*WARNING THIS POST WILL CONTAIN GRAPHIC IMAGES OF DEVIL FACIAL TUMOUR DISEASE*
If you read my Animal Travels: Australia post you will know that Tasmanian Devils are suffering from a infectious tumour disease known as DFTD (Devil Facial Tumour Disease). This post will delve deeper into this disease that is causing the rapid decline of the Tasmanian Devils!
Loh et al. (2006) said that the disease was a disfiguring and debilitating neoplastic condition. Neoplastic refers to a new or abnormal growth of tissue. In 2006 DFTD had affected 51% of the natural population leading to a decline of up to 80%. The tumours presented themselves as large, solid, soft tissue masses which were usually flattened with centrally ulcerated surfaces. The tumours normally first appeared in the oral, facial or neck regions. The tumours were locally aggressive and metastasised in 65% of cases. Metastasised refers to when a tumour starts in one location on the body and then moves to another location. Loh et al. concluded that Devil Facial Tumour Disease is an undifferentiated soft tissue neoplasm.
Murchison et al. (2010) also studied DFTD in the Tasmanian Devil. They discovered that DFTD is clonally derived and is an allograft (tissue graft of one individual of the same species to another) transmitted between individuals by biting. They also found that DFTD is of Schwann cell origin.
A further study by J.H Brown (2008) found that DFTD had lead to a change in the life history of Tasmanian Devils as many individuals face mortality after their first year of adult life. This lead to a 16-fold increase in precocious sexual maturity. This is believed to be the first known case where an infectious disease has lead to an increased amount of early reproduction within a mammal species.
These studies show us why Devil Facial Tumour Disease has spread so rapidly within the Tasmanian Devil population. They also pose important questions about how diseases can drive evolution within a species. Although it is clear that evolution is happening within the Tasmanian Devil species, it is important to note that this evolution is not sufficient to maintain the survival of the species and conservation projects are needed to help the species back into a sustainable population that is no longer in danger of extinction.