Update of fasciolosis-transmitting snails in Egypt (review and comment).

Several snail species may contribute in transmission of fasciolosis in Egypt. These molluscs show a variable sensibility to natural infections with Fasciola species. Radix natalensis is considered to be the essential intermediate host for F. gigantica based on field and experimental studies. Cercarial production from R. natalensis experimentally infected with F. gigantica is affected by the species of definitive host from which the eggs are obtained, as well as the different laboratory conditions. Another lymnaeid, Galba truncatula, may play a role in transmitting this parasite in Egypt, as it was found naturally infected with F. gigantica. Latter snail species, originated from France, was susceptible to experimental infections with Egyptian miracidia of F. gigantica and it had a cercarial production close to that of local R. natalensis. Two other snails, Pseudosuccinea columella and Biomphalaria alexandrina, were naturally found harboring larvae of Fasciola sp. At the level of intermediate hosts of F. gigantica, the conditions are thus favorable in Egypt to transmit fasciolosis which could also be caused by another fasciolid, F. hepatica, as the existance of this fluke was confirmed in Egypt.