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Source: Modeled from death rate of the L3 population in ‘Simulation of pasture larval populations of Haemonchus contortus’ by IA Barger, PR Benyon & WH Southcott. Proceedings of the Australian Society of Animal Production (1972) 9: 38
| Factor | Time or conditions | Effect |
| Minimum time before worm eggs can become infective larvae. | 4–10 days | Short 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 |
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. Footnotes: 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. |
| Maximum time worm eggs can live awaiting suitable hatching conditions. | Brown stomach worm: 21 days (Note that 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. |
Cold – Maximum temperature: < 15℃ Time for 90% larvae to die: 4 months Warm – Maximum temperature: about 22℃ Time for 90% larvae to die: 3 months Hot – Maximum temperature: about 35℃ Time for 90% larvae to die: 1.5 months Very Hot – Maximum temperature: > 40℃ Time for 90% larvae to die: 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. |
When using anthelmintic products in goats, a veterinary prescription is often required because:
While cattle drenches can be used at the label rates on goats in South Australia and sheep drenches on goats in Victoria, a veterinary prescription is still required for dose rates recommended for goats. |
| Drench groups and actives | Worms | Examples* of brand names/comments |
| BZ or benzimidazole group (‘white’)B albendazole fenbendazole oxfendazole |
barber’s pole worm, ‘scour worms’, adult liver fluke, nodule worm. Aids control of intestinal tapeworm (Moniezia) |
Albendazole: Alben, Valbazen, WSD Albendazole Fenbendazole: Beezed, Panacur 25, Oxfendazole: Beezed LV, Oxfen LV |
| LV or levamisole group (‘clear’)B morantel levamisole |
barber’s pole worm, ‘scour worms’, nodule worm | Morantel: Oralject Levamisole: None registered |
| ML or macrocyclic lactone groupB (sometimes called ‘mectins’) ivermectin abamectin moxidectin |
barber’s pole worm, ‘scour worms’, nodule worm | Abamectin: Virbamec Ivermectin: None registered Moxidectin: None registered |
| AAD or amino-acetonitrile derivative groupB monepantel |
barber’s pole worm, ‘scour worms’ | None registered |
| SI or spiroindole groupM derquantel |
barber’s pole worm, ‘scour worms’, nodule worm | None registered |
| OP or organophosphate groupM naphthalophos (NAP) (OPs have lower or variable efficacy against ‘scour worms’ in the upper GIT and immature barber’s pole worm) |
barber’s pole worm, ‘scour worms’ | None registered |
| TZ or benzimidazole group (flukicide)N triclabendazole |
Liver fluke (all stages); not effective against round worms | Triclabendazole: Flukare C, Fasinec, Exifluke |
| SA or salicylanilides/phenols groupN closantel |
Liver fluke (> 9 weeks and adult) and barber’s pole worm | None registered |
| IQ or isoquinolone groupN praziquantel |
Intestinal tapeworm (Moniezia) | None registered |
*These are all of the commercial anthelmintics registered and commercially available for goats at June 2023. In most states of Australia, sheep drenches can be used in goats with an off-label veterinary prescription.
Breadth of activity across different worm species: BBroad-spectrum; MMid-spectrum; NNarrow-spectrum
Actives: An ‘active’ is the chemical in a drench responsible for killing worms. Some drenches have more than one active and are called ‘multi-active’ or ‘combination’ drenches.
Combination or multi-active treatments: Proprietary treatments containing more than one active. Formulated to be compatible as a mixture. Note: Do not mix your own drenches unless the labels state that you can.
Product formulation: All single actives are available as oral drenches. Moxidectin is also available in injectable products. Moxidectin is not registered for use in goats and an off-label prescription is required from your veterinarian. Pour-on products should not be used in goats for worm control.
Length of protection: Varies from short-acting (‘knock-down’ that kills susceptible worms within the animal) to mid-length (1–6 weeks) and long-acting (approx. 3 months), which not only kill susceptible worms already in the animals, but also infective larvae that the goats eat during the protection period.
‘Scour worms’: Mainly black scour worm and (small) brown stomach worm, but also others.
Label: Check product labels for full details. Follow the label or veterinarian’s instructions.
Using sheep drenches in goats: Veterinarians can prescribe sheep drenches for goats, but must provide written details of withholding periods and dose rates.
Other parasites: The Drench Decision Guides show effectiveness of groups against other parasites of minor importance.
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