Changes

The prepatent period of ''Fasciola hepatica'' is 10-12 weeks. In untreated sheep it may survive and continue to infect for many years. In cattle it is usually less than 1 year.

The prepatent period of ''Fasciola hepatica'' is 10-12 weeks. In untreated sheep it may survive and continue to infect for many years. In cattle it is usually less than 1 year.

=== Snail biology ===

=== Snail biology ===

[[Image:Lymnaea truncatula.jpg|thumb|right|150px|''Lymnaea truncatula'' - Francisco Welter Schultes, Wikimedia Commons]]

[[Image:Lymnaea truncatula.jpg|thumb|right|150px|''Lymnaea truncatula'' - Francisco Welter Schultes, Wikimedia Commons]]

==== ''Lymnaea truncatula'' ====

==== ''Lymnaea truncatula'' ====

*5-10mm long

''Lympnea truncatula'' is around 5-10mm long. It has a distinctive brown-black shell, with 5-6 spirals present on the outer surface.  The first spiral is approximately half the total length of the snail.

*Brown-black shell with 5-6 spirals

 

*1st spiral is greater than half the total length

It feeds on green slime, and when this is present in abundance, they may multiply rapidly.

 

*Feeds on green slime

Most die in the British winter, due to the harsh, cold conditions, but they may survive in milder winters.  Survivors will lay egg in spring, which will hatch in June.

*Multiplies rapidly when food is abundant

*Most die during the British winter (unless very mild)

*Survivors lay eggs in spring, which hatch in June

==== Habitats ====

==== Habitats ====

*''Lymnaea'' are found in muddy areas (but not on highly acidic soils)

''Lymnaea'' are found predominantly in muddy areas, but do not survive well in highly acidic soils.  Habitats may be permanent; seen in dry summers or temporary; found in wet summers.

*Habitats may be permanent (dry summer) or temporary (wet summer)

=== Epidemiology ===

=== Epidemiology ===