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Tommy Leung
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Of Chimps, Leopards, And Toxoplasma
Some of you may be familiar with the story about a little cat parasite call Toxoplasma gondii. It seems to be able to alter rodent behaviour so that they are more likely to be eaten by a cat, but it can also infect humans (and any warm-blooded vertebrate animal) and supposedly mess with human behaviour as well. Spoooooky. At least that's how the story goes. Like any other story, there is some grain of truth to it, but it is buried within a whole mass of (more sensationalised) dross. Any studies into Toxoplasma and host behaviour manipulation has the potential to go viral as it includes all the elements that makes a good headline - it contains cats, brain parasites, and zombies (in the form of host behaviour manipulation).

The literature on Toxoplasma and host behaviour is MASSIVE - some of it is good science, others are more like tabbies dressed as tigers. But for this post, I'm going to focusing on one story within a larger narrative, I want to talk about a paper recently published in Current Biology which had whipped the media into a frenzy (again) about how human behaviour is affected by Toxoplasma. http://www.cell.com/current-biology/abstract/S0960-9822%2815%2901517-1

Here's a tl;dr version of the study. The study found that compared with uninfected chimps, chimpanzees infected by Toxoplasma are not as averse to the odour of leopard (their natural predator) urine. The researchers concluded that this is because Toxoplasma is manipulating the chimps' behaviour so that they will be more likely to be eaten by a leopard (the final host for Toxoplasma are felines).

1) While the media coverage seems to be focused on how the parasite affects human behaviour, this experiment was done on chimps, and the media is extrapolating the conclusion of that study to humans. Humans and chimps may be genetically similar on some level, we have been separated by 5-7 million years of evolution, and our ancestors evolved in very different environments. There are some very key differences in the behaviour of chimps versus humans.
 
2) The study was not only correlative in nature, it was based on testing chimps for presence of Toxoplasma antibodies - not the parasites themselves, just a potential indicator of the parasites presence (having antibodies for something doesn't guarantee the presence of the said thing in the body). The researchers didn't confirm the presence of the parasites themselves. I understand they can't exactly do the latter for ethical reasons, in which case, maybe don't cannonball your way into such sensationalised conclusions?

3) The study tested how chimps response to the odour of urine and other big cats - the question is, just how much of a role does the sense of smell play in chimpanzees' predator avoidance repertoire? There is surprisingly little research on that. Is the sense of smell that important for predator avoidance compared with their other senses? Also, considering that chimpanzees are social animals, they would also rely upon other individuals in the group to warn of the presence of predators - you can't consider the vulnerability of a chimp to predation without the context of its social structure.

4) They mention potential behaviour variations between individuals (i.e. personalities) which may account for different level of aversion towards leopard urine odour which are pre-existing, regardless of the parasite. Good. But then, they just dismiss that possibility outright, by citing a single study that has found Toxoplasma is associated with disrupted fear response - in rat. Studies in other animals have shown that propensity for "recklessness" varies between individuals, even without the influence of parasites. So they're essentially saying Toxoplasma is the only possible explanation for why those chimps behaved slightly differently (in one aspects - response to leopard urine odour), even after bringing up the possibility that these behaviour variations exists regardless of parasitism, and discounting the dozens of other equally valid potential explanations. Not Wow.

5) Furthermore, when I dig into the methods, I found that the study was conducted on captive chimpanzees. Captive animals (especially behaviourally complex animals such as chimps) are known to exhibits behaviour which deviate significantly from their wild relatives. So we have no way of establishing whether such behaviour is representative of how they would behave in a natural setting (let alone extrapolating it to humans as the media has done). Once again, I understand that it would be extremely difficult to conduct such a study on wild chimps, in which case, the point I bring up in (2) still applies - don't jump to such sensationalised conclusions

6) Given the correlative nature of the study, we have no way of establishing how these chimps would have behaved before getting infected with Toxoplasma. So you can't rule out that maybe the chimps that behaved "oddly" are simply more likely to pick up Toxoplasma. They did mention this possibility, but they dismissed it just as quickly in the same manner as I described for (4).

7) The paper has 10 references in total (the supplementary material has 2 additional reference, but they were for methodological techniques), but did not cite a review recently published in 2014 in Advances in Parasitology which discussed at length the wide array of inconsistencies and seeming contradictory results from rodent-toxoplasmosis behavioural studies.
https://books.google.com.au/books?hl=en&lr=&id=ftnEAgAAQBAJ&oi=fnd&pg=PA109

And that's all I have to say about that. Peace out.
MFW I read another over-hyped "Toxoplasma gondii + host behaviour modification" paper pic.twitter.com/hOf8i62zWn · Tommy Leung – @The_Episiarch. I don't always subtweet, but when I do, it's about papers on Toxoplasma gondii and behavioural modification. Embedded image. 5:27 PM - 10 Feb 2016 ...
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When A Fluke Hits Your Eye
I've written a new Parasite of the Day blog post! This one is about a species of parasitic fluke which lives in the eye of a fish. But the fish is only a temporary stop in its life-cycle and the fluke gets up to all kinds of mischief while it is in there. Not only does it feed on the fish's eye jelly, it also partially blinds it during certain time of day. To find out more, follow the link below!

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There are many examples in nature where parasites are able to alter their host's behaviour in some way. More recently, some scientists have been investigating just how the parasite are altering or controlling host behaviour. ...
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Bad Romance For Frogs
It's guest posts time over at the Parasite of the Day blog! This is the fourth (and final for 2016) post in a series of guest posts that have been written by students from my Evolutionary Parasitology class this year. This particular posts was written by Sierra Weston and it is about about how male túngara frogs end up receiving a parasitic present while trying to serenade female frogs. Follow the link below to find out more!

Next month, it's back to my usual posts about newly published parasite-related papers which you might not have noticed, and/or papers that were not as widely covered by the press - so stay tuned!
This is the fourth and final posts in a series of posts written by students from my third year Evolutionary Parasitology unit (ZOOL329/529) class of 2016. This particular post was written by Sierra Weston and it is about how ...
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Nasty Monkey Botflies
It's guest posts time over at the Parasite of the Day blog! This is the second in a series of guest posts that have been written by students from my Evolutionary Parasitology class this year. This particular posts was written by Gabrielle Keaton and it is about some nasty botfly maggots that live in the neck warbles of howler monkeys. Follow the link below to find out more!

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This is the second post in a series of blog posts written by students from my third year Evolutionary Parasitology unit (ZOOL329/529) class of 2016. This particular post was written by Gabrielle Keaton and it is about a nasty...
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Arctic Body-Snatchers
I've written a new Parasite of the Day blog post! This one is about a species of parasitic hairworm (Nematomorpha) which infects beetles from the Arctic Circle. Not only do hairworms take up much of their host's internal space, they also take over their mind. To find out more, follow the link below!

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We have featured hairworms (Nematomorpha) quite a few times before on this blog, but for those who are new to them, they are parasitic body snatchers of insects and other terrestrial arthropods. The hairworm larvae are parasi...
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Glad to hear it
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Cuckoo Moth And Ant Anarchy
Accompanying audio here: https://soundcloud.com/abcnsw/creepy-but-curious-dr-tommy-leung-and-the-destructive-cuckoo-moths
The radio show I was doing last year - Creepy but Curious - has returned for 2016, and I recently recorded an episode talking about a brood parasitic moth with a "cuckoo-like" habit. It is a tale of deception, regicide, and anarchy. To find out more, you can listen to that episode on SoundCloud here: https://soundcloud.com/abcnsw/creepy-but-curious-dr-tommy-leung-and-the-destructive-cuckoo-moths

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A Liking For Lichen
I've written a new Parasite of the Day blog post! This one is about a species of parasitic fungus that infects lichen and cause them to develop black galls. But as a side-effect of the infection, the fungus also makes the lichen more palatable for snails. To find out more, follow the link below!

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Lichens can be found all over the world, even in the most barren and inhospitable environments (even near active volcanoes). They grow on exposed surface like moss, but they are very different to those plants. Lichens are the...
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Doing Science Communication Online
A few weeks ago, I was invited by the University of New England Student Science & Technology Association (UNESSTA) to give a talk about doing #scicomm  online and this is what happened. I talked about blogging, tweeting, #sciart , and how to "Be the weirdo that you want to see in the world". 
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Leeches And Monster Girls
People who have been following my work online would know that I've been drawing a series of Parasite Monster Girls (http://goo.gl/VLxB9o) in addition to writing blog posts about new parasitology-related papers. Well, I've just finished working on the latest one - meet Delilah the Leech Monster Girl. She is very pleased to meet you and is particularly interested in your blood type...
Another month, another Parasite Monster Girl - this time one based on leeches. Meet Delilah - a leech monster girl who is not interested in your sign, but is very curious about your blood type.&nbs...
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Tender Love And Care With Parasitoids
It's guest posts time over at the Parasite of the Day blog! This is the third in a series of guest posts that have been written by students from my Evolutionary Parasitology class this year. This particular posts was written by Jarrod Mesken and it is about the caring, maternal side of a parasitoid which paralyses the host with venom and allows her larvae to consume it alive. Follow the link below to find out more!

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This is the third post in a series of blog posts written by students from my third year Evolutionary Parasitology unit (ZOOL329/529) class of 2016. This particular post was written by Jarrod Mesken the more maternal side of a...
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Picky Bat Flies
It's guest posts time over at the Parasite of the Day blog! Some of you might recall during August last year I featured some guest posts written by students from my ZOOL329 Evolutionary Parasitology class - well, it's happening again this year! All this month I will be presenting a series of guest posts on the blog, all of which have been written by students who did my Evolutionary Parasitology class. To kick things off, here's a post by Melissa Chenery about some flies that live on bats call bat flies. And while not all of them can fly, they can be very picky about their hosts, and where they live on their hosts. Follow the link below to find out more!

#scienceeveryday  
Those who have been reading this blog for a while will know that August is student guest post month! All this month this blog will be featuring posts written by students from my Evolutionary Parasitology (ZOOL329/529) class...
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The Cuckoo Moth
I talk about Eublemma albifascia - a brood parasitic moth that targets the nests of African weaver ants here: https://soundcloud.com/abcnsw/creepy-but-curious-dr-tommy-leung-and-the-destructive-cuckoo-moths
 
Cuckoo Moth And Ant Anarchy
Accompanying audio here: https://soundcloud.com/abcnsw/creepy-but-curious-dr-tommy-leung-and-the-destructive-cuckoo-moths
The radio show I was doing last year - Creepy but Curious - has returned for 2016, and I recently recorded an episode talking about a brood parasitic moth with a "cuckoo-like" habit. It is a tale of deception, regicide, and anarchy. To find out more, you can listen to that episode on SoundCloud here: https://soundcloud.com/abcnsw/creepy-but-curious-dr-tommy-leung-and-the-destructive-cuckoo-moths

#scienceeveryday  
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Tommy's Collections
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Parasitologist, Evolutionary Biologist, Researcher, Lecturer
Introduction
Parasitologist and evolutionary biologist who also happen to write for a blog about parasites, and likes to draw things sometimes.

I am a biologist who conduct studies on various ecological and evolutionary biology aspects of parasitism/symbiosis. I also write for the Parasite of the Day blog, which I co-administrate with its founder, Susan Perkins of the American Natural History Museum.

Outside of my professional field, my favourite thing to do is drawing - some of which (but not all) are inspired by my scientific work. My drawings can be found on my dA account.
Basic Information
Gender
Male
Work
Occupation
Evolutionary biologist, parasitologist