Equine Multinodular Pulmonary Fibrosis in Horses: Symptoms and Treatment

Quick Answer
  • Equine multinodular pulmonary fibrosis, or EMPF, is a serious scarring disease of the lungs that has been strongly associated with equine herpesvirus-5 (EHV-5).
  • Common signs include weight loss, cough, fever, exercise intolerance, fast breathing, and obvious effort when breathing in.
  • Early cases can look like severe equine asthma or pneumonia, so imaging and airway testing are often needed to sort out the cause.
  • Treatment usually focuses on anti-inflammatory care, supportive care, and sometimes antiviral medication, but response is variable and prognosis can be guarded.
  • Prompt evaluation matters. Horses with labored breathing, blue-tinged gums, or rapid worsening should see your vet immediately.
Estimated cost: $1,200–$8,500

What Is Equine Multinodular Pulmonary Fibrosis in Horses?

Equine multinodular pulmonary fibrosis, often shortened to EMPF, is an uncommon but serious lung disease in horses. It causes widespread inflammation and scarring inside the lungs, which makes it harder for the horse to move oxygen normally. Over time, that scarring can reduce lung function and make breathing more difficult, especially during exercise.

EMPF has been strongly associated with equine herpesvirus-5 (EHV-5), a gammaherpesvirus. Researchers and clinicians have found EHV-5 in many affected horses, but the exact role of the virus is still being studied. In other words, the virus is closely linked to EMPF, but it is not always clear whether it is the direct cause in every case.

This condition is reported most often in adult and middle-aged horses, though younger horses can be affected too. Many horses show a gradual decline at first, with weight loss, lower stamina, and intermittent fever. Others become noticeably short of breath and need urgent veterinary care.

Because EMPF can resemble other lower-airway diseases early on, it is important not to assume a horse has asthma, shipping fever, or a routine respiratory infection without a full workup from your vet.

Symptoms of Equine Multinodular Pulmonary Fibrosis in Horses

  • Fast breathing at rest
  • Increased breathing effort
  • Cough
  • Exercise intolerance
  • Weight loss or poor body condition
  • Fever
  • Lethargy or reduced appetite
  • Abnormal lung sounds

Mild signs can be easy to miss at first, especially in horses that are not in regular work. A horse that is losing weight, coughing, or breathing faster than usual deserves a veterinary exam, even if the signs seem subtle.

See your vet immediately if your horse has labored breathing at rest, worsening respiratory distress, collapse, or gum color changes. Those signs can mean the lungs are struggling and the situation may become an emergency.

What Causes Equine Multinodular Pulmonary Fibrosis in Horses?

EMPF is most strongly linked to equine herpesvirus-5 (EHV-5). Studies and case reports have repeatedly found EHV-5 in lung tissue or airway samples from affected horses, and experimental work has supported a connection between this virus and the development of fibrosing lung disease. Still, the exact cause-and-effect pathway is not fully settled.

What vets do know is that EMPF is not the same thing as a routine viral cold. Instead, it appears to involve a more complex process in which viral infection, inflammation, and abnormal healing lead to fibrosis, or scar tissue, within the lungs. Once fibrosis forms, it can be difficult or impossible to reverse completely.

Not every horse carrying EHV-5 develops EMPF. That suggests other factors may matter too, such as the horse's immune response, timing of infection, overall health, or additional inflammatory triggers. In some cases, other gammaherpesviruses have also been identified in horses with EMPF-like disease.

For pet parents, the key point is this: EMPF is a serious lower-airway disease with a viral association, not a management issue that can be fixed with rest alone. If your horse has ongoing respiratory signs, your vet may need to investigate beyond common causes like equine asthma or bacterial pneumonia.

How Is Equine Multinodular Pulmonary Fibrosis in Horses Diagnosed?

Diagnosis usually starts with a careful history and physical exam. Your vet will look at breathing rate and effort, body condition, temperature, and lung sounds. Basic bloodwork may show inflammatory changes such as neutrophilic leukocytosis, increased fibrinogen, or anemia, but bloodwork alone cannot confirm EMPF.

Imaging is a major part of the workup. Thoracic radiographs often show an interstitial to reticulonodular lung pattern, and thoracic ultrasound may help identify pleural changes or other abnormalities. Because EMPF can mimic other respiratory diseases, imaging helps your vet narrow the list of possibilities.

Airway sampling is often the next step. Your vet may recommend bronchoalveolar lavage (BAL) or other respiratory sampling for cytology and PCR testing. Detecting EHV-5 in pulmonary secretions supports the diagnosis, especially when the imaging findings fit. In some horses, a lung biopsy is needed for stronger confirmation, particularly when the diagnosis remains uncertain after less invasive testing.

In practical terms, diagnosis often happens in stages. Some horses can be managed with a field workup plus referral imaging, while others need hospital-based testing because they are too unstable, need oxygen support, or may require more advanced procedures.

Treatment Options for Equine Multinodular Pulmonary Fibrosis in Horses

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

Budget-Conscious Care

$1,200–$2,500
Best for: Horses with mild to moderate signs when finances are limited, or when the goal is to gather enough information to guide comfort-focused care and next steps.
  • Farm or clinic exam with focused respiratory assessment
  • CBC/fibrinogen and basic bloodwork
  • Limited thoracic imaging, often ultrasound and/or a smaller radiograph set
  • Supportive care such as rest, dust reduction, hydration support, and anti-inflammatory medication if your vet feels it is appropriate
  • Discussion of referral versus palliative management based on breathing effort and quality of life
Expected outcome: Guarded. Some horses may stabilize temporarily, but EMPF often progresses, especially if significant fibrosis is already present.
Consider: Lower upfront cost, but less diagnostic certainty and fewer treatment tools. This approach may miss the chance to confirm EHV-5 involvement or identify complications early.
Most Common

Recommended Standard Treatment

$2,500–$5,500
Best for: Most horses that are stable enough for a fuller workup and whose families want a practical, evidence-based treatment plan.
  • Complete respiratory workup with bloodwork and thoracic radiographs
  • Bronchoalveolar lavage or other airway sampling for cytology and PCR testing for EHV-5
  • Systemic anti-inflammatory treatment, often corticosteroid-based when your vet decides benefits outweigh risks
  • NSAIDs and supportive nursing care as needed
  • Monitoring of oxygenation, appetite, weight, fever, and breathing effort
  • Recheck imaging or follow-up exams to assess response
Expected outcome: Guarded to poor overall, but earlier cases may have a better chance of temporary improvement or longer-term management.
Consider: More information and a more targeted plan, but still no guaranteed response. Fibrosis can be irreversible, and treatment may require repeated visits and medication monitoring.

Advanced / Critical Care

$5,500–$8,500
Best for: Horses with severe respiratory compromise, unclear diagnosis after initial testing, or pet parents who want every reasonable diagnostic and treatment option explored.
  • Referral hospital admission and continuous monitoring
  • Expanded thoracic imaging and repeat imaging as needed
  • BAL plus PCR testing and possible percutaneous lung biopsy
  • Oxygen therapy and intensive supportive care for horses in respiratory distress
  • Combination medical management that may include corticosteroids, NSAIDs, and consideration of antiviral therapy such as valacyclovir under your vet's direction
  • Management of secondary complications and detailed prognosis counseling
Expected outcome: Often poor in advanced disease, though individual outcomes vary. Horses identified earlier in the course may have a better chance than those with extensive fibrosis and marked distress.
Consider: Highest cost and most intensive care. Antiviral treatment can add substantial expense, and published outcomes remain mixed, with many reported cases still having a poor long-term outcome.

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

Questions to Ask Your Vet About Equine Multinodular Pulmonary Fibrosis in Horses

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

  1. What findings make you most suspicious for EMPF instead of asthma or pneumonia?
  2. Which tests are most important first if we need to control the cost range?
  3. Does my horse need thoracic radiographs, ultrasound, BAL, or referral for lung biopsy?
  4. Are you recommending corticosteroids, NSAIDs, antivirals, or supportive care only, and why?
  5. What side effects or risks should I watch for with the medications you are considering?
  6. How will we monitor whether treatment is helping over the next few days or weeks?
  7. What is my horse's likely prognosis for comfort, turnout, and future athletic work?
  8. At what point would you consider this an emergency or discuss humane euthanasia?

How to Prevent Equine Multinodular Pulmonary Fibrosis in Horses

There is no proven way to fully prevent EMPF at this time. Because the disease is strongly associated with EHV-5 and the exact disease process is still being studied, prevention is less straightforward than it is for common contagious respiratory infections.

Good general respiratory management still matters. Reducing dust exposure, improving barn ventilation, avoiding moldy hay or bedding, and addressing cough or exercise intolerance early may help support lung health overall. These steps do not specifically prevent EMPF, but they can reduce other airway stressors that make respiratory disease harder on the horse.

Routine biosecurity is also sensible, especially when horses travel or mix with new groups. However, it is important to know that currently available equine herpesvirus vaccines target EHV-1 and EHV-4, not EHV-5. That means standard herpesvirus vaccination is still valuable for overall herd health, but it is not a known prevention tool for EMPF.

The most practical prevention strategy is early recognition. If your horse develops unexplained weight loss, fever, cough, or increased breathing effort, involve your vet sooner rather than later. Earlier workup may give your horse more treatment options before lung scarring becomes extensive.

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