Treatment: For the last ten years, the antihelmintic drug praziquantel (Biltricide, EMBAY 8440) has been successfully used to treat liver fluke infection. Praziquantel was introduced in 1975 to treat schistosomes, a parasite that can lead to urinary bladder cancer. This drug is a pyrazinoisoquinole that has proven safe and effective against trematode and cestode infection in humans and other animals. The suggested dosage is 25 mg/kg of body weight, three times a day or two days. This dosage has demonstrated a 100% cure rate for eliminating liver flukes11. However, the removal of liver flukes from the body has not prevented cholangiocarcinoma.
Despite the introduction and usage of praziquantel, the prevalence of cholangiocarcinoma in high-risk areas, such as northeast Thailand, have not decreased substantially. This suggests that some irreversible changes must occur early on in infection because cancer still results, even though the liver fluke is no longer present. This information has serious implications for the efficacy of treatment programs and suggests that prevention of fluke infection may be a much more effective strategy.
Prevention: Efforts to prevent liver fluke infection have focused on interrupting its lifecycle. This involves preventing fecal parasites from reaching the water supplies, decreasing snail hosts, and promoting adequate cooking methods for cyprinoid fish.
Much of this involves educating the local people about the risks associated with liver fluke infection and what they can do to minimize them. The National Public Health Development Plans is currently operating a national liver fluke control program in Thailand. The program involves stool examination and treatment with praziquantel, health education for infection prevention, and improvement of hygienic defecation7.
Currently, most of the indigenous people have latrines, which greatly decrease the risk of fecal parasite ova contaminating the water supplies, in which snails reside. Contamination still takes place during the rainy season when flooding occurs and infected dogs and cats can also cause contamination. Elimination of either this snail or fish host is not feasible, as the chemicals required to kill the snails would wipe out many other organisms and the cyprinoid fish are the major protein source for the region. Nonetheless, the percentage of infected fish has decreased dramatically.
The most probably route for interrupting the liver fluke lifecycle is preventing infection of the human host. Simply eliminating the consumption of raw or improperly cooked fish can do this. However, there is a tradition of eating raw fish and since the effects of infection are not immediate, the warnings may be ignored. In many regions, such as Japan, economic growth has had to occur before the problem of liver fluke could be eradicated11.
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