Foal Pneumonia
New
Research brings hope to preventing this
potentially fatal disease.
Story
& Photos by Tracy Williams
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| January
1 ushers in the foaling season for much of the breeding world,
signaling hours of preparation and sleep deprivation to bring
forth new, healthy lives. Breeders know all too well the myriad
of factors that can go awry during and after a foal’s
birth: malpresentation, failure of passive transfer and sickness,
to name just a few. Foals are fragile creatures, prone to disease
and accident from before they take their first breaths, but
according to the latest research, breeders may one day have
one less potential problem to fear. Researchers at Texas A&M
University have discovered that gallium, a rare metal, may be
instrumental in preventing the devastating foal pneumonia as
caused by Rhodococcus equi bacteria. |
The
Disease
Rhodococcus equi is a bacterium that lives and thrives in
horse farm soil, feeding off nutrients in manure. It exponentially
multiplies in the warm, dry days of late spring and summer,
coinciding with the window where foals are most susceptible
to disease – 1 to 6 months of age. Although foals receive
passive immunity from ingestion of colostrum at birth, this
immunity eventually begins to taper off, leaving the foal’s
still immature immune system open to attack. In addition,
during this window, many farms are housing large mare and
foal bands in outdoor paddocks, where it becomes easy for
one foal to spread the disease to the entire band. While the
disease doesn’t appear to be directly contagious, foals
can infect others by passing R.equi bacteria in their manure,
which is inhaled with dust particles by their pasture mates
who are already suffering from a compromised ability to fight
infection. In the busy foaling season, signs of the early
onset of this disease may slip by unnoticed until many foals
are affected.
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Foals often appear perfectly normal until the disease is
well-established and difficult to treat. |
Signs,
Symptoms and Diagnosis
Foal pneumonia can be a sudden attack or chronic and progressive
condition, but most often sick foals appear perfectly normal
until the disease is well-established and much more difficult
to treat. Early detection, however difficult, is critical.
The clinical signs include fever, lethargy, coughing, abnormal
breathing, increased pulse, watery eyes, diarrhea and nasal
discharge. Daily physical exams of foals and history of the
disease on the farm in question are the best starting point
of diagnosis. Potentially infected foals can be given blood
tests to detect infection and X-rays and ultrasounds to uncover
lung abscesses. Fibrinogen levels can be taken to test for
inflammation and antibody tests may also indicate illness.
Autopsies of foals usually reveal lung lesions – a hallmark
of the disease – as well as lesions of the intestines,
lymph glands and liver. Many breeders advocate taking foals’
temperatures daily; an elevated temperature may unmask sick
foals who are masquerading as healthy.
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Treatment
Treating R.equi pneumonia is both costly and time-consuming,
and early detection is critical to its success. Weeks of antibiotic
therapy are required, and anti-inflammatories and intravenous
fluids are often necessary as well. Add in diagnostic tests,
veterinary exams, possible hospitalization, and secondary complications,
and you have an expensive undertaking. Even with successful
treatment, some foals may sustain permanent lung damage, which
could jeopardize an athletic career. However, not all foals
are severely affected; some may protract a minor infection.
The severity depends on the strength of the bacteria strain
pitted against the strength of the foal’s immunity. |
Foals receive disease immunity from drinking their dam's first
milk, or colostrum, but this immunity eventually begins to wane,
leaving them susceptible to infection. |
Prevention
While there is no vaccine for R.equi, there are ways to guard
against the disease.
1. Hyperimmune Plasma
Plasma is taken from adult donor horses that have been given
killed R.equi bacteria and developed antibodies against them.
The plasma can be given to foals at birth and has shown great
success in warding off an R.equi infection.
2. Management
Since R.equi infections stem from inhalation of bacteria-infested
dust, try to house mares and foals in areas that are as well-ventilated
and dust-free as possible, and avoid crowding large groups
in small paddocks.
3. Observation
Knowing your foals’ normal behavior will help you quickly
detect abnormal behavior. Carefully observe your foals daily
for signs of illness, and consider taking their temperatures
daily as well. Isolate sick foals and compost manure to prevent
an infection from spreading.
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The
Latest Discovery
Ronald Martens, DVM at Texas A&M University, released a
study in 2006’s Journal of Veterinary Pharmacology and
Therapeutics, documenting gallium’s potential in preventing
an R.equi infection from becoming a full-blown disease. R.equi
organisms, while circulating in the body, pick up iron in the
bloodstream to use in several enzyme systems. Gallium strongly
resembles iron, and R.equi bacteria mistake one for the other
and pick up gallium from the bloodstream instead. However, R.equi
bacteria can’t use gallium in these enzyme systems; therefore,
they can no longer multiply and eventually die off. Given this
information, in this study, Martens gave mice oral doses of
gallium before infecting them with R.equi, and a control group
of mice was given a non-gallium treatment. The mice who received
gallium had significantly lower body wide concentrations of
R.equi bacteria than the control group six days later after
the treatments. Martens believes these encouraging results warrant
further investigation in foals. He hypothesizes that oral administration
of gallium for short periods after birth could protect against
R.equi infection until the foal’s immune system can control
the bacteria on its own. Furthermore, studies have shown that
the required amounts of gallium can be safely given to foals. |
Foals
contract R.equi pneumonia by inhaling contaminated dust, so
if possible, avoid housing mares and foals in crowded, dusty
paddocks. |
Although R.equi pneumonia is a potentially devastating illness,
both to the foal population and financial condition of a breeding
farm, prevention is possible. With management strategies in
tune to the problem and carefully honed observation skills,
breeders can avoid an outbreak while the researchers develop
a consistent method to prevent foal pneumonia.
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Tracy
Williams is a graduate of Colorado State University
with degrees in Equine Science and Journalism. She is
a freelance writer and photographer living in New Mexico.. |
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