Theileriosis (Tick Fever) — The Silent Killer of Dairy Cows

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 1.Introduction

Theileriosis is an extremely destructive tick-borne protozoal illness mainly caused by Theileria annulata. One of the most economically striking diseases is the spread of Theileria annulata in the dairy and livestock sector of Pakistan, especially the Friesian, Jersey breeds, and their crossbreeds to high-yielding of the imported exotic breed.

Theileriosis in cattle


2. Vector & Transmission

The disease causing intravascular hemolysis is transmitted by the bites of infected ixodid ticks, particularly the genus Hyalomma. The louse is localized in the tick's salivary glands and is injected into the host's bloodstream during the tick's feeding.

3. Pathogenesis:

 The cellular invasion

The life cycle of Theileria in the cow host is remarkable and is comprised of two separate phases two-fold:

Lymphoproliferative Phase: 

On entering, Sporozoites adhere to and invade the host Lymphocytes (White Blood Cells). They turn into the form of Schizonts, which trigger the overstimulated, uncontrolled multiplication of the host cells, as a consequence, the lymph nodes are swollen to an enormous degree.

Erythrocytic Phase:

 The parasites then go through a transformation into Piroplasms and invade the Red Blood Cells (RBCs). Due to that, the RBCs are destroyed and the anemia is very severe, and the person develops jaundice.

Life cycle of theileria in cattle


4. Clinical signs and symptoms 

A patient with Theileriosis usually shows the following typical "Red Flags": 

Fever: 

Persistent high temperature of 105°F to 107°F. 

Swollen Lymph Nodes: 

Noticeable eye-catching enlargement of the superficial lymph nodes (Pre-scapular and Pre-femoral). 

Anemia and Jaundice: 

Pale or yellowish mucous membranes of the eyes and gums. 

Protrusion of Eyeballs: 

Outward swelling or "bulging" of the eyeballs. 

Petechial Hemorrhages: 

Conjunctiva (eye lining) has a few small red blood spots on it. 

Breathlessness:

 In the final stage, pulmonary edema obstructs the breathing process.

5:Diagnosis

​Microscopy:

 Examination of Giemsa-stained thin blood smears. Look for piroplasms inside the RBCs, which often appear as small, "safety-pin" or ring-shaped structures.

​Biopsy: 

Lymph node aspiration to detect Koch’s Blue Bodies (Schizonts) within the lymphocytes.

​Differential Diagnosis: 

Must be differentiated from Babesiosis (which presents with red urine) and Anaplasmosis.

​6. Treatment & Control Protocol

​Specific Therapy: 

Buparvaquone is the drug of choice, administered at a dose of 2.5 mg/kg body weight (deep intramuscular).

​Secondary Prevention: 

Long-acting Oxytetracycline is often used to prevent secondary bacterial infections.

​Supportive Care: 

Administration of hematinics (Iron/B12) to combat anemia and NSAIDs to manage the high fever.

​Prevention: 

The most effective strategy is Strict Vector Control (using Acaricides like Amitraz or Cypermethrin) and the use of the Theileria live attenuated vaccine.

https://vetinsightpak.blogspot.com/2026/03/tick-infestation-in-livestock.html

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