Slaughterhouse and field surveys for evidence of Fasciola gigantica infection were conducted in five northern provinces of Laos during 2010 and 2011, providing prevalence estimates of 34.1% (95% CI 26.0-42.2) in 2010 and 17.2% (95% CI 13.5-20.9) in 2011. The field survey examined for Fasciola sp. eggs using a sedimentation method in single faecal samples from 1,262 cattle and buffaloes over 12 months old from 75 randomly selected villages. This survey identified widespread infection, with 73.3% of villages having at least one faecal egg count-positive animal. The slaughterhouse survey of 123 livers found that 70.7% of livers had gross liver and bile duct lesions consistent with F. gigantica infection that were characterised as mild (22.8%), moderate (17.9%) or severe (30.1%). Higher rates of gross cholangiohepatopathy were observed in buffaloes (95.6%) compared with cattle (40.0%). Regression analysis showed that province was significantly associated with F. gigantica infection status (P ＜ 0.05), suggesting geographical differences in the prevalence of F gigantica in northern Laos. Similarly, a geographical pattern of F. gigantica infection in Cambodia in association with the Tonle Sap is well described. Although suboptimal production is caused by a multitude of factors, our findings suggest that F gigantica is a major parasitic pathogen in northern Laos. Control strategies for fascioliasis should be considered because the high prevalence of infection is likely to result in substantial production losses, as well as pose a potential human health risk through continued and widespread contamination of the environment with F gigantica eggs and consumption of contaminated products.
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