Ehrlichiosis is a tick-borne disease caused by the organism Anaplasma phagocytophila. This organism is found in ticks of the genus Ixodes. It gains access to the bloodstream and colonizes certain types of inflammatory blood cells (granulocytes), and causes inflammation of blood vessels (vasculitis).
This disease is regional, being common in Northern California but has also been diagnosed in a handful of other Western states and in Europe.
Signs of disease include depression, loss of appetite, reluctance to move, fever, leg and belly swelling, wobbliness and yellow gums.
This disease can range in severity from mild to severe. In horses less than 1 year old, it tends to be mild and often limited to fever and mild depression. In adults, disease can last for 7-12 days and can be quite severe.
Diagnosis requires identification of the organism on a blood smear, and other laboratory blood tests.
Treatment requires the use of the tetracycline antibiotics. This requires a diagnosis or at least suspicion of disease.
Other Diagnoses Considered
Treatments May Include
Prognosis & Relevant Factors
The prognosis depends on the severity of the disease coupled with the promptness of diagnosis and provision of effective treatment.
The prognosis is good with treatment with the antibiotic oxytetracycline. Other antibiotic classes are not effective. Horses not treated with oxytetracycline may have severe and lengthy illness, but usually survive. These horses often lose weight and occasionally develop complications like pneumonia or laminitis.
Once a horse recovers from EGE, they have immunity for at least 2 years. Disease is rare in horses less than 1 year old.
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