Rhodococcus equi and Rattles in the Young Horse

Oct 16, 2011
Chris Thomas

Foals' Health Should be Individually Assessed - C. Thomas

Commonly termed rattles, this respiratory disease is caused by Rhodococcus equi bacteria that live in the soil.

Foals from 2 – 6 months of age tend to be the most susceptible to acquiring this respiratory disease. At this young age, the protection that was acquired through antibodies in their dam’s colostrum is diminishing, and young horses haven’t yet established a very effective immune system of their own, making them quite susceptible to opportunistic bacteria.

These bacteria inhabit soil and manure. When the ground becomes dusty, the bacteria are able to be transported in the dust. This tends to occur in warmer months of the year, when the ground dries out. It is the inhalation of the dust and the bacteria that result in foals introducing the potential for disease into their fragile systems.

Signs of Rattles

Not all foals will display obvious signs of having this problem. Indications can include a raised temperature, depressed foal, loss of condition and a cough. Once at the state of coughing, the foal may have had the condition for a while.

Diagnosis of rattles involves scanning the foal’s lungs to determine if there is any sign of abscessing. The bacteria live protected within these abscesses, greatly diminishing the foal’s breathing capabilities. Foals with this condition may have a rattling sound when they breathe, hence the term ‘rattles’.

Managing the Causes of Rattles

It is important to consider limiting the amount of dust on properties, especially around young horses. The transport of any young horses should be done at a moderate walk if carried out on laneways that are known to be dusty. Alongside this, staff should be discouraged from tearing about on ATVs (four wheeler bikes), especially past mare and foal paddocks.

There are other factors that can also lead to a reduction of the foal’s normal defence mechanisms. Horse owners should work to avoid environmental stressors such as:

poor nutrition
overcrowding of horses – groups of up to 6 mares and foals should be ok in sufficiently sized paddocks
weaning at a young age or when foals are already compromised with regards to health status
unnecessary transport of young horses.

It is important with any foal that appears not quite right, to get a vet out for a diagnosis. Antibiotics erythromycin and rifampin are commonly administered orally to foals a couple of times a day, after a vet has assessed the foal and diagnosed rattles as the culprit.

These antibiotics over other more general forms, have been recognised to have a success rate in excess of 80% due to their ability to penetrate deep within the foal’s lungs to where the bacteria are encysted. Prompt recognition along with treatment will help to determine the best possible outcome for the foal’s health and wellbeing.