Urban Possum: Friend or Foe?

The possums are then driven to the veterinary clinic for examination. With the help of a veterinary nurse, they are anaesthetized and their temperature, heart rate, and respiratory rate are noted. Hill also records their weight and size and checks the state of their teeth, often a good indicator of the animal's age.

The possums are then inspected from the outside for injuries and illnesses and hair, blood and faecal samples are collected. Hill delights in finding fleas, ticks, and other parasites on the possums’ coats which she studies under her microscope. Once the animals are examined, they recuperate in separate cages, a necessary condition since possums are very territorial. They are fed apples, bananas, and home-made muesli bars before being released later in the evening in the same place that they were found.

Tracking the diseases

A six month old possum in its mother's pouch.

Back in the lab, Hill analyses the data she has collected. By identifying antibodies in the possums’ blood plasma, she can find out which diseases they could be carrying. Hair and faecal samples are viewed under the microscope to identify other potentially harmful microorganisms and external parasites.

Hill has found that possums do carry a range of parasites and pathogens. However, most of them exhibit host-adaptation, which means that the diseases have become suited to possum hosts and would not be able to thrive in humans. The evolutionary divergence of marsupials and humans has left few pathogens that are able to swap hosts and survive. ‘At this stage of my research, I would say that possums are unlikely to act as a reservoir for zoonotic disease in urban areas,’ says Hill.

Sick possums

Ironically, research has shown that possums themselves are prone to catching fatal infections like toxoplasma from domestic cats. ‘Possums have adapted their biology to exploit the higher concentration of resources in urban areas, but there is a flip side in that they have to live in an environment where there is a range of introduced pathogens,’ explains Hill. As the possums have not co-evolved with these pathogens, they often have not developed immune protection, and can die from the infections.