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Roundworm monitoring tools

What can faecal egg counts tell us?

Are roundworms the problem?

  • Evidence-based treatment
    • establish whether roundworms are the cause of diarrhoea and ill-thrift
    • confirm the presence of adult roundworms
  • Testing could save the time and costs of worming sheep if roundworms are not the problem

Pooled FEC

 

When to treat?

  • Regular pooled egg counts ~2-4 weeks apart
    • Frequent monitoring can provide an indication of which fields are more wormy
  • Highlights the optimal time for treatment
    • Can be useful to improve flock productivity
  • Correct timing = greatest benefit from wormer treatments

Pooled FEC

Which animals to treat?

  • Targeting individual animals or groups
  • Treating only those animals which need reduces excess chemical usage and costs

Pooled FEC
Individual FEC

Did the treatment work?

  • Only viable test to check if anthelmintic treatments are working
  • Avoid wasting money & labor on treatments which are ineffective
  • Wormer resistance is common – understand what works on your farm to treat effectively

Pooled or individual FEC

What egg counts CAN’T tell you…

  • Inhibited larvae cannot be detected by faecal egg counting (e.g. type 2 Ostertagia infection)
  • Other tools (e.g. weightgain) are better suited to monitoring productivity
  •  A single faecal egg count only provides a snapshot of what is happening…frequent testing is required to maximize benefit
  • Egg count results do not always reflect the number of adult worms in cattle.
    • Different types of worms produce different numbers of eggs and egg counts can’t tell you which type of worms are present
    • High egg counts don’t always mean low productivity. Some animals can maintain production despite harboring worms (resilience)

 

 

 

Diagnostic tests and when to use them

Serum pepsinogen

Elevated pepsinogen levels (>3.0 IU tyrosine) are observed in clinically affected calves. Serum pepsinogen concentration is an indicator of abomasal damage caused by Ostertagia (cattle brown stomach worm) infection. This method is useful in young animals (<2yrs old), in older animals results may be influenced by previous exposure to infection.

(Bulk tank) milk antibodies

Ostertagia (cattle brown stomach worm) ELISA. This test can be performed at the end of the grazing season on bulk tank milk to measure exposure of the herd to roundworms. High values are those above 0.8 ODR.

Monitoring live weight gain in calves

Build a picture of the expected pattern and range of weight gain for your farm through regular monitoring of calves. Comparing weight gain to previous years can highlight a problem and trigger further investigation (e.g. faecal egg counting). Live weight gain is not parasite-specific, changes could indicate nutritional status or even individual differences between calves.

Grazing/management history

The accumulation of parasitological and risk assessment data together with information on animal performance, nutritional inputs and grazing management, taken at different times within a season and over several seasons, provides a true indication of the threat posed by roundworms on a farm. This information should be taken into account by vets and advisors when discussing anthelmintic treatments. “Risks” are summarised below:

Factor Low risk Medium risk High risk
Age/exposure >2 years / adult 1-2 years / second season grazers <1yr /first season grazers
Herbage mass (kg dry matter/ha) >2000 kg/ha 1000 – 2000 kg/ha <1000 kg/ha
Sward height >8cm 4-8 cm <4cm
Pasture type Newly sown, “clean” grazing Silage/hay aftermath Permanent pasture
Previous grazing history (last 12 months) Mixed or rotational grazing; grazed by adult cows, sheep or other species Grazed by cattle 1-2 years old Grazed by cattle <1yr old

Information on risk factors adapted from Animal Health Ireland

Specific considerations for different management systems

Enterprise Calving Areas to think about
Beef Spring
  • Adult cows tend to have developed good immunity and have minimal roundworm infections. They do however produce large quantities of faeces and so can add to pasture contamination
  • Pre-weaned calves consume mostly milk therefore have a lower intake of roundworm larvae
  • Once cattle are eating grass they are exposed to roundworm infection
  • Monitoring in autumn advised
  • May delay the development of immunity and be prone to type II ostertagiosis
Autumn
  • Mostly housed early
  • Turned out calves will be eating grass early therefore they will be exposed to roundworms earlier than spring born calves
  • Early season monitoring advised
Dairy Spring
  • May go to pasture early following milk substitute and concentrates therefore exposed to roundworms early
  • Early season monitoring advised
Autumn
  • Turned out calves will be eating grass early therefore they will be exposed to roundworms earlier than spring born calves
  • Early season monitoring advised

Understanding the risk factors associated with particular practices and grazing strategies can help guide treatment choices and timings. Roundworm infections are acquired by cattle eating roundworm larvae from grass therefore it is worth considering the timings of turn out and housing to minimise the risk at high challenge times.