Changes

=== Life-cycle stages ===

=== Life-cycle stages ===

'''Egg''': the ''Fasciola'' egg is a large egg (twice the size of a standard strongyle egg). It is oval and brown with an operculum at one end. It is a relatively dense structure that will not float in saturated salt solution (used for routine egg-counts), so a flotation fluid with a higher specific gravity is required (e.g. ZnSO4). Better still, a sedimentation technique can be used. Initially, the egg is full of nutrient material. It need moisture and temperatures greater than 10 degrees Centigrade for the miracidium to develop inside the egg.

'''Egg''': the ''Fasciola'' egg is a large egg (twice the size of a standard strongyle egg). It is oval and brown with an operculum at one end. It is a relatively dense structure that will not float in saturated salt solution (used for routine egg-counts), so a flotation fluid with a higher specific gravity is required (e.g. ZnSO4). Better still, a sedimentation technique can be used. Initially, the egg is full of nutrient material. It need moisture and temperatures greater than 10°C for the miracidium to develop inside the egg.

'''Miracidium''': the first larval stage develops inside the egg. It has two light sensitive spots and will only hatch out of the egg if the light intensity is correct and the egg is covered with a film of water. After hatching, it has to find the molluscan intermediate host. It is therefore covered with cilia for locomotion. When penetrating the snail, it releases proteases.

'''Miracidium''': the first larval stage develops inside the egg. It has two light sensitive spots and will only hatch out of the egg if the light intensity is correct and the egg is covered with a film of water. After hatching, it has to find the molluscan intermediate host. It is therefore covered with cilia for locomotion. When penetrating the snail, it releases proteases.

'''Metacercaria''': the cercaria swims onto vegetation, loses its tail, secretes a tough protective wall around itself to form the metacercaria which waits to be ingested by a suitable host.

'''Metacercaria''': the cercaria swims onto vegetation, loses its tail, secretes a tough protective wall around itself to form the metacercaria which waits to be ingested by a suitable host.

'''Immature fluke''': on ingestion, the immature fluke excysts from the metacercaria and migrates to its predilection site (this is in the liver in the case of Fasciola).

'''Immature fluke''': on ingestion, the immature fluke excysts from the metacercaria and migrates to its predilection site (this is the liver in the case of ''Fasciola'').

'''Adult fluke''': in the predilection site, the fluke matures and eventually starts to lay eggs.

'''Adult fluke''': in the predilection site, the fluke matures and eventually starts to lay eggs.