Special Report: #WAAVP2013 Part II (tongue-biters, eye flukes and parasites gone wild)

This is Part 2 of my report on the 24th International Conference of the World Association for the Advancement of Veterinary Parasitology (WAAVP 2013) I attended last month. If you had missed Part 1 of my report, you can read it here. 

photo credit: Don Ward

At the end of my previous post about WAAVP 2013, I was writing about a whole bunch of parasites from marine animals and I will start this post by continuing with that theme. During Tuesday afternoon, I attended a session on parasites of aquatic animals and the first talk was on parasitic isopods of fish by Nico Smit who happens to be a world-renowned expert on these parasite (he is the also the person who took that infamous photo of the tongue-biter parasite). It turns out that even though the tongue-biter has become a bit of an online celebrity, there is still very little is known about parasitic isopods in general. They seem to be found all over the world and they display different degrees of host specificity relating to latitude, with species in the tropical region being host specialist and those found in more temperature, high latitudinal region being less picky about their host than their tropical relatives.

photo credit:
Maria Sala-Bozano/University of Salford

One of the parasitic crustacean is the infamous tongue-biter, which was the subject of the next talk by Melissa Martin. Her study focused specifically on Cymothoa (the tongue-biter genus) in Australian waters. While most people are intrigued/horrified by their creepy mouth-dwelling antics, it turns out Cymothoa also have an interesting sex life.

The individual that act as the "prosthetic tongue" is always a female and she can produce hundreds of eggs in a brood sac on her belly. The sex of a newly arrived Cymothoa is actually dependent on whether the fish is already carrying another tongue-biter. If there is already a female sitting in the host fish's mouth, the new arrival turns into a male and mates with the female. If another juvenile Cymothoa comes along, the Johnny-come-lately will turn into a male, but he doesn't get in the way of the first male. Instead, he waits in line and if the original female dies, the first male will turn into a female and take her place on the fish's atrophied tongue

Later in the session on parasites of aquatic wildlife Katie O'Dwyer talked about her research was on a species of philophthalmid fluke. The species she is studying is in the same family as a eye fluke that we have previously featured on this blog and is also found in the Otago Harbour. But instead of infecting the mud snail (Zeacumantus subcarinatus) which are abundant on the mudflats of Otago Harbour, this species infects two species of perwinkles - the Banded Periwinkle (Austrolittorina antipodum) and the Brown Periwinkle (Austrolittorina cincta) found on the rocky shores of New Zealand.

Left: Philophthalmid rediae in snail
Right: Philophthalmid larva encysted on a Petri dish

Just like other philophthalmid eye flukes, the species O'Dwyer is looking at also releases free-living larvae that encyst in the environment (see photo on the left). But this one also has an alternate strategy for transmission - encysting in the snail itself and waiting for the snail to be eaten. Her research involves looking at what might be triggering the switch in strategy - so far, the results indicate that it is a combination of environmental and host factors.

During the day, I checked out some posters on thorny-head worms of marlin, trematodes in wrasses of the Great Barrier Reef, worms in dingoes, blood parasites in gobies and coccidians in small mammals. A poster that really caught my attention was one by Amanda Worth, questioning whether the interpretation of altered behaviour in rodents infected with Toxoplasma gondii has simply been a story which has been overblown due to its appeal. It questions whether the role that cats play in the life cycle of T. gondii has been over emphasized seeing as the parasite is capable of being transmitted between hosts just fine without a cat being involved. There's no denying that T. gondii can indeed alter rodent behaviour, but whether it is actually adaptive for the parasite to do so or if it is simply a side effect of the infection pathology should be reevaluated. While T. gondii is often cited as a classic example of parasite host behavioural manipulation, is it because the evidence supporting such an interpretation are really compelling or if it is simply a story that has all the elements that makes it an appealing to us (C'mon, cats AND mind-controlling/zombifying parasites)?

Photo credit: Stefan Kraft

On the last day of the conference, I attended a session on tick borne infections which ended up being really well-attended. There was certainly plenty of tick talks at WAAVP 2013, one of which was from Peter Irwin who was looking at the tick fauna of Australia for potential tick-borne diseases that can infect humans (turns out there are not all that many in Australia - yet) and the possibility of using dogs as sentinels for the presence of Lyme disease in Australia. As a follow-up from all the tick talks, the wildlife parasitology session featured a presentation by Andrea Paparini on tick-borne piroplasm parasites in the platypus. The study Paparini talked about set out to sequence piroplasm parasites from evolutionary unique hosts (such as the duck-billed platypus) to try and sort out the evolutionary relationship within this group of parasite. Apparently piroplasm is very commonly in the platypus (sometimes in conjunction with trypanosome parasites) and they don't seem to cause visible signs of disease to their host.

For a change of pace, Linda Ly presented research on parabasalid flagellates from some Australian termites. Those flagellates are not quite parasites and might actually be mutualists, but they are still very interesting. In a single termite species she was able to identify at least ten brand-new morphotypes of flagellates and considering there are 260 species of native Australian termites in total, those ten are just the tip of the diversity iceberg for termite gut flagellates. This was followed by a talk from Edward Green about some of the morphological features of the springbok louse Linognathus euchorse and the session ended with Mary Shuttleworth presenting her research on the hidden genetic diversity and structure of Cloacina - a genus of parasitic nematode found in swamp wallabies.

While the majority of the talks were on veterinary parasitology, which as I mentioned in my previous post was not really my scene, there were plenty at the conference which held my interest the entire time. This post is only a very small and selective sampling of a fairly well-attended international conference. We will be back with the usual parasite posts next month - I already have a few papers lined up to write about so watch this space!

Special Report: #WAAVP2013 Part I (lancet fluke, dolphin poop and a turtle parasite)

Last month, I attended the 24th International Conference of the World Association for the Advancement of Veterinary Parasitology (WAAVP 2013). While veterinary parasitology is not my usual scene, it was also a joint conference with the annual Australian Society for Parasitologists meeting, and there were also plenty of wildlife and aquatic parasitology on the program that caught my interest. The major themes of this conference included food security and public health in relation to parasites. As this was a big international conference and there were multiple concurrent sessions, the talks that I will be writing about here will be heavily biased towards my own experience and interests - but if any of you reading this also happen have attended WAAVP 2013, feel free to leave your own highlights in the comment section.

The conference reception night kicked off with a public event call "Parasites and Pets, Pets and You" which I live-tweeted (see the storify here). The presentations were about the critters that live in and on people's beloved pet as well as addressing many myths and misconceptions about parasites. The presentation addressed zoonosis and how while it is possible to catch parasites from your pets, you are more likely to catch parasites from the people around you, also that you are more likely to get infected with Toxoplasma gondii from contaminated food than from cats. (On a side note, during the reception night I also picked up some appropriately themed souvenirs - see photo above)

Photo by MONGO

The first day of the conference began off with a plenary session on the history of veterinary parasitology in Australia by Ian Beveridge and Brown Besier. Later in the morning I saw a talk by Melissa Beck on Dicrocoelium dendriticum. For those who don't know, D. dendritium is also known as the lance fluke - the parasite well-known for hijacking the brain of its ant host, causing it to climb to the top of the blade of grass and stay there all night, waiting to be eaten by its next host (a grazing mammal such as a sheep or a deer). Beck's study looked at the age-related pattern of lancer fluke infection in free-ranging wapiti (Cervus candensis) in Alberta, Canada. The study was carried out in Cypress Hills Provincial Park, Canada (so I guess you can say that the ants in that area which are infected with lancet flukes are *[don sunglasses]* - Insane In The Membrane?). She found that the elks seem to become less infected as they get older, with the majority of flukes in the host population found in younger individuals. This may be due to the adult elks having a more robust immune system which prevents them from becoming reinfected by the lancet fluke, or it might even involve some kind of behavioural defence that develop in mature individuals (adult elks learning to avoid eating ant-laden grass?).

Later on that same day, I gave a talk on a study I conducted with my collaborator Amanda Bates on the global pattern of disease outbreaks in aquaculture (which you can read for free here), afterwards I saw a session on the wide variety of parasites that currently plague aquaculture the world over. There was a talk by Ronald Kaminsky on the development of anti-parasite compounds and the salmon lice that are evolving resistance to them. This was followed by Supranee Chinabut who discussed the different types of parasites that infect captive fish in southeast Asia such as monogeneans (ectoparasitic flatworms), parasitic crustaceans, and infectious protozoans (like the startlingly beautiful Trichodina), emphasising the importance of having multiple strategies for dealing with outbreaks of different types of parasites.

In the same session, Kyle McHugh presented a study looking at how introduction of popular angling and aquaculture species such as the large mouth bass and grass carp has brought with them various parasites such as anchor worm and the Asian fish tapeworm that now infest South Africa's own native freshwater fish. Finally Zoe Spiers presented some results from an investigation into the aetiology of oyster winter mortality syndrome - a disease which causes significant loss to oysters farms along the coast of New South Wales, Australia every year. The investigation involved a combination of ecology, histopathology and molecular biology, and while it is commonly believed that oyster winter mortality syndrome is a disease caused by the protozoan parasite Bonamia roughleyi, the result Spiers presented indicates that the symptoms of the disease is not always associated with B. rougleyi and that the actual agent(s) causing winter mortality is still unclear.

Photo by Richard Ling

Keeping the theme underwater, I attend a session the next morning on aquatic parasitology Sarah Catalano (she presented a talk about those parasites at last year's Australian Society for Parasitology meeting) about using the weird and wonderful dicyemid parasites to distinguish different sub-populations of cuttlefish in the waters of South Australia. Dicyemids are very odd parasites that live exclusively in the renal sac of cephalopods, and their exact taxonomic position on the tree of life is currently unknown.

Carlos Hermosilia presented a study which was quite astonishing in its the method of execution. Hermosilia conducts research on the parasites of dolphins but while most studies on dolphin obtain sample from dead stranded dolphins, he chases after parasites from live dolphins, and I mean that quite literally. His methodology involves swimming after dolphins with a tube and scooping up their poop (or vomit). That's right, just like how a responsible dog owner might scoop up after their pooch, but with dolphins - which are powerful swimmers - not to mention dolphin poop comes out in a cloud instead of Fido's neat little turds. Needless to say, chasing down flipper with the aquatic equivalent of a pooper scooper sounds like no mean feat. He found that dolphins harboured all the usual parasitic protozoan and intestinal worms one would expect from a marine mammal, but one unexpected finding was a cymothoid isopod in a dolphin vomit sample. Cymothoids are usually fish parasites (including the infamour "tongue-biter") so it is quite likely that the crustacean might have been from a fish that the dolphin just ate.

Hermosilia's tale of dolphin chasing and poop scooping was followed by a talk on the spirochiid blood fluke of marine turtles by Phoebe Chapman. Spirochiid blood fluke can cause disease in sea turtles and there are 91 species of spirorchiids described worldwide, 30 of which are found in marine hosts.  The species found in sea turtles live in the cardiovascular system of the host where they mate and lay eggs - which is the main cause of disease (at this point it is unknown how the eggs reach the outside environment - there is even a hypothesis that they simply wait for the host to die to be released). The eggs of spirochiid can become lodged in the turtles organs, causing embolism, thrombosis, lung fiborsis, and a long list of other internal injuries. Currently there is no way of detecting the presence of spirochiids in the host while it is still alive and a part of Chapman's research involve developing a method for diagnosing spirochiid infection in live animals.

I will be writing about the rest of Tuesday and the rest of the conference in Part Two of my special report on WAAVP 2013. Stay tuned as there are more to come including tongue-biters, snails and flukes on the rocks, ticks (real ticks, not plastic ones) and parasites of various weird and wonderful wildlife.