What is Rhodococcus (R Equi)?

R Equi is an intracellular pathogen that is found in the soil on most farms. The VapA gene present in the bacteria causes disease seen in foals from one to five months of age. The risk of infection is much higher on larger farms with a large amount of movement. The condition can be transmitted via inhalation or infected foals manure will also carry the disease. Some foals will have the disease without any symptoms, others can become very sick and require veterinary intervention.

What are the main symptoms?

Signs of respiratory disease are often only detected when infection levels are peaking. Pneumonia is the most common sign, foals will have an increased breathing rate and be dull in appearance. They will often have a temperature. As vets, we will detect a change in the lung noise when we listen to their chest.

Other symptoms which are a lot rarer include, swelling of joints and lameness. This can occur alongside or in absence of respiratory signs.

How do we diagnose this disease?

A definitive diagnosis is obtained by sending off a sample of fluid from the foals trachea. This can be a stressful procedure so it will be at the vet’s discretion. The VapA gene is detected in this sample if rhodococcus is present. Alongside this, the lungs can be visualised using x-ray or ultrasound. Abscesses are detected and can be measured to decide on the severity of disease, this can also act as a screening process.

How is it treated?

Antibiotics are given for a long period of time. This gives them time to penetrate the abscesses that are present and cause a resolution in clinical signs. A macrolide alongside rifampin will be the preferred combination when large abscesses are present. Treatment times range from 2-12 weeks with an average of 4-6 weeks being most common. Tracheal fluid samples will be cultured to ensure there is no resistance to the antibiotics being used. In some respiratory cases oxygen or nebulisation treatments may be required. If the joints are affected alternative antibiotics may be required.

Prevention

There are no current vaccinations available against this condition. Some larger farms will chose to ultrasound chests at specific intervals to detect disease early, this can however be very costly.

Administering hyperimmune plasma at birth can also decrease the severity of disease but will not completely prevent it.

Prognosis

Most cases of foals with Rhodococcus Equi do make a good recovery, however those with abdominal abscesses do have a poorer prognosis.