What are Babesiosis?

Babesiosis is a tick-borne infection and is also known as equine piroplasmosis. The parasites B. caballi and T. equi are the hosts for this disease. Found predominantly in countries other than the United States, such as Europe and South and Central America, the reality of the disease entering North America is evident due to horses in California testing positive for the illness in recent years. The importation of equines from other countries may allow for the transfer of the disease across the ocean.

Signs of the condition may be evident within one to four weeks of the tick bite. Additionally, transmission of the illness via the blood (transfusions or infected tools) has been noted. Horses with this illness are often euthanized or quarantined for lengthy periods, including for life.

Babesiosis is a condition that results from your horse’s contact with ticks carrying the infection. The infection is from the protozoa Babesia caballi or Theileria equi.

Symptoms of Babesiosis in Horses

The symptoms your horse may experience if he has come into contact with Babesiosis can vary greatly.

  • Pyrexia – Your horse may begin to suffer a fever, these fevers tend to be mild 
  • Lethargy 
  • Anorexia
  • Weight loss
  • Depression
  • Jaundice -  Your horse’s skin and eyes may begin to turn a yellowish color 
  • Mucous membrane changes – Your horse’s mucous membranes may become pale in color 
  • Heart changes – There can be an increase in his heart rate 
  • Breathing changes - Your horse’s breathing may become rapid 
  • Sweating
  • Skin lesions
  • Dark urine
  • Dry fecal matter 
  • Colic
  • Incoordination – Stumbling and gait changes 


The two types of Babesiosis are dependent upon the protozoan that the tick carries. The two types are: 

Babesia equi

  • Has a wider distribution than its counterpart
  • 12 to 19 day incubation period 
  • Causes a more severe disease than Babesia caballi 
  • Horses will be permanently be infected with the infection 

Babesia caballi 

  • 10 to 30 day incubation period
  • Horses can be carriers for up to 4 years, with the possibility of becoming clear of the infection eventually


Causes of Babesiosis in Horses

There are certain risk factors that may make your horse more susceptible to contracting these tick-borne infections. 


  • Africa
  • Middle East 
  • Asia
  • Central America
  • South America
  • Caribbean
  • Europe
  • Southern United State


  • Ticks become infected with the parasite when they ingest them
  • They transfer the infection when they attach to your horse
  • Via infected needles or surgical tools
  • Blood transfusion 

Time of Year

  • Transmission via the tick happens most often during the summer and fall seasons


Diagnosis of Babesiosis in Horses

Diagnosis is not always straightforward. Differentials that must be ruled out could be conditions like plant toxicosis, dourine, and equine infectious anemia. Because of the possibility of these other more common illnesses, the veterinarian may want to do standard blood tests that can be indicative of these conditions. More tests, specific to the diagnosis of Babesiosis may be utilized.

  • Blood smear to investigate parasitic involvement
  • ELISA test to detect antibodies in equines who are infected
  • Indirect fluorescent antibody test
  • Polymerase chain reaction test
  • Packed cell volume
  • White blood cell count  

Clinical signs, such as jaundice and lack of coordination may lead the veterinarian to do tests specific to Babesiosis.



Treatment of Babesiosis in Horses

There are a few treatment options for your horse if he is diagnosed with Babesiosis. It is important to note that if treatment is not provided in time, your horse can lose his life. This can happen within 24-48 hours of the onset of symptoms. 

Imidocarb dipropionate is the present medication of choice for treating horses with Babesiosis. Additionally, diminazene aceturate has shown some success (documentation is mainly suggestive of dogs and cattle; however, therapy in equines has been noted with resolution as well) . In order to help with secondary symptoms, your veterinarian may suggest anti-inflammatory medications, corticosteroids and even possibly blood transfusions for horses that have severe anemia. Relapse is possible if your horse is not treated correctly or if he continues to be a carrier for an extended period.



Recovery of Babesiosis in Horses

Side effects may be severe with the use of Imidocarb; your veterinarian may choose to keep your horse for a period of hours to days to be certain that there is no danger. Diarrhea and colic may need to be treated if your horse experiences them as a result of the medication. Horses with Babesiosis typically face long term quarantine, though completion of a certified FDA program may allow for clearance after a specified time.



Babesiosis Questions and Advice from Veterinary Professionals

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© 2022 Wag Labs, Inc. All rights reserved.