B111 - THEILERIOSIS

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B111 - THEILERIOSIS

Nature of the disease
Theileriosis is a serious disease of Bovidae due to the infection by the protozoa Theileria parva causing East Coast Fever (ECF) or Theileria annulata causing Tropical Theileriosis or Mediterranean Coast Fever (MCF). Both parasites are transmitted by ticks.  
Classification
OIE List B disease
Susceptible species
ECF and MCF are diseases of cattle and domestic buffaloes. Other Theileria spp. can infect caprine and ovine.
Distribution
ECF is essentially present in central and eastern Africa. MCF is present in northern Africa, southern Europe, Middle East and central Asia. Serological evidences of Theileria orientalis (Syn. Theileria buffeli) have been found in many places in the Pacific however this organism is not pathogenic.
Clinical signs 
ECF and MCF have similar courses and after an incubation period of 1 to 3 weeks, symptoms include:
  • Augmentation of lymph nodes,
  • High fever and anorexia,
  • Drop in milk yield,
  • Nasal and ocular discharge,
  • Dyspnoea,
  • Diarrhoea,
  • Emaciation, weakness and recumbency,
  • Death after occurs after 7-10 days in 90 % of cases.

In ECF there is sometimes a turning sickness which is due to a brain involvement. Digestive symptoms are usually milder with ECF but death is more frequent.

In MCF there is sometimes cutaneous signs, the skin is thicker and covered with cutaneous ulcers. Petechia and abortion are commonly observed with MCF.

Post-mortem findings 
  • Massive pulmonary oedema,
  • Hyperaemia, emphysema,
  • Enlargement of lymph nodes and spleen,
  • Ulceration of the abomasum and intestines
Differential diagnosis 
  • Babesiosis
  • Anaplasmosis
  • Besnoitiosis (MCF)
  • Trypanosomis
  • Malignant Catharal Fever
Specimens required for diagnosis 
Visualisation of the parasite in the cells can be attempted from thin smears prepared from blood and from biopsy material of lymph nodes or liver, and stained with Giemsa.

Blood conserved on EDTA and on an appropriate transport medium can be submitted for PCR.

Serological techniques are available including an indirect fluorescent antibody test and an more recently an ELISA test.

Transmission
Theileriosis is not a contagious disease and the parasite must be transmitted by an Ixodid tick. Theileria parva is transmitted by Rhipicephalus appendiculatus. Theileria annulata is transmitted by Hyalomma anatolicum anatolicum, Hyalomma detritum and Hyalomma excavatum
Risk of introduction   
Introduction of Theileriosis could happen through the introduction of infected animals. The establishment of the disease will depend on the presence of competent vector. The introduction of infected vectors will probably have a greater impact but seems to be  at a lower risk.
Control / vaccines  
Safe vaccines have been recently developed for both diseases.

Treatment is possible using naphtoquinones but are expensive. The control of ticks is very important and allow control of other diseases as well. 

References
  • BUSSIERAS J, CHERMETTE R, Protozoologie In Parasitologie Vétérinaire, Ecole Nationale Vétérinaire D'Alfort, 1992, p 70-73; 119-122.
  • GEERING WA, FORMAN AJ, NUNN MJ, Exotic Diseases of Animals, Aust Gov Publishing Service, Canberra, 1995, p 372-375
  • Office International des Epizooties, 2002
  • Theileriases, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p 31-33
  • Theilerioses, In Veterinary Medicine, Saunders, Eight ed, 1997, London p. 1207-1212