Download 13-June - The Horse Gazette

Rhodococcus
By Dr. William Symm
Your foal is now several months old and things have been going great. You are looking forward to halter breaking and
weaning your next champion, but you go out to the pen and he is breathing hard and has a cough! Upon closer examination you
feel his skin and he feels hot. You have been instructed by your veterinarian to take his rectal temperature and he has a 104.5
degree F rectal temperature. Oh no!
Unfortunately this is an all too common problem that we see in our area with foals. Of the many things that can cause a
foal to get sick, pneumonia caused by Rhodococcus equi is one of the most frustrating problems that we see in our practice area.
R. equi is a bacterium found in the environment that is one of the more common causes of bacterial pneumonia in pre-weaning
and weanling aged foals. The exact way in which an individual foal contracts the infection is not entirely understood, as research
into the disease is ongoing. Much of the research is focused on how exactly do individual animals contract the bacteria and then
how do certain individuals ultimately end up getting abscesses and pneumonia?
It seems that there are some regional variations in the disease incidence. It seems from our experience and from the
research that is available that early in life foals are exposed to the bacteria that is aerosolized in the air which leads to infection
later on in life in susceptible individuals. There is not a single diagnostic tool that can be used to diagnose foals prior to them
getting sick. In farms that have a history of the infection it has been recommended that regular veterinary examinations, early
blood work and ultrasound exams be performed to facilitate early detection. Also, in some populations of horses and locations
that have a history of infection prophylactic treatment with hyperimmune plasma has been advocated and seems to help lower
infection rates and severity.
The peculiar thing about R. equi is that it has a unique propensity to cause abscesses, specifically in the lungs. These
foals can seem perfectly normal one day and then the next be near death. This is due to the innate ability of a young animal to
compensate for respiratory deficits caused by severe injury and dysfunction of the lungs caused by the infections.
The R. equi bacteria can also cause abscesses in other locations of the body, such as within the lymph nodes within the
abdomen, joint infections and bone infections. Uncommonly it can also infect older animals. Treatment is often successful, but
requires specific medications and sometimes long-term care and treatment. Also, we often need to run diagnostic blood work,
endoscopically collect and culture the tracheal fluid and do ultrasounds of the lungs to determine the severity of infection. If you
notice your foal coughing, having a runny nose, not eating or just acting depressed, call a veterinarian to schedule an exam.
Although R. equi is common in our area there are many other causes for young pre-weaning to weanling age horses to
get sick. It is important to know that a young horse should be bright, alert, active and eat/nurse regularly. A foal that is several
weeks old should have a resting rectal temperature between 98.5-101.5 degrees F. Keep in mind that foals will often lay out in
the sun and have an elevated temperature momentarily and that their temperature can be elevated briefly by strenuous exercise.
Healthy foals that are within an hour or two of birth may have a seemingly elevated respiratory rate of 70-90 breaths per minute.
Normally though, a foal that is several weeks to a few months old will have a regular resting respiratory rate of less than 30
breaths per minute.
In our experience it is very important to monitor young horses very closely for any signs of illness and communicate
with your veterinarian about any symptoms that might be of concern. Young horses; and foals particularly, tend to rapidly
deteriorate medically if left untreated. If you are ever worried about your foal, call your local veterinarian.
You can contact Retama Equine Hospital at 210-651-6385 or visit www.retamaequinehospital.com.