What about the parasites? | By: Michelle Gordy

I recently had the pleasure of attending the 55th annual meeting of the Canadian Society of Zoologists (CSZ). This year, the meeting was hosted by Western University, located in “the second best London”, London, Ontario. Not having ever been to the first best London—you know, the one in England—I still found it quite funny, how this small city in Ontario (and as I’ve recently learned, the surrounding area of southern Ontario) has adopted the gothic architecture style and the names of famous English places and landmarks, including the Thames River.

Western University really is the heart of London. Making up the Western portion of the city, this large campus, with its majestic gothic style buildings (consistent across the whole campus I might add) is home to nearly 30,000 students. I was quite impressed with the research coming out of this University, as many of the students not only gave presentations at CSZ, but competed in the W.S. Hoar Award Competition for best student oral presentation.

The CSZ annual meeting is one that every Canadian student of Biology should attend at least once, well, at least those that study animals in any respect. The scope of the society is broad and encompassing, to span the study of animals, from genetics to ecosystems, and everything in between. In fact, the society is divided into multiple sections: Comparative Morphology and Development (CMD), Comparative Physiology and Biochemistry (CPB), Ecology Ethology and Evolution (EEE), and Parasitism Immunity and Environment (PIE). With such a broad range of topics presented at the meeting, you end up learning much more than you expected to, and even sometimes get inspiration for your own project with a new perspective.

This year’s meeting was organized much differently from previous meetings I’ve attended, in that rather than having each section in the society have their own separate sections for presentations, it was organized by topic. So, my talk this year was in the section entitled “Ecologically relevant stressors,” to include talks about heat stress in Atlantic Salmon, hypoxia in killifish, mosquito fecundity, immune defense in a caterpillar, cold stress on the mating success and migration of sparrows, and the patterns of natural variation of snail-digenean communities and how they may be affected by differences in environmental factors. I thought it was an interesting strategy by the organizing committee to arrange the talks in this way, as it encourages us as members of the society to remember that we need to think about our science beyond our section and incorporate ideas from other fields to address the broader topic at hand. Maybe that wasn’t their intention, but that’s what I took from it.

With the obvious caveat of my bias towards parasites, I thought some of the most interesting talks of the CSZ meeting this year were by Parasitologists, in particular, those by Dr. Martin Olivier (McGill University), Dr. George Dimopoulous (Johns Hopkins Bloomberg School of Public Health), and Dr. Shelley Adamo (Dalhousie University). The most interesting facts I took away from some of the talks, in particular, were not the focus of their talks per say, but encompassed aspects of the evolutionary interactions among parasites and viruses (dare we say ancient hyperparasitism?) that has led to certain disease outcomes or strategies for host manipulation. For instance, Dr. Martin Olivier, who won the R. A. Wardle award this year, discussed the discovery of a double stranded RNA virus infecting Leishmania (cleverly called Leishmaniavirus or LRV-1) that causes increased pathology during infection by worsening the lesions caused by infection with particular species of the Leishmania parasite. They do this by activating TLR3-dependent macrophages and secreting pro-inflammatory mediators. While Dr. Olivier did not make this discovery himself, he did highlight the need for understanding how this evolutionary relationship has led to the differences in pathology that we see, and the importance for learning more about the host-pathogen interactions occurring at the parasite-macrophage interface.

Dr. Adamo was invited to give the Zoological Education Trust (ZET) lecture this year, which is a public lecture meant to invoke interest in Zoology. Her talk was on “Making Zombies: How a parasitic wasp hijacks the brain of its host,” a caterpillar (A.K.A. hornworm).

This whole system is incredibly amazing, in that this parasitic wasp is able to cause a caterpillar to stay alive, stop developing (metamorphosing), not eat the wasp larvae as they grossly emerge from the caterpillar and just hang out, even defending the developing wasp larvae. However, the best part of it all that I found was revealed during the question and answer section: the female wasp injects a polydnavirus into the caterpillar when she lays her eggs to immunosuppress the caterpillar, so the larvae can develop within the host without being attacked. The genomes of these viruses are incorporated into the genomes of the female parasitoid wasps. What an incredible evolutionary development for host manipulation!

Finally, Dr. Dimopoulous was a treat to have speak at CSZ because he really represents one of the “big wigs” in public health research involving mosquito-borne diseases. He spoke in the PIE symposia “Microbiomes: Shaping Parasitism and Immunity”, and gave an excellent talk about his largely encompassing research that looks at the mosquito microbiome and its influence on infections with Plasmodium (malaria parasite) and dengue virus. It’s the kind of research that you look at and go “so that’s what I could do with several teams of people.” It was truly impressive.

In general, one of the most interesting talks of the conference is usually that by the winner of the T.W.M. Cameron Outstanding Ph.D. Thesis Award. This year was quite interesting in that the winner, Dr. Adam T. Ford, wasn’t actually present to give his talk and so we listened to a pre-recorded PowerPoint lecture. More so, his research was like a National Geographic episode, in that he looked at the trophic interactions occurring between large predators (leopards and wild dogs), prey (impala and dik dik) and plants in African rangelands. He shows that risk-avoidance behaviour and plant defenses (giant thorns) interact to determine tree distributions. I really wish he was present for a question and answer session after his talk because I wanted to ask him two questions: 1) what did you use the helicopter for? (because he showed some pretty awesome pictures, including one of something very large hanging off a helicopter), and 2) how might you view these trophic interactions differently if you also factored in the effects of parasites? I thought of this question because parasites have been recognized as “ecosystem engineers” meaning they can affect the overall structure of an ecosystem by affects on their hosts, host behaviour, and thus downstream interactions between species and the resulting structure of the community. After watching Dr. Ford’s presentation and starting to think about how parasites might be playing a role, I started thinking about this in every presentation I had seen after that wasn’t about parasites, and then, even those that were.

Though I hate leaving open ended questions, particularly in a title, as I have done here, my attendance at CSZ left me inspired to continually ask the question: What about the parasites? Though the CSZ meeting this year was excellent in the way of parasite-related talks, having the opportunity to see other aspects of zoological studies made me realize that parasites – the effects on their hosts, and the downstream effects on the ecosystems they and their hosts live within – remain grossly overlooked, despite their presence in every known system. This is not a criticism directed toward anyone in particular, nor the society, or zoological research, but an observation-inspired perspective – if we thought about “(insert field topic here) study A” and included parasites, would the answer change, and if so, how? We can even ask this question in regards to parasite studies, as parasites are often themselves parasitized, as demonstrated through the examples above in regards to viruses.

Overall, I’m appreciative to HPI for sending me to this conference and giving me the opportunity to gain a new perspective and inspiration.

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