Myxoma virus

Classification

Taxonomy

• Family: Poxviridae.
• Subfamily: Chordopoxvirinae.
• Genus:Leporipox.
• Species:myxoma virus.

Etymology

• Gk:muxa- slime, mucus.

Distribution

• Endemic to South America where it causes a benign local fibroma in its natural host, the native forest rabbit (Sylvilagus brasiliensis)   Cottontail  .
• Initially isolated in Uraguay in 1896 in laboratory rabbits (Oryctolagus cuniculus) imported from Europe.
• Introduced to France in 1936 to control wild rabbits (Oryctolagus cuniculus), spread through Europe and was first reported in the UK in 1953.
• Deliberately introduced into Australia in the 1950s to control the plague proportions of introduced rabbits.
• A related strain is found in the North American brush rabbit (Sylvilagus bachmani)   Cottontail   which also causes benign infection in this natural host.

Significance

• Found to be pathogenic only in lagomorphs.
• Causes myxomatosis   Myxomatosis   in susceptible European rabbits (Oryctolagus cuniculus) and occasional clincial signs in European Brown Hares.
• Several strains of the virus occur; these vary extensively in virulence.
• In Australia the initial high fatality of susceptible rabbit populations was reported to be 90%. In succeeding years, it is thought that genetic selection in the rabbit population for innate resistance and less virulent field strains emerging, have decreased fatality to a reported 30% in some areas of Australia.
• Clinical signs include purulent conjunctivitis     , and subcutaneous swelling     .
• The case fatality rate is high in susceptible domestic rabbits.