The Science & Control: Myxomatosis, RHDV and the Evolutionary Arms Race

When rabbits became an agricultural and ecological crisis, Australians tried all the usual tools: fences, shooting, poisoning and warren destruction. But the scale of the problem demanded larger-scale solutions — and that led to two landmark biological controls that are now textbook examples of host–pathogen coevolution: myxomatosis (the myxoma virus) and rabbit haemorrhagic disease virus (RHDV, a calicivirus). csiropedia.csiro.au+1

Myxoma and the first big crash

• When and what: In the 1950s (after trials earlier), Australia intentionally released the myxoma virus — a poxvirus causing myxomatosis — which produced catastrophic mortality in European rabbits and led to dramatic population declines. This is widely considered the world’s first successful large-scale biological control of a mammalian pest. csiropedia.csiro.au+1

• Evolution followed: Within a few years, rabbit populations rebounded partially because survivors had genetic resistance and because less-virulent viral strains emerged. The myxoma episode thus became a seminal, real-time example of reciprocal evolution (virulence attenuation in the virus; resistance in the host). This coevolutionary dynamic has been intensively studied by ecologists and evolutionary biologists. CSIRO+1

RHDV (calicivirus): a second wave

• 1990s introduction: Rabbit haemorrhagic disease virus (RHDV) was released in the 1990s (notably from Wardang Island trials) and rapidly spread across the mainland. The initial RHDV wave produced very high mortality in many regions (some areas lost >90% of rabbits). BioMed Central

• Why control wasn’t permanent: As with myxoma, subsequent patterns of immunity, benign caliciviruses circulating in coastal/temperate zones (e.g., RCV-A1), and viral evolution meant that control effects varied across space and time. Epidemiologists, virologists and managers have documented virus persistence, immunity patterns, and environmental survivability in extensive reviews and field studies. PubMed Central+1

Lessons in disease ecology

• Biological control using pathogens can produce rapid and large benefits, but rarely yields permanent eradication for wide-ranging pests.

• Host immunity, benign cross-protective viruses, viral evolution, and landscape refugia are predictable mechanisms by which control efficacy declines over time.

• The rabbit case is now taught as a canonical example of applied disease ecology: it demonstrates benefits, limits, and the ethical/policy tradeoffs of using disease agents for pest control. CSIRO+1

Research highlights and where to read more

• CSIRO’s historical summaries and reviews explain the myxoma program and its long-term outcomes. CSIRO

• Scholarly reviews on RHDV document the virus biology, environmental persistence and the epidemiological outcomes after the 1995 releases. BioMed Central+1