A REVIEW OF THEILERIA INCIDENCE IN CATTLE POPULATION, ITS IMPACT ON HEMATOLOGY OF THE INFECTED ANIMALS AND THERAPEUTIC APPROACH TOWARDS THE INFECTION

Theileria is an obligate intracellular parasite infecting both domestic as well as wild bovines and small ruminants. In cattle, the most important species responsible for the infection are T. annulata and T. parva. Theileria parva is prevalent in 13 Sub-Saharan countries of Africa and causes East Coast Fever (ECF) while T. annulata is prevalent in Asia, North Africa, and Southern Europe and causes Mediterranean or tropical theileriosis. The disease is highly incident in exotic breeds and crossbred cattle irrespective of age groups in tropical areas. Transmission occurs through ixodid ticks associated with genera Hyalomma, Rhipicephalus, Amblyomma, and Haemaphysalis. Ticks have been classified into three families, out of which two families are of veterinary importance viz Argasidae and Ixodidae, commonly known as soft ticks and hard ticks, respectively. Biochemical and clinical variations, seen in the disease show relationship to the degree of parasitemia, degree of anemia, and the severity of hypoxia. Hemoglobin level is adversely affected in positive cases and reduced up to 8mg/dl. In severely infected cases hemoglobin level is reduced to 3mg/dl. Packed cell volume percentage decreases to 9% and the total erythrocytic count is reduced to 2.3 million per cm2. Marked clinical signs of theileriosis include lymph nodes enlargement, anorexia, depression, listlessness, dullness, dyspnoea, pyrexia up to 107°F, suppressed cough, ocular and nasal discharges. In severe cases, diarrhea or dysentery and systemic changes are seen. Control can be achieved using different means including chemotherapeutic control, biological control, genetic control, and vaccines. The most authentic and effective control is the use of parasiticidal drugs harmless to the host. But, due to the emergence of resistance, in some cases the efficacy becomes marginal. However, buparvaquone is found to be the most effective drug against theileriosis.