East Coast fever

Previous Authors: J A LAWRENCE, B D PERRY AND S M WILLIAMSON

Current Authors:
J A LAWRENCE - Extraordinary Professor, DPhil, BSc, MRCVS (ret.), DTVM, Department of Paraclinical Veterinary Science, University of Zimbabwe, Harare, Zimbabwe 
K P SIBEKO-MATJILA - Senior Lecturer, BSc, PhD, Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, Private Bag X04, University of Pretoria, Gauteng, 0110, South Africa 
B J MANS - Principal Researcher, BSc, BSc (Hons) Biochemistry, MSc (Biochemistry), PhD (Biochemistry), Agricultural Research Council, Onderstepoort Veterinary Research, 100 Old Soutpan Road, Gauteng, 0110, South Africa

GENERAL INTRODUCTION: THEILERIOSES OF CATTLE

Introduction

East Coast fever in its classical form is a usually fatal disease of cattle caused by Theileria parva. It is transmitted principally by the brown ear tick Rhipicephalus appendiculatus and is characterized by the proliferation of lymphoblasts infected with theilerial schizonts throughout the body, particularly in the lymph nodes, spleen and lymphoid aggregatesin the kidneys, liver and lungs. The disease occurs widely through the range of its main vector in eastern, central, and southern Africa north of the Zambezi River (see Vectors: Ticks). It was introduced into the region south of the Zambezi River in 1901/02 and spread through most of the range of its vector but was subsequently eradicated (Figure 29.1).

The classical disease is seen in cattle of European origin which have been exposed to infected ticks. Cattle of African origin have a very variable response to infection and the disease may be insignificant or subclinical in Zebu calves born from immune dams and raised in endemically infected areas.

The disease was first described as an unusually virulent form of babesiosis by Gray and Robertson⁵⁷ in 1902, following its introduction into Zimbabwe. It was initially named Rhodesian redwater. Koch⁶⁹ identified the parasite with one that he had seen in 1897 in cattle on the coast of Tanzania. He named the disease African Coast fever, the name being subsequently modified to East Coast fever in South Africa. The causal organism was named Piroplasma kochi by Stephens and Christophers in 1903, but the name was changed to Piroplasma parvum by Theiler¹⁵⁹ and subsequently to Theileria parva by Bettencourt, França and Borges in 1907 (as quoted by Henning⁵⁹). Uilenberg¹⁶⁸ proposed that the organism be named Theileria parva parva to distinguish it from other subspecies of T. parva which cause diseases that can be differentiated from East Coast fever on epidemiological grounds. However, it has since been agreed that East Coast fever be known as cattle-derived theileriosis and that it is caused by the same parasite as that causing Corridor disease and January disease.^{3, 135}

East Coast fever has long been endemic in eastern Africa. The parasite probably originated from African buffalo (Syncerus caffer) populations in eastern Africa and became adapted to cattle following their introduction and dissemination in the region, especially in the Lake Victoria Basin and along the coastal strip.¹²⁸ It spread widely through the region during the early part of the nineteenth century as a result of European settlement, which involved changes in patterns of movement, extensive use of ox-drawn transport, and importation of susceptible cattle breeds from overseas. The First World War (1914 to 1918), during which the campaign in what was then German East Africa, now Tanzania, took place, also resulted in unusual cattle movements and further dissemination of the disease.

East Coast fever was introduced into the area south of the Zambezi River in the period 1901 to 1903 by cattle which were imported from Kenya and Tanzania for the purpose of restocking the region after the ravages of the rinderpest epidemic of 1896 and the South African War (1899 to 1902).⁷¹ The disease initially appeared in Zimbabwe, southern Mozambique and the northern parts of South Africa, and then spread southward along the east coast of southern Africa, through Swaziland, KwaZulu-Natal, and the Eastern Cape Province. In the period up to 1914 it is estimated to have killed one and a quarter million of the four million cattle that were present in the affected territories at the beginning of the outbreak. The southward advance was halted in the region of East London in the Eastern Cape Province, and the disease was subsequently eradicated in a prolonged campaign consisting of movement control, tick control, destocking of infected pastures, and slaughter. It was eradicated from southern Mozambique by 1917, from Zimbabwe by 1954, and from South Africa by 1955. The last case south of the Zambezi River occurred in Swaziland in 1960. The disease has persisted in the region north of the Zambezi River to the present day and is a major constraint on the development of cattle production.

East Coast fever, if uncontrolled, may cause over 90 per cent mortality of the susceptible cattle following its introduction into a region. In an area where it is endemic, mortality among locally adapted Zebu-type cattle may be negligible but there is evidence that the disease causes a significant reduction in growth and productivity. Susceptible cattle introduced into an endemic area are very vulnerable to infection and the cost of the control measures required is a continuous financial burden on both livestock owners and state...