Paul-Félix Armand-Delille: Europe’s Rabbit Killer

In the 1950s, Australian sheep and cattle farmers decided to tackle the country’s rabbit problem by unleashing a biological weapon—the myxoma virus. This poxvirus causes only mild symptoms in its natural hosts, the cottontail rabbits, but is usually fatal on European rabbits abundant in Australia. The introduction of the virus dramatically reduced Australia’s rabbit population, resulting in a rapid economic recovery for the wool and meat industries, generating millions of dollars within two years. Unfortunately, efforts to implement similar biological measures in Europe ended in a catastrophe.

Rabbits around a waterhole at the myxomatosis trial enclosure on Wardang Island in 1938. Photo credit: Wikimedia Commons

Rabbits were first introduced in Australia in 1788 for their meat and were originally bred in rabbit farms and enclosures, until a busybody decided to release rabbits on his property so that his guests could have fun hunting. Some of the rabbits escaped his property, as expected, and began proliferating as rabbits do. Within a few years, the furry pest had overrun the country, eating off vegetation, shrubs and plants leading to erosion and ecological devastation.

In 1887, loses from rabbit damage were so great that the Inter-Colonial Rabbit Commission offered a £25,000 prize “to anyone who could demonstrate a new and effective way of exterminating rabbits.” Thousands of suggestions were received. Shooting and poisoning rabbits were the most common method suggested to tackle the problem. Eventually, a huge fence was erected between 1901 and 1907 to keep out rabbit population from pastoral areas in Western Australia. Known as the rabbit-proof fence, it originally stretched for 1,800 kilometer. It was extended and reinforced with additional fences, but in vain. Rabbits continued to be a headache for cattle farmers.

In 1906 and 1907, Jean Danysz, of the Pasteur Institute of Paris, conducted trials of a strain of Pasteurella bacteria he had developed, which proved to be fatal to rabbits. However, experiments proved to be unsatisfactory, and although Danysz's successor, Frank Tidswell, continued Danysz's trials with different microbes, the federal government was less than willing to grant him funds. That is, until Australian virologist Frank Fenner showed that the myxoma virus killed off rabbits in 9 to 11 days and had a fatality rate of close to 99.8 percent. To prove to the authorities that the virus was harmless to humans, Fenner and two of his colleagues even injected themselves with myxoma virus without any ill effects.

The first infected rabbits were released in Wardang Island, South Australia, in 1937 as part of a trial. Photo credit: CSIRO/Wikimedia Commons

In 1950, the myxoma virus was released for the first time into the rabbit population. Within three months, the rabbit population collapsed from an estimated 600 million to around 100 million. Although the rabbits eventually developed some resistance to the disease, enabling some of them to survive and the population recovered to some extent but never to pre-1950 levels.

News of the myxoma virus’s effectiveness eventually reached Europe, where French bacteriologist Paul-Félix Armand-Delille decided to put it to use on his 600-acre estate in Maillebois in Eure-et-Loir, not far from Paris. Armand-Delille injected two rabbits with the virus acquired from a laboratory in Lausanne, and released the pair on his estate. Within six weeks, 98 percent of rabbits on his estate was dead. However, after four months, it became evident that the virus had escaped, as the corpse of an infected rabbit was discovered 50 km away.

Paul-Félix Armand-Delille

Within a year of the initial release, nearly half of the wild rabbits in France had perished from the disease, along with one-third of domestic rabbits. The malady subsequently spread throughout western Europe, decimating rabbit populations in the Netherlands, Belgium, Italy, Spain, Germany, Britain, and beyond. The impact on France's rabbit population was staggering. In the hunting season of the virus's release year, 1952–1953, the total number of rabbits killed in 25 hunts exceeded 55 million. By 1956–1957, only 1.3 million rabbits were shot by hunters—a 98 percent reduction.

Armand-Delille faced condemnation from rabbit hunters but received accolades from farmers and foresters. He was prosecuted and, in January 1955, convicted and fined 5,000 francs. Despite this, he was later honored, receiving a gold medal in June 1956 to commemorate his achievement from Bernard Dufay, the honorary director-general of the French Department of Rivers and Forests. The medal features Armand-Delille on one side and a deceased rabbit on the other.

Over the decades, the rabbit population in Europe has improved as the animal developed natural resistance to the disease. A survey conducted in UK in 2005 reported that the rabbit population had been increasing three-fold every two years.