|
Sheep
Gut:
male and female adult worms mate
|
|
Female
lays eggs
|
|
|
|
|
|
Both
larval stages feed on bacteria in dung and are vulnerable
to adverse weather conditions and are digested and destroyed
if eaten by sheep (time taken to develop into infective
larvae dependant on favourable stimuli, see below).
|
|
Passed
out in dung onto pasture |
|
|
 |
1st
stage larvae hatch out and then develop into 2nd stage larvae |
|
|
|
| 3rd
stage larvae are infective and wriggle up moist sward
and are eaten by grazing stock |
|
|
| Once
ingested, they burrow into mucous membrane of stomach
or small intestine |
|
|
| Within
1 week 3rd stage larvae become immature adult worms which
return to gut surface |
|
|
| Within
1 week 3rd stage larvae become immature adult worms which
return to gut surface |
|
|
| Within
another week males and females have mated and the cycle
begins again |
|
| Epidemiology
of ovine parasitic gastroenteritis in temperate zones of the
nothern hemisphere, showing periparturient rise in the faecal
egg counts of ewes and the midsummer ries of infective larvae
on pasture.
Source: Veterinary Parasitology, 1998. GM Urquhart et al. |
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