Jaagsiekte in Sheep: What This Contagious Lung Tumor Means
- Jaagsiekte, also called ovine pulmonary adenocarcinoma (OPA), is a contagious lung tumor in sheep caused by jaagsiekte sheep retrovirus (JSRV).
- Affected sheep often develop chronic weight loss, faster breathing, exercise intolerance, and a moist lung discharge that may be more obvious when the rear end is lifted.
- There is no curative treatment. Flock management usually focuses on confirming the diagnosis, separating or culling affected animals, and reducing spread.
- Most clinical cases are seen in adult sheep, often over 2 years old, although infection can occur earlier before signs appear.
- Typical U.S. veterinary cost range for exam, farm call, and diagnostic workup is about $250-$900 per sheep, with necropsy and lab confirmation often adding $150-$450+.
What Is Jaagsiekte in Sheep?
Jaagsiekte is the common name for ovine pulmonary adenocarcinoma (OPA), a contagious cancer of the lungs in sheep. It is caused by jaagsiekte sheep retrovirus (JSRV), which infects lung tissue and can trigger tumor growth over time. The disease is progressive, and once sheep show clear clinical signs, the outlook is poor.
This condition matters because it can spread within a flock before anyone realizes there is a problem. Some sheep carry infection for months or longer before obvious breathing trouble develops. By the time a sheep is thin, short of breath, or producing fluid from the nose, there may already be significant lung damage.
Jaagsiekte is not the same as routine pneumonia, even though the signs can look similar at first. Sheep may keep eating for a while, which can make the illness easy to miss in early stages. If one sheep has chronic respiratory signs and poor thrift despite basic care, your vet may want to consider OPA along with other causes of lung disease.
Symptoms of Jaagsiekte in Sheep
- Progressive weight loss despite a fair or normal appetite
- Increased breathing effort or faster breathing at rest
- Exercise intolerance, lagging behind, or tiring easily
- Chronic moist cough or wet-sounding breathing
- Nasal discharge or frothy lung fluid, especially when the hindquarters are raised
- Open-mouth breathing or marked respiratory distress
- Sudden worsening if secondary bacterial pneumonia develops
When to worry: See your vet immediately if a sheep has labored breathing, open-mouth breathing, marked weakness, or fluid coming from the nose. Those signs can happen with advanced jaagsiekte, severe pneumonia, or other urgent lung disease.
Milder cases can be harder to spot. A sheep that is slowly losing condition, breathing faster than flockmates, or struggling after handling may need a closer workup. Because early OPA can look like chronic pneumonia or parasite-related illness, it is important not to assume the cause without veterinary guidance.
What Causes Jaagsiekte in Sheep?
Jaagsiekte is caused by jaagsiekte sheep retrovirus (JSRV), a betaretrovirus that infects the lungs. The virus is shed in respiratory secretions and spreads mainly through aerosol transmission, meaning nearby sheep can inhale infected droplets. Transmission through colostrum and milk has also been reported, which helps explain why flock-level control can be difficult.
Not every infected sheep becomes visibly sick right away. Many animals are infected long before tumors are large enough to cause obvious signs. Clinical disease is uncommon in very young lambs and is seen most often in adult sheep, with many cases recognized after 2 years of age.
Crowding, close contact, and keeping infected and uninfected animals together can increase the chance of spread. Introducing replacement animals without a clear health history can also bring JSRV into a flock. Because there is no vaccine and no reliable pen-side screening test for every stage of infection, prevention depends heavily on biosecurity and flock management.
How Is Jaagsiekte in Sheep Diagnosed?
Your vet will usually start with the flock history, age of the sheep, body condition, and breathing pattern. Jaagsiekte is often suspected when an adult sheep has chronic weight loss and progressive respiratory signs that do not fit a straightforward pneumonia case. A wet nasal discharge, especially if fluid increases when the hindquarters are elevated, can raise concern.
In live sheep, transthoracic ultrasound can help identify lung changes that support OPA. This is useful because early or moderate disease may not be obvious from listening to the chest alone. Your vet may also consider other causes of chronic respiratory disease, including bacterial pneumonia, parasitism, or other flock health problems.
A definite diagnosis is often made through necropsy and histopathology after death or euthanasia. PCR testing for viral DNA or RNA may support diagnosis in some settings, but routine diagnosis still relies heavily on clinical findings, pathology, and flock context. If OPA is suspected in one sheep, your vet may recommend evaluating the broader flock rather than focusing on that animal alone.
Treatment Options for Jaagsiekte in Sheep
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm call or herd consultation
- Physical exam and breathing assessment
- Immediate isolation from flockmates
- Quality-of-life discussion
- Planned culling or humane euthanasia if clinical signs are advanced
Recommended Standard Treatment
- Farm call and full veterinary exam
- Thoracic ultrasound when available
- Assessment for concurrent pneumonia or other respiratory disease
- Isolation and culling recommendations
- Necropsy and histopathology planning for confirmation
- Flock-level biosecurity and monitoring plan
Advanced / Critical Care
- Repeat herd visits or referral consultation
- Ultrasound of multiple suspect sheep
- Necropsy with histopathology and selected PCR or ancillary lab testing
- Broader flock investigation for age groups and transmission patterns
- Segregated lamb-rearing or replacement strategy review
- Embryo-transfer discussion for preserving valuable genetics in heavily affected flocks
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Jaagsiekte in Sheep
Bring these questions to your vet appointment to get the most out of your visit.
- Does this sheep's breathing pattern fit jaagsiekte, pneumonia, lungworms, or another condition?
- Would thoracic ultrasound help us decide whether this is likely OPA?
- Should this sheep be isolated right away, and which flockmates are most important to watch?
- Is humane euthanasia or culling the most appropriate next step for this animal?
- Would a necropsy give us useful answers for the rest of the flock?
- If this ewe is affected, should her offspring be managed differently?
- What biosecurity steps should we use before bringing in replacement sheep?
- How should we monitor the flock over the next 6 to 12 months for additional cases?
How to Prevent Jaagsiekte in Sheep
Prevention focuses on keeping JSRV out of the flock and limiting spread if it is already present. The most practical steps are buying replacements from flocks with no known history of OPA, avoiding unnecessary mixing of age groups, and isolating sheep with chronic respiratory signs until your vet can assess them. Regular flock observation matters because early cases can be subtle.
If OPA is confirmed or strongly suspected, prompt removal of affected sheep is a key control step. Some programs also recommend removing offspring of infected ewes, because transmission through colostrum and milk has been documented. In valuable flocks, your vet may discuss more intensive options such as segregated lamb rearing, strict biosecurity, and preserving genetics through embryo transfer.
There is no vaccine and no treatment that stops the infection from progressing once tumors develop. That means prevention is really about flock management, not medication. A written plan with your vet can help you decide how to handle suspect animals, necropsy testing, replacement purchases, and long-term monitoring.