- Email: [email protected]
Time to end our neglect of liver flukes
Newsdesk
Time to end our neglect of liver flukes For more on the Asian Liver Fluke Network see http://tdr. kku.ac.th/liverflukenetwork/ For more on liver fluke infections in Asia see PLoS Negl Trop Dis 2: e232; DOI:10.1371/journal. pntd.0000232 For more on liver flukes and cholangiocarcinoma see PLoS Med 4: e201; DOI:10.1371/ journal.pmed.0040201
Banchob Sripa
For more on PCR screening for liver flukes see PLoS Negl Trop Dis 3: e367; DOI:10.1371/journal. pntd.0000367
Clonorchis sinensis, one of the species of liver fluke that causes human infection has just been upgraded to a grade 1 carcinogen by WHO and the International Agency for Research on Cancer. It joins another liver fluke, Opisthorchis viverrini, which was given this classification in 1994. Infection with either pathogen is strongly associated with cholangiocarcinoma, the primary liver cancer that arises from biliary epithelial cells. “Rates of cholangiocarcinoma in regions where liver flukes are endemic are unprecedented: it is responsible for about 86·5% of cancers in Thailand’s Khon Kaen region, the highest occurrence of liver cancer anywhere in the world”, confirmed Banchob Sripa (Liver Fluke and Cholangiocarcinoma Research Center, Khon Kaen University, Thailand). A staggering 45–50 million people in southeast Asia have active liver fluke infection, with about 550 million more at risk of contracting it. C sinensis is endemic in southern China, northern Vietnam, and parts of Korea; O viverrini is found mainly in Thailand, Laos, Cambodia, and central Vietnam. The prevalence of O viverrini approaches 70% in some endemic areas in northeast Thailand and Laos. “Liver flukes are also a concern in South America, where prevalence in
A patient is receiving an ultrasound to diagnose liver fluke infection
276
endemic areas in Peru and Bolivia can reach 68%”, Eduardo Gotuzzo of the Universidad Peruana Cayetano Heredia in Lima, Peru told TLID. Paul Brindley (George Washington University Medical Center, Washington, DC, USA) adds that human fascioliasis, which affects around 10 million people worldwide, is a public health problem in north Africa, the Middle East, and parts of South America. “In the poorest countries of Asia, such as Laos, there is a lack of good quality basic research to show the full extent of the problem”, reported James Conlan (Murdoch University, Perth, Australia). “Only a very small proportion of development-assistance money is directed toward liver flukes, and this is usually limited in its scope”, he added. “Liver flukes are certainly one of the most neglected tropical diseases, virtually ignored by major health organisations”, Peter Hotez of the Sabin Vaccine Institute (Washington, DC) told TLID. Liver fluke control includes mass treatment combined with sanitation improvements and health education. “In areas where prevalence exceeds 20%, such as Laos, anthelmintic chemotherapy with praziquantel and health education are provided free of charge once a year to the entire population of the affected district”, explained Sripa. Where prevalence is 5–20%, mass treatment and education is organised every 2 years, with treatment on an individual basis in areas of lower endemicity. However, Sripa observes that “although these measures have been practiced for 30 years in Thailand and for 10 years in Laos, the prevalence of Opisthorchis spp infection is still 85·5% in southern Laos and 74·1% in northeast Thailand”. The success of control measures could be improved by more specific diagnosis. Currently, faecal samples are examined for liver fluke eggs by use of the formalin-ether concentration technique, which cannot distinguish
between different species. Definitive diagnosis requires identification of the adult flukes expelled after chemotherapy. New research in Australia and Thailand suggests that a non-invasive PCR screening method could identify liver and intestinal fluke species if used in future epidemiological surveys. “Many flukes use canids and felids as definitive hosts, which has important implications for intersectoral approaches to surveillance and control. The newly developed and tested PCR could be used to screen dogs and cats for zoonotic flukes to a species level during baseline geographical mapping surveys to determine whether veterinary intervention is required”, explained Rebecca Traub (University of Queensland School of Veterinary Science, Brisbane, Australia). An additional and immediate finding of research to validate the new diagnostic test was the first report of a C sinensisendemic community in central Thailand. “This extends the known range of this liver fluke in southeast Asia”, comments Traub. Fundamental shifts in global attitude and policy are also required. Brindley would like to see agencies such as WHO and the US National Institutes of Health taking a stronger lead in encouraging mass chemotherapy backed up by health-information campaigns to educate the endemic populations of the danger associated with eating undercooked fish dishes, which harbour the infective stage of the liver fluke. These agencies “could also fund basic research into why fluke infection causes liver cancer”, he recommended. Sripa welcomes new techniques such as the mapping of high endemic areas using geographic information systems, but concludes that success will depend on “strengthening government policy so that control strategies are sustainable and cover all required areas”.
Kathryn Senior www.thelancet.com/infection Vol 9 May 2009
Time to end our neglect of liver flukes For more on the Asian Liver Fluke Network see http://tdr. kku.ac.th/liverflukenetwork/ For more on liver fluke infections in Asia see PLoS Negl Trop Dis 2: e232; DOI:10.1371/journal. pntd.0000232 For more on liver flukes and cholangiocarcinoma see PLoS Med 4: e201; DOI:10.1371/ journal.pmed.0040201
Banchob Sripa
For more on PCR screening for liver flukes see PLoS Negl Trop Dis 3: e367; DOI:10.1371/journal. pntd.0000367
Clonorchis sinensis, one of the species of liver fluke that causes human infection has just been upgraded to a grade 1 carcinogen by WHO and the International Agency for Research on Cancer. It joins another liver fluke, Opisthorchis viverrini, which was given this classification in 1994. Infection with either pathogen is strongly associated with cholangiocarcinoma, the primary liver cancer that arises from biliary epithelial cells. “Rates of cholangiocarcinoma in regions where liver flukes are endemic are unprecedented: it is responsible for about 86·5% of cancers in Thailand’s Khon Kaen region, the highest occurrence of liver cancer anywhere in the world”, confirmed Banchob Sripa (Liver Fluke and Cholangiocarcinoma Research Center, Khon Kaen University, Thailand). A staggering 45–50 million people in southeast Asia have active liver fluke infection, with about 550 million more at risk of contracting it. C sinensis is endemic in southern China, northern Vietnam, and parts of Korea; O viverrini is found mainly in Thailand, Laos, Cambodia, and central Vietnam. The prevalence of O viverrini approaches 70% in some endemic areas in northeast Thailand and Laos. “Liver flukes are also a concern in South America, where prevalence in
A patient is receiving an ultrasound to diagnose liver fluke infection
276
endemic areas in Peru and Bolivia can reach 68%”, Eduardo Gotuzzo of the Universidad Peruana Cayetano Heredia in Lima, Peru told TLID. Paul Brindley (George Washington University Medical Center, Washington, DC, USA) adds that human fascioliasis, which affects around 10 million people worldwide, is a public health problem in north Africa, the Middle East, and parts of South America. “In the poorest countries of Asia, such as Laos, there is a lack of good quality basic research to show the full extent of the problem”, reported James Conlan (Murdoch University, Perth, Australia). “Only a very small proportion of development-assistance money is directed toward liver flukes, and this is usually limited in its scope”, he added. “Liver flukes are certainly one of the most neglected tropical diseases, virtually ignored by major health organisations”, Peter Hotez of the Sabin Vaccine Institute (Washington, DC) told TLID. Liver fluke control includes mass treatment combined with sanitation improvements and health education. “In areas where prevalence exceeds 20%, such as Laos, anthelmintic chemotherapy with praziquantel and health education are provided free of charge once a year to the entire population of the affected district”, explained Sripa. Where prevalence is 5–20%, mass treatment and education is organised every 2 years, with treatment on an individual basis in areas of lower endemicity. However, Sripa observes that “although these measures have been practiced for 30 years in Thailand and for 10 years in Laos, the prevalence of Opisthorchis spp infection is still 85·5% in southern Laos and 74·1% in northeast Thailand”. The success of control measures could be improved by more specific diagnosis. Currently, faecal samples are examined for liver fluke eggs by use of the formalin-ether concentration technique, which cannot distinguish
between different species. Definitive diagnosis requires identification of the adult flukes expelled after chemotherapy. New research in Australia and Thailand suggests that a non-invasive PCR screening method could identify liver and intestinal fluke species if used in future epidemiological surveys. “Many flukes use canids and felids as definitive hosts, which has important implications for intersectoral approaches to surveillance and control. The newly developed and tested PCR could be used to screen dogs and cats for zoonotic flukes to a species level during baseline geographical mapping surveys to determine whether veterinary intervention is required”, explained Rebecca Traub (University of Queensland School of Veterinary Science, Brisbane, Australia). An additional and immediate finding of research to validate the new diagnostic test was the first report of a C sinensisendemic community in central Thailand. “This extends the known range of this liver fluke in southeast Asia”, comments Traub. Fundamental shifts in global attitude and policy are also required. Brindley would like to see agencies such as WHO and the US National Institutes of Health taking a stronger lead in encouraging mass chemotherapy backed up by health-information campaigns to educate the endemic populations of the danger associated with eating undercooked fish dishes, which harbour the infective stage of the liver fluke. These agencies “could also fund basic research into why fluke infection causes liver cancer”, he recommended. Sripa welcomes new techniques such as the mapping of high endemic areas using geographic information systems, but concludes that success will depend on “strengthening government policy so that control strategies are sustainable and cover all required areas”.
Kathryn Senior www.thelancet.com/infection Vol 9 May 2009