Pneumonia is an infection of the lungs that causes respiratory dysfunction which leads to oxygen deficiency. While not the main cause of pneumonia in foals, Rhodococcus equi (R. equi) is a bacterial infection that is the most serious type of pneumonia in foals aged 1 to 6 months. This type of pneumonia leads to significant economic loss due to cost of treatment, prevention and potential death of the foal. Understanding its causes, presentation and preventive measures is crucial for effective management

R. equi is a gram-positive bacterium commonly found in soil, especially in environments with high concentrations of horse manure. Foals primarily become infected through inhalation of dust particles. Once inhaled, the bacteria create an infection in the lungs leading to pulmonary abscess formation. Foals are particularly susceptible in the first week of life due to their immature immune systems.

The disease tends to advance gradually, making it difficult to detect early until the lung lesions become significantly extensive. Most foals are lethargic, have a fever and display increased respiration rates. In some cases, owners may notice a cough or nasal discharge or hear crackles and wheezes while breathing. In severe cases, the foal may have diarrhea, swollen joints, abdominal abscesses and a poorer prognosis. Although rare, Rhodococcus equi infections can cause abscesses in bone which can lead to vertebral fracture and spinal compression.

A combination of antibiotics has been shown to be more effective in reducing the infection. Treatment duration typically ranges from four to 12 weeks, depending on disease severity and response. Nonsteroidal anti-inflammatories (NSAIDs) can be used to reduce fever. Intravenous fluids and intranasal flushes may help the foal expel extra secretions, and in severe cases, oxygen may be prescribed when foals have severe respiratory difficulty. Maintaining a clean, cool, well-ventilated environment with adequate hydration and nutrition are vital to the recovery process.

With prompt and appropriate treatment, the survival rate for foals with R. equi pneumonia ranges from 60% to 90%. However, foals with extrapulmonary complications or those receiving delayed or inappropriate treatment have a significantly higher death rate, approaching 80%.

Owners should focus on preventive strategies to minimize exposure and enhance early detection. Reducing dust levels and overcrowding, while maintaining clean dry stalls can reduce the chance of infection. Plasma can be administered to foals within the first few days of life to provide additional immunity on farms with known Rhodococcus issues. Foals with pneumonia should be quarantined and their stall waste composted.

If you are concerned about the potential of pneumonia on your farm, work with your veterinarian to create an early detection program. While there is no vaccine available to prevent infection, maintaining a clean environment, utilizing pasture rotation and limiting herd size can help reduce the potential spread of infection.

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