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Pigeon Fever in a horse via thermography
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Endemic to California and Texas, pigeon fever has been spreading north and east the past few years, with recent outbreaks in Oregon, Washington and Colorado, and reported cases as far east as Kentucky and Florida.
Pigeon fever, while not necessarily life-threatening, is highly contagious. Once introduced into the environment, the hardy bacterium that causes it is difficult to eliminate, resulting in unpredictable future outbreaks.
Also referred to as dryland distemper or Colorado strangles, pigeon fever earned its name from the characteristic swelling of a horse’s chest from abscesses in the pectoral muscles. Swellings can also occur along a horse’s ventral midline (belly) area and in the groin region, affecting sheaths and udders. The initial clinical signs can be vague, sometimes showing only as lameness or a reluctance of the horse to move.
The equine version of the disease isn’t caught from pigeons; instead, the transmission route is thought to be flies, especially cattle horn flies, carrying the bacteria Corynebacterium pseudotuberculosis . While rarely contagious to humans, we can easily transfer the infection from horse to horse via our hands or equipment that has touched a draining abscess. A similar strain of pigeon fever affects goats and sheep; cattle are susceptible to both versions. All it takes is a single bacterium entering a wound, abrasion, or break in the horse’s skin or mucous membranes for the disease to take hold.
THREE FACES OF PIGEON FEVER
Inspiritus Equine, located in Napa, California, is in the hot zone when it comes to pigeon fever. Founder Joanna L. Robson, DVM, CVSMT, CVA, uses an integrated approach with her equine pigeon fever patients, providing treatment options to help eliminate the abscesses and shorten the duration of the disease.
“Pigeon fever is very contagious,” says Robson. “Evidently it’s found worldwide, but it’s endemic to California because it’s both dry and hot here, with lots of dust and flies.”
Robson reports that pigeon fever takes three forms:
* most common is a ventral midline and chest swelling with abscesses appearing externally
* less common is swelling of the limbs, with cellulitis and edema, referred to as ulcerative lymphangitis
* also less common but by far the most serious form settles into and affects internal organs such as the lungs, liver, spleen, and kidneys
Robson’s findings are supported by research conducted by Sharon J. Spier, DVM, PhD, Dipl. ACVIM, at the University of California-Davis School of Veterinary Medicine. One study found that ulcerative lymphangitis occurred in only 10% of cases, while internal abscesses occurred in 8% and external abscesses in 81% of cases studied. Spier’s research also found that early diagnosis was key for successful outcomes.
Robson points out that a horse who is immunosuppressed or has a weak constitution is going to be most at risk. “In addition, horses living outside are typically the ones more prone to scrapes and cuts, and more prone to ventral midline dermatitis or ‘fly strike,’ which appear to be predisposing conditions for pigeon fever infection,” she says.
EARLY TESTING AND DIAGNOSIS
Since early diagnosis is important, it’s essential to remain watchful during the late summer and early fall months, when pigeon fever typically appears. “It’s likely that flies introduce the bacteria during the hot summer months, then it sits in there and festers until it erupts into abscesses,” says Robson.
Initial symptoms can be as subtle as a decreased appetite and lethargy, or can extend to indicators such as weight loss, abdominal pain, fever, or signs of respiratory disease. “Other things can mimic pigeon fever, such as strangles, or even the odd lumps and bumps that horses sometimes get,” says Robson.
Different tests can be used for diagnosis, including ultrasound (for the internal form), blood titers, or a culture grown from an abscess swab. “Titers detect a level of antibodies, or immune system response, to a certain antigen. For pigeon fever, a serum synergistic hemolysin inhibition (SIH) test is the titer test of choice,” Robson says.
It’s typically thought that horses with internal abscesses will have higher titers than those with external abscesses, according to Robson; however, culturing an abscess is still the definitive test. “Some horses without any active infection will still have positive titers, indicating possible exposure, and should be watched closely for any signs of illness,” she says.
Getting a culture is essential to know what you’re dealing with, according to Kay Aubrey-Chimene, RMT, co-owner and director of Grand Adventures Ranch (GAR) in Sonoita, Arizona. “The only way to truly diagnose pigeon fever is to culture the material from the abscess,” she says.
In 2006, Aubrey-Chimene encountered a rash of pigeon fever-symptomatic horses who were having repeated abscess breakouts; they were brought to GAR, where she was conducting a study on the efficacy of intensive ozone treatment on pigeon fever horses. To help resolve the mystery of what was causing the ongoing problems, she sent abscess swab samples to several labs, including the University of Arizona.
“Despite the clinical signs of pigeon fever, some turned out to have Corynebacterium kutcheri , a related disease the University of Arizona lab insisted exists only in rats,” says Aubrey-Chimene. “We found literature showing C. kutcheri has happened in horses in England, and it’s far more serious than pigeon fever. For anyone who has a horse they suspect has pigeon fever, I hope they’ll spend the extra money and get the abscess cultured so they know how to treat it, and whether there are also any opportunistic infections present that might complicate treatment.”
TREATING PIGEON FEVER, INSIDE AND OUT
When diagnosed properly and early on, a number of holistic modalities and treatments with demonstrated success can be used for pigeon fever (see Holistic Treatment Options). However, an integrated Eastern-Western approach is considered necessary for horses with internal abscesses. “The internal abscesses can be very thick walled, reducing penetration of medicines, and they can affect many organs, so it’s important to support the patient with both traditional and alternative means,” says Robson.
Treatment of sick horses also involves careful environmental management to mitigate long-term contamination of the location, plus minimize chances of spreading the illness to other horses. Keeping the sick horse isolated is important, as is putting all contaminated manure, bedding, and cleaning supplies into plastic bags and into the trash.
“After each treatment session, we sanitize the area and the equipment,” says Aubrey-Chimene. “We spray the horse, the handler, the shoes, the hands; anything that might carry infection.” For horses and humans, GAR’s spray solution is 30 drops of grapefruit seed extract in a 32-ounce spray bottle of water.
For the surroundings, “We use one cup bleach to a gallon of water, and use a garden sprayer, like one you’d use for pesticides, except this one is used only for this purpose,” Aubrey-Chimene explains. “Bleach is cheaper for spraying our dirt stall floors, and we also spray the stall walls, hay feeders, and feed and water buckets.” When using bleach on any items the horse will eat from, be sure to give it a thorough rinse. Wear latex gloves when handling or treating sick horses, and wash your hands well to avoid carrying germs to other horses.
Both Robson and Aubrey-Chimene agree that fly prevention and a clean environment are instrumental in minimizing your risks when it comes to pigeon fever. But since flies don’t pay attention to land boundaries, it’s important to get your neighbors involved in the efforts, too. “If a farm down the road gets it, and a fly comes over to your farm and bites your horses, next thing you know you have it on your farm. Barns have to work together as a community, especially if someone in the area had it as an issue in the past,” says Robson.
To minimize an area’s fly density, Robson recommends using fly predators, tiny gnat-sized parasitic wasps that deposit their eggs inside fly pupae, consuming the developing fly and preventing it from hatching as an adult. Fly sheets and masks are a good idea, and Robson cautions horse owners not to forget fly spray.
“There are definitely some good holistic sprays, using ingredients like citronella, marigold, and peppermint,” she says. “A lot depends on the types of flies and the horses involved; sometimes it’s just trial and error to find what works for you.” Other fly control methods include feed-through garlic or apple cider vinegar, or using products such as apple cider vinegar-based fly spray, or even Avon’s Skin So Soft as an external fly repellant.
Fly management also involves your environment including removing manure and bedding, trash, and anything else that would be attractive to flies. Aubrey-Chimene uses zeolite, an odor absorbing pellet frequently used in commercially available urine minimizers. It’s available either in small quantities or by the pallet or truckload for larger barns. Zeolite is placed on top of dirt or packed clay stall floors as a urine and ammonia absorber, with clean bedding placed on top.
And last but not least, Aubrey-Chimene points out that the best fly control is to detox your horses. “Flies have a job to do; they carry away junk. The more junk your horse is sweating, peeing, or pooping out, the more flies will be attracted to him,” she points out, adding that a horse that’s been cleared of toxins will also have a cleaner liver and a stronger immune system to help him combat any bacteria he encounters.
As for preventive treatments, a daily once-over to locate any new wounds or abrasions is ideal, combined with dressing and covering wounds to prevent fly contamination.
THE BOTTOM LINE ON PIGEON FEVER
While primarily confined to California in the past, pigeon fever is advancing quickly on the rest of the country. Your best defense is a good offense: through preparation and proactive measures, with an emphasis on boosting each horse’s immunity, controlling fly populations and their access points, and managing the environment, you’ll have done your best to fortify your horse’s resistance to pigeon fever.
Pigeon Fever Primer
* Fly management is your #1 prevention strategy. Use fly masks and sheets, fly spray on everything from horses to stall walls to trailers, feed-through options, and fly predators. Organize your community so everyone’s working to minimize flies.
* Detox your horse to help with both fly prevention and immune support.
* Compost or dispose of manure properly, and keep your property tidy and trash-free.
* Immune support and stress reduction options are important to help fight off any bacteria.
* Dress and cover any wounds immediately to prevent infection.
* Early diagnosis is ideal for the best results. During the summer and fall, be especially vigilant to any symptoms, swellings, or behavior changes; call your veterinarian if you suspect pigeon fever.
* Since pigeon fever can mimic several other diseases, run a culture from an abscess swabbing for a definitive diagnosis.
* Immediately isolate sick horses and any equipment used for them.
* Holistic approaches help resolve the external abscess and ulcerative lymphangitis types of pigeon fever; an integrated approach is needed for the more serious internal abscess type of the disease. Antibiotics are contraindicated for an external abscess, since they prevent it from coming to a head and draining properly; they are, however, considered necessary for complete resolution of internal abscesses.
* Use disease containment precautions such as wearing latex gloves, disposing of all infected or contaminated waste, and disinfecting surfaces appropriately.
* Bag and dispose of contaminated bedding properly; putting it on the manure pile will contaminate your environment via bacteria, since it’s been shown to survive for up to two months on hay and bedding, and more than eight months in the soil.
* Use supportive methods to keep your horse comfortable and ease his suffering during recovery.
HOLISTIC TREATMENT OPTIONS
* Acupuncture: Points to relieve heat and boost the immune system might be helpful, but there’s some concern about needling a pigeon fever patient because of the possible dissemination of bacteria and spread of the disease.
* Chinese Herbal Medicine: The TCM diagnosis for pigeon fever is ‘external pathogen – heat toxin’ and patients typically have a red tongue and a fast or wiry pulse. Using Wei Qi Booster can increase the immune system’s response and the body’s immune Qi. Also, the topical medicine Golden Yellow Powder, when mixed with vinegar to make a paste, can be used to treat abscesses topically.
* Dynamite Miracle Clay: A food-grade bentonite clay, it can be mixed into a ‘runny paint’ consistency and applied topically to help draw out abscesses.
* EqStim Immunostimulant: An injectable product that boosts the equine immune system, it’s been used successfully to decrease the severity and duration of the disease. The active ingredient in EqStim is inactivated Propionibacterium acnes, a naturally occurring bacterium recognized as a safe but potent stimulator of cell-mediated immunity; a number of research and field studies have been conducted and published, showing no toxicity or adverse side effects.
* Homeopathic: Remedies include high potency Silicea and Arsenica Album, both at a 200C potency, for cleansing the blood and lymphatic systems and helping the body purge abscess material. Check out the Academy of Veterinary Homeopathy ( www.theavh.org ) and the National Center for Homeopathy 703-548-7790.
* Homeopathic nosode (i.e., vaccine or immunization): Made by Hahnemann Laboratories and labeled Corynebacterium nosode, a nosode contains disease material during the preparation process, however, no disease material remains after the nosode is produced. Used annually at the beginning of the fly season, it works by energetically educating the body. Hahnemann does not sell to the general public; a veterinarian or certified homeopath can establish an account with Hahnemann and purchase the Corynebacterium nosode for you.
* Ozone: Treatments can be applied either rectally or directly into the abscess by a veterinarian. Since the C. pseudotuberculosis bacteria is anaerobic, introducing oxygen is detrimental to its survival. Another alternative is magnesium ozonate, a stabilized ozone that’s put directly into the horse’s food, or is mixed into water with a few drops of vinegar. It causes a chemical reaction, breaking off the nascent oxygen from the magnesium and releasing it into the digestive system, where it then enters the bloodstream.
* Wound care: A dressing made of five parts olive oil to one part tea tree oil can be sprayed directly on abscesses or wounds help them heal and to repel flies.
Lisa Kemp is an award-winning writer and marketing consultant for the equine industry. Her definition of a good day is one filled with any combination of horse people, horse images, horse stories, and yes, actual horses. For additional information, visit www.KempEquine.com