Tasmanian Devil Facial Tumour Disease

Published Date: 02 Nov 2017

Rebecca Dumesny

Scientific Writing

SLE115: Essential Skills in Bioscience

Waurn Ponds

Topic: Tasmanian Devil Facial Tumour Disease: what is it and what can be done?

Part A: Literature Search Using Databases

Web of Knowledge:

Hamede, RK; McCallum, H; Jones, M 2013, ‘Biting injuries and transmission of Tasmanian devil facial tumour disease ‘, Journal of Animal Ecolog, vol. 82 no. 1, p182-190.

Hamede, RK; Mccallum, H; Jones, M. 2008, ‘Seasonal, demographic and density-related patterns of contact between Tasmanian devils (Sarcophilus harrisii): Implications for transmission of devil facial tumour disease’, Austral Ecology, vol. 33, no. 5, p614-622.

Jones, ME; Jarman, PJ; Lees, CM; Hesterman, H; Hamede, RK; Mooney, NJ; Mann, D 2007, ‘Conservation management of tasmanian devils in the context of an emerging, extinction-threatening disease: Devil facial tumor disease’, Ecohealth, vol. 4, no. 3, p326-337.

Kreiss, A; Cheng, YY; Kimble, F; Wells, B ; Donovan, S; Belov, K; Woods, GM 2011, ‘Allorecognition in the Tasmanian Devil (Sarcophilus harrisii), an Endangered Marsupial Species with Limited Genetic Diversity’, PLOS One, vol. 6, no. 7, p1-8.

Loh, R; Bergfeld, J; Hayes, D; O'Hara, A; Pyecroft, S; Raidal, S; Sharpe, R. 2006, ‘The pathology of devil facial tumor disease (DFTD) in Tasmanian devils (Sarcophilus harrisii)’, Veterinary Pathology, vol. 43, no. 6, p890-895.

Pyecroft, SB; Pearse, AM; Loh, R; Swift, K; Belov, K; Fox, N; Noonan, E; Hayes, D; Hyatt, A; Wang, L; et al. 2007, ‘Towards a case definition for devil facial tumour disease: What is it?’, Ecohealth, vol. 4, no. 3, p346-351.

Science Direct:

Bode, M; Hawkins, C; Rout, T; Wintle, B. 2009, ‘Efficiently locating conservation boundaries: Searching for the Tasmanian devil facial tumour disease front’, Biological Conservation, vol. 142, no. 7, p1333-1339.

Czarny, N.A; Rodger, J.C. 2010, ‘Vitrification as a method for genome resource banking oocytes from the endangered Tasmanian devil (Sarcophilus harrisii)’, Cryobiology, vol. 60, no. 3, p322-325.

Holz, P.H. 2012, ‘Chapter 50 – Tasmanian Devil Facial Tumor Disease’, in R.Eric Miller; Murray E. Fowler (eds), Fowler's Zoo and Wild Animal Medicine. St. Louis, Mo: Elsevier, p386-389.

McCallum, H. 2008, ‘Tasmanian devil facial tumour disease: lessons for conservation biology’, Trends in Ecology & Evolution, vol. 23, no. 11, p631-637.

Pearse, A; Swift, K; Hodson, P; Hua, B; McCallum, H; Pyecroft, S; Taylor, R; Eldridge, M; Belov, K. 2012, ‘Evolution in a transmissible cancer: a study of the chromosomal changes in devil facial tumor (DFT) as it spreads through the wild Tasmanian devil population’, Cancer Genetics, vol. 205, no. 3, p101-112.

Siddle, H; Kreiss, A; Tovab, C; Cheng, Y; Belov, K; Swift, K; Pearse, A; Skjodt, K; Woods, G; Kaufman, J. 2012, ‘Immune escape strategies of a contagious cancer, devil facial tumour disease’, Molecular Immunology, vol. 51, no. 1, p30.

Part B: Essay Plan

Introduction:

Tasmanian Devils are the world’s largest carnivorous marsupials which live within habitats in the island of Tasmania. (Loh et al. 2006)

A new disease was discovered during the 1990’s that severely affected Tasmanian Devils. (Pyecroft et al. 2007)

This was named the Tasmanian Devil Facial Tumour Disease (TDFTD) due to the disfigurement it caused in the facial tissue of these endangered animals. (Pyecroft et al. 2007)

This fatal disease is becoming increasingly prevalent within several populations in Tasmania, and it is becoming obvious that without a cure this endangered species is threatened by extinction. (Pyecroft et al. 2007)

Lacking a treatment for this aggressive disease (Hamede, McCallum & Jones 2013), we are forced to seek alternate solutions such as management during mating season, carrying out programs to increase genetic diversity as well as basic conservation management.

Body 1: The Characteristics and Symptoms of Tasmanian Devil Facial Tumour Disease

This cancerous disease has tumours that generally affect the facial area, but can also spread to the lympth nodes and visceral organs. (Loh et al. 2006)

The lesions on the Tasmanian Devils were greater than three centimetres in 74% of the cases. (Loh et al. 2006)

Scientists analysis of the DFTD tumours showed them to be aggressive yet too simple and lacking specialised cellular organelles to have a specific function. (Loh et al. 2006)

The tendency for DFTD to form in the lips, oral mucosa or face of the Tasmanian Devil suggests transmission of this disease may be via fighting or biting. (Loh et al. 2006)

The cancer is transmissible through direct contact where tumour cells can be passed on between animals through intimate contact live. (Hamede, McCallum & Jones 2013)

Body 2: MHC & Tasmanian Devil Facial Tumour Disease

These tumours have characteristics similar to a microparasite including the ability to replicate itself inside the host. (Hamede, McCallum & Jones 2013)

Tasmanian Devils have low genetic diversity, especially in the Major Histocompatibility Complex (MHC) which produces immune responses in these animals. This could potentially increase the chance of transmission and infection. (Hamede, McCallum & Jones 2013)

This means a Tasmanian Devils immune system cannot recognise foreign cancerous cells as non-self and these cells can more easily infect and cause disease within the host. (Hamede, McCallum & Jones 2013)

Body 3: Conservation through Managing Sexual Interaction between Tasmanian Devils

Devil suggests transmission of this disease may be via fighting or biting. (Loh et al. 2006)

During autumn and winter following the mating season biting injury rates increased. Fighting and biting may be initiated by males to obtain a female mate as well as sexual interaction between mates. (Hamede, McCallum & Jones 2013)

Through finding and removing the more violent individuals in a population it will reduce the phenotype and genotypes that are responsible for most of the transmission of disease. (Hamede, McCallum & Jones 2013)

In managing the networks of contacts between these organism, their behaviours and reproductive habits, the transmission of this fatal disease may be inhibited. (Jones et al. 2007)

In order to sustain a wild population there must be random mating, however sexual interaction must be monitored to minimise mating with any diseased devils. (Jones et al. 2007)

Body 4: The S. harrisii Oocyte Preservation Program

In order to retain genetic diversity, scientists have developed a S. harrisii oocyte preservation program that can be utilized to preserve genetic diversity which is already dwindling in the Tasmanian devil population. (Czarny & Rodger 2010)

This program is derived from a study that shows immature occytes from S. harrisii that have been enzymatically isolated are able to survive cold temperatures and a high concentration of cryoprotectants. (Czarny & Rodger 2010)

Once thawed, approximately 75% of these occytes are still viable. These cells can then potentially assist in the reproduction and reintroduction of genotypes that have been lost via TDFTD. (Czarny & Rodger 2010)

Body 5: Conservation Management

Many Tasmanian devils are held in conservation habitats in four zoos in mainland Australia in addition to a handful of international zoos to provide further insurance. (Jones et al. 2007)

These populations include orphans from deceased mothers and animals sourced from the wild. (Jones et al. 2007)

The captive populations aim to contain rare alleles that are useful for long-term adaptation and survival. (Jones et al. 2007)

In order to ensure no infected organisms enter the captive populations, a "trap, test and remove" method is used in the absence of a vaccine. (Jones et al. 2007)

Conclusion:

In certain areas, the population of the Tasmanian devil has declined by up to 80% due to the Tasmanian Devil Facial Tumour Disease. (Loh et al. 2006)

To prevent the extinction of such a unique animal is difficult with such a complex cancer that is so easily transmissible yet without an appropriate vaccine.

Managing mating, the S. harrisii oocyte preservation program in conjunction with basic conservation management can be the key to preserving the threatened populations of Tasmanian Devils.