The survival rates for horses diagnosed with pneumonia look reassuring on paper: In a cohort of adult horses with confirmed bacterial pneumonia treated at North Carolina State University, 73% survived to discharge. However, survival is only the first hurdle, and not a guarantee that the horse will return to its previous level of work, said Katie Sheats, DVM, PhD, DACVIM, PGCHE, associate professor of Equine Primary Care at NC State.
“The athletic question is what the recovered lung can support at maximal effort—after pain, inflammation, and deconditioning are accounted for,” she noted.
Sheats delivered a presentation on the athletic impacts of pneumonia during the 2026 Equine Sports Medicine Symposium. Here are the key takeaways.
Pneumonia’s Physiologic Toll
Discharge from the hospital doesn’t mean a rapid return to the show ring or the track. In the literature, adult horses that return to racing or sport after bacterial pneumonia range from 61-78%. Sheats said factors that lower a horse’s return to performance include “severe lesion phenotype, physiologic severity, complications experienced, prior performance levels, and how much training time has been lost.”
She emphasized that these ranges vary based on the individual horse. A horse might recover easily from pneumonia and still come back short of its prior athletic ability. This is because pneumonia can be detrimental to a horse’s athletic performance through several mechanisms that negatively impact the lungs:
- Airway + alveolar exudate. Fluid and inflammatory material build up in the airways and alveoli, resulting in less space for air in the lung.
- Consolidation + V/Q mismatch. Mucus and inflammatory cells prevent air from reaching alveoli, which are the tiny sacs where air exchange with blood occurs. This can cause hypoxemia (low blood oxygen) at rest or during exertion.
- Pleural pain + restriction. Pleural (lung surface) inflammation is painful, and horses with pleural pain don’t breathe as deeply.
- Inflammation + inactivity. The broader inflammatory response and forced rest lead to deconditioning and delayed return to training.
Factors That Affect Performance Outcomes
Sheats reviewed several studies showing a wide range of survival and return to performance estimates in horses. Given this variability in the literature, she looked for other factors within cases that can help predict a horse’s athletic ceiling post-pneumonia, including:
- Severe lesion phenotype, such as fibrin, loculation (pockets of fluid), septic pleuritis, and persistent fluid.
- Severe physiology, such as evidence of respiratory distress, tachycardia, hypoxemia, and organ dysfunction.
- In foals, disease outside the lung (extrapulmonary) as well as inside.
- Parenchymal destruction, such as abscesses and bronchopleural fistula, which leads to lung scarring.
- Suboptimal treatment, including delayed diagnosis, inadequate duration, or resistant infection.
- Deconditioning, which Sheats said is particularly important. “How long the horse is out of work, muscle loss, prolonged inactivity may affect how well they come back to performance,” she noted.
“In order to optimize return to athletic performance, we need to focus on what we can modify when treating pneumonia in horses. Those things are timely recognition, early source control, culture-guided treatment, careful monitoring, and protected reconditioning,” she added.
Return to Sport Protocol
Sheats emphasized that there is no validated equine return to sport protocol after pneumonia, and a fixed calendar approach is unlikely to be effective. Rather, she said, the decision to return to performance should integrate clinical resolution of disease, systemic inflammation, structural trajectory, functional reserve, and demands of the intended sport:
- Clinically, the horse should be afebrile and free of cough, dyspnea, or pain.
- Systemically, CBC and serum amyloid A or fibrinogen should be stable or normalizing.
- Structurally, clinically important pleural fluid and fibrin should be resolved, and lung lesions should be improving.
- Functionally, resting, breathing, and oxygenation should be normal.
- The cause should be controlled, treatment completed, and a recheck and escalation plan should be established outlining what will be evaluated as the horse returns to work.
“A practical approach to reconditioning should progress from base activity to aerobic work, then discipline-specific work, and finally, the highest level of performance,” said Sheats.
For example, she said, start with turnout and walking to restore mobility, appetite, and routine. Then add trotting with low-intensity aerobic work while monitoring respiratory recovery. Next, introduce canter and discipline-specific tasks, increasing duration before intensity. Fast work, hills, jumping, or intervals should come only after the horse tolerates the earlier phases.
“There isn’t a set amount of time for each of these phases, because that probably needs to be toggled and adjusted to reflect the initial severity of disease, pleural complications, the amount of training lost, and the discipline,” Sheats said. “Things that could be reasonably monitored at every phase could include temperature, looking for evidence of cough or breathing effort, respiratory recovery, appetite, and just how the horse seems to be handling the increasing workload.”
As the horse progresses through these phases, any backward change is a reason to pause and reassess, she added.
Take-Home Messages
Sheats closed with the following advice for practitioners managing bacterial pneumonia cases in performance horses:
- Fever is an insensitive screen; athletic change, risk history, and breathing pattern deserve attention.
- Ultrasound maps the pleural surface, while radiographs and airway/pleural sampling complete the diagnosis.
- Start appropriate broad therapy in sick horses, then narrow with microbiology and serial response.
- Survival is not performance; complications, lesion burden, and deconditioning shape the athletic ceiling.
- Foal prognosis is generally encouraging after uncomplicated recovery, but racing outcomes vary by cohort and endpoint.
The throughline of her talk was that survival statistics can answer one question, but athletic outcome depends on lesion severity, complications, and how much conditioning the horse lost—factors that must be evaluated case by case.
Related Reading
- Daily Vet Life: A Donkey With Severe Respiratory Disease
- Dysphagia in Hospitalized Horses: Prevalence, Management, and Prognosis
- Diagnosing Respiratory Ailments in Horses: Wash or Lavage?
Stay in the know! Sign up for EquiManagement’s FREE weekly newsletters to get the latest equine research, disease alerts, and vet practice updates delivered straight to your inbox.
