Opisthorchiasis - Prevalence

Prevalence

Opisthorchiasis is prevalent in geographical regions where raw cyprinid fishes are a staple of the diet of humans. The prevalence of human infection can be as high as 70% in some regions, for example in Khon Kaen Province in Thailand. The parasite establishes in the bile ducts of the liver as well as extrahepatic ducts and the gall bladder of the mammalian (definitive) host.

Children under the age of 5 are rarely infected by Opisthorchis viverrini.

In the Lao People's Democratic Republic, the prevalence of opisthorchiasis was:

• 40% in 1992 causing about 1 744 000 people infected

In Thailand, the prevalence of opisthorchiasis was:

• scaterred reports by Verdun & Bruyant (1908), Leiper (1911), Prommas (1927), Bedier & Chesneau (1929)
• The national control programme have started in Thailand in 1950.
• 25% in 1953 causing about 2 million infected people. The first widespread report of opisthorchiasis in Thailand was in 1953.
• 1965: over 3.5 millions infected people
• 14% in 1980-1981 causing about 7 million infected people.
• 63.6% in 1984-1987, but another WHO report mention prevalence 35% in Nort-east Thailand for 1984.
• 35.6% in 1988
• 30% in 1989
• The decline of opisthorchiasis was caused by opisthorchiasis control programme, that includes health education including mass distribution of cooking pots and using praziquantel, that was available since 1984.
• 15.2% in 1991 causing 7 million infected people. About 45 million people were at risk of infection. There was prevalence 22.8% in North Thailand, 24.0% in North East Thailand, 7.3% in Central Thailand and 0.3% in Southern Thailand.
• 12% in 1996
• In 1992-1996 the National Public Health Development Plan used the strategy by the Faculty of Tropical Medicine, Mahidol University against opisthorchiasis.
• 7% in 2000
• 9.4% in 2001 In Thailand, the prevalence of opisthorchiasis is 9.4% in 2001, causing about 6 million people are infected with Opisthorchis viverrini.

Opisthorchis viverrini was thought to be the only species of liver fluke in Thailand, but PCR techniques have revealed also Clonorchis sinensis in (central) Thailand in 2008.

Another reference from 2002 lists worldwide number of cases about 9 million (without year of estimation). In Thailand, about 7.3 million. About 50 million people are at risk of infection.

In 2005, 67.3 million of people worldwide are at risk of infection.

Keiser & Utzinger (2005) have speculated that aquaculture development is the key risk factor for foodborne trematodiases including opisthorchiasis caused by Opisthorchis viverrini.