the other hand, some authors have observed that donkeys and pigs contribute to disease transmission in Bolivia. Among wild animals, it has been demonstrated that the peridomestic rat (Rattus rattus) may play an important role in the spread as well as in the transmission of the parasite in Corsica. In France, nutria (Myocastor coypus) was confirmed as a wild reservoir host of F. hepatica.<ref>{{cite journal | doi = 10.1051/vetres:2001141 | last1 = Menard | first1 = A. | last2 = Agoulon | first2 = A. | last3 = L'Hostis | first3 = M. | last4 = Rondelaud | first4 = D. | last5 = Collard | first5 = S. | last6 = Chauvin | first6 = A. | year = 2001 | title = Myocastor coypus as a reservoir host of Fasciola hepatica in France | journal = Vet. Res. | volume = 32 | issue = 5| pages = 499–508 | pmid = 11592619 }}</ref> Humans are infected by ingestion of aquatic plants that contain the infectious cercariae. Several species of aquatic vegetables are known as a vehicle of human infection. In Europe, Nasturtium officinale (common watercress), Nasturtium sylvestre, Rorippa amphibia (wild watercress), Taraxacum dens leonis (dandelion leaves), Valerianella olitoria (lamb's lettuce), and Mentha viridis (spearmint) were reported as a source of human infections. In the Northern Bolivian Altiplano, some authors suggested that several aquatic plants such as bero-bero (watercress), algas (algae), kjosco and tortora could act as a source of infection for humans. Because F. hepatica cercariae also encyst on water surface, humans can be infected by drinking of fresh untreated water containing cercariae. In addition, an experimental study suggested that humans consuming raw liver dishes from fresh livers infected with juvenile flukes could become infected. Intermediate hosts Intermediate hosts of F. hepatica are freshwater snails from family Lymnaeidae. Snails from family Planorbidae act as an intermediate host of F. hepatica very occasionally. Mechanism The development of infection in definitive host is divided into two phases: the parenchymal (migratory) phase and the biliary phase. The parenchymal phase begins when excysted juvenile flukes penetrate the intestinal wall. After the penetration of the intestine, flukes migrate within the abdominal cavity and penetrate the liver or other organs. F. hepatica has a strong predilection for the tissues of the liver. Occasionally, ectopic locations of flukes such as the lungs, diaphragm, intestinal wall, kidneys, and subcutaneous tissue can occur. During the migration