Résumé
Emerging infectious diseases are rising globally and understanding
host-pathogen interactions during the initial stages of disease emergence
is essential for assessing potential evolutionary dynamics and designing
novel management strategies. Tasmanian devils (Sarcophilus harrisii) are
endangered due to a transmissible cancer – devil facial tumour disease
(DFTD) – that since its emergence in the 1990’s, has affected most
populations throughout Tasmania. Recent studies suggest that devils are
adapting to the DFTD epidemic and that disease-induced extinction is
unlikely. However, in 2014 a second and independently evolved
transmissible cancer – devil facial tumour 2 (DFT2) – was discovered at
the d’Entrecasteaux peninsula, in southeast Tasmania, suggesting that the
species is prone to transmissible cancers. To date, there is little
information about the distribution, epidemiology and effects of DFT2 and
its interaction with DFTD. Here we use data from monitoring surveys and
road-kills found within and adjacent to the d’Entrecasteaux peninsula to
determine the distribution of both cancers and to compare their
epidemiological patterns. Since 2012, a total of 51 DFTD tumours have been
confirmed among 26 individuals inside the peninsula and its surroundings,
while 40 DFT2 tumours have been confirmed among 23 individuals, and two
individuals co-infected with both tumours . All devils with DFT2 were
found within the d’Entrecasteaux peninsula, suggesting that this new
transmissible cancer is geographically confined to this area. We found
significant differences in tumour bodily location in DFTD and DFT2, with
non-facial tumours more commonly found in DFT2. There was a significant
sex bias in DFT2, with most cases reported in males, suggesting that since
DFT2 originated from a male host, females might be less susceptible to
this cancer. We discuss the implications of our results for understanding
the epidemiological and evolutionary interactions of these two
contemporary transmissible cancers and evaluating the effectiveness of
potential management strategies.