Once people exorcised devils, now we immunize them. Researchers and wildlife officers are celebrating the forthcoming release into the wild of the first Tasmanian devils vaccinated against a cancer that has been devastating their species. The release represents hope in the battle against a disease that threatened to drive the largest surviving carnivorous marsupial to extinction, and it may also provide insights for tackling human cancers.
The devil facial tumour disease (DFTD) is one of only two known examples of a disease where cancer cells are infectious agents, rather than being triggered by a virus like in the case of cervical cancer. If one can look past the threat it poses to the survival of an apex predator, and last representative of its genus, the tumor represents a fascinating opportunity to learn more about cancer genetics.
The disease was first detected in 1996, and has since killed so many Tasmanian devils (Sarcophilus harrisii), their prey are losing their fear of coming to ground. Its virulence comes from a combination of the devils' tendency to bite each other, providing an easy method of transmission, and its remarkable mechanism for hiding from the devil's immune system. All DFTD cancers are genetically identical, while having different genetics to any known devil. This means it didn't develop from each host, thus supporting the transmission theory.
The genetic consistency represents a point of weakness, allowing researchers to stimulate immunity against the disease. However, this has proven easier said than done. Cedric, a devil whose apparent immunity carried the hopes of his species for a while, turned out to be more susceptible than thought, and eventually died as a result.
While researchers searched desperately for a cure, uninfected devils were moved to the Australian mainland and offshore islands.
Now, 19 captive-bred devils have been immunized multiple times with a more advanced version of the vaccine, microchipped and will get one more shot before being released into Narawantapu National Park in September.
Associate Professor Greg Woods of the University of Tasmania told IFLScience that even with all this effort, no one knows whether the immune response is strong enough to save a bitten devil in the wild. “We don't know if the antibody response increases after repeated vaccinations,” Woods said. “We still need to check the antibodies after the subsequent rounds. But the devils are important to the ecosystem and we are introducing them into an area where the disease is already at a low prevalence and we hope the immunization will help.”
Should the immunized devils prove immune, Woods says there is no prospect of them passing this on to their offspring. Consequently, even in the best-case scenario, defeating the disease will involve vaccinating enough devils for herd resistance to control the tumor's spread.
Devils infected with DFTD are too repulsive for us to show, so here is one looking confident in the success of the immunization program. Credit: Curioso/Shutterstock
The Save the Devil campaign depends heavily on public donations.
[H/T: Sydney Morning Herald]