Carrada-Bravo T

Language: Spanish
References: 10
Page: 21-27
PDF size: 190.16 Kb.

ABSTRACT

The definite hosts of Fasciola hepatica are sheeps, cows, and humans. The intermediate host is a hermaphroditic lymnaeid snail Major sources of human´s infections are fresh watercress, alfalfa, lettuce or drinking water. When encysted metacercaria are swallowed by a human, they excyst in the lumen of the intestine and migrate toward the liver, where it feeds upon hepatocytes, causing necrosis and haemorrhages. F. hepatica grows slowly achieving maturity after two months into the bile–ducts, the parasite is hermaphroditic, and self–mating occurs. Eggs are laid unembrionated and are passed from bile–ducts to duodenum, to be excreted by faeces. The egg must be deposited in fresh, slow–moving water to complete development. After hatching, the ciliated miracidium swims and seeks a snail and multiplies asexually within its tissue. Larval morphogenesis proceeds sequentially from mature sporocyst to the first and second redia–stage. Each redia gives rise to many cercaria which may encyst upon aquatic plants producing metacercaria, mildly resistant to environmental changes. Livestock infections induces productivity losses of meat and milk, of adverse economic consequences. Human fasciolosis is an important reemerging disease: 17 million humans are probably infected, but in Latinoamerican countries the known incidence of human infection has increased significantly. Prevalence–rates between 72 and 100% have been recorded in the Bolivian Highlands.

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