An attack of anaplasmosis - The Horse Owner's Resource

An attack of anaplasmosis

Just as a rescue mare Mindi got back on her feet, a tick-borne disease threatened to knock her down again.
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This poor horse,” I muttered to myself while texting my veterinarian about Mindi ---again. The past four months had been a roller coaster ride as we worked to restore my petite mare to health. Our veterinarian, Maral Avetian, VMD, had seen Mindi multiple times for issues related to her previous starvation and neglect. But we had had a month of steady improvement (and zero veterinarian visits), and I truly thought that she was out of the woods.

As I keyed in the message relaying her signs to Avetian, Mindi moved hesitantly and painfully around her pasture. She had been fine when I checked on her the night before, but this morning she had considerable swelling in her hind legs. As most horse owners do, I went through a mental checklist of possible causes and treatments.

I didn’t think it was regular stocking up---a harmless pooling of fluid in a horse’s lower legs related to inactivity ---because Mindi’s swelling was much more severe than any case I had ever seen. Also, stocking up is far more likely to occur in horses confined to stalls rather than on pasture, where they can engage in at least moderate exercise.

Mindi had enjoyed plenty of turnout over the past few days. The weather had been so mild that I had been able to extend my usual autumn 24-hour turnout schedule into the holiday season. So, the previous day, December 22, 2015, she had been turned out all day and all night. I checked her for any cuts or scratches and there were none, nor did I find any bumps or marks. I ran my hands up and down each leg and, although they seemed sensitive, I didn’t notice any sore spots that would have indicated trauma. Without any other options, I brought her into her stall, snapped a picture and waited for Avetian to arrive.

Rehomed and rehabbed

Four months earlier, in August 2015, I had been mindlessly scanning Facebook when a “plain brown mare” on a kill-pen rescue page caught my eye. Described as a Thoroughbred, “hip number 249” looked to be a malnourished little horse, with a patchy coat, a knotted, long mane and a hopeless expression. I realize that these are not usually the qualities one looks for in a prospect, but I have a barn full of healthy and happy horses who all started out looking this way. I saw potential. My husband and I decided we were ready to take on the challenge and help this mare.

So, I made several phone calls and found out that Hip 249 was actually a traceable, tattooed Thoroughbred. Searching for information on her lip tattoo revealed that she was a 9-year-old mare registered with the Jockey Club as Sweet Mindi. With a little more on-line searching, we found her five-year race record. She was foaled in Florida and ran her way through West Virginia and Ohio, then ended up running the majority of her 70 races at Penn National Race Course in Pennsylvania. Some big names in racing, including Alydar, Buckaroo, Danzig and Red Ryder, could be found in her pedigree. Her life was pretty well documented until she stopped racing as a 7-year-old.

When I met Mindi, two years had lapsed since her last race, and her whereabouts during that time are still unknown. But it was obvious that her life could not have been easy. When I got her home, I washed matted, muddy scabs off of her back. I treated scratches0 on her legs. I started a re-feeding program to safely bring her weight back to a healthy level. I eased her into my existing herd.

While Mindi was in quarantine at my farm, Avetian checked her multiple times and treated her for a persistent respiratory infection with three different antibiotics. Mindi also was treated for ulcers. I gave her medicated baths and used longer-term treatments on her scratches to reduce the discomfort. After a few weeks, I could start to see a little bit of the shiny little mare from the winner circle photos that I had found on-line.

Mindi was gaining weight and muscle. I thought she was on her way to health until I found her in the pasture that day with both hind legs swollen.

Diagnosis made

When Avetian arrived, we discussed Mindi’s condition. A single swollen leg might suggest cellulitis or an injury, she said. But two swollen legs were more indicative of some type of systemic illness. Avetian did an examination and took Mindi’s temperature. It was mildly elevated---more evidence of something systemic. In our area of northeast Pennsylvania, tick-borne diseases are common and, with the mild winter we were having, it was very possible the pests were still active.

Avetian drew blood to test for tick-borne infections, such as anaplasmosis and Lyme disease. The test came back positive for anaplasmosis. Although I had not found a tick on Mindi recently, she must have been bitten and infected within the previous week or two. I immediately started to research her condition.

The tick that infected her carried the bacterium Anaplasma phagocytophilum, which invades white blood cells and causes fever, swollen limbs, reluctance to move, lack of appetite and depression. This poor mare had every symptom and was miserable.

Thankfully, the organism is susceptible to the antibiotic doxycycline. Avetian gave Mindi an intravenous shot of the antibiotic, then left us with a two-week supply of pills and instructions to call her if Mindi didn’t improve in a few days. Anaplasmosis could weaken her immune system, and if she had any other infections she could become much worse.

Within two days of the start of treatment, I saw a dramatic improvement in Mindi. The swelling slowly began to subside, and she seemed more comfortable. Within a week she was completely back to normal. She fin-ished the course of antibiotics and I haven’t noticed any residual effects from the infection.

There is no vaccine against anaplasmosis and natural immunity to the organism is short-lived, so Avetian warned me that Mindi could, theoretically, contract the disease again. The good news is she shouldn’t be at a higher risk of infection than any other horse.

Sweet Mindi has continued on her journey back to health both mentally and physically. She has a refined head and sweet disposition, and it tuns out she is a fancy mover. The “plain brown mare” from the kill-pen photo has really blossomed.

This article was originally published in EQUUS 485, February 2018