Theileriosis in Cows (Bovis) | Vetlexicon
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ISSN 2398-2993

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Synonym(s): Theileriosis, T. parva, T.annulata, T orientalis (Ikeda), vector borne, theileria annulata parva mutans orientalis rhipicephalus vector, East coast fever, Tropical fever Corridor disease


  • Cause:
    • Theileriae are obligate intracellular protozoan parasites that infect both wild and domestic bovidae throughout much of the world.
    • Theileria parva is responsible for East Coast Fever in Eastern and Central Africa.
      • Buffalo-derived Theileria parva is responsible for a related condition known as "Corridor disease", a fatal condition of cattle. It was previously believed that the two diseases were caused by two separate Theileria parasites, T. parva parva and T. parva lawrencei.  However, genetic analysis has concluded that these two diseases are caused by the same parasite, T. parva, with differences in pathogenicity and virulence. 
    • Theileria annulata is responsible for tropical theilerioses in Mediterranean countries.
    • Theileria orientalis is found worldwide, but countries affected by clinical oriental theileriosis include Australia, New Zealand, Japan, Korea, China, Vietnam and the United States of America. The Asian Long-horned tick is the vector for T orientalis Haemophysalis longicornis . 11 genotypes of T orientalis have been identified:
      • Theileria orientalis chitose (type 1) – associated with severe disease.
      • Theileria orientalis ikeda (type 2) – associated with severe disease outbreaks in Asia, Australia, New Zealand and the US.
      • Theileria orientalis buffel (type 3) has been reported in the UK but is considered non-pathogenic.
      • Types 4 to 8 and N1 to N3 have also been identified.
  • Signs: see below.
  • Diagnosis: indirect fluorescent antibody test; Giemsa stained impression smears form the blood or lymph nodes in live animals, or from most internal organs in necropsies; PCR.
  • Treatment: anti-protozoal drugs, such as buparvaquone, parvaquone, and halofuginone and the antimicrobial oxytetracyline have been advocated.
  • Prognosis: guarded.

Geographic incidence

  • Worldwide.

Age predisposition

  • All age groups may be affected.

Breed/Species predisposition

  • European Bos taurus types are more susceptible than indigenous Bos indicus based breeds of cattle.

Public health considerations

  • None.

Cost considerations

  • Depressed milk production, abortions, still births and mortality.

Special risks


Predisposing factors


  • Naïve cattle introduced into an endemic area.
  • Infected cattle introduced into an uninfected area.
  • Infected ticks transported on cattle into an uninfected area.


  • Sporozoites are inoculated via infective ticks into lymphocytes which undergo schizogony and lymphoid proliferation.
  • Further lymphoid proliferation occurs and schizonts differentiate into merozoites and invade nearby erythrocytes.
  • Here they form piroplasms which are the infective form for ticks.


  • The incubation period after infection is 10-25 days.


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Further Reading


Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Eamens G J, Bailey G, Gonsalves J R, Jenkins C (2013) Distribution and temporal prevalence of Theileria orientalis major piroplasm surface protein types in eastern Australian cattle herds. Aust Vet J 91, 332-340 PubMed.
  • Izzo M M, Poe I,  Horadagoda N, De Vos A J, House J K (2010) Haemolytic anaemia in cattle in NSW associated with Theileria Infections. Aust Vet J 540, 45-51 PubMed.
  • Oakes V, Yabsley M, Schwartz D, et al (2019). Theileria orientalis Ikeda Genotype in Cattle, Virginia, USA. Emerging infectious diseases:1653-1659.
  • Watts J, Playford M, Hickey K (2015). Theileria orientalis: A review. New Zealand veterinary journal 64:1-21.
  • Cook E et al (2021) Clinical evaluation of Corridor Disease in Bos Indicus (Boran) cattle naturally infected with buffalo derived Theileria parva Front Vet Sci   731238 PubMed.
  • Taylor M (2000) Protozoal disease in cattle and sheep. In Practice 22, 604-617 PubMed.

Other sources of information

  • OIE technical disease card (2009) Theileriosis. pp 1-6: Website: Last accessed 20th February 2017.
  • Brown C & Torres A (2008) USAHA Foreign Animal Diseases. Seventh Edition. In:
    Committee of Foreign and Emerging Diseases of the US Animal Health Association. Boca
    Publications Group Inc, Canada. pp 401-404.
  • Radostits O M, Gay C C, Blood D C & Hinchcliff K W (2005) Diseases caused by protozoa. In: Veterinary Medicine. 9th edn. W B Saunders, USA. pp 1324-1329.