Little is known about the impact of the diseases carried by invasive species that spread throughout the food chains of our native animals.
TSR Hub researcher Dr Nelika Hughes (Project 1.4) from The University of Melbourne is looking closely at one such disease – toxoplasmosis – a parasitic disease that was introduced to Australia in cats.
Toxoplasmosis is caused by parasitic protozoa (Toxoplasma gondii) and is capable of infecting most (if not all) mammals. A high proportion of humans have contracted toxoplasmosis but most will experience only mild flu-like symptoms (if they experience any symptoms at all).
In humans, the biggest threats associated with the disease are faced by those with compromised immune systems and by pregnant women, as toxoplasmosis can spread through the placenta and is associated with foetal death.
Similar risks are likely to apply to pregnant native species.
“There are still a lot of unanswered questions about how this disease affects threatened species in Australia. We know marsupials can be highly susceptible to acute infections, but we don’t necessarily know what the acute or chronic effects mean for the future of many native species,” says Dr Hughes.
“The ways toxoplasmosis can interfere with the breeding success of mammals are a cause for concern. Lab studies have shown that not only can the disease cause the prenatal death of offspring, it can also increase the proportion of males born,” says Dr Hughes.
“Further studies have revealed that the parasite actually causes behaviour change- infected mice and rats no longer seek to avoid the ‘warning signs’ of cat urine or cat fur. This could spell disaster for Australian species – who don’t necessarily share the same avoidance behaviours developed by animals that have co-existed with cats for a long time.”
While many species are capable of hosting the parasite, it is only known to reproduce sexually in felines. Dr Hughes is analysing samples from feral cats sent to her lab from around Australia, to determine which particular strains are present.
“So far we have received about 50 samples, mostly from islands such as Bruny Island, French Island, and Kangaroo Island, and also a few from Victoria. This project will genotype at least 500 samples to discover where the most virulent strains of the disease are present,” says Dr Hughes.
“Once we have a better understanding of the problem, we can begin to consider possible solutions.”
Image: toxoplasmosis by Yale Rosen (CC BY-SA 2.0)
Conservation managers considering the implementation of nest boxes programs need to give careful consideration to design, colour, placement and shade profile of nest boxes.
The vast brigalow forest that extended from northern New South Wales to southern Queensland has been cleared in the space of 60 years and it seems that many species have become threatened as a result. Rod Fensham and co-workers have identified the plant species that are likely to have become threatened and many of these species were not previously recognised as imperilled.
Monitoring is fundamental to good policy and effective conservation management. Data derived from monitoring underpin the process for listing of species as threatened, which is a precursor to recognition in policy.
TSR Hub researcher David Lindenmayer and colleagues embarked on a four-year case study examining the impacts of a biodiversity offset which established nest boxes to compensate for the losses of natural tree hollows caused by the widening of sections of the Hume Highway (the road linking Sydney and Melbourne).
In recent months you may have noticed some energetic public debate about what is the biggest threat to threatened species in Australia. Is it feral cats and foxes or is it the clearing and degradation of native vegetation?