Transcript HERPESVIRIDAE

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
LEARNING OBJECTIVES
Students 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.
FAMILY
CHARACTERISTICS:
ROTAVIRUSES (RVs)
DISEASE & PATHOGENESIS
ROTAVIRUSES (RVs)
ANTIGENICITY:
ROTAVIRUSES (RVs)
HOST RANGE
ROTAVIRUSES (RVs)
EPIZOOTIOLOGY:
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 RV+ve diseased
animals with the number of RV+ve
unaffected, age-matched animals on the
farm. Diagnosis of outbreaks should not
be based on single faecal samples.
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.
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.
AFRICAN HORSE SICKNESS
VIRUS (AN ORBIVIRUS)
ANTIGENICITY: Nine serotypes.
AFRICAN HORSE SICKNESS
VIRUS (AN ORBIVIRUS)
HOST RANGE: Horses; mules, donkeys &
zebras appear to be more resistant to the disease.
AFRICAN HORSE SICKNESS
VIRUS (AN ORBIVIRUS)
CONTROL:
OTHER MEMBERS
Many REOVIRUSES infect the alimentary
and/or respiratory tract of cattle, sheep, dogs
and cats without causing disease (REO=
Respiratory-Enteric-Orphan).
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.