Myxomatosis
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Myxomatosis is a disease which infects only rabbits. It is caused by the myxoma virus. First observed in Uruguay in the early 1900s, it was deliberately introduced into Australia in an attempt to control rabbit infestation there—see rabbits in Australia.
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Effects of the disease
At first, the disease is visible by lumps and puffyness around the head and genitals. It then may progress to acute conjunctivitis and possibly blindness. The rabbit becomes listless, loses appetite, and develops a fever. In typical cases where the rabbit has no resistance, death takes an average of 13 days.
Spread of the disease
After its discovery in imported rabbits in Uruguay, a relatively harmless strain spread quickly throughout the wild population in South America. In Australia, the virus was first field-tested for population control in 1938. A full-scale release was performed in 1950. It was devastatingly effective, reducing the estimated rabbit population from 600 million to 100 million in two years. However, the rabbits remaining alive were those least affected by the disease. Genetic resistance to myxomatosis was observed soon after the first release and most rabbits acquired partial immunity in the first two decades. Resistance has been increasing slowly since the 1970s, and the disease now only kills about 50% of infected rabbits. In an attempt to increase that number, a second virus (rabbit calicivirus) was introduced into the rabbit population in 1996.
Myxomatosis was deliberately introduced to France by Dr. P. F. Armand-Delille in 1952. By 1954, 90% of the wild rabbits in France were dead. The disease spread throughout Europe. It reached the UK in 1953, apparently without human action. Some in the UK deliberately spread the disease, placing sick rabbits in burrows, while many others deplored the cruelty and suffering. The government refused to legislate to make deliberate spread of the disease illegal. By 1955, about 95% of rabbits in the UK were dead. Rabbits suffering in the last stages of the disease, commonly called "mixy" rabbits, are still a common sight in the UK in 2005.
Myxomatosis is spread by fleas and mosquitos. Therefore, pet rabbits should be kept away from these pests.
Use of Vaccine
A vaccine is available for pet rabbits, but is illegal in Australia because of fears that the immunity conferred by the vaccine could be transmitted through the wild rabbit population, because the vaccine uses a live virus, the shope fibroma virus. The name of the vaccine is Nobivac Myxo and it can be acquired with a prescription.
Natural Resistance
The development of resistance to the disease seems to have taken different courses. In Australia, the virus initially killed rabbits very quickly, about 4 days after infection. This gives little time for the infection to spread. As a result of this, a less virulent form of the virus has become prevalent there, spreading more effectively by being less lethal. In Europe, rabbits which are genetically resistant to the original virus have spread. It is conjectured that this is because the main transmission vector in Australia is the mosquito, while in Europe it is the flea.
Cultural references
Myxomatosis is also the name of a song on Radiohead's 2003 album Hail to the Thief.
The Hitchhiker's Guide to the Galaxy mentions Myxomatosis in Chapter 24. It incorrectly applies the disease to mice.
External Links
- Society & Animals Journal of Human-Animal Studies, Volume 9, Number 2, 2001 (http://www.psyeta.org/sa/sa9.2/kean.shtml)
- An interview with Frank Fenner (http://www.science.org.au/scientists/ff.htm#myxomatosis)
- Coalition against Myxomatosis (http://members.iinet.net.au/~rabbit/coalition.htm) - an organisation campaigning for legalisation of vaccine in Australia.da:Myxomatose