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  • Writer's pictureSarah L Rhoades, DVM

Pigeon Fever in St Louis - It's Baaaaaaaaaaack!

If you live in the St Louis area, you may have heard of a little (big really) disease called Pigeon Fever, or perhaps you are very lucky and haven't - but you should know and be on the look out for it, it is that time of year again.

***WARNING AHEAD - there are some graphic photographs and video ahead!***

While Pigeon Fever use to occur sporadically in this area, it really wasn’t very common. That is, up until last year. In most parts of the country, Pigeon Fever actually does typically present sporadically during the peak of insect season in the late summer and early fall.

Last year, however, things changed, and probably, forever. In the St Louis area, Pigeon Fever found itself a nice population of horses whose immune systems were pretty naive and had never been really exposed to the disease. Last year was a MESS! Instead of sporadically popping up here and there, Pigeon Fever could be diagnosed in multiple horses, on the same farm, at the same time. I take that back, it wasn’t a mess, it was a nightmare - one that was very frustrating for everyone involved.

Pigeon Fever, actually isn’t caused by pigeons at all - PLEASE, do not start pigeon eradication measures around your barn property for this reason! (Now fly control measures on the other hand…)

It is caused by a specific bacterium, Corynebacterium Pseudotuberculosis. The disease name comes from its classical, textbook presentation, where horses develop abscesses and significant swelling of their pectoral musculature – this makes the horse’s chest resemble the keel of a pigeon (see the video above). And occasionally, but not always, you’ll see a fever too.

Believe it or not, Pigeon Fever is NOT contagious between horses - It’s actually spread by flies, that pick the bacteria up from the dirt and contaminate bites, wounds and similar breaks in the skin.

The problem is once the bacteria has found its way on a premise, it’s usually there to stay. C. pseudotuberculosis is a very tough bug, that survives for a long time, and particularly well in manure contaminated soil... like pastures and dry lots for example. Worse, the flies really like those abscesses and that yummy drainage, which has a very large amount of C. pseudotuberculosis contamination. So the flies pick up the C. pseudotuberculosis, spread it around and get even more of bacteria scattered about on the property and, eventually, into bites and open wounds on other, healthy, horses that can then become infected and develop the disease which drains and starts the cycle anew.

So, although it’s not contagious directly between horses, the purulent material should be treated as infectious waste – as much as possible, horses with draining abscesses should be placed in a situation where the drainage can be cleaned and disinfected, like rubber mats and concrete floors. You want to try and isolate the drainage, although not necessarily the infected horse itself.

Bleach and other common disinfectants are deactivated by organic material. So, you can imagine a dry lot or a stall with a dirt floor, wood stall and barn walls, would all make post treatment disinfection basically impossible. Believe me, the fact that I probably just described and included every single barn and stalling situation in the St Louis area does not actually escape me - I did say, the disease is incredibly frustrating... Limiting the area where drainage and treatment clean up occur is the goal in those cases.

What I am getting at, is although I just got done saying the disease isn’t actually contagious, you’re basically going to have to treat it like it is. Fly control, as you have probably already realized, is also incredibly important here, and maybe the single most effective thing you can do to limit its spread in addition to containing purulent discharge. Meticulous wound care is also something you really need to consider during the insect season.

The disease Pigeon Fever usually occurs in one of three forms.

An abscess caused by Corneybacterium pseudotuberculosis, commonly referred to as Pigeon Fever. Affected horses will classically develop abscesses on the chest and ventrum.
An abscess caused by Corneybacterium pseudotuberculosis, commonly referred to as Pigeon Fever. Affected horses will classically develop abscesses on the chest and ventrum.

The first is the classical presentation, external abscesses, usually appearing on the chest and ventrum (belly) and even the sheath. But... they could appear anywhere, as I found out so haphazardly, last year - as another example of something that really never follows the textbook (like… Potomac Horse Fever, but I digress, that’s another story for another day). They can also develop quite deep within the horse's musculature - sometimes taking weeks to come to a head. Antibiotic therapy can be a double edged sword in these cases, they may slow the growth of deep abscesses, therefore prolonging the course of disease or, if caught especially early, prevent them from developing at all - all of course assuming the specific strain involved is susceptible to commonly used antibiotics. There is great debate on their use and I cannot stress the importance of getting a veterinarian involved in the management of the disease.

Along the same lines, you can also get internal abscesses. As you might imagine, an abscess on one of your internal organs might pose a significant (life threatening) problem. Thankfully, these aren’t super common, albeit most certainly on my mind when I treat and diagnose these cases. This cases usually require aggressive antibiotic therapy and often require more in depth diagnostics to identify.

Finally, Pigeon Fever can also appear in a form called ulcerative lymphangitis. What this is describing is an infection, that occurs in the horses lymphatic drainage system. It will specifically develop in areas that have a tendency to drain less well, like the lower limbs, particularly the hind limbs - you may see swelling, lameness, and deep ulceration of the tissue. Important support structures of the limb can become involved, or destroyed in this form of the disease. Equally as bad, these cases can be refractory to treatment - basically, they can pretend to be treated, then re-occur, again and again, sometimes months later - it goes without saying these cases can be very frustrating to deal with for everyone involved. Antibiotic use can be long term to try and treat these cases, and again, microbial antibiotic sensitivity testing can make or break the outcome.

So, be vigilant, and be on the look-out.

Please bear in mind, I cannot give out medical advice without an examination and a veterinary-client-patient relationship. But, if you have any questions or need advice, I’m happy to set up and appointment to look at your horse(s) and get you on the right track - you can reach me at 573-484-6950.

Please also be aware that the views expressed here are one veterinarian’s opinion and that medical diagnosis, treatment, and advice should be obtained through a good veterinary-client-patient relationship. Absolutely, nothing here is meant to take the place of medical advice and treatment recommendations obtained from a licensed, veterinary professional.

If you are interested in learning more, here is a quick article from the American Association of Equine Practitioners (AAEP):

And this is a fantastic PDF provided through AAEP: AAEP PDF

Finally, here are a few articles I found to have decent, general information:

Sarah L Rhoades DVM, is a graduate of the University of Missouri - College of Veterinary Medicine. She has practiced general equine medicine in the St Louis area for the last 6 years and has also performed regulatory racetrack work and is licensed to work in Missouri and Illinois and is located west of St Louis in Franklin County, Missouri. Sarah enjoys riding barrel horses and ranch western performance.

Be aware that the views expressed here are one veterinarian’s opinion and that medical diagnosis, treatment, and advice should be obtained through a good veterinary-client-patient relationship.

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