Pulmonary Emphysema, Edema, and Interstitial Pneumonia in Cattle
- See your vet immediately. This condition can cause sudden, severe breathing distress and sometimes sudden death in adult cattle.
- It is often called fog fever, acute bovine pulmonary emphysema and edema, or atypical interstitial pneumonia.
- Classic cases often appear 5-10 days after adult cattle move onto lush, rapidly growing pasture, especially in the fall.
- Affected cattle may breathe fast, stand with the neck extended, breathe with the mouth open, grunt on exhalation, drool, and worsen with even mild handling.
- There is no reliably effective treatment once severe signs start, so early veterinary guidance, low-stress handling, and herd-level prevention matter most.
What Is Pulmonary Emphysema, Edema, and Interstitial Pneumonia in Cattle?
Pulmonary emphysema, edema, and interstitial pneumonia in cattle is a serious lung disorder that causes sudden breathing difficulty. Your vet may also call it fog fever, acute bovine pulmonary emphysema and edema (ABPEE), or atypical interstitial pneumonia (AIP). In classic pasture-associated cases, the lungs become inflamed and damaged, with fluid buildup, trapped air in lung tissues, and poor oxygen exchange.
This problem is most often seen in adult cattle on pasture, especially after a recent move to lush forage. Many cattle in a group may be mildly affected, while a smaller number develop life-threatening distress. Nursing calves are usually not affected in the classic pasture form.
The condition can look dramatic. A cow may seem normal one day and be in severe respiratory distress within hours. Because cattle with this disease often have very little breathing reserve, even walking them, loading them, or forcing them through a chute can make things worse. That is why rapid veterinary input and calm, low-stress handling are so important.
Symptoms of Pulmonary Emphysema, Edema, and Interstitial Pneumonia in Cattle
- Rapid breathing
- Labored breathing or obvious respiratory distress
- Open-mouth breathing
- Expiratory grunt
- Drooling or tongue extension
- Subdued behavior with reduced grazing
- Minimal or absent cough
- Sudden death, especially after exertion
- Subcutaneous emphysema along the back or withers
See your vet immediately if a cow has open-mouth breathing, marked effort to breathe, grunting, drooling, blue or gray mucous membranes, collapse, or sudden worsening after being moved. Mild cases can be easy to miss at first, but this condition can progress fast. Keep affected cattle quiet, avoid unnecessary handling, and contact your vet before moving them if possible.
What Causes Pulmonary Emphysema, Edema, and Interstitial Pneumonia in Cattle?
In the classic pasture-associated form, this condition is linked to a recent move from dry feed or poorer pasture onto lush, rapidly growing forage. The key problem is not an infection in the usual sense. Instead, rumen microbes convert the amino acid L-tryptophan from lush plants into 3-methylindole, a compound that becomes toxic to lung tissue after it is absorbed and metabolized. The result is sudden lung injury, fluid leakage, and air trapping in the lung tissues.
Outbreaks are most often reported in adult beef cows, but dairy cattle and other adult cattle under similar management can also be affected. Cases usually appear 5-10 days after the pasture change and are uncommon once cattle have been on the same field for more than about 3 weeks. Fall pasture changes are classic, but similar problems can occur whenever forage conditions favor high-risk intake.
The broader term interstitial pneumonia can also describe a lung lesion pattern caused by other problems, including some toxins, severe viral disease, moldy sweet potato toxicosis, lungworm-associated reactions, and feedlot AIP syndromes. That is one reason your vet will look closely at the herd history, age group, season, feed or pasture changes, and any recent disease events before deciding what is most likely.
How Is Pulmonary Emphysema, Edema, and Interstitial Pneumonia in Cattle Diagnosed?
Your vet usually starts with the history and the pattern in the herd. A recent move to lush pasture, sudden onset of breathing distress in adult cattle, and multiple animals showing signs in the same group are strong clues. On exam, your vet may hear surprisingly quiet lung sounds early on, then harsher sounds or crackles later. Because affected cattle can decompensate with stress, the exam is often done as calmly and efficiently as possible.
Diagnosis is often presumptive in live cattle, based on signalment, management history, and clinical signs. Your vet may also consider other causes of respiratory distress, such as bacterial pneumonia, bovine respiratory syncytial virus, aspiration, toxic exposure, lungworm, or severe allergic-type airway disease. In some herds, response pattern, age distribution, and timing after pasture turnout help narrow the list.
If a cow dies or is euthanized, necropsy can be very helpful. Typical findings include lungs that are heavy and fail to collapse normally, with edema and interstitial emphysema. Histopathology may confirm the characteristic lung injury pattern. In herd outbreaks, postmortem testing on one animal can guide decisions for the rest of the group.
Treatment Options for Pulmonary Emphysema, Edema, and Interstitial Pneumonia in Cattle
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Urgent farm call or teleconsult guidance with your vet
- Low-stress observation in the field or a nearby quiet pen
- Avoiding driving, crowding, chute work, or transport unless your vet advises it
- Supportive nursing care such as easy access to water, shade, and feed
- Herd-level management changes, including removing unaffected cattle from future high-risk pasture exposure when advised
- Discussion of realistic prognosis and humane euthanasia if breathing distress is extreme
Recommended Standard Treatment
- Full veterinary exam and herd history review
- Careful triage to separate mild cases from cattle in crisis
- Judicious use of anti-inflammatory medication or other supportive drugs if your vet believes they may help in that specific case
- Treatment of concurrent problems when indicated, such as secondary bacterial pneumonia on your vet's assessment
- Written herd plan for pasture transition, feeding hay before turnout, and gradual exposure to suspect pasture
- Discussion of preventive ionophore programs such as monensin or lasalocid before future pasture risk periods, when appropriate and label-compliant
Advanced / Critical Care
- Referral or intensive on-farm critical care when available
- Repeated veterinary monitoring and reassessment
- Oxygen supplementation if logistics allow
- Ultrasound, blood gas evaluation, or additional diagnostics in selected high-value animals
- Aggressive supportive care for valuable breeding stock or diagnostically unclear cases
- Humane euthanasia planning if distress remains severe despite care
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Pulmonary Emphysema, Edema, and Interstitial Pneumonia in Cattle
Bring these questions to your vet appointment to get the most out of your visit.
- Does this look most consistent with fog fever/ABPEE, or are you more concerned about another cause of interstitial pneumonia?
- Is it safer to leave this cow where she is, or should we move her to a quiet pen?
- Which signs mean this animal is in immediate danger and may need euthanasia for welfare reasons?
- Are any medications likely to help in this case, and what are the expected tradeoffs?
- Should we necropsy a dead animal to confirm the diagnosis and guide herd decisions?
- What pasture or feeding change likely triggered this outbreak in our herd?
- How should we transition cattle onto risky pasture more safely next time?
- Would a preventive ionophore program such as monensin or lasalocid fit this herd, and what are the label and withdrawal considerations?
How to Prevent Pulmonary Emphysema, Edema, and Interstitial Pneumonia in Cattle
Prevention focuses on pasture management and gradual adaptation. High-risk situations often involve turning adult cattle onto lush, rapidly growing pasture after a period on dry forage or poorer grazing. Practical steps include feeding hay before turnout, limiting initial grazing time, and increasing exposure gradually over several days instead of making an abrupt full-time switch.
Other herd strategies may include using suspect pasture before it becomes very lush, delaying use until after a hard frost when appropriate for your region, strip grazing, or first grazing with less susceptible stock such as younger cattle. Once cattle have already been exposed to the offending pasture, moving them may not stop new cases from appearing, so prevention works best before the transition.
Your vet may also discuss preventive ionophore use, such as monensin or lasalocid, in herds with a known history of this problem. These products are used before exposure to reduce formation of the lung-damaging metabolite in the rumen, but they are not helpful after clinical signs begin. Because feed medication rules, label directions, and herd circumstances vary, build the plan with your vet before the risk season starts.