Strongyloides Life Cycle and Treatment
What are Strongyloides?
Strongyloides are tiny roundworms that can affect sheep, cattle and goats. They are most important in young stock on wet, warm country. This page explains what a Strongyloides finding means, who is at risk, how to test, and how to manage them in Australian conditions.
What a Strongyloides result means
Routine worm egg counts are designed for roundworms like strongyles. Strongyloides eggs are often larvated and can be missed or under counted with standard flotation. Your lab may use a Baermann technique to recover larvae from faeces when Strongyloides is suspected. Ask your lab which method they use and how to interpret the numbers for your species and season.
Why regular faecal testing matters
Regular faecal testing shows if treatment is needed and whether your last drench worked. It also helps you target the right class of drench and avoid unnecessary use. For a simple walkthrough of reading worm egg count reports, see:
Understand WEC test results.
Who is most at risk
- Young stock such as lambs and calves on wet or muddy yards and calving or lambing areas.
- Properties with warm, humid periods or irrigation that keeps ground moist.
- Periparturient dams because Strongyloides can be passed to offspring via skin contact or milk.
Signs to watch
- Scouring and pasty or watery faeces in young stock.
- Poor growth, rough coat, loss of bloom.
- In heavier burdens, dehydration and weight loss.
Testing options
- Faecal egg count for a quick screen, note that sensitivity varies for Strongyloides.
- Baermann test to recover and identify larvae when Strongyloides is suspected.
- Follow up testing 10 to 14 days after treatment to check that it worked.
When to act
- No single universal threshold exists for Strongyloides. Treat based on clinical signs, age of stock, lab method and seasonal risk.
- Focus on young stock and problem paddocks or yards first.
- Recheck after treatment to confirm success and adjust your plan.
Drench choices and resistance
Choose drenches by active ingredient, not just brand. Many broad spectrum actives list Strongyloides on the label. Macrocyclic lactones are commonly effective, some benzimidazoles and levamisole products may also be effective, but always confirm the claim on the label you use. Use combinations to manage roundworms where needed, avoid repeating the same single active back to back, and keep treatments targeted to what testing shows. For plain language summaries of every active used in Australia and how they differ, visit our
Drench actives hub.
Regional risk snapshot across Australia
- New South Wales: risk rises in warm, wet periods on the coast and tablelands, especially where calving or lambing yards become muddy.
- Victoria: winter to spring wet paddocks and yards increase risk for lambs and calves, monitor Gippsland and the south west closely.
- Queensland: summer rainfall and irrigation raise risk, focus on hygiene for calves and lambs on wet country.
- South Australia: south east and irrigated pockets carry higher risk, pastoral zones are lower risk but watch after summer rain.
- Western Australia: south west winter rainfall and irrigated areas can see cases in young stock on wet ground.
- Tasmania: cool, wet conditions in lambing paddocks and yards can drive problems in young stock.
- Northern Territory: mainly a calf issue on improved and irrigated pastures during the wet.
- ACT: similar to nearby NSW tablelands with risk peaking after rain when yards are wet.
Management checklist
- Keep calving and lambing areas dry where possible, replace wet bedding, improve drainage.
- Move young stock onto clean, well rested paddocks as early as practical.
- Use faecal testing to target treatments and confirm success after dosing.
- Choose drenches by active ingredient and check the label for Strongyloides claims.
- Clean and disinfect feeding areas and trough surrounds to reduce mud and manure build up.
FAQs
Does a standard worm egg count always detect Strongyloides?
Not always. Strongyloides eggs can be larvated and counts may under read. Ask your lab about a Baermann test if Strongyloides is suspected.
Which drenches work on Strongyloides?
Check the label of the product you use. Macrocyclic lactones are commonly effective, some benzimidazoles and levamisole products list Strongyloides, but claims vary by label.
Can Strongyloides pass from dam to young stock?
Yes. Transmission can occur via skin contact or milk. Good hygiene in calving and lambing areas helps lower risk.
How often should I test?
Test young stock more often in wet, warm periods. Recheck 10 to 14 days after treatment to make sure it worked. For help reading reports, see
Understand WEC test results.
More on choosing actives
For quick comparisons of MLs, white drenches, levamisole, AADs and flukicides, including how they differ and when to use them, visit the
Drench actives hub.
Important: always follow the product label for species, dose, meat withholding period, milk withholding period and export slaughter interval.
STRONGYLOIDES
Strongyloides stercoralis is a human pathogenic parasitic roundworm causing the disease strongyloidiasis. Its common name in the US is threadworm. In the UK and Australia, however, the term threadworm can also refer to nematodes of the genus Enterobius, otherwise known as pinworms.
