Tickborne Diseases in Horses

The prevalence of tickborne diseases in our equine friends is on the rise, with Lyme Disease being the most commonly reported followed by Anaplasmosis and rarely Pirplasmosis.  There is disagreement whether Rocky Mountain spotted fever occurs in equine, but a study conducted in Columbia and published in The American Journal of Tropical Medicine and Hygiene suggests it does.  I created a table (below) describing the characteristics of each disease for easy reference.

Without a doubt, prevention is the best policy.  This however can be difficult, particularly if your horses live out 24/7 as ours do.  Early in the season we were pulling deer ticks off our horses at an alarming rate.  We took an aggressive approach by reducing the size of our fields with electric fence and mowing our fields very short.  Ticks are not as happy in this kind of environment.  Other measures that may be helpful include: fencing off or removing brush from your pastures; removing wood piles in or near your pastures; discouraging deer from grazing in your fields and spraying your horses frequently with permethrin containing products.  Some veterinarians are experimenting with the Lyme vaccine licensed for use in dogs but not horses.  The protocol involves 3 x 1 ml doses always administered alone and never with other vaccines concurrently.  The first 2 doses are administered 3 weeks apart with the 3rd dose, 3 months after the first.  Boosters are then administered every six months.  As always, be sure to consult with your veterinarian first if you live in a high risk area.  Just as important, pray for your horses regularly and ask the Lord to alert you to any potential dangers lurking in your fields.  Prayer is free, has no side effects and is guaranteed to be a blessing!  Have a peaceful week and join me next time to learn about our positive experiences with AquarPacer therapy.

Psalm 121

I lift up my eyes to the mountains—
    where does my help come from?
My help comes from the Lord,
    the Maker of heaven and earth.

He will not let your foot slip—
    he who watches over you will not slumber;
indeed, he who watches over Israel
    will neither slumber nor sleep.

The Lord watches over you—
    the Lord is your shade at your right hand;
the sun will not harm you by day,
    nor the moon by night.

The Lord will keep you from all harm—
    he will watch over your life;
the Lord will watch over your coming and going
    both now and forevermore.

 Tick species Lyme DiseaseDeer tick AnaplasmosisDeer/Western black-legged ticks PiroplasmosisTropical horse tick, Cayenne tick, dog tick
Causative agent B. burgdorferi A. phagocytophilum B. caballi and B. equi
Target joint/skin collagen, aqueous humor of the eye, meninges of the brain and heart tissue neutrophils and eosinophils RBC
High season summer-fall late fall – early spring year round in warmer climates
Time from infection to symptoms weeks – months 1-3 weeks 7-22 days
Symptoms chronic weight loss, low-grade fever, sporadic or shifting leg lameness, muscle tenderness, arthritis, behavioral changes, neurologic signs, poor performance, skin hypersensitivity. fever, depression, inappetence, ventral edema, orchitis, petechiation, icterus, recumbency, muscle stiffness, rarely death anemia, jaundice, fever, lethargy, weight loss, limb edema, poor performance, increased heart/respiratory rate, and even death
Test SNAP 4Dx, Multiplex Test (Cornell) SNAP 4Dx, blood smear, PCR assay cELISA test
Can look like… almost anything! PHF laminitis, colic or azoturia
Treatment oral doxycycline, IV oxytetracycline IV oxytetracycline Injectable imidocarb dipropionate. The treatment itself can cause colic symptoms requiring pre-treatment with antispasmodic drugs

Note:  Equine Piroplasmosis is a serious disease that must be reported.  Options for owners with an EP positive horse are humane euthanasia, lifetime quarantine or enrollment in a USDA-APHIS treatment program designed to clear T. equi from the horse while in quarantine.


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