Question

when researchers first brought the rabbit myxoma virus to australia to kill introduced rabbits, it was 99.8% effective. however the rabbit mortality rate quickly dropped 70-95% in the years following. what caused the change in morality rate?

Answer 1

The decrease in rabbit mortality rate from the myxoma virus in Australia, from 99.8% to 70-95%, was due to the evolution of both the virus and the rabbits, with the virus becoming less virulent and rabbits developing resistance.

Step-by-step explanation:

When researchers first brought the myxoma virus to Australia to control the population of introduced rabbits, the virus initially had a 99.8% effectiveness in causing rabbit mortality. However, the rabbit mortality rate quickly dropped to 70-95% in the years following. This change is attributable to two main factors: viral evolution and the rabbit population itself developing resistance to the virus. The initially virulent strains of myxoma virus evolved to become more benign, as lethal viruses tend to kill their hosts too quickly, thereby reducing chances to spread. Concurrently, the rabbit populations in Australia began to evolve resistance to the myxoma virus, resulting in lower mortality rates with each successive epidemic.