The Threat of Rhodococcus equi

Rhodococcus equi (R.equi) poses a significant threat to young foals, ofen leading to pneumonia [1], [2], [3]. This bacterium thrives in soil and horse feces, creating a contaminated habitat, especially on densely populated breeding farms. The aerosolization of the bacterium, influenced by wind, dry conditions, and soil disturbances, allows foals to inhale it, leading to potential infection.

Virulent vs. Avirulent Forms

It is crucial to distinguish between the two forms of R. equi. The avirulent form is generally harmless to foals, while the virulent form is disease-causing.The virulent form contains a plasmid, a specific genetic element, wiht a gene that codes for a protein called VapA, or virulence-associated protein.

The Role of VapA

According to Noah cohen, VMD, MPH, PhD, Dipl. ACVIM, professor of equine internal medicine at Texas A&M University’s College of Veterinary Medicine & Biomedical Sciences, The VapA protein enables R. equi to replicate inside immune cells in the lungs of foals, alveolar macrophages, leading to abscesses forming in the lung. This disease process is similar to what happens in tuberculosis,where the bacterium known as Mycobacterium tuberculosis is able to replicate in alveolar macrophages of humans to cause pneumonia.

FAQ: Rhodococcus equi in Foals

• What is Rhodococcus equi? It is a bacterium that can cause pneumonia in foals.
• Where is it found? It lives in the soil and horse feces.
• How do foals get infected? By inhaling the aerosolized bacterium.
• What are the signs of infection? Fever, lethargy, and coughing.
• Why is it a concern? It can lead to high mortality rates and costly treatments [1].