Theileriosis is an important disease in exotic and cross bred dairy cattle in India characterized by high rise of temperature, anaemia and swelling of lymph nodes.
Distribution
Theileriosis is an important disease of dairy cattle in fifteen African countries, seven Middle-East countries, Russia, parts of China and many countries of Asian subcontinent.
Bovine Theileriosis was reported in India as early as 1905 by Lingard. The prevalence of the disease in Indigenous cattle has been reported by different workers.
The disease has been reported in cross bred cattle by Gautam (1970), Sharma (1970, Mathur (1971)), Chhabra (1972), Rao (1973). The disease has been reported from all the States of India.
Aetiology
The species of Theileria those affect cattle are T. annulata, T. parva and T. dutans. T. annulata is the most extensively distributed parasite and causes tropical theileriosis. T. parva has been reported by Prasad (1970) and Rahman (1972). The parasites remain in two forms. Erythrocytic form and Schizont (Koch’s blue bodies) form. About 80% of T. annulata remain in erythrocytic form as round or annular shaped and the rest as oval or coma shaped. Few may appear as dots or Anaplasma like forms. Peripheral blood smear shows one or more parasites in each erythrocyte but some may show 4-7 parasites.
Schizonts are observed in the lymphocytes and monocytes as well as free states in lymph node biopsy. Schizonts may also be seen in peripheral blood smears. Under Giemsa stain the schizonts look blue and contain purple particles. Number of particles vary from one to several.
Based on the size of these particles the schizonts are ascribed as macro or micro schizonts. The micro schizonts appear subsequent to macro schizonts.
Susceptible Hosts
Exotic cattle used to suffer from the disease during their first summer. All age groups of exotic cattle are highly susceptible to the disease. The adult cross bred cattle also suffer but they show comparatively mild manifestation than the exotic cattle. The young indigenous calves are very much susceptible.
Mode of Transmission
The disease is mostly observed during summer and rainy seasons. This preponderance is attributed to higher activity of vector during this season (May to October). This is also influenced by stress due to hot and humid weathers.
The disease is transmitted by the bite of the ticks of the genus Hyaloma. The erythrocytic forms of the parasite are ingested by the larval and nymphal stages of the tick along with blood, while fedding on an infected animal. The subsequent stages of the tick transmit the disease during their feeding on a susceptible hosts (Transtadial transmission). This has been expementally established in Hyaloma spp. The disease can experimentally be established in calves by inoculation of ground up tick supernates containing particles of T. annulata.
The disease can also be transmitted mechanically by inoculation of infective blood and tissue suspension made from spleen, lymph node and liver of infected animals. The disease has been recorded in 2-3 days old calves suggesting the probability of intrauterine infection. But, this has been established.
Clinical Findings
- High rise of temperature (40.5° C to 41.5° C).
- Enlargement of regional superficial lymph nodes.
- Increase in heart and respiration rate.
- Slight anorexia, restlessness and rough coat.
- Tense eye balls along with watery lacrimation.
- Laboured respiration, serous nasal discharge and coughing.
- Depression and petechial haemorrhages on conjunctiva.
- Declination of fever and development of anaemia with high coloured urine in later stage.
- Bilirubinuria and jaundice in some cases.
- Urticarial type skin lesions.
- Occasional nervous signs.
- Weakness, prostration and death.
Diagnosis
This based on the following:
- Clinical findings
- Clinical pathology
(a) Demonstration of Theileria in blood smear as well as in spleen smear.
(b) Blood picture: Anaemia is the main feature. Haemoglobin level falls as low as 2 g/100 ml. Erythrocyte count decreases to 1.5 to 2.0 million/Cu mm. Packed cell volume decreases to 7 – 9 percent.
(c) Lesions: Visible mucous membrane are pale. There is enlargement of superficial lymph nodes, spleen and liver. Gall bladder is distended. The kidneys and lungs are congested. There is punched necrotic ulcers in the abomasum.
Microscopically, the lymph nodes show depletion of lymphoid follicles and necrotic focci in the cortical areas. The liver shows varying degree of degenerative changes. The kidney shows sub-acute interstitial nephritis. The lungs show pulmonary oedema.
The impression smear made from lymph node, spleen, liver, abomassum and kidneys show presence of Koch’s blue bodies. Cerebral theileriosis cases show Koch’s blue bodies in the impression smears made from the brain.
(d) Serology
- Complement fixation test.
- Capillary agglutination test.
- Haemagglutination inhibition test.
- Conglutinating complement absorption test.
- Agar gel precipitation test.
- Indirect fluorescent antibody technique.
These tests have been used successfully to detect theileriosis.
Treatment
- Broad spectrum antibiotics like tetracycline, oxytetracycline, chlortetracycline have been used with success.
- Single intramuscular injection of Buparvaquone @ 2.5 mg/kg body weight is an effective drug.
- Halofuginone lactate @ 1.2 mg/kg body weight orally can bring about recovery.
- Berenil has been used with success.
- Clexon @ 10 mg./kg body weight intramuscular two doses at 48 hours interval has been reported to give adequate recovery.
Control
Control of tick population is necessary. But, it is a difficult task. No systemic work of any dimension has been taken up in India as yet. Vector control is a difficult proportion as Hyalomma Spp. not only infect cattle but feeds on wild animals and rats. Systemic application of insecticide and rotational grazing may minimize the tick population. Exotic and cross bred cows should be kept in tick free shed as far as possible.
Chemoprophylaxis
Chlortetracycline @ 16 mg/kg body weight orally for 8 days or rolitetracycline @ 4 mg/kg body weight intramuscularly for 3 days have been found to immunize calves against theilerial attack.
Immunoprophylaxis
In India, Punjab Agricultural University, Haryana Agricultural University, Indian Veterinary Research Institute and Madras Veterinary College have controlled attenuated schizontal vaccine.
An effective and safe vaccine has been developed for immunization of susceptible cattle under field condition from Anand and named as Rakshavac-T. This is a commercial vacine. The vaccine can be had from Indian Immunologicals, Hyderabad.
