infected patients due to its large number of canals and dams built along river Nile, a campaign was carried out to give shots of tartar emetics to the patients from late 1950s till the early 1980s.Unfortunately however, instead of controlling one disease, this led to the spread of Hepatitis C virus through unclean needles. This proves the necessity of proper campaigns.
