Teladorsagiosis in Sheep

Quick Answer
  • Teladorsagiosis is caused by the brown stomach worm, Teladorsagia circumcincta, which lives in the abomasum and can reduce appetite, growth, and feed efficiency.
  • Common signs include scours, poor weight gain, weight loss, rough fleece, and reduced thrift, especially in lambs on pasture.
  • Diagnosis usually combines flock history, pasture risk, body condition, and fecal egg counts. Your vet may also recommend a fecal egg count reduction test to check for dewormer resistance.
  • Treatment is not one-size-fits-all. Your vet may recommend targeted deworming, supportive care, and pasture management based on age group, season, and local resistance patterns.
  • Typical US cost range is about $8-$25 per sheep for basic exam plus deworming decisions in a flock setting, or roughly $150-$600+ for a flock workup with fecals and resistance testing.
Estimated cost: $8–$25

What Is Teladorsagiosis in Sheep?

Teladorsagiosis is a parasitic disease caused by Teladorsagia circumcincta, also called the brown stomach worm. This parasite lives in the abomasum, which is the sheep's true stomach. It is one of the most important gastrointestinal worms in sheep and is especially relevant in grazing lambs and young stock.

The parasite damages the stomach lining and interferes with normal digestion. That can lead to poor appetite, reduced weight gain, scours, and production loss. In many flocks, the biggest impact is not sudden death but a quieter pattern of lambs that do not grow as expected.

Disease severity depends on worm burden, age, nutrition, pasture contamination, and how much parasite resistance is present on the farm. Some sheep carry worms with mild outward signs, while others become noticeably thin and unthrifty. Because this condition overlaps with other parasite problems, your vet usually looks at the whole flock picture rather than one symptom alone.

Symptoms of Teladorsagiosis in Sheep

  • Poor weight gain or failure to thrive
  • Weight loss despite access to feed
  • Scours or loose manure
  • Reduced appetite
  • Rough fleece or poor body condition
  • Weakness or marked depression in heavily affected lambs
  • Dehydration from ongoing diarrhea
  • Deaths in severe or mixed parasite burdens

Watch closely for lambs that fall behind the group, develop scours, or lose condition over a few weeks. Teladorsagiosis often shows up as a production problem before it becomes a crisis.

See your vet promptly if multiple sheep are scouring, lambs are not gaining, or any animal becomes weak, dehydrated, or stops eating. Severe illness can involve more than one parasite at the same time, so a flock-level evaluation matters.

What Causes Teladorsagiosis in Sheep?

Sheep develop teladorsagiosis after eating infective larvae from contaminated pasture. The larvae are picked up while grazing, then move into the glands of the abomasum. As they mature, they damage the stomach lining and trigger inflammation, which reduces digestive efficiency and protein use.

Pasture-based systems are where this parasite matters most. Lambs are usually more vulnerable because they have less immunity than mature sheep. Heavy stocking density, repeated grazing of the same paddocks, and warm, moist conditions can all increase exposure.

Another major factor is anthelmintic resistance, which means worms survive a dewormer that used to work. Resistance has been reported across the major dewormer classes used in sheep, so treatment failure is a real concern. That is why your vet may recommend targeted treatment, fecal monitoring, and grazing changes instead of routine whole-flock deworming on a fixed schedule.

How Is Teladorsagiosis in Sheep Diagnosed?

Diagnosis usually starts with the basics: age group affected, season, pasture history, body condition, manure quality, and recent deworming history. Your vet will often look for a pattern such as lambs with poor growth, scours, and reduced thrift on contaminated pasture.

A fecal egg count is a common next step. This helps estimate strongyle-type worm shedding, but it does not always tell the whole story for one individual sheep. In young animals, egg counts often correlate better with worm burden than they do in adults. Your vet may test individual sheep or pooled flock samples depending on the situation.

If resistance is a concern, your vet may recommend a fecal egg count reduction test. That means checking egg counts before treatment and again about 10 to 14 days later to see whether the chosen dewormer actually worked. In deaths or severe outbreaks, necropsy and direct worm identification can provide the clearest answer and help guide the flock plan.

Treatment Options for Teladorsagiosis in Sheep

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$8–$20
Best for: Mild to moderate disease in stable sheep, especially when the goal is to control losses while keeping costs predictable.
  • Physical exam and flock history review
  • Targeted treatment of affected or high-risk sheep rather than automatic whole-flock dosing
  • Use of an appropriate labeled dewormer selected by your vet
  • Basic supportive care such as improved nutrition, easy water access, and reduced stress
  • Short-term pasture adjustments if practical
Expected outcome: Often good if affected sheep are identified early and the chosen dewormer is still effective on that farm.
Consider: Lower upfront cost, but there is a higher risk of under-treating the flock if resistance status is unknown or if multiple parasites are involved.
Most Common

Recommended Standard Treatment

$150–$600
Best for: Most flocks with recurring scours, poor growth, or uncertain dewormer performance.
  • Veterinary exam with flock-level risk assessment
  • Fecal egg counts on selected sheep or pooled samples
  • Targeted deworming plan based on age group, season, and pasture pressure
  • Drug choice guided by likely efficacy and label approvals for sheep abomasal nematodes
  • Follow-up fecal testing or recheck to confirm response
  • Pasture and stocking recommendations to reduce reinfection
Expected outcome: Good to very good when diagnosis, treatment, and prevention are combined and resistance is addressed early.
Consider: Costs more at the start, but it usually gives better long-term control and helps avoid repeated ineffective deworming.

Advanced / Critical Care

$300–$1,200
Best for: Severe outbreaks, repeated treatment failure, high-value flocks, or farms with suspected multi-drug resistance.
  • Comprehensive flock investigation with repeated fecal egg counts
  • Fecal egg count reduction testing to evaluate resistance
  • Necropsy or laboratory submission in deaths or severe outbreaks
  • Individual supportive care for weak or dehydrated sheep
  • Detailed parasite-control redesign including quarantine protocols, culling strategy, and grazing rotation planning
  • Close veterinary follow-up for high-value breeding stock or heavy production losses
Expected outcome: Variable but often improved when resistant parasites are identified and the flock plan is rebuilt around testing and management.
Consider: Highest upfront cost and more labor, but it can prevent ongoing production losses and repeated ineffective treatments.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Teladorsagiosis in Sheep

Bring these questions to your vet appointment to get the most out of your visit.

  1. Based on our flock's signs and season, how likely is Teladorsagia compared with other stomach or intestinal worms?
  2. Should we run individual or pooled fecal egg counts, and which sheep should we sample first?
  3. Do you recommend a fecal egg count reduction test to check whether our current dewormer is still working?
  4. Which sheep should be treated now, and which ones can be monitored instead?
  5. What withdrawal times and food-animal drug rules apply to the products we are considering?
  6. How should we change grazing, stocking density, or pasture rotation to lower reinfection pressure?
  7. Are there animals in this flock that should be culled because they need repeated parasite treatment?
  8. What monitoring plan should we use this season so we catch production losses earlier?

How to Prevent Teladorsagiosis in Sheep

Prevention works best when it combines pasture management, monitoring, and selective treatment. Sheep become infected by grazing larvae on pasture, so reducing exposure matters. Your vet may suggest rotating paddocks, avoiding overstocking, and using lower-risk pastures for lambs when possible.

Routine flock observation is also important. Watch body condition, growth rates, manure consistency, and overall thrift. Fecal egg counts can help track parasite pressure before losses become obvious. On farms with repeated problems, your vet may recommend periodic testing through the grazing season rather than deworming by calendar alone.

Use dewormers carefully. Underdosing and repeated blanket treatment can push resistance faster. Weigh sheep accurately, use the correct sheep dose and product, and quarantine new arrivals with a veterinary plan before they join the flock. Some farms also benefit from culling animals that repeatedly need treatment, because those sheep may contribute more eggs back onto pasture.

A written flock health plan is one of the most practical prevention tools. It helps match parasite control to your region, pasture system, and resistance risks. That approach is usually more sustainable than relying on one product or one treatment date every year.

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