‘TIS THE SEASON FOR PIGEON FEVER!

For a long time now, Pigeon Fever has been a ‘California Disease’.

But, that simply isn’t true.  It is everywhere… just not very prevalent like it has been in California.  So, I wanted to tell you about it in case Pigeon Fever comes your way and your vet doesn’t know the symptoms to recognize it.  (I’m not saying your vet is ignorant. I’m just saying that if a disease is unexpected, the mind doesn’t always go there when diagnosing.)

THE NAME PIGEON FEVER

This disease has nothing to do with pigeons so don’t go shooting them or anything like that.  The name came from how the fever appears when it affects a horse in the most common way – through a chest abscess.  Because a horse’s chest will balloon to accommodate a pectoral abscess (the most common area), the chest looks like a pigeon’s chest and hence the name.

WHAT IS PIGEON FEVER?

Pigeon fever is caused by Corynebacterium pseudotuberculosis, which lives in dirt, and is worldwide.  It can effect any horse especially young adult animals but rarely in foals.  It is suggested that a suppressed immune system makes the horse more susceptible.  Foals seem to be protected by mother’s milk colostrum.

SEASON AND CONDITIONS

Flies are the known transmitters.  Fly bites in open wounds or scrapes infect the horse.  So, the highest season for Pigeon Fever is when there are the most flies – at the end of a dry, hot summer.  Usually the peak season is October and early November.

If the pre-season has been especially wet – which helps breed flies – Pigeon Fever is worse.

Of course, a horse with an open wound can just roll in the dirt and contract the disease… but flies seem to be the indicator.

ALSO KNOWN AS…

Pigeon fever is also called:  Pigeon fever, pigeon breast, breastbone fever, dryland distemper, dryland strangles, false strangles and false distemper.

THREE TYPES OF PIGEON FEVER

Although all three types of fever show as abscesses, they vary in severity and care.

1)  The most common type of Pigeon Fever is an external abscess.  Usually, this will appear in the pectoral muscle.  However, pigeon fever can appear anywhere on the body.  Sheath, hip, leg, neck, chin…  Generally, the horse will run a fever, be lethargic, lose interest in food and feel lousy. Usually, a culture will show the infection which will collaborate why there is a big bump.  (Also, a culture will rule out Strangles…)

The external pigeon fever is the easiest on the horse and owner although sometimes gruesome.  The horse’s immune system will encapsulate the bacteria and form an abscess.  Eventually, it will break and drain.  Since an abscess has much pressure and can be very painful for the horse, some owners put hot compresses on the area to bring it to a head faster.  Or, a vet can come out and lance it.  If necessary, the vet can use ultrasound to guide the incision.

Once the abscess has drained, the horse generally feels much better and will heal in a few weeks.  It is best to keep the horse free of flies and to put a topical on the draining wound to keep it free of infection.

If a horse has had pigeon fever, one should keep an eye on him during the season to see if another abscess appears.  This is common.  However, once the horse makes it through the season, they generally never contract it again.  Antibodies.

2)  Internal abscesses

This is bad and can be fatal.  If your horse is off and exhibiting signs of fever and not getting better, it is best to do an ultrasound to see if the poor animal has an organ abscess.  The most common sites for these abscesses to develop are in the liver, spleen, kidneys, and lungs.  About half of the cases with internal abscesses currently have, or have recently had, an external abscess.  Others have no history of having an external
abscess, but have recently been exposed to another horse that has.

It can be difficult to diagnose an internal organ abscess.  I am cutting and pasting this from Dr. Molly Dinucci, DVM:

“We often draw a blood sample for blood
cell and chemistry analysis and submit another sample for a Corynebacterium pseudotuberculosis
antibody titre. Horses with internal abscesses typically have
inflammatory bloodwork, with elevated white blood cells and
fibrinogen. Their blood chemistry also commonly shows an elevation in
globulins in addition to other various serum chemistry abnormalities.”

The treatment for internal pigeon fever is certain antibiotics.  If a horse is not treated for internal Pigeon fever, it is 100% fatal.  If it is treated, there is a good chance of survival if caught in the early stages.

I’m guessing this is very painful for the horse.

3)  Ulcerative lymphangitis

Ulcerative lymphangitis is several small abscesses above the fetlock.  Generally this only effects one leg at a time.  This is very painful and can be fatal.  Luckily, there are very few cases in the US.  However, worldwide, this is the most common form of the disease.

It is also treated with antibiotics and anti-inflammatories.  If caught early, this clears up within 2 months.

VERY CONTAGIOUS

Pigeon Fever is very contagious.  Isolate any horse with this infection and make sure you clean your feet, buckets, towels, stall, shavings, tack or whatever has come in contact with the wounds.  Humans can spread the disease to other horses via transmitting the bacteria on the soles of their shoes or on their hands.

DO OTHER ANIMALS CARRY THIS?

The only strain that can effect a horse is the same one which effects cows.  The strain in goat or sheep do not transfer to horses.

CONTROVERSY

There is argument over the use of antibiotics for external pigeon fever as it inhibits the growth of the abscess.  For internal abscesses, the vets usually recommend penicillin.

I hope you never need this information but it is good to have!

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