A passion for parasites

Published 15 November 2017

When asked his favourite parasite, UNE lecturer Tommy Leung can’t go past the “zombie ant fungus” – Ophiocordyceps unilateralis – a creature straight from the script of a horror movie.

Once it infects it’s host, the fungus takes over an ant’s mind, causing it to stagger in a drunken fashion, then climb the nearest plant stalk.

Clinging to the underside of a leaf, the ant is then slowly killed and mummified, allowing fungal spores to rain on the soil – and other ants below that can serve as future hosts.

But then there are also barnacles that castrate crabs, parasitic worms that induce crickets to jump into water, and crustaceans that bite the tongues of fish – it’s so difficult to choose from the thousands of beautifully adapted parasites on Earth.

“I was always into weird and unusual things as a kid,” Tommy said.

“I liked all of nature, not just the pretty birds and butterflies, and wanted to look below the surface, to go deeper to see what was going on behind-the-scenes.

“I was self-taught on a lot of the parasitic stuff. They are just so weird and unusual in the way they make their living, and the weird and unusual are quite revealing about life in general.”

However, the Lecturer in Parasitology and Evolutionary Biology sometimes finds it hard to engender a similar appreciation in others.

“Most people simply think of parasites as degenerate organisms, and use the word ‘parasite’ as an insult,” Tommy said.

“But nature doesn’t have a moral compass. Living things do the things they do to survive and reproduce, and parasites have evolved lifestyles that require highly specialised adaptations to live on or in something else.

“I try to look at things from the parasite’s perspective. They just want to live a full life, and must constantly respond to their host. That’s just what they do. What makes them successful is endlessly fascinating.”

Tommy is a committed science communicator and his popular blog posts, which commonly read like a murder mystery, celebrate a “parasite of the day”.

His passion for parasites is infectious, literally.

“Parasites are all different, with different ways of making a living,” he said.

“They are constantly under attack from their host, so they have to develop some interesting adaptations to survive.”

Those bizarre adaptations are often highlighted in Tommy’s sci-fi-esque artwork, another of his passions.

Known online as “The Episiarch” – after a fictional alien being with the power to alter the shape of reality – Tommy commonly uses real parasites as inspiration for his drawings.

“I use a lot of scientific references, and try to put as much passion, knowledge and professionalism into my art as I do my science, ” he said.

“It’s a creative dimension through which I can explore science, and my artwork often leads people to my peer-reviewed papers, so it works both ways.

“My art draws from reality but changes it to give a different perspective. I hope I encourage people to see that they are not the centre of the universe.”

With parasites like roundworms and liverfluke being costly to the livestock industry, and drug resistance developing, Tommy believes it’s never been more important that we understand the life cycle and ecology of parasites.

“We have to recognise that parasites will always be in the environment and find other ways to work around them,” he said.

“If we can better understand how different ecological factors influence their environment, then we have a better chance of controlling them.”

Dozens of parasites live within humans.

“We have co-evolved with parasites like intestinal worms and blood flukes,” Tommy said.

“Most have disappeared in the developed world, but there is evidence that auto-immune disorders and allergies are developing from a lack of exposure to some parasites.

“I feel strongly towards underappreciated organisms. They often play important roles. On the surface, it may seem that a parasite doesn’t provide a benefit to its host – it just hangs around and absorbs nutrients – but some tapeworms act as a weird kind of toxic sink, absorbing and accumulating heavy metals such as mercury, zinc and cadmium that would otherwise end up in their host’s organs.

“And forests with trees that are infected by mistletoes – a parasitic plant – have more species of birds.

“Parasites can have cascading effects on entire ecosystems.”

Most recently, Tommy has collaborated with researchers in Canada to study a group of nematodes that infest birds. By comparing migratory and non-migratory birds, the scientists are trying to understand how the parasite load is influenced by the birds’ habitat and food.

But there is still much we don’t know about the thousands of complex and curious parasites found in a multitude of environments, including our bodies.

“In sheer numbers, their way of living is the norm,” Tommy said.

“Theirs may turn out to be the most common lifestyle on the planet, and we might be the weird ones.

“The weird and wonderful might not be so weird.

“I still feel a sense of wonderment about what’s still out there to learn.”