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Introduction
Fasciolosis caused by Fasciola hepatica and Fasciola gigantica remains a public health problem with a worldwide distribution (Mas-Coma et al., 2009). As a major livestock infection, it also has a marked economic impact through liver condemnation and reduced milk and meat yields (Dalton, 1999). Due to different epidemiological and sociological factors, fasciolosis is one of the most important food-borne trematodoses in Asian countries. For many decades Vietnam has been recognized as endemic for human fasciolosis (WHO, 2007). However, the real impact of human fasciolosis was poorly known and the disease was reported sporadically. For instance, only two cases were reported in 1978 (cited by Tran et al., 2001). Recently, the number of recorded cases has increased dramatically and 47 out of 63 Vietnamese provinces have reported human infections. The central-highland region is considered to be highly endemic, with more than 10,000 reported cases between 2006 and 2009 (Trieu et al., 2012). Fasciolosis is a well-known animal disease in Vietnam and is responsible for marked economic losses (Phan, 1983; T.G.T. Nguyen et al., 2011). Fasciolosis transmission is dependent on different species of Lymnaeidae freshwater snails, which act as intermediate hosts (Dalton, 1999). Some vectorial aspects of faciolosis in Vietnam are still very confusing. The present review aims at describing the present status of human and animal fasciolosis in Vietnam and surrounding countries, in relation to malacological data. Publications were collected through an online search, from the libraries of universities and institutes, or directly by request to the authors. Publications in national journals (including thesis and conference proceedings) were translated from Vietnamese. Fasciolosis in humans and animals, and Fasciola spp. in lymnaeid snails were mapped by using Arcgis software v10.2 (ESRI, Inc., California, USA). The graphs were made with Stata Statistical Software, Release 12 (StataCorp, College Station, Texas, USA).
Identification of Fasciola species
Adult stage
Fasciola gigantica and F. hepatica are the two species responsible for human and animal fasciolosis (Dalton, 1999). Fasciola hepatica is common in temperate zones, especially in Europe, America and Australia, whereas F. gigantica is the most prevalent species in tropical regions of Africa and Asia (Mas-Coma et al., 1999, 2009). In Vietnam, both species were reported in cattle long ago, based on morphological characteristics (T.L. Nguyen