Blackwell Publishing

Coevolution - Are parasites and their hosts coevolving?


An example: myxomatosis

The myxoma virus (which causes myxomatosis) in Australian rabbits provides the classic illustration that the virulence of a parasite can change evolutionarily.

The rabbits in question belong to a species (Oryctolagus cuniculus ) which is native to Europe but was introduced to Australia, where it thrived and became a pest. In 1950 the virus was deliberately introduced into Australia in an attempt to control the pestiferous rabbits.

It was, initially, a deadly success. It spread from rabbit to rabbit by means of mosquitoes and the large population of those biting insects enabled the myxoma virus to sweep dramatically through the southeast Australian rabbit population. Myxomatosis initially almost annihilated the rabbit population: it declined by 99% in some hard hit areas.

The myxoma virus was highly virulent when it first hit the Australian rabbit population; it killed 100% of infected hosts. Soon, however, the kill-rate declined. What could have caused this decline?

This extremely unpleasant image shows a rabbit suffering from the myxomatosis virus.

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