Schistosomiasis, a grave and debilitating disease of socioeconomic importance, is increasing in incidence despite concerted efforts to control and contain the disease in all the endemic areas. While a multipronged method of control using health education, sanitation and snail control has been used,
chemotherapy and
chemoprophylaxis play the most important and crucial role in containing/preventing the transmission of the disease.
Schistosomicides such as antimonials were introduced, as early as the 1990s as the drugs of choice and continued to be used until the early 1960s. The antimonials were administered intravenously, and produced severe side effects; the various variables that determined their effects at the site of action made their application difficult and adversely affected their use in large scale
chemotherapy. The antimonials were then replaced by
hycanthone and
lucanthone which were administered intramuscularly. These drugs produced immediate side effects such as hepatotoxicity and gastrointestinal disturbances, and were consequently withdrawn. It was then decided that the alternative was to produce
synthetic drugs that could be administered orally.
Niridazole,
oxamniquine, and
metrifonate were introduced as schistosomicidal agents, with drugs like
oltipraz and
amoscanate still at clinical trial phase. Therapeutic doses of drugs like
hycanthone,
niridazole and
amoscanate have been found to cause many major side effects. A significant advance in the control of
schistosomiasis chemotherapy is the introduction of a relatively safe, effective, broad spectrum oral helminthic agent,
praziquantel. Studies have also shown that
oxamniquine is as effective as
praziquantel in eliminating intestinal S. mansoni
infection, and
metrifonate is as effective as
praziquantel in eliminating urinary S. haematobium and S. mansoni
infections.
Praziquantel has been found to be effective in treating S. haematobium
infections compared with
metrifonate and more effective in treating S. mansoni
infection when compared with
oxamniquine. Because the
drug is effective even when treating advanced hepatosplenic
schistosomiasis, with few side effects,
praziquantel is currently the
drug of choice for the treatment of any kind of
schistosomiasis. The only limitation is the cost which restricts its use in many developing countries. While effective, safe drugs for mass
chemotherapy are being developed, the problem of therapeutic failure and drug resistance is being reported from certain developing countries. Under these circumstances, alternative drugs must be resorted to. Mass treatment, a crucial goal in the eventual control of
schistosomiasis, awaits a well-tolerated and nontoxic
drug that will ultimately prove to be effective where cure is definite. Until such a time, while eradication of the disease is a near impossibility, reducing the intensity of
infection can ultimately reduce morbidity and even mortality.(ABSTRACT TRUNCATED AT 400 WORDS)