PIGEON FEVER: A DISGUSTING TIME CONSUMING DISEASE
When it comes to Pigeon Fever, I wish I had a recorded message on a “900” pay per minute phone number when they were all the rage! Why? Because when we are experiencing an “outbreak,” I find myself on the phone, answering the same questions, trying to find new ways to answer them to avoid sounding robotic. If I had collect the “900” number over all the years Pigeon Fever created all those questions, I might have been able to retire! Not that I want to, or that I don’t enjoy speaking with every horse owner, but you get my drift, this disease is time consuming in so many ways. At any rate, since I lost the “900” opportunity, my loss is your gain: internet freebies. So here we go, let’s answer all those questions.
What is Pigeon Fever? Also called Dry land Distemper, is a disease of abscessation. The causative agent being a bacteria named, Corynebacteria psuedotuberculosis. Which takes way to long say, and even longer to type (and you have to underline it or all the bacteriologist get a little bent), which is probably why we don’t call it that in the field. The name Pigeon Fever was penned because the most common external form of the disease is characterized by a large swelling (in the form of abscessation) of the pectoral muscles, causing the horses chest to blow up, which may have caused some bird vet to declare, “Hey, that looks like a pigeon’s breast.” (Frankly, I see roosters do this way more than pigeons, but Rooster Fever sounds rather lame.)
So, how does this bacteria with the long name get into my horse? Answer: An insect vector. Which, in this case, is a cool way to say it is primarily flies. I am leaving the word “insect” intact just in case further research discovers some other pest a potential culprit. While flies are top on the list, I personally believe, and I have no scientific proof her, that perhaps the bacteria, living in the soil, enters our horses when they lay down. They may have minor cuts, scrapes, even micro abrasions in their skin that the bacteria can use as an entry portal. Both this and the insect, are modes of transmission that can explain why we see this disease externally in the chest, and the ventral abdomen (midline and belly), many times extending from stem to stern, involving the sheath or mammary glands.
AH HA! Sheath or mammary glands leads into a couple of the commonly asked questions. “Will my boy be able to pee?” Answer: Usually, yes. In fact, I will say, that in my experiences, every horse with Pigeon Fever located in the sheath has been able to urinate. He may not be willing to drop his penis to do so. It may not be particularly comfortable to do so, but he will find a way. For the mare, if she’s nursing, we worry about the foal, and if she is not, we do worry about a “scarring” or loss of use of a teat.
So the next logical question is, if it can be in the sheath, where else can it manifest? Answer: Simply, pretty much anywhere, we just tend to see it in certain locations more regularly. The afore mentioned chest and ventral abdomen are the most common, at least the ones I see in my practice. For the external form other common sites are the shoulder, the back, the neck, and the legs. Yes, I have seen abscesses involving the eye, and ear too, but rarely.
All the above information is great, but your horse looks like a balloon, and is miserable. So what should you do, what should you expect, and what about your other horses? How contagious is this disease? Well, first off, let me emphasize that so far this article has been about the EXTERNAL form of Pigeon Fever. The INTERNAL form is a subject for another article. Many of the external forms of Pigeon Fever are self-limiting. That is to say, it runs its course, and is over within a few weeks. Hopefully. Sometimes, the abscess comes to a head on its own, breaks open, drains, and the horse, and you are happy. This is not to say that those few weeks were not filled with angst and annoyance, and even some moments of disgust, but at least it’s over. Sometimes however, the abscess doesn’t break and drain on its own. It may disperse itself over a larger area, allowing the horse’s immune system to vanquish the bacteria on its own. Or, it has just become a bigger, more annoying abscess spread over a larger area. This is when we are looking for that “soft spot’” that we call “coming to a head.” At this point we can lance the abscess and watch the lovely pus and blood come pouring out. Many times, we can use ultrasound to guide us to the area we need to drain, stick it, and use a form of suction to assist the healing/draining.
Antibiotics: Should we use them? Here’s where we are art and science and wives tales and experiences meet at a crossroads. Many of us have heard it said, “If we give antibiotics, it may take the external form internally, just like Strangles (Streptococcus equi)” The scientific veterinary community has proven this false for both Pigeon Fever and Strangles. Now, does that mean I put my Pigeon Fever patients on antibiotics? No, at least not immediately. Antibiotics are a God send, and are appropriate under many circumstances, but they do have other issues that need to be considered: the potential of allowing the organism to build a resistance, the possibility of an antibiotic induced colitis (colon inflammation/diarrhea/colic) are just two. If the horse can rid itself of the bacteria by itself, or with minimal help by me, I’m happy. A caveat here though: The disease can affect the legs of the horse, and if this happens, my concern is that the organism may have infiltrated the lymphatic system. I have rarely seen a horse recover this easily without antibiotics. The antibiotics I like to use are Doxycycaline, Rifampin (if you want to spend the money, I love this one). Fortunately, the bacteria is susceptible to a number of antibiotics; penicillin is great, but after the third injection, your horse would rather have the Pigeon Fever. SMZ/TMP tablets are okay, but not the best for this in my experience, but I will use them. I have seen horses respond to the SMZ/TMP, but I have seen just as many continue to build and blow abscess while on it. How long on antibiotics? I’m hoping for 2-3 weeks, but will go longer if needed, or switch to a different antibiotic if I feel I am not getting enough improvement.
How long is my horse going to suffer with this disease? As I mentioned earlier, a good case last 2-4 weeks, but I have seen some drag on for 3 -4 months, even up to 8 months. Why? I and a few others are beginning to think that perhaps, the individual horse’s constitution, the ability of their immune system to deal with this bacteria may be at play here. (I know what some of you are thinking. What about boosting the immune system? There are various immune mediators/”boosters” available, and they are worth a try, but there is little to no data supporting their efficacy, especially for this disease.)
Do I need to quarantine my facility? Frankly, yes. At least you need to try to get the affected horse(s) isolated as best you can. That’s the standard veterinary response. My reality response is basically the same, but with some caveats based on years of observations. First off, this is a bacterium and, theoretically, is contagious. So, yes, other horses are at risk to the exposure. However, I have seen 10 horses in a pasture, 2 of them with Pigeon Fever, rubbing pus on the other 8, with flies buzzing all around, and none of the others have contracted the disease. Then I have seen it seemingly hit every horse, or every other horse in the stable. So is it the contagious aspect of the disease, or each individual’s constitution? Or are other factors at play? Suffice to say, that it is best to keep your affected pony at home, away from any other equines, at the very least this will keep you from popping up on Facebook as the scourge of the local equine community.
Another question is, how can we prevent it? Dr. Sharon Spier at U.C Davis Veterinary Teaching Hospital is hoping to develop an immunization, but that is a long way off. So until then, common sense dictates fly control. This incorporates everything from Fly Predators, to fly sprays, Fly sheets and horse wear, fly traps etc. If the disease drains on your property, or in a stall, good sanitation and cleansing are essential. If you have questions, call or email our office.