Age-Structured and Vaccination Models of Devil Facial Tumor Disease

Abstract

Tasmanian devil populations have been devastated by devil facial tumor disease (DFTD) since its first appearance in 1996. The average lifespan of a devil has decreased from six years to three years. We present an age-structured model to represent how the disease has affected the age and breeding structures of the population. We show that with the recent increase in the breeding of juvenile devils, the overall devil population will increase but not nearly to pre-DFTD levels. The basic reproductive number may be increased with the influx of young breeding devils. In addition, our model shows that the release of nearly 100 captivebred, vaccinated devils into infected, wild populations may help eliminate the disease and hence enable the population's recovery. Specifically, we demonstrate that with this release of captive-bred, vaccinated devils the basic reproductive number is decreased to below one.

Disruption of Metapopulation Structure Reduces Tasmanian Devil Facial Tumour Disease Spread at the Expense of Abundance and Genetic Diversity

“…Vaccination has been proven to be effective in reducing disease spread in other wildlife diseases, such as rabies [57]. The release of captive-bred, immunised devils into local populations has been previously suggested to be a viable option in reducing DFTD spread [37]. Devils have been injected with sonicated DFTD cells with the aim to stimulate adaptive immunity as a potential vaccine [58], however, there is no evidence that attempted immunizations are prophylactic in the wild [59,60].…”

“…Previous work has generated a good understanding of how DFTD spreads between individuals, how it leads to population decline and how it drives demographic changes within local populations [30,[35][36][37][38]. However, we still know surprisingly little about the processes that drive the spread of DFTD on a regional scale.…”

Disruption of metapopulation structure effectively reduces Tasmanian devil facial tumour disease spread at the expense of abundance and genetic diversity

“…Previous work has generated a good understanding of how DFTD spreads between individuals, how it leads to population decline, and how it drives demographic changes within local populations (Jones et al 2008;McCallum et al 2009;Beeton & McCallum 2012;Bruno et al 2017;Wells et al 2019). However, we still know surprisingly little about the processes that drive the spread of DFTD on a regional scale.…”

“…. The release of captive-bred, immunised devils into local populations has been previously suggested to be a viable option in reducing DFTD spread(Bruno et al 2017). Devils have been injected with sonicated DFTD cells with the aim to stimulate and adaptive immunity as a potential vaccine (Tovar et al 2017), however, there is no evidence that attempted immunizations are prophylactic in the wild(Pye et al 2018; which was not certified by peer review) is the author/funder.…”

“…. The release of captive-bred, immunised devils into local populations has been previously suggested to be a viable option in reducing DFTD spread(Bruno et al 2017). Devils have been injected with sonicated DFTD cells with the aim to stimulate and adaptive immunity as a potential vaccine (Tovar et al 2017), however, there is no evidence that attempted immunizations are prophylactic in the wild(Pye et al 2018; Whilst it is too late to prevent DFTD from spreading across Tasmania, it is hoped that alternative management options can be developed to prevent the spread of a second and independently evolved transmissible cancer affecting Tasmanian devils, devil facial tumour 2 (DFT2)(Pye et al 2016) from causing another wave of catastrophic population decline(James et al 2019;Flies et al 2020).…”