With IAEA support, Latin America controls liver fluke (Fasciola hepatica) in livestock and humans

Although the countries of Latin America are geographically and culturally diverse, they have a major problem in common, one that affects the health of both its peoples and its animals. From the Patagonian steppe to the tropics of the Caribbean, from the endless flatland of the Pampas to the remote highlands of the Andes, there occurs the ever present common liver fluke: Fasciola hepatica. It is know by many different names throughout this vast land mass, but the problem is the same wherever it occurs: infected animals show poor productive performance and sub-optimal growth. In addition, humans can acquire infection from contaminated pastures and watercourses, leading to severe liver disease. Even though this parasite has been known for centuries it is still evading control and elimination strategies due to changes in its infection pattern as it expands into new territories. In order to mount a more aggressive and focused control strategy against the disease and its pathogen, several Latin American countries have come together to share their expertise and knowledge and thereby facilitate this endeavour.

Fasciola hepatica is a trematode flatworm that parasitizes a wide range of mammals, including humans. It has a worldwide distribution and the importance of this disease in Latin America has been well documented. In some countries it is mainly a problem in humans i.e. Bolivia and Peru, while in others it is a major constraint to livestock production with important economic consequences. The disease causes serious ill-health in its host with extensive haemorrhaging and inflammation of the liver, and thickening and dilation of the bile ducts and gallbladder. The prevalence in Central and Latin America in animals is in the range of 25% but could reach 70% in cattle, goats and sheep in some countries. This high prevalence is also seen in other parts of the world. The prevalence in humans has not been well studied and it is possible that the extent of its occurrence is underestimated; however, worldwide estimates are that around 20 million people are infected in more than 51 countries from 5 continents.

With IAEA support, Latin America controls liver fluke (Fasciola hepatica) in livestock and humans With the support of an IAEA Technical Co-operation Project (RLA 5049): “Integrated Control of Fascioliasis in Latin America (in Support of National Programmes)”, and guidance from IAEA staff and international Fascioliasis experts, seven countries in the region namely, Argentina, Bolivia, Cuba, Mexico, Panama, Peru and Uruguay came together to develop control strategies incorporating the latest knowledge, tailored and adapted to, their particular national requirements. The objectives of the project were to improve the countries’ diagnostic capabilities thereby gaining more accurate data on the occurrence of Fasciola in order to be able to better formulate appropriate control strategies in each country. This approach has enabled participating countries to acquire essential data on the epidemiology of the disease and provide greater understanding of the prevalence and incidence of the disease in animals and humans.

The IAEA also supported regional training courses that covered a wide range of topics including the pathology of the disease, molecular epidemiology and molecular characterization of this pathogen. Different types of control measures and approaches were reviewed in these courses in order to optimize the transfer of appropriate technologies to the end-users. The courses were not just a one-way information channel, but formed interactive and fruitful discussion forums where individuals from all participating countries could share their knowledge and experience for the benefits of all.

A major problem for combating this complex parasite is to use a standardized, validated, accurate definitive diagnostic test for identifying infected animals. Within the project, the standardization of the serological and coprological techniques has been achieved; including the production of a manual describing in detail recommended standard operating procedures to enable specific diagnosis. The various partners were able to agree on the harmonization of Fasciolosis diagnostic techniques, both in animals and humans. This was a critical step to allow more effective evaluation and comparison of the disease situation in different countries. With these harmonized diagnostic protocols, a coordinated approach to the monitoring and surveillance of the disease is now possible and with greater knowledge of the occurrence of disease it will be easier to implement appropriate control measures.

With IAEA support, Latin America controls liver fluke (Fasciola hepatica) in livestock and humans The TC programme was wide-ranging in its approach. In addition to considering serological and parasitological methods, special emphasis was placed on the use of molecular techniques that gave a comparative advantage in investigating and understanding this disease‘s complex epidemiology. To define baseline information, a thorough bibliographical review was prepared by each of the participating countries. This information will soon be published and will contribute greatly to the general understanding of the disease and the real impact that Fasciolosis has in the region.

During their life-cycles, Fasciola hepatica requires a period of development in a snail intermediate host. More studies are still needed to identify the different species of snails that are possible vectors and their distribution in Latin America. Decades of morphological characterization with frequent misclassification has been obscuring the real picture of the pathogen’s snail vectors. The use of molecular tools for the genetic identification and characterization of snails has been one of the highlights of this project and many of the participating countries are already actively working with reference centres identifying the vectors and making efficient use of the knowledge and skills acquired during the TC programme.

With IAEA support, Latin America controls liver fluke (Fasciola hepatica) in livestock and humans At present, the control strategies have to be tailored to suit each of the different eco-epidemiological situations, and adequate resources have to be found and allocated to lead to their successful implementation. With the IAEA’s support and guidance, countries in Latin America have already started to travel the road leading to the control of Fascioliasis. Beneficiaries of this new scenario will be millions of individuals who live in endemic areas, profiting either directly from preventive control measure against Fascioliasis or indirectly, with an increase in profitability and sustainability of their cattle, sheep, and goat populations - in many regions the backbone of the economy.

Written Valeria Gayo (Uruguay) and Roberto Mera y Sierra ( Argentina)