Fasciola gigantica: parasite

Classification

Taxonomy

• Trematoda; Fasciolidae; Fasciola gigantica.

Etymology

• There are two species of Fasciola that infect cattle:
  • Fasciola hepatica in temperate climates
  • Fasciola gigantica mainly found in tropical climates, such as sub-Saharan Africa.
• Species distribution can overlap as it is governed by the presence of snail intermediate host species that are integral to Fasciola species life cycles.
• Losses in production are related to the Fasciola species complex lifecycle and subsequent disease termed fasciolosis.
• Ruminant infections account for £2.5 billion of production losses per annum globally with the impact specifically on F. gigantica infected animals undefined.
• Adult and juvenile migratory stages of the parasite contribute to disease in cattle.
• Fasciolosis, was first described also the 13th century in sheep:
  • Similar findings in cattle were first described in the 17th century, although disease in cattle is more associated with chronic infections.
  • However the intermediate host stages were not discovered until 19th century with the complete life cycle in sheep elucidated in 1926.
• Ruminants such as cattle, buffalo, sheep and goats are affected by infection.  Man may also be affected in certain areas.

Distribution

• Global distribution in tropical and sub-tropical distribution:
  • Including most of sub-Saharan Africa, the Middle East, the Indian sub-continent and Southern Asia.
  • Some pockets are present in Eastern Europe, the Pacific islands and Australasia.
• Fasciola gigantica is the most important helminth in cattle and buffalos in Africa and Asia with cattle prevalences ranging between 50-90%.
• Various intermediate host species exisit of the Radix auricularis complex (aquatic snails).
• Fasciola gigantica infection has never been reported in the UK cattle population. Patent infection could occur in imported animals.

Significance

• A subclinical production-limiting disease of cattle, leading to poor growth rates, reduced milk yield and poor fertility.
• Fasciola species have also been shown to be associated with certain co-infections leading to misdiagnosis or increased risk of disease.
• The parasite is zoonotic (like F. hepatica Fasciola hepatica ) although not directly from parasite stages within cattle, but related to cultural practices of consumption of metacercariae stages encysted on raw herbage that is growth within intermediate snail host habitats. Particularly plants used directly in soups and fresh teas in some parts of sub-Saharan Africa, the Middle East and Asia.