Award winning research could lead to new drugs to fight common parasitic infection

Kathryn Parker winner of Sprent Prize 2020, Toxoplasma gondii

In high school, Kathryn Parker was selected to fly over Antarctica as a Young Science Ambassador with the Royal Society of Victoria. Today, she continues to reach soaring heights in her research and medical studies.

 “I’ve always wanted to be a doctor and witnessing close family members go through significant medical procedures inspired me further,” explains Kathryn.  “During my undergraduate course, the Bachelor of Philosophy (PhB), I did a reasonable amount of research training, so the next natural step was to do a Doctor of Philosophy (PhD). The idea of making an original contribution to human knowledge was also alluring. Fortunately, I found out I could do both as a conjoint program.”

In January 2019 Kathryn submitted her PhD thesis on a parasite called Toxoplasma gondii (T. gondii). Her ground breaking work has recently been awarded the John Frederick Adrian Sprent Prize for 2020 by the Australian Society for Parasitology. The prize is given to the most outstanding PhD thesis in Australia in the field of parasitology over a 3-year period.

Kathryn has been fascinated by parasites ever since she took a parasitology course in her undergraduate degree. “Parasites do really interesting things like manipulating their hosts. Some parasites, including T. gondii, have lifecycles involving transmission between a predator animal, such as a cat, and a prey animal, such as a mouse. The parasites can cause changes in the appearance or behaviour of infected prey animals, which make it more likely that the prey animal will be eaten by the predator. This way, the parasite ensures it is transmitted between its two hosts so its lifecycle can continue. In the case of T. gondii infected rats seem to lose their fear of predators.”

T. gondii infects about 40% of the worldwide population and most people don’t even know they have it. It can only be passed from mother to foetus with no other human transmission. It is capable of infecting virtually all warm-blooded animals (birds and mammals) and within those animals, almost any cell, which is quite unique amongst parasites.

When a cat excretes the parasite it contaminates the environment. Other animals like birds and rodents catch the parasite from contact with the excrement. When cats eat the birds or rodents, the cycle continues.

The meat of infected animals isn't just infectious to cats - it can infect any animal. Humans can catch T. gondii by eating undercooked meat from animals infected by the parasite, especially lamb or pork. Symptoms in humans usually appear like the flu - body aches, fever, headaches and fatigue.

Congenital toxoplasmosis (infection of the developing foetus) can happen if a human or animal is infected for the first time while pregnant. This disease can result in severe birth defects, miscarriage or still birth. It’s the reason pregnant women are told to stay away from kitty litter.

Image: supplied by Kathryn Parker demonstrates the three ways humans can catch the Toxoplasma gondii parasite – from cat excrement, from undercooked meat and through transmission from mother to baby.

In Australia, our native wildlife isn’t used to this parasite and is very susceptible to it. As a result, birds, possums, wombats and wallabies are dying.

 “My research looked at how Toxoplasma parasites steal nutrients from the host animals in which they live. I discovered that one protein is particularly adept at stealing the amino acid glutamine, which the parasite uses as both an energy source and a building block for making proteins. The glutamine-stealing protein only exists in parasites, not in humans, meaning the protein is a good target for a drug. If a drug can be developed to block the parasites from acquiring nutrients it will starve and kill them, thereby curing T. gondii infections,” explained Kathryn.

“The fact that the Australian Society for Parasitology thought my thesis was the most outstanding is the best possible acknowledgement that I didn’t compromise on quality, despite the challenge I set myself when I decided to do the conjoint PhD/MChD program,” states Kathryn.

Kathryn has a few more challenges ahead, including completion of her medical degree this year and the commencement of an internship in 2021. Even with all that is on her plate she plans to return to research soon. “I hope to do some hospital based research projects in the next couple of years and longer term, I’d like to move into a clinician-researcher role.”