Ascarids in Young Horses
Ascarids, what they are and how to manage them
Ascarids are large roundworms with thick shelled eggs that persist in the environment. In Australian grazing systems they are most relevant to young cattle, especially calves in warmer regions. This page explains what an ascarid finding means, who is at risk, how to test, and how to manage them under Australian conditions.
What an ascarid result means
Ascarid eggs are larger than strongyle type eggs and have a thick shell. They are sticky, they survive for long periods in yards and on pasture, and they can contaminate calving areas. In cattle, Toxocara vitulorum is the key ascarid of concern in calves. Goats and sheep are less commonly affected in Australia, however young stock can still face issues on contaminated ground.
Why regular faecal testing matters
Routine faecal egg counts help you decide if treatment is needed and they confirm that your last treatment worked. Keeping to a simple testing rhythm saves money and helps slow drench resistance because you only treat when you need to. For a quick walkthrough on reading reports and targets, see:
Understand WEC test results.
Who is most at risk
- Calves in their first months of life, especially in warm, humid or tropical districts.
- Young stock reared on wet, muddy or heavily used calving and lambing areas.
- Herds with poor drainage around troughs, feeders and shelter where manure builds up.
Signs to watch
- Scouring, pot belly, poor growth and a rough coat in young stock.
- Occasional coughing or respiratory signs due to larval migration.
- In heavier burdens, dehydration and weight loss despite adequate feed.
Testing options
- Faecal egg count detects the large, thick shelled ascarid eggs. Ask your lab to report ascarid eggs separately from strongyles.
- Follow up testing 10 to 14 days after treatment to check that the drench worked.
- Environmental focus if repeat problems occur, review hygiene and drainage in calving areas and yards.
When to act
- Treat based on faecal result, age of stock and clinical signs. There is no single national threshold that fits every property.
- Prioritise calves and young stock on contaminated or wet ground.
- Recheck after treatment to confirm success, then adjust timing for future groups.
Drench choices and resistance
Choose drenches by active ingredient, not just brand. Many broad spectrum actives list ascarids on the label. Macrocyclic lactones are commonly effective in calves, some benzimidazoles and levamisole products also include ascarid claims, however this varies by product and species. Always confirm the label for your stock class, age and withholding periods. Use combinations where you also need roundworm control, 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 northern tablelands, focus on calf areas and yards.
- Victoria: manage drainage in calving paddocks and around feeders during winter and spring.
- Queensland: higher risk in summer rainfall and tropical zones, hygiene for calves on irrigated or wet country is critical.
- South Australia: south east and irrigated pockets carry higher risk, pastoral zones are lower risk but watch after rain events.
- Western Australia: south west winter rainfall and irrigated districts can see issues where calf areas get muddy.
- Tasmania: cool, wet conditions around calving yards can drive problems in young stock, keep bedding dry where possible.
- Northern Territory: warm, humid conditions and wet season paddocks increase risk in calves on improved or irrigated pastures.
- ACT: similar to NSW Southern Tablelands, manage yard hygiene after rain and during peak calving periods.
Management checklist
- Keep calving areas as dry and clean as practical, replace wet bedding and improve drainage.
- Move calves onto clean, well rested paddocks early, avoid overstocking wet corners and gateways.
- Use faecal testing to target treatments and to confirm success after dosing.
- Choose drenches by active ingredient and check that the label includes ascarids for your species and age group.
- Clean around troughs and feeders to reduce manure build up and standing mud.
FAQs
Do standard worm egg counts always detect ascarids?
Yes for many cases, the eggs are large and distinctive. Ask your lab to report ascarid eggs separately from strongyle type eggs so you can plan the right response.
Which drenches work on ascarids?
Macrocyclic lactones commonly work in calves, some benzimidazoles and levamisole products also list ascarids. Always check the specific product label for species, age and dose.
How soon should I treat calves?
Base timing on faecal results, age and clinical signs. In higher risk regions many producers target early life windows, however always follow label directions and local advice.
Will one treatment fix the problem?
Ascarid eggs persist in the environment. Combine testing and treatment with hygiene, drainage and paddock rotation to lower reinfection pressure.
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.
