Tasmanian devil numbers have been decimated by devil facial tumour disease, an ‘infectious cancer’ that has spread across 85 per cent of the range of devils in Tasmania. A massive effort has gone into saving the devils and now that effort is being extended to their parasites. We believe that our research will contribute to the long-term success of the save the devil effort.
Parasites can be good for you, despite being better known for their ability to cause disease and the negative connotations the word conjures. Parasites aren’t typically recognised for their beneficial influence on their host’s immunity, which drives the evolution of both host and parasite, and enables their hosts to combat other diseases. Nor are parasites recognised for their crucial role in maintaining healthy ecosystems and contributions to biodiversity.
The relationship between parasites and their hosts can be highly specific, some hosts are the sole ecosystem for some parasites. So, what is happening to the Tasmanian devil’s parasites given the animal is endangered? Is threatened species management of the Tassie devil impacting their parasites’ life cycle? And what impact are humans having when they encroach on the habitats of Tasmanian devils? These are the questions our team have been asking as part of the Save the Tasmanian Devil Program, which is working to ensure the Tassie devil and its parasites don't become extinct.
Our first study describes prevalence and diversity of the protozoan parasites Cryptosporidium and Giardia in Tasmanian devils. Both parasites have direct life-cycles with environmentally robust infective stages passed in faeces of an infected individual. Water acts as a vector for transmission and human outbreaks are often associated with contaminated swimming pools and drinking water. Species identification within both genera is only possible though molecular techniques and host specificity can be used to infer transmission sources.
We tested faecal DNA (n = 216) from captive and wild devils using parasite specific PCR protocols followed by DNA sequencing to identify species within a phylogenetic framework. Prevalence of both Cryptosporidium and Giardia were significantly higher in wild Tasmanian devils compared to captive devils (p < 0.05); Cryptosporidium and Giardia prevalence was 37.9% and 24.1% respectively in wild devils compared to 10.7% and 0.82% in captive devils.
Molecular analysis revealed three known Cryptosporidium species; The marsupial specific C. fayeri, and C. muris and C. galli which are associated with rodents and birds. For Giardia, strains that associated with humans were identified in captive devils. Novel genotypes of both parasites were identified in captive and wild devils.
The lower prevalence of both Cryptosporidium and Giardia in captive devils compared to wild devils suggests that captive management may be changing host-parasite interactions. The identification of species associated with humans indicates the potential for parasites to move between these hosts and flags consideration for non-DFTD disease risk management. The discovery of novel parasites require further data to determine if they are only found in devils and may also be endangered.