Special Report: #NZASP15 Part II: Ups and downs of shark parasites, networks, and Toxoplasma gondii

This is Part 2 of my report on the joint annual meeting for the New Zealand Society of Parasitology (NZSP) and Australian Society for Parasitology (ASP) in Auckland, New Zealand (#NZASP 2015), which I attended earlier this month. If you had missed Part 1 of my report, you can read it here.

#SharkSelfie

My previous post ended on a note about shark tapeworms, so I thought we should start this one off on the same note. In the previous post, it was established that the giant squid (at least in its juvenile form) is a part of some shark's diet, and is thus used by some tapeworms to reach their shark host. The talk by Trent Rasmussen from Otago University further expands on the role played by such prey items in determining the tapeworm community of sharks.

The parasite fauna of any given species is governed by a wide range of different factors. For tapeworms in sharks, a previous study showed that body size and depth range were good predictors for the diversity of tapeworms found in any given shark species. Trent's study expand upon that by including dietary range as an additional factor, and found that while body size and depth range were good predictors for tapeworm diversity, diet breadth - or the diversity of prey consumed by the said host shark - was an even better indicator.  With each type of prey harbouring different types of tapeworm larvae, having a varied diet is a great way to acquire an eclectic set of parasites. It seems that for sharks, your tapeworms are what you eat

Speaking of which, that leads into Robert Poulin's talk about the ups and downs of parasite life cycle. Many parasites have complex life cycles and have to go through many different animals in order to complete it. The problem with such a way of life is that there is massive attrition at each stage of the life cycle: for some parasites (like the tapeworms which infection sharks) they need their current host to be eaten by the next host to complete its life cycle (known as "trophically transmitted parasite"), and the likelihood that the parasitised prey will be eaten by the right predator species out of all the prey individuals in a population is very, very low. Given this cost, do such parasites have adaptations to offset the losses at each stage of their lives?

Digenean trematode cercariae
(free-swimming larvae)

That was the central question behind the study described in Robert's presentation, which he conducted with postdoctoral researcher Clément Lagrue and their team. From their study, it seems digenean trematodes (or flukes) seems to have evolved a key innovation that allows them to offset that some of that losses - and all it takes is the body of a snail at the first stage of their life cycle. The study itself was a massive undertaking which involved taking samples from four New Zealand lakes, at four different spots at each lake for a total of sixteen sites. At each of the site, they collected pretty much everything they could which added up over 650 thousand individuals animals, and they ended up dissecting over 400 thousand invertebrates and counted all the parasites that they found.

From this, they found that while was a reduction in the number of individuals for trophically transmitted parasites like tapeworms or roundworms, for digean flukes, there was actually an increase in the number of individuals in the population by two- to three-folds between their first host and the second host. Because flukes converts its first host, the snail, into a parasite clone factory, it is able to turn a single successful infection into thousands of infective larvae for the next step of their life cycle. The final stage of the life cycle of the fluke still involves being eaten by the right host, which means they are in the same boat as the tapeworms and roundworms, but at least they had been working with better odds than those other parasites.

Events like conferences are all about networking, but out in the wild amongst reptiles, "networking" is not so much about exchanging email and ideas as much as it is about exchanging parasites. Stephanie Godfrey from Murdoch University presented a talk about her research on how parasites can spread among social network in reptiles, and how models of such networks can be used to manage wildlife disease.

Photo by Caroline Wohlfei

One of the study she described involved testing the prediction strength of different epidemiological models, using the parasite-host system of ticks on Sleepy lizards (Tiliqua rugosas). These lizards live in the semi-arid desert of outback Australia where there are few shelters for the ticks. In such habitats, the parasites have an infectious window of 11-24 days to hop on a lizard or they will they expire, so the bushes where such where lizards congregate and take shelter inadvertently become places for tick exchange. When the lizard stop at those sites, they drop off tick larvae which lay in wait for another host to come along. Her study was a mark recapture experiment which involved releasing two "pulses" of tick larvae with known genotypes to see where they end up.

She test the ability of three different types of models to predict how the ticks would spread in the lizard population; one based on (1) social network, another based on (2) spatial proximity, and finally one based simply on (3) lizard behaviour. It turns out that network model had the highest predictive power, but the spatial model was not far behind, and it also depended on whether it was modelling the first or second larval pulse; a variability which was most likely due to seasonal variations that affected tick larvae survival

Finally, I end this post with a note about Toxoplasma gondii - the famed rodent-whisperer. If there is ever a parasite that has captured the public's imagination, it is this one. In the eyes of most people, Toxoplasma gondii might as well be called "Deus ex Parasita" or "Plot Parasite" as it has been suggested as being responsible for everything from schizophrenia, to brain tumours, to influencing human culture and even for making the French so, well, French.

Is that a rodent I see before me?

But what is the basis behind this reputation? Amanda Worth and other scientists from Murdoch University have been questioning whether such behavioural alteration necessarily benefits the parasite. In contrast to the usual narrative, T. gondii seems to do really well without ever ending up in a feline - the cat can act as a site for sexual reproduction, but it seems T. gondii can get by perfectly fine with just asexual reproduction (for a full coverage of this, see this from the zombie ants blog here).

Additionally, studies which investigated the question of T. gondii host manipulation often do not take into account pre-existing behavioural difference between individual rodents. In her study, Amanda compared the behaviour of both uninfected and T. gondii-infected mice, and to control for within-species variations, she observed the behaviour of the experimental rodents both before and after exposure to the parasite. Her results were...well, not as clear-cut as the other studies may have made it out to be.

For example, she noticed that some mice already had preference for cat urine before they were exposed to T. gondii. And while the T. gondii-infected mice spent more time hanging out in the open, they did not show a particular preference for cat pee (in contrast to the usual narrative about T. gondii). In the non-exposed mice, individuals that are more bold also tend to be more active, thus these two behaviour seems to be linked. But in T. gondii-infected mice, those two behaviour are not as well connected. While uncoupling certain behaviours in some cases may render an animal more susceptible to its predator, but whether that would make a rodent more likely to be eaten by a cat is another question.

So it seems that in this particular study, the effect that the infamous T. gondii inflicted upon their rodents hosts is relatively limited. Maybe there are variations between different T. gondii strains in regards to their capacity for altering host behaviour. Studies on other parasites have shown that within a given species, individual parasites or strains are known to vary in their propensity for host manipulation. Either way, it seems that there is Toxoplasma gondii the parasitic organism,  and then there is Toxoplasma gondii - the near-mythical entity which exists in our collective imagination; a parasite which is capable of masterfully manipulating people's behaviour so that they will believe just about any story that has "cat parasite" in its headline.

Next month, it will be guest posts time on this blog and I will be posting the best student blog posts from the Evolutionary Parasitology class of 2015 - so be sure to stay tuned for that! Until then, you can check out some of the student blog posts from last year here.

Special Report: #NZASP15 Part I: From seashells on the seashore to giant squid of the deep

Recently I attended the joint annual meeting for the New Zealand Society of Parasitology (NZSP) and Australian Society for Parasitology (ASP) in Auckland, New Zealand. It has been quite a while since the Kiwis and the Aussies had a joint parasitologist conference, and seeing as many of my former colleagues are located in New Zealand, it was a great opportunity to catch up with some of them. Note that the content covered in this blog post reflect my own interests (which in turn in is reflected in the kind of papers I cover for this blog) - there were many other presentations which I did not attend, so if you attended this conference, my post may not necessarily match that of your experience. However, here are some of the highlights from my perspective.

The conference began on a poignant note with the posthumous election of Ian Whittington, who sadly passed away in October 2014, as a fellow of the ASP. Ian Whittington was a very prolific scientist whose main research focus was on the biology and ecology of fish parasites, in particular a group of ectoparasitic flatworms call the monogeneans. The monogeneans are a ubiquitous and diverse group of parasites, and some of them are major pests for aquaculture. He was also a great mentor and his research group took a holistic approach to studying parasites which considered multiple aspects of their biology including their structure, behaviour and ecology throughout the entirety of their life cycles. He is greatly missed by many.

Photo of monogenean-covered kingfish by Kate Hutson

Fish parasitologist Andrew Shin gave a presentation dedicated to Ian Whittington on the cost of parasites to aquaculture. In his presentation, he talked about how parasites (such as monogeneans, but many others as well) cost the aquaculture industry millions of dollars in stock losses and treatment cost, and important role that parasitology plays in controlling such problems. He also described a system that he co-developed with Ian Whittington which automated the process of identifying and quantifying parasites on farmed fishes.

The process involves briefly dunking an afflicted fish in a freshwater bath, then this system - which consist basically of a flatbed scanner, microscope, and special software - is able to scan through the resulting soup of fish scales, mucus, and parasites to not only detect and count the number of monogenean parasites present, but also identify what stage of development they might be at, based on various characteristics of their body. The system can process 260 parasite specimens in 90 seconds, allowing aquaculture managers to quickly ascertain the level of infestation and act accordingly.

As a follow up to Andrew Shin's talk, Kate Hutson, a researcher and senior lecturer from James Cook University, provided an overview about a monogenean parasite call Neobenedenia, a genus that is developing into a major aquaculture pest. There are six recognised species of Neobenedenia - one particularly precocious species is found all over the world, infecting many different types of fish - this is the species which causes major problems for aquaculture. This is a very adaptable parasite which is able to change its form depending on the host they end up on, thus genetically identical individuals can end up looking quite different depending on their host species. Studies using fluorescent dye to keep track of the parasites found that while they initially settle randomly on the body of their host, as they grow, they move to specific body parts. In particular they congregate around the fish's fins where they will find potential mates (this invokes a mental image of parasite orgies happening on fish fins). And it doesn't take Neobenedenia long to get to that stage - they can reach sexual maturity and start pumping out eggs at 10 days old, and if no one else is around, as hermaphrodites, they can simply self-fertilise for at least 3 consecutive generation without suffering any ill effects.This makes them a formidable obstacle for any aquaculture system. But there are potential treatments under development on the horizon, ranging seaweed extracts that inhibit embryonic development, and cleaner shrimps which can eat up these pesky parasites and their eggs.

Photo of Austrolittorina antipodum by
Graham Bould

Some of you might recognise the name Katie O'Dwyer from a recent guest post. Well, for the last few years she has been working on her doctorate studying the diversity of parasites in periwinkles from New Zealand and Australia. While there has been a long history of research on parasites found in periwinkles in Europe, the perwinkles of the southern hemisphere have been mostly neglected despite, being one of the most common and abundant animals on the rocky shores. In her research, Katie examined two species of New Zealand perwinkles - Austrolittorina cincta and A. antipodum - the latter is also known as the banded periwinkle.

From these two snails alone, she discovered four new species of flukes, two of which are exclusively found in the banded periwinkle. She also examined the Australian periwinkle A. unifasciata (which confusingly is also called the banded periwinkle), in which she found four species of flukes, one of them happened to be Gorgocephalus sp., a species of parasite which is known from its adult form living in the gut of fish, but rest of life cycle and its other life stages were unknown prior to her discovery. These flukes do very nasty things to their snail hosts - causing them to lose their appetite and their gonads to shrivel away. They also compromise their ability to stay attached onto rocks and other surfaces, which is a big deal for snails living on the rocky shores. In mark-recapture studies, Katie found that infected snails were recaptured less often than their non-parasitised conspecifics, presumably because they were more likely to get swept off the rocks.

Fluke cysts in the foot of a clam

Sticking to seashells on the seashore, there was a talk by Master student Sorrel O'Connell-Milne (also from Otago University like Katie O'Dwyer) who is working on one of the parasite species that I studied during my PhD - a fluke call Curtuteria australis. This parasitic fluke has larvae that encyst in the foot of the clam Austrovenus stutchburyi, where it waits to be eaten by the final host which is the oystercatcher. When these parasites occur in sufficient numbers in the foot of these clams, they can affect the bivalves' ability to dig themselves into the sand, which makes them more vulnerable to predation. However, this also has other effects as the shells of the exposed clams act as habitats for other animals and can affect the biodiversity of the surrounding ecosystem.

Through a series of studies which included assessing the parasite load of clams from commercially harvested sites to those from unharvested area, as well as placing caged juvenile clams from different sites, Sorrel found that clams at site subjected to commercial harvesting had over one-third higher infection load than clams from unharvested sites. It possible that commercial harvesting decrease the density of clams, less individual around to soak up and "dilute" the pool of parasites in the environment. She also performed experimental infection of clams at various doses of C. australis and found that after 3 months of being exposed to C. australis, infected clams have reduced shell growth, body condition, and foot length. Considering the ecological role that these parasites can play through their bivalve hosts, these changes can have potentially cascading effects on the rest of the ecosystem.

Photo by NTNU
Museum of Natural history and Archeaology

One of the highlights of the conference for me was no doubt Haseeb Randhawa's talk about the parasites of the giant squid. He recently had an opportunity to dissect one of these giant mollusc for parasites, and it seems that while it is a predator in its own right, the giant squid also serves as a transmission vehicle for the larval stage of various parasites, particularly shark tapeworms. But the part that it plays in the transmission of these tapeworm larvae depends on the tapeworm species in question, and an individual squid can either be a transmission pathway or a dead end - depending on the size and age of the squid. Before they end up in the squid, the larvae of these marine tapeworms dwell in tiny crustaceans, which are consumed at various stage of the squid's life either directly or indirectly (through the squid's prey). The tapeworm then reach maturity in a shark's gut when it consumes an infected squid.

Throughout its life, the giant squid ends up acquiring a community of different tapeworm larvae, all of them go to different sharks, and ending up in the wrong host is a basically a death sentence for these tapeworm. So inevitable, success for one species can spell disaster for another. Haseeb found that there are at least four species of tapeworm which uses the giant squid as their ticket to the gut of their shark host - two of them infect skates, one infect porbeagle sharks, and one infect sleeper sharks. All these host species inhabit very different environments.

Giant squids start out life in more shallow waters, then moving to the open ocean as they grow into paralarvae. In such habitats, they are potential prey to skates (in the shallows) and porbeagle sharks (out in the open ocean), and presents tapeworms of such hosts an opportunity to complete their life cycle. But as the squid ages and moves into the deeper waters, the window of opportunity for those skate and porbeagle shark tapeworms closes. So as the giant squid matures, it literally sinks their chances of ever reaching their final host - while at the same time offers a glimmer of hope for another group of tapeworms - those that need to reach the deep dwelling sleeper sharks to complete their life cycle. The deep sea might be the final destination for the squid's life, but it is also the case for the tapeworms that parasitises sleeper sharks.

As a side note, I asked Haseeb if he also found any other parasites from the giant squid, in addition to tapeworm larvae. He replied that there were also some anisakid nematodes (which use marine mammals as a final host) and the larval stage of a fluke which infects sperm whales. But the role that giant squid plays in the life cycle of those parasites will have to be another story, another time...

Speaking of shark parasites, Part 2 of my Special Report on #NZASP15 will include more on shark parasites, the ups and down of parasite life cycles, networking in reptiles (and their parasites), and a re-examination of Toxoplasma gondii and its reputation for behavioural manipulation. Stay tuned!

Special Report: #ASP2014 (Australia) Part II: Something Fishy This Way Come

This is Part 2 of my report on the annual meeting of the Australian Society for Parasitology (ASP 2014) I attended earlier this month. If you had missed Part 1 of my report, you can read it here. 

Barramundi photo by Nick Thorne

At the end of the previous post about ASP 2014, I alluded to the abundance of fish and their parasites. In this post I cover research on fish parasites presented at the conference - and there was quite a bit of it. There were a quite a few talks and posters that were focused on the parasite of Barramundi / Asian seabass (Lates calcarifer), which is a prominent aquaculture species in Australia. Like many other production animal, they have their fair share of parasites and there were a number of presentations focused on those said parasites from the Hutson lab including their identification, tracking, and means of control.

 One of the most persistent and common parasites of barramundi in Australian aquaculture is a tiny parasitic flatworm call Neobenedenia. Though they can be quite numerous on an afflicted fish, they are also are tiny and transparent, making them difficult to spot and even harder to study in situ. However, Alejandro Gonzalez presented a method for making these otherwise near-invisible parasites visible by labelling the parasite larvae with a fluorescent dye. Under the sight of an epifluorescence microscope, these treated parasites stands out like glow sticks at a rave club. Gonzalez was able to track how they distribute themselves over the fish's body

But Neobenedenia is just one of many different parasite species clinging to barramundi, a poster presented by Soranot Chotnipat found that there are at least eight different species of parasitic flatworms from the Diplectanidae family alone which are found on the skin of farmed barramundi of Asia-Pacific. But with all these parasites, what can be done about them? Kate Hutson presented a poster with a number of methods being trialled for treating farmed barramundi, including garlic and seaweed extracts, but of which the most novel is the use of cleaner shrimp. She found that fish housed with these shrimps have half as many external parasites as those without, and those shrimps consume all stages of the parasites - including their eggs which the shrimps happily grind up like crunchy treats.

Cleaner shrimp photo by Chris Moody

While there is still much to be learned about the parasites of farmed fish, that is nothing in comparison with the diversity of fish parasite outside of captivity, where there is a wild world of parasites full of murky unknowns. A parasite which has captured the imagination of the public is the tongue-biters which are related to a plethora of parasitic crustaceans in the Cymothoidae family. This family encompasses 361 described species and they range in life-style from skin-clingers to face-huggers to gill-tuggers and belly-burrowers. So how are face-huggers like Anilocra related to belly-burrowers like Ourozuektes? Melissa Martin presented a poster on some preliminary results on their interrelationship which seems to show that they might have independently evolved their respective attachment sites.

For most fish parasites, we do not even know what is out there let alone how they are related to each other, especially on a site of rich biodiversity like the Great Barrier Reef (GBR). Thomas Cribb from University of Queensland has been studying and describing flukes for over 20 years and he presented an overview of the current sum of knowledge about parasitic flukes on the GBR. Currently 326 species of flukes are known from 505 species of fish on the GBR, yet that represent only a small fraction of the 16000 or so species of fish found the the GBR, most of which are yet to be examined for parasites. The fluke fauna on the GBR are also very picky about their host, sticking to just two or so host species on average, and about 45% of them are found exclusively on the GBR. Cribb estimated that at this rate, it will take another 150 years to describe all the flukes (not even counting the other groups parasites) inhabiting the fishes of the GBR.

It is clear that underneath the surface of a tropical reef like the GBR is an extensive network of parasite life-cycles and transmission. To get a glimpse into this hidden world, Abigail Downie examined over 700 fish from 191 species, finding a trove of fluke larvae that utilise those fish as a mean of reaching their final host. She found that one species of goby - Amblygobius phalaena - seems to be a parasite hotspot with 16 species of flukes infecting it. Seeing as all those flukes require their temporary fish host to be eaten to complete their life-cycle, it is not surprising that they have all homed in on a small fish which would be a tasty dish for a range of predators, many of which may serve as potential hosts. Indeed, comparatively small fish species also tend to harbour proportionately more larval parasites than adult stages.

Epaulette shark photo by Strobilomyces

Aside from diversity, Downie also found that the ecology of the fish can influence what families of flukes infect them. For example, flukes in the Heterophyidae family produce free-living larvae that are energetic swimmers that hang out near the water's surface. Accordingly they were mostly found in surface or shallow water fishes such as mullets and halfbeaks. In contrast, flukes from the Opecoelidae family have nub-like tails and move by crawling along the seafloor like microscopic leeches. There they encounter fish that spend most of their time near or resting on the seafloor such as damselfishes and gobies.

One of the surprising finds by Downie was an epaulette shark which was heavily infected with opecoelid cysts. The flukes larvae were lodged in the fins which, when viewed under a microscope, looked like a bag of (gross) marbles. While epaulette sharks do spend a lot of time resting on the sea floor, fluke larvae are not usually known to infect elasmobranchs. At this point, it is unknown if shark serves as a viable transmission pathway for the opecoelids or if it is simply a dead-end parasite sink?

On that note, that is it for for my reports on the ASP 2014 (Australia) conference. It was fun to catch up with some colleagues and see some new research on parasites being presented. Start from next month, it is back to the usual parasite blog posts. Well kind of - as I did last year, next month I will be posting the best student blog posts from the Evolutionary Parasitology class of 2014 - so be sure to keep an eye out for that! Until then, you can check out some of the student blog posts from last year here.

Special Report: #ASP2014 (Australia) Part I: The Wild World of Parasites

Photo by Lisa Jone

Recently I attended the annual meeting of the Australian Society for Parasitology (ASP) - it also happened to be the 50th anniversary of the Society, so it was kind of a big deal for the ASP. The first day featured an opening speech by Australian Chief Scientist Ian Chubb. In it, he discussed the many people of the world of dying and suffering from preventable infectious diseases which is the price of poverty, poor sanitation and ignorance. He also talked about how the political priorities of Australia's current government does a great disservice to science, and the lack of long range strategies regarding science, technology, and engineering is holding back Australia as a nation.

He likened it to scattering pieces of a jigsaw puzzle with no means of connecting them, and it is detrimental to Australia's future. Chubb also emphasised that science is vital to the future of Australia and the importance of engaging the public and the next generation with the importance and awe of science (which I hope that I am playing at least a tiny part in by writing this blog!). Speaking of science, as that is what you came to this blog for after all, what kind of parasitology research caught my attention at the conference? For this post I will mostly discuss the presentation on wildlife parasites I saw at the conference.

There was a very interesting plenary talk by Vanessa Ezenwa about how multiple parasites infecting the same animal can influence the resulting pathology inflicted by those parasites upon the host. She presented a case in African buffaloes whereby the removal of parasitic worms affected the disease severity of bovine tuberculosis (bovine TB). There appears to be a trade-off between being resistance to macroparasites (worms) and microparasites (TB bacteria), with buffaloes that are more resistant intestinal worms being less able to mount a response to invasion by the tuberculosis bacteria. It seems as if the worms are pre-occupying the host immune budget, thus allowing the TB bacteria to slip by. However, if the buffaloes are treated with anti-parasite drugs that rid them of their worms, they were able to stop the TB bacteria dead in their tracks. Who would have thought treating buffaloes for their worm infections would also rid them of TB? Ezenwa's study shows the importance of considering the entire parasite community of a host animal and taking an ecological approach to considering host-parasite interactions.

On the subject of ecology, Haylee Weaver presented a talk based on a project that we have been collaborating on regarding parasites that infects animals with semelparous life-cycle - like the Sockeye Salmon, or the Antechinus - better known as the the little Australian marsupial that "has so much sex it disintegrates" followed by a talk I gave on a comparative analysis study I conducted on with Janet Koprivnikar which compared the nematodes fauna of migratory and non-migratory birds.

Photo of sea lion family by DaveDiver from Wikipedia

Jan Šlapeta presented research into a species of hookworm in Australian Sea Lions (Neophoca cinerea). This parasite - Uncinaria sanguinis - exploits the dependency between mother and offspring. The hookworm lives in female sea lions but unlike other hookworms, it does not lay eggs which are passed out in the host's fece, instead it is transferred to the pup via the mother's milk - only then does the worm mature into an egg-laying adult stage like other hookworms. Because of this transmammary transmission, male sea lions are considered to be a dead-end host for U. sangunis.

Because female sea lions do not tend to dispersed, it would be expected that the population of the parasite would be highly structured, but Šlapeta and colleagues found that was not the case, and that the population genetics of U. sanguinis is not as well segregated as expected. This raise many questions about the ecology of this parasites, such as whether other species of sea lions and seals serve as alternative hosts? Or perhaps the males are not dead-end hosts after all? Or can crustaceans like shrimps act as paratenic (transport) hosts for the parasite?

Elsewhere at the conference, there were many posters and talks on Cryptosporidium which seems to be a popular topic of research among Australian parasitologists. There are many different species of Cryptosporidium and not all of them infect humans - though some have potential to jump from their usual hosts into humans. For example, Australian marsupials and multitude of other wildlife are host to various species of Cryptosporidium and Michelle Powers presented a talk on the current state of knowledge about this genus of parasite and concluded there are still many different host species that can be harbouring undescribed species of Cryptosporidium.

Mammal ectoparasites were also also featured at the conference, with a poster presentation by Clare Anstead on the specificity of ticks that infects small mammals as well as their bacterial communities - just as there are generalists ticks that feed from a variety of host species and more picky specialists that stick to just one or two, it seems that the same goes for their bacterial occupants in regards to the species of ticks they inhabit. Speaking of ticks, Stephen Barker announced the launch of a 140 page monograph he and Alan Walker wrote on the ticks of Australia which are found on domesticated animals and humans. And it is available for free for all to download here, which I am sure will tickle the fancies of all tick fans.

Photo of crocodile farm by Cecil Lee

Moving on from parasites of furry hosts to more scaly ones, Simon Reid presented an unusual case of parasitism on a crocodile farm. We have featured various crocodilian parasites on this blog before, in this case these crocodiles on the farm end up being infected with a muscle-burrowing worm due to human action.

The practice of raising crocodilians in a farm setting has come about due to the demand for crocodilian skin product, but another product of such farms is crocodile meat. Since the meat is meant for human consumption, this has led to them being tested for parasites and pathogens, which in turn led to the discovery of an unexpected species parasitic worm in the muscles - Trichinella papuae. Trichinella is also known as "the worm that would be a virus" and normally, crocodiles are known to be infected by their own species of Trichinella - Trichinella zimbawensis. But T. papuae is normally a pig parasites - so how did they end up in a crocodile? Well the obvious answer is that those crocodiles were being fed with pigs - but it also provides an interesting insight into the biology of the parasite itself because their presence in crocodile muscles means that even though  T. papuae normally dwell in an mammal, it is also adaptable enough that it can also survive in a host with a rather different physiology to its usual host.

Speaking of scaly hosts, fish are the most diverse vertebrate animal on the planet and talks about their parasites had a considerable presence at this conference. In Part Two of my special report on ASP 2014, I will be covering fish parasites - including how to make invisible parasites visible, what is the relationship between tongue-biters and face-huggers, and what parasite you might find in the fins of an epaulette shark. All that and more will be revealed in my next post on ASP 2014.

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.

Special Report: #ASP2012 (American) - Part II: 'Omics, Roasts, and Yoda

Sunday morning started off with the Associate Editor's symposium, a fairly new feature of the ASP meetings where 3 of the associate editors of the Journal of Parasitology give talks about their own research. Ramon Carreno began and talked about his work on the pinworms of arthropods - people went crazy over these beautiful worms (I know, we're weird folk). Ash Bullard then showed us the results of his recent work following up on the effects of the Deepwater Horizon oil "spill" on parasite fauna. For most types of parasites, there wasn't a significant difference, but for a few, oiled sites had more and for a few others, oiled sites had less. The symposium concluded with my AMNH colleague, Mark Siddall, up on a soapbox about doing 'omics studies of parasites and asking folks to collaborate to get more genomes and transcriptomes of parasites as they represent a lot of phyla that we don't have reference genomes for. Armand Kuris later gave his presidential address, this time talking about humans as parasites and describing patterns across the globe. I headed to the taxonomy and systematics talks for the afternoon, which included the one given by my grad student, Bryan Falk.

That evening, we had our banquet at the Lewis Ginter Botanical Garden. Though the clouds were horribly menacing, soon we were all eating and drinking merrily. As the desserts rolled out, there was suddenly a toast -- er, a roast! -- of Jerry Esch, our out-going editor.

The meeting wrapped up on Monday with another session of taxonomy and systematics for me, including several talks by folks from Gerardo Pérez-Ponce de Leon's lab from UNAM who I met while visiting last fall and then my talk, where I talked about a way to eradicate Plasmodium falciparum - taxonomically, that is. Posters were presented over lunch and then we headed into our business meeting. Lihua Xiao of CDC recapped his childhood in China and how it prompted him to have an interest in parasitology and then, as an introduction to Bill Font's acceptance of the Mentor Award, Charles Criscione and Michelle Steinauer did a little skit comparing him to Yoda - complete with voices.

Looking forward to seeing everyone in beautiful Quebec City in 2013. If you're interested in joining the American Society of Parasitologists, click here.

Special Report: #ASP2012 (American) - Part I: What's a Parasite? Zombie Ants, and Bidding Wars

The 2012 American Society of Parasitology meetings were held July 13-16 in Richmond, Virginia. There were over 150 papers presented and an additional 50 or so posters and being just one person, I obviously couldn't see all of them! Here are a few of the highlights of the meeting from the ones I did see, though. The first talk I saw was my Ron Fayer of the USDA, who studies Blastocystis in livestock. Seems that the prevalence of this parasite can be quite high, but detection methods have improved a lot, making its prevention and control more hopeful. Heather Stigge then gave a nice talk about how digeneans (like this one) choose sites in their frog hosts - apparently no one likes bullfrog mouths! This was followed by another digenean talk by Stephen Greiman, who presented data on pathogenic bacteria being transmitted by these parasites in some cases. At the end of this first afternoon, there was a new feature of the meetings - shorter talks by more junior grad students who presented their ideas and plans for Ph.D. projects in order to solicit some feedback from us sage old members. It was very impressive to me how many of the faculty forewent dinner in order to do this. The next morning started rather somberly - it was the final editorial breakfast for Jerry Esch, who has been at the helm of the Journal of Parasitology for 19 years (more on that to come). The President's Symposium followed and that was great fun. ASP President Armand Kuris kicked it off with a summary of the patterns of evolution of parasitism and a search for unifying themes in ecological modeling. His presentation began some debate in that he narrowly defined "parasite" and perhaps prompted a few later speakers to justify why they were at a Parasitology meeting! David Hughes then wowed us with his work on "zombie ants" - behaviorally modified ants who are infected with fungal parasites. It is really elegant, systems-biology-style work that looks at manipulation from many different angles, including ecological, neurological, and phylogenetic. Ryan Hechinger, a former student of Kuris's, finished up the symposium with a great talk highlighting how large a role that parasites plan in understanding energy fluxes in ecosystems. There were some other nice talks in the afternoon in the parallel sessions. A current student of Kuris, Sarah Weinstein, set the place abuzz when her analyses suggested that parasitism as a lifestyle has evolved 175 times and then a few talks on gregraines by the Clopton and Cook labs set my mind adrift to Dr. Seuss characters. That evening, we held our annual Live and Silent Auctions to raise money to support the student travel grants and once again had a slew of really fun donations by the creative community. Highlights are always paintings that Bill Campbell has done - they fetch hundreds of dollars - but Kristin Jensen's felted iPhone and iPad covers have also grown in popularity (and I was thrilled to win one again this year!). The high-drama auction item of the night turned out to be a pair of hand-painted wine glasses with snails and cercariae, done by author and artist (oh, and parasitologist), John Janovy, Jr.

Special Report: #ASP2012 (Australia) Part IV: Swimming with the Parasites

This post is part 4 (and final) of my special report on the #ASP2012 (Australia) meeting at Launceston, Tasmania - see part 1 here, part 2 here, and part 3 here.

Photo by Kate Hutson

The last day of the conference was a bumper day for marine parasitology so I will just write as briefly as I can on what I saw to cover some highlights. The day kicked off with a series of plenary lectures on; sea lice on farmed salmonids in British Columbia, the history of using parasites as biological markers to identify stock and age of orange roughy (Hoplostethus atlanticus), and an overview of the various parasitic infections that pose a threat to aquaculture by Prof. Barbara Nowak.

But out of those, the presentation which stood out as being most relevant to the original mission of this blog was a talk by Terry Miller - a research officer from the Queensland Museum. He discussed the outcome (so far) of a project to explore to categorise the diversity and genetics of parasites found in fishes of Lizard Island and Heron Island on the Great Barrier Reef, as well as Ningaloo Reef on Western Australia as a part of the Census of Marine Life project. The sheer biodiversity of parasites was the reason why this blog was started and a subject that we discussed in an essay at the end of 2010 - Terry Miller, with his many collaborators, have certainly been busy finding, describing, and classifying this overlooked wealth of biodiversity. They found all manners of myxozoans, flukes, tapeworms, and roundworms, and have already described 56 new species so far. But there are still many unanswered questions relating to biogeography, life-cycles, phylogenetics of these parasites and their significance for fisheries. With 2000 species of parasitic flukes (not counting other fish parasites) estimated to be in the fishes of Australia alone - that's a lot of species descriptions to come!

Photos and drawings used with permission from Leonie Barnett

Speaking of the weird and wonderful, Leonie Barnett from Central Queensland University presented a poster on the molecular phylogeny of a family of parasitic flukes call acanthocolpids which have very odd-looking and remarkably ornate cercariae (the free-living stage which emerge form the first host in the fluke life-cycle). Most cercariae simply look like microscopic tadpoles, with a leaf-shaped body followed by a tapered tail. Leonie has given those acanthocolpid "funky cercariae" nicknames such as "Ducks" and "Starship Enterprise"(see photo on the right). The question must be asked (which at this point can only be rhetorical) - why produce such remarkably elaborate-looking larvae when the majority of them will die after a day or two? What hosts do these parasites infect which warrant such amazing extravagance?

There were a number of presentations thorough the day which were relevant to the fisheries and aquaculture industry, including talks on the detection and treatment of blood-flukes in ranched tuna, identifying and characterising anisakid nematode larvae (which normally infect marine mammals but can cause disease in human if accidentally ingested) from fishes in Australasian waters, and a presentation by Kate Hutson on assessing risks pose to barramundi and mulloway aquaculture by various parasites.

Different Philophthalmus sp. rediae morphs
(insert: specialised morph attacking
the sporocysts of a rival species)

Ian Whittington started off the afternoon session with some videos of monogeneans and to follow that, I talked about potential caste formation and eusocial-like traits amongst the asexual stage of Philophthalmus sp. and how these specialised morphs may in fact be playing a in interspecific competition (see photo on the right or my alternative rendering here)

Sarah Catalano from the Hutson lab talked about a bizarre and little-known group of parasite called the dicyemids which are found in the kidneys of cephalopods (octopus, squid, cuttlefish). These parasites have a very simple body structure, but a very complicated life-cycle. They are astonishingly diverse and also display high levels of host specificity with each species occurs exclusively in a single host species. Because of their specificity they can also be used as a biological marker to reveal different host species where before they were simply considered as subpopulations.

Also from the Hutson lab was Alex Brazenor who presented a study looking at the effects of different water temperature and salinity levels on Neobenedenia - the little worm mentioned in the previous post which is capable of consecutive bouts of self-fertilisation and kick off an outbreak on its own. Alex found that at higher water temperature, Neobendenia lived a faster life -  whereas it took 18 days to reach sexual maturity at 22°C, it only took 10 days to reached that stage at 30°C. Their eggs are more likely to hatch successfully at the higher temperature and salinity level, although if the temperature reached beyond 32°C they start suffering detrimental effects.

Well, that does it for my reports on the #ASP2012 (Australia) conference. Overall, I had a great time - I got to catch up with some colleagues I haven't seen for a while,we talked about a lot of interesting science, and I saw some great presentations and posters - just about all that you can ask for at a conference really. So for me, it's back to writing up blog posts about new papers being published on all manners of interesting parasites - and I already have quite a few lined up...

Special Report: #ASP2012 (Australia) Part III: Sleepy Lizards, Painted Dogs

This post is part 3 of my special report on the #ASP2012 (Australia) meeting at Launceston, see part 1 here and part 2 here.

Photo by Caroline Wohlfeil

There were a number of interesting talks from the wildlife session, first up was a talk by Caroline Wohlfeil - a student from Michael Bull's lab. She gave a talk on sleepy lizards (see right) and the reptile tick, Bothriocroton hydrosauri. These ticks go through 3 stages in their life-cycle, alternating between feeding on a lizard and dropping off in a sheltered area to develop once they are fully engorged. It is in this latter stage that there ticks are transmitted - when lizards take shelter at refuges that have previously been used by infected lizards, they pick up ticks that were dropped off from the previous lizard. Using GPS loggers which continuously recorded the lizard's activity and location, Caroline was able to use that data to work out how often each of the tracked lizard had opportunities for infection. Her network analysis revealed that lizards that are highly-connected also had higher tick loads.

This was followed with a talk by Luz Botero Gomez, a student at Murdoch University, on trypanosome infections in little marsupial call the Brushed-Tail Bettong or Woylie. We have previously covered trypanosomes in another marsupials on this blog, namely the koala, but as it turns out, there is a great diversity of Trypanosoma in native marsupials - most of it still unknown. Woylie are known to be infected with 3 species - T. cruzi (the species which causes Chagas disease), T. copemani, and an as yet unnamed clade of Trypanosoma. Some of those Trypanosoma species are also found in other Australian marsupials but only the woylie is known to carry all three. Much like the koala-infecting trypanosome, T. copemani seems to only cause problem when it occurs in mixed infection with other Trypanosoma species - such co-infections can leads to inflammations and lesions in the tissue. In addition, these different trypanosomes also seem to have varying degrees of tissue specificity, with some species occurring in the blood, while other in muscle tissues, but overall mixed infections are more likely to occur in organs and muscles. Given the Woylie is currently critically endangered, it is very important to know what kind of diseases are induced by these trypanosomes and how it is affected by whether they are single or mixed infections.

Photo from Wikipedia by Helenabella

For a change of pace from parasites threatening a critically endangered mammal, Amanda Ash (also from Murdoch University) presented a talk call "Parasite: embrace not erase" which praised the important functional roles played by parasites in various ecosystems, and discussed the results of a study she conducted looking at the inestinal parasites of African Painted Dogs. She collected fecal samples from captive and wild Painted Dogs and compared the types of parasite eggs and cysts found in those sample. She found that the intestinal fauna of captive dogs was comparatively depauperated, populated only by Giardia whereas the wild dogs had a more eclectic mix of tapeworms, hookworms, and various protozoan parasites - in addition Giardia. Another stark contrast between the captive and wild dogs is that whereas parasitic infection was ubiquitous in the wild population, with 99% had some sort of parasite, only 15% of the captive dogs carried intestinal parasites of some sort.

This has enormous implications for conservation measures such as captive breeding programs - animals which have not been exposed to a wide range of parasites and pathogens can grow up to become immunologically naive so that when they are release into the wild, they may not be able to cope with the wide range of parasites they encounter. In addition, it is unknown what other physiological side-effects may result from lack of exposure to parasites. According to the hygiene hypothesis, the numerous types of allergies and auto-immune diseases which afflict some of us living in western societies have result from the lack of exposure to parasitic worms which are masters at manipulating and modulating our immune system. By limiting both the prevalence and variety of parasitic infections in those captive African Painted Dogs, are we consigning them to the same fate?

During the poster presentation, we saw some students who have come up with creative ways of presenting a 2 min talk - a student from James Cook University read a poem about whether wild dingoes pose a threat to the health of Indigenous communities in Queensland, while a student from University of Western Australia was literally singing the praises of using volatile chemicals for malaria parasite detection. Some of the most fascinating poster talks may present nightmarish scenarios to some people, but for different reasons.

Photo by Kate Hutson

For non-parasitologists, the tongue-biter seems like a one-off freak of nature. But in fact there are actually many species of tongue-biting isopods and other parasitic crustaceans which inhabit the mouth, gills, and branchial cavity of fish. One genus of tongue-biter isopod - Ceratothoa - encompasses 29 known species worldwide, 6 of which are found in Australia waters. However, a new study by Melissa Martin from University of Tasmania revealed that there at least 12 species of Ceratothoa (from 7 families of fish), and 4 of them are new to science.

Dinh Hoai Truong, a student from the Hutson lab at James Cook University presented a horror of a different kind - less visceral than having a parasite in your mouth, but more of a biosecurity nightmare to aquaculturists. He presented a poster on Neobenedenia - a hermaphroditic monogenean which infects the skin of Barramundi. His experiment showed that a single Neobenedenia is able produce eggs through self-fertilisation for consecutive generations without suffering any deleterious effects of inbreeding - each consecutive generation of inbred Neobenedenia are just as infective as the last. This means that even a single worm can start an entire sustained infestation at a fish farm. Unlike the widespread monogenean Gyrodactylus - a notorious aquacuture pest which has the viviparous "Russian Doll"-style "worm-within-a-worm" reproductive set-up (which allows them to swarm a fish like aphids on a rose bush) - Neobenedenia does what most monogeneans do and simply produce eggs. However because they are able to self-fertilise and have very short generation time, they can still become a serious pest to aquaculture.

In the next and final post on #ASP2012 (Australia), we will talk about how environmental factors can affect the generation time of Neobenedenia, and meet many other weird and wonderful marine parasites.

Next post: Swimming with the Parasites