I want information about

I want information about
Home WormBoss Worm Control Program for Goats – South Australia Factors Contributing to Paddock Contamination With Worms in SA Region

Factors Contributing to Paddock Contamination With Worms in SA Region

The following table applies to:

FactorTime or conditionsEffect
Minimum time before worm eggs can become infective larvae.4–10 daysShort graze periods (less than 4 days) prevent ‘auto-infection’ (animals becoming infected by larvae arising from worm eggs the same mob have recently deposited onto the pasture).
Conditions required for significant numbers of worm eggs to hatch and become infective larvae.4–10 days of:

Brown stomach worm
Temperature: daily maximum >8°C1
Moisture in this time: >10–15 mm rainfall2

Black scour worm
Temperature: daily maximum >15°C for
T. colubriformis or >12°C for T. vitrinus
Moisture in this time: >10–15 mm rainfall3

Barber’s pole worm
Temperature: daily maximum >18°C1
Moisture in this time: >10–15 mm rainfall3
1Some hatching of worm eggs of all worm species can occur below these daily maximum levels, but this is usually at a small and insignificant rate.
2Brown stomach worm eggs can develop at low rates without rainfall even in a relatively dry faecal pellet.
3Development to infective larvae may occur without rainfall if soil moisture profile is high.
Unsuitable conditions prevent eggs hatching and developing into infective larvae.Note: The eggs of the brown stomach worm are much more tolerant of cold and dry conditions, and in general, grazing management has less effect on its control.
Maximum time worm eggs can live awaiting suitable hatching conditions.Brown stomach worm: 21 days
Some brown stomach worm eggs may survive for longer periods. 
Black scour worm: 16 days
Barber’s pole worm: 5 days
Prolonged periods without the right conditions (temperature/moisture) for egg development will result in the eggs dying. This lowers the worm-risk of paddocks.However, once hatched, infective larvae of both black scour and brown stomach worm can remain in the faecal pellet until conditions are more suitable.
The time for about 90% of the barber’s pole worm infective larvae (L3s) to die (making paddocks low worm-risk).
Note: larvae of brown stomach worm and black scour worm can survive longer because they can remain in the faecal pellet for extended periods.
 Maximum temperature (ºC)
Cold: < 15
Warm: about 22
Hot: about 35
Very hot: > 40

Time for 90% to die
Cold: 4 months
Warm: 3 months
Hot: 1.5 months
Very hot: 1–2 weeks
L3 larvae do not feed. While waiting to be eaten by animals, they wriggle randomly in drops of moisture, more so in warmer conditions. Increased activity in warm weather depletes their energy reserves faster, hastening death.In extremely hot, dry and windy conditions the larvae dry out and die.
Minimum time for infective larvae eaten by animals to mature and lay eggs (the ‘pre-patent period’).Sheep: minimum of 18 days for most sheep roundworms.
Goats: minimum of 14 (typically 21) days for barber’s pole worm and 21 days for scour worms.
Worm larvae eaten by animals soon after an effective drench will take at least 18 days (in sheep) or 14–21 days (in goats) before they can lay eggs. During this period after administering an effective drench, animals are not re-infecting the pasture.

Return to Summary page

Subscribe to the Boss Bulletin

Subscribe the the Boss Bulletin for monthly updates and articles about all things parasite management

Subscribe here

Notice: you are leaving the ParaBoss main website

www.wecqa.com.au is a secondary ParaBoss website hosted by the University of New England (UNE). Whilst this is still an official ParaBoss website, UNE is solely responsible for the website’s branding, content, offerings, and level of security. Please refer to the website’s posted Privacy Policy and Terms of Use.