What are the symptoms of Theileria in horses?

Theileria infections in horses are primarily caused by Theileria equi (formerly Babesia equi) and Theileria haneyi, which are protozoan parasites transmitted by ticks. The disease is often referred to as equine theileriosis or equine piroplasmosis. Symptoms can vary depending on the severity of infection and the horse's immune status.

Common Symptoms of Theileria in Horses:

1. Fever – High temperature (often over 102°F or 39°C).

2. Anemia – Pale or jaundiced (yellow) mucous membranes (gums, eyes) due to red blood cell destruction.

3. Weakness & Lethargy – Reluctance to move, exercise intolerance.

4. Loss of Appetite – Reduced feed intake.

5. Dark Urine – Due to hemoglobinuria (red blood cell breakdown).

6. Swollen Lymph Nodes – Enlarged glands, particularly under the jaw.

7. Edema – Fluid retention (e.g., under the belly or legs).

8. Increased Heart & Respiratory Rates – Due to anemia and hypoxia.

9. Neurological Signs (in severe cases) – Ataxia, seizures, or collapse.

10. Sudden Death (in acute cases) – Especially in naïve or stressed horses.

Chronic or Carrier State:

Some horses may become chronic carriers without showing obvious symptoms but can still transmit the parasite to ticks, which can then infect other horses. Stress (e.g., transport, illness) can trigger a relapse.

Diagnosis & Treatment:

Diagnosis: Equine Theileriosis Antibody Test (LFIA ), Blood smears (identifying parasites in RBCs), PCR, IFA, ELISA

Treatment: Antiprotozoal drugs (e.g., imidocarb dipropionate), supportive care (fluids, blood transfusions in severe cases).

Prevention:

-Tick control (acaricides, environmental management).

-Screening and quarantine of new horses.

-No commercially available vaccine (management is key).

-If you suspect Theileria in your horse, consult a veterinarian immediately, as early treatment improves outcomes.