REOVIRIDAE: ROTAVIRUSES AND ORBIVIRUSES

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REOVIRIDAE ROTAVIRUSES AND ORBIVIRUSES

• PETER H. RUSSELL, BVSc, PhD, FRCPath, MRCVS
• Department of Pathology and Infectious Diseases,
  The Royal Veterinary College,
• Royal College Street,
• London NW1 OTU.
• E-mail Web site

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LEARNING OBJECTIVESStudents should be able to

• Relate the pathogenesis of rotaviruses to the
  methods used for their control.
• Discuss the difficulties of making an accurate
  rotavirus diagnosis.
• Explain the control measures adopted for African
  horse Sickness Virus.

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FAMILY CHARACTERISTICS
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ROTAVIRUSES (RVs)

• DISEASE PATHOGENESIS

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ROTAVIRUSES (RVs)

• ANTIGENICITY

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ROTAVIRUSES (RVs)

• HOST RANGE

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ROTAVIRUSES (RVs)

• EPIZOOTIOLOGY

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ROTAVIRUSES (RVs)

• DIAGNOSIS
• Care is needed to interpret positive results as
  RVs are commonly found in the faeces of
  clinically normal neonatal animals. Compare the
  number of RVve diseased animals with the number
  of RVve unaffected, age-matched animals on the
  farm. Diagnosis of outbreaks should not be based
  on single faecal samples.

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ROTAVIRUSES (RVs)

• CONTROL
• The following relates to group A RVs but may also
  relate to the other groups.
• By an inter-relationship between passive immunity
  virus exposure. It is impossible to prevent
  infection of the young but disease can be
  supressed/eliminated by keeping the infection
  pressure low and ensuring neonatal animals
  receive adequate levels of passive antibody
  orally while at risk.

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AFRICAN HORSE SICKNESS VIRUS (AN ORBIVIRUS)

• "orbis" ring (latin) - ring-shaped capsomeres
  are seen on the surface of virions by electron
  microscopy. Recognized in Africa since 1780. It
  is one of the most feared viral diseases of
  horses but does not occur in the UK.

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AFRICAN HORSE SICKNESS VIRUS (AN ORBIVIRUS)

• ANTIGENICITY Nine serotypes.

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AFRICAN HORSE SICKNESS VIRUS (AN ORBIVIRUS)

• HOST RANGE Horses mules, donkeys zebras
  appear to be more resistant to the disease.

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AFRICAN HORSE SICKNESS VIRUS (AN ORBIVIRUS)

• CONTROL

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OTHER MEMBERS

• Many REOVIRUSES infect the alimentary and/or
  respiratory tract of cattle, sheep, dogs and cats
  without causing disease (REO Respiratory-Enteric-
  Orphan).

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Summary

• Rotaviruses pathogenesis is confined to the gut
  passive maternal antibody in the gut lumen is
  important to control the disease.
• Care is required in RV diagnosis as RVs are
  also found commonly in sub-clinical infections
• Control of African Horse Sickness Virus centres
  around vaccination and removal of infected horses
  and vectors.