Theileriasis

THEILERIOSIS

Definition

  • Theileriosis is an acute disease of cattle characterized by high fever, swelling of the superficial lymph gland, rough hair coat, salivation, respiratory distress caused by various species of Theileria

Aetiology

  • Theileria parva – causes East coast fever in Africa, not recorded in India
  • T.lawrencei affects cattle and buffaloes and causes Buffalo disease in Africa
  • T.annulata is seen in India
  • T.mutans is seen in India without any symptoms

Transmission

  • It is transmitted through ticks

Pathogenesis

  • Theileria may appear as rod shaped, coma shaped or ring shaped forms.
  • Schizogony takes place in lymphocytes and monocytes
  • It is transmitted through ticks and on entry into blood of host infect lymphocytes and monocytes of blood, lymph gland and spleen where they develop
  • The schizonts are called koch’s blue bodies and are pathognomonic of the disease and may be seen in biopsy material from lymph gland. Following break up of koch's blue bodies they enter erythrocytes

Gross lesions

  • Enlargement of the lymph nodes, white foci of various sizes in renal cortex and punched out ulcers in the abomasum.
  • Pulmonary oedema, emphysema, subcutaneous and intramuscular oedema and excessive pericardial and pleural fluid, spleen may be enlarged, enlarged liver
  • Meninges may be congested and focal haemorrhages are seen in the brain
  • Respiratory distress may follow pulmonary oedema and death may be result from asphyxia

Microscopic lesions

  • Proliferation of lymphatic cells in the lymph nodes, spleen and peyer’s patches may be observed with the presence of koch's blue bodies
  • Effect of anaemia is evident in bone marrow

Immune mechanisms

  • Animal that survive an infection have a solid immunity
  • The parasite can invade both T cells and B cells
  • The parasite then triggers certain pathways result in the production of interleukin 2 and its receptors.
  • The schizont stage of Theileria develops within the lymphocyte, the infected lymphocytes enlarge to form lymphoblasts and begin to proliferate.
  • Since the parasite divides along the host cell, this leads to very rapid clonal expansion of parasitized cells. In most cattle, this results in overwhelming infection and death.
  • Cytotoxic CD 8+ cells kill infected lymphoblasts.

Diagnosis

  • Demonstration of the organisms in the erythrocytes and lymphocytes (Koch's blue bodies)
  • ELISA test is being used increasingly for seroepidemiological studies
Last modified: Thursday, 22 March 2012, 7:39 AM