Symptoms and pathology of experimental bovine tropical theileriosis (Theileria annulata infection)

Abstract

Summary.Bovine tropical theileriosis (Theileria annulata infection) is of great economic impor tance to several countries of Asia and Africa where millions of cattle are at risk of exposure to this disease. The authors describe symptoms, sequence of appearance of the parasite and pathology of the infection by three virulent strains of the parasite in fully susceptible calves.Symptoms observed were: enlargement of local lymph gland, fever, haemorrhages on visible mucous membranes and sometime on skin, anaemia and jaundice particularly in subacute and chronic forms of the disease.The parasite "schizont" was first detected in the swollen local lymph gland draining the site of attachment of ticks, then in other lymph glands which concurred with the onset of fever.Main post-mortem findings were: oedema and enlargement of, and haemorrhages in lymph glands and spleen, haemorrhages in subcutis and on most of the serous and mucous membranes, on endocardium, pericardium and epicardium, and ulcers in abo masum which rarely extended to intestine, oesophagus, tongue and gums. The microsco pic lesions were characterized by hyperplasia of lymphoid cells at the haemopoietic cen tres in lymph glands and spleen followed by regression and degeneration of the ger minal centres. Infiltration by lymphocytes and macrophages was observed in intermysial (heart) and periportal (liver) areas and in interstitial spaces in kidneys. T. annulata para sitises lymphoid cells. It provides stimulus for accelerated production of the cells which results in hyperplasia of the lymphoid tissue. Increased activity of the reticular tissue is a protective phenomenon.

Comparative pathogenicity ofTheileria annulatastrains

“…Anaemia was the consistent feature in all the animals infected with T. annulata strains. Similar results have been reported by Gill, Bhattacharyulu and Kaur (3). All the strains of T. annulata studied produced severe theileriosis with classical symptoms in susceptible calves, the mortality in which was 2/4 (Ludhiana), 2/4 (Hissar), 4/5 (Jaipur), 3/5 (Uruli-Kanchan) and 4/5 (Bangalore) ( Table 1).…”

Molecular and pathological studies on natural cases of bovine theileriosis

“…The gross and cytopathological changes observed in lymph nodes, abomasum and other visceral organs in the present investigation of field cases of bovine theileriosis were similar to those describe previously by Gill et al (1977), Sandhu (1996) and Tuli et al (2015). Tuli et al (2015) also examined Giemsa stained thin blood smears immediately after blood collection and observed microscopically different forms of Theileria parasite in the erythrocytes.…”

“…In India, T. annulata is predominantly transmitted by Hyalomma anatolicum anatolicum in dairy animals (Tuli et al 2015). The affected animals show fever, anemia, enlargement of lymph nodes, anorexia and progressive loss of body weight (Gill et al 1977;Aulakh and Singla 2006).…”

A dual role for immunosuppressor mechanisms in infection with Theileria annulata: well-regulated suppressor macrophages help in recovery from infection; profound immunosuppression promotes non-healing disease

“…The two carrier calves and the immunised/challenged calves were treated with buparvaquone (2.5 mg/kg) on day 35 of the challenge infection to ensure that all parasites had been eliminated before the animals' cells were retested approximately 8 weeks later. The Hisar stock was described by Gill et al (1976), the Batan 2 and Jed 4 stocks (as CL2 and CL4, respectively) by Darghouth et al (1996). All calves were maintained throughout on commercial food and hay and water ab libitum.…”