Spring Fever: Drought, Heat and a Disease Called Pigeon Fever May Threaten U.S. Horses This Year

I have a favorite detour that I take in the spring. I swing over to the backroads through a neighboring village so I can watch the spring high water in the river rush over the rocks and old dams on its way out into the marshes and, eventually, the big mouth of Ipswich Bay and the North Atlantic.

Where’s the river gone©

The trouble is, there’s no river this year. All I can see is just a little brook meandering its way below the bridge. It is anything but rushing.

Massachusetts is in a drought, and chances are the state where you live is in one too. March 2012 was the tenth driest and second warmest March in the last 118 years in Massachusetts, according to the National Climate Data Center. The three-month period for January through March was the fourth driest and first warmest on record.

For this time of year, our usually-rushing local river is at its lowest flow rate in 80 years.

And if you don’t think that affects you and your horse, just wait until you buy your hay this summer.

Or, wait until your farm’s well goes dry.

Or, wait until you see your paddocks go dusty instead of green.

But droughts have a bigger, badder down side in that, if prolonged, they can alter the chemistry of the soil, for want of a better description. When there’s a drought, we start hearing about anthrax and pigeon fever becoming a problem in western states, where droughts are common. But last year we heard much more about pigeon fever in the midwest.

When it rains too much, we complain about mosquito-borne diseases, rainrot and moldy hay, but drought is nothing to have on a wish list.

As the United States emerges from a warm, dry winter, several states are warning that pigeon fever may be a problem this year. At the end of 2011, Louisiana had 30 cases of the disease. The Veterinary Teaching Hospital (VTH) at the Louisiana State University School of Veterinary Medicine treated ten cases of pigeon fever in horses and the Louisiana Animal Disease Diagnostic Laboratory (LADDL) reported 20 positive cases from referring veterinarians.

LSU estimated there were at least 100 cases in Louisiana in 2011 and suspect that the number of cases may have been related to drought and heat.

How far from its normal territory will pigeon fever travel?

“Pigeon fever” is the common term for an infection caused by the bacterial organism Corynebacterium pseudotuberculosis. This bacterium can form abscesses in the pectoral region (chest) and ventral abdomen (often in the girth area) of the horse.

Pigeon fever is not related to pigeons, so don’t spend more time than usual shooing them out of the rafters. The abscesses cause swelling and give the horse a “pigeon-breast” appearance. The illness is also known as “dry-land strangles”.

Two videos should help explain this disease to you, if you are not familiar with it. You’ll learn what areas to watch carefully on your horse, and learn how the disease is transmitted between horses.

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Oklahoma State University’s Dr. Todd Holbrook explains pigeon fever in comparison to other problems in horses that involve abscesses and swelling.

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Dr. Tiffany Hall, who is board certified by the American College of Veterinary Internal Medicine, works at Brazos Valley Equine Hospital in Texas; in this video she discusses some additional aspects of pigeon fever in horses.

The most important thing to learn about pigeon fever is how to recognize it, but how to prevent it is a close second. Prevention begins with isolating horses that may be suspected of having the disease, but efforts should be underway now, early in the season, to plan how to minimize flies around horses, since they can be involved in transmission.

An infectious disease program for every barn is important; bacteria can live on buckets and bedding and stall mats and tack and even your clothing.


Download Dr. Hall’s five-page summary sheet on pigeon fever in horses from Brazos Valley Equine Hospital

Read the Arkansas state government announcement about pigeon fever cases in 2012

Read the Louisiana state government summary of pigeon fever cases in 2011

Louisiana State University informational web site on pigeon fever

Photo credits: spring river by Kevan Williams, river reflections by Patrick Hoesly.




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