POLL: What is a vector?

Next week, I’m going to write a post about vectors. This week, I want your input! So tell me: what is a vector? (I took these definitions from the literature, but I’m not going to tell you where they came from until next week.)

Definition 1A: “Any organism (vertebrate or invertebrate) that functions as a carrier of an infectious agent between organisms of a different species.”

Definition 1B: “Any organism (vertebrate or invertebrate) or inanimate object (i.e., fomite) that functions as a carrier of an infectious agent between organisms.”

Definition 2: “Any organism that can transmit infectious diseases between humans or from animals to humans.”

Definition 3A: “Hosts that transmit a pathogen while feeding non-lethally upon the internal fluids of another host.”

Definition 3B: “Blood-feeding arthropods such as mosquitoes, ticks, sandflies, tsetse flies and biting midges that transmit a pathogen while feeding non-lethally upon the internal fluids of another host.”

 

 

Visiting the UCSB Parasite Ecology Lab

[I don’t usually post about my own science adventures on this blog, but I’m going to make an exception today because I think that the topic could be broadly interesting for you guys. This is cross-posted from the UCSB Parasite Ecology Lab’s Adventure Science blog, which you should follow!]

The University of California Santa Barbara Parasite Ecology Lab seems to host a perpetual stream of visiting scientists – including me! I’m currently a PhD candidate at Virginia Tech, but in Fall 2016, I had the opportunity to be the Queen of the Salt Marsh Parasites while I visited UCSB for a semester. I had a great time, I learned a ton, and I highly recommend that you – yes you! – try to visit the UCSB Parasite Ecology Lab, too.

The first step in visiting is finding the funding to do so. I’m incredibly lucky to be supported by an NSF Graduate Research Fellowship, which pays my salary and tuition. NSF Fellows are also invited to apply for professional development opportunities, like the Graduate Research Internship Program (GRIP). The GRIP pairs fellows with mentors in federal agencies, and through their internships they work on “enhancing professional skills, developing networks, and preparing for a wide array of career options.”  Fortunately for me, one of my science heroes – Dr. Kevin Lafferty from the USGS – was on the mentor list last year, and in an extra stroke of good luck I was successfully funded through the GRIP to go work with him.

It’s a ~40 hour drive from Virginia to Santa Barbara, California, so I had the opportunity to see a good chunk of our beautiful country with my faithful and fuzzy copilot while traveling to the internship. (Here he is cheesing for a photo at Ozone Falls, Tennessee.)

But when I reached Santa Barbara, I was disappointed to discover how hideous it was. There was unlimited sunshine and nice weather, and I could see the beach from my office window. And there was an authentic Mexican restaurant every 20 feet, including right near the salt marsh nature preserve where I did my field work (see next photo). It was rough. All I can say is that you’ll just have to learn to live with it if you visit.

Though Santa Barbara legitimately lacked one of my all-time-favorite things (caves), it made up for it by having many of my other all-time-favorite things: snails, parasites, and mud. I have seen some Virginia ponds with high snail densities, but nothing I’ve seen compared to the number of California horn snails that I found in the Carpinteria Salt Marsh (see every bump in the mud in the next photo). The majority of those snails harbored first intermediate host trematode infections.

And trematodes were my parasite of interest during my tenure at UCSB. A postdoc in the lab, Julia Buck, had recently found some interesting differences in the types of trematodes that infect male versus female snails. So I did some field and laboratory experiments to see if the foraging behaviors of male and females might explain sex-based trematode infection dynamics. For instance, some trematodes infect snails after the snails ingest trematode eggs from bird feces, so I did experiments to determine whether male or female snails were more likely to hang out near bird feces. You might say it was a “crappy” project.

Anyways, my visit was a blast, and I met a bunch of really amazing scientists from all career stages while I was there. I hope to go back soon, and maybe I’ll see you there when I do.

Soldier trematodes

Many animal species have fascinatingly complex social systems, but the pinnacle of sociality is relatively rare: the reproductive division of labor. Taxa that have separate castes of reproductive and non-reproductive individuals include the hymenopteran insects (ants, bees, and wasps), gall-forming aphids, termites, ambrosia beetles, sponge-dwelling shrimp, naked mole rats, and – because this is a Parasite Ecology blog – trematode parasites.

You’ve probably seen photos of the insane phenotypic differences between castes in some species; for instance, the difference between a queen fire ant and a worker fire ant (amazing photo by Alex Wild):

Or between queen, worker, and soldier termites (photo from here):

Trematode rediae have equally obvious caste differences, where reproductive rediae are huge and full of developing offspring, whereas soldier rediae are tiny with relatively large pharynxes (photo from here). And they don’t just look different; these castes are also spatially segregated, and they have unique behaviors. Reproductive individuals tend to hang out in the host snail’s gonads, while soldier trematodes tend to hang out in the mantle. And reproductive rediae rarely attack rediae from other trematode species, whereas soldier rediae readily attack invading species.

But despite these differences between reproductive and soldier rediae, the reproductive division of labor in first intermediate host trematode colonies wasn’t discovered until a few years ago. And until January (Garcia-Vedrenne et al. 2017), soldier rediae had only been documented in one trematode superfamily: the Echinostomatoidea.

It would not have been surprising if echinostomoids were the only trematodes to have soldier rediae, because echinostomoids are known for their ability to “fight” other trematode species. For instance, in a well-studied salt marsh system, echinostomoids sit at the top of a trematode dominance hierarchy, where they can successfully invade and conquer a California horn snail infected by a different trematode species, and they can successfully fight off invasions of their snail by other trematode species. But we now know that at least four species of heterophyid trematodes, which fall in the middle of that dominance hierarchy, also have a distinct soldier caste (Garcia-Vedrenne et al. 2017)!

This is a pretty big addition to our existing knowledge of these systems, and it makes one wonder how many other trematode species have undocumented soldier castes. Check out the paper to learn more!

Reference:

Garcia-Vedrenne, A.E., A.C.E. Quintana, A.M. DeRogatis, C.M. Dover, M. Lopez, A. Kuris, and R.F. Hechinger. 2017. Trematodes with a reproductive division of labour: heterophyids also have a soldier caste and early infections reveal how colonies become structured. International Journal for Parasitology, 47(1): 41-50.

Parasite Valentines

I usually blog about STIs on Valentine’s Day. But this year, I’ve decided to spread the parasite love in a different way – with a few awesome links and a valentine. If you want to help spread the parasite love, you are more than welcome to send me parasite valentines via Twitter. I’ll be waiting.

Why killer viruses are on the rise

An awesome new symbiont was recently discovered. It’s a beetle that pretends to be an ant’s butt.

Superspreaders played a big role  in the Ebola epidemic

What’s on my reading list

The flu and job search committee duties have contributed to me falling behind in reading and blogging. In an attempt to get back on track, I’m posting this week’s reading list (in no particular order).

1. Pepin, et al. (2017). Inferring infection hazard in wildlife populations by linking data across individual and population scales. Ecology Letters.
2.  Cizauskas et al. (2017). Parasite vulnerability to climate change: an evidence-based functional trait approach. Royal Society Open Science.
3. Betini et al. (2017). Why are we not evaluating multiple competing hypotheses in ecology and evolution? Royal Society Open Science.
4. Weinersmith et al. (2017). Tales from the crypt: a parasitoid manipulates the behaviour of its parasite host. Proceedings of the Royal Society B.
5. Cohen et al. (2017) The thermal mismatch hypothesis explains host susceptibility to an emerging infectious disease. Ecology Letters.
6. Garcia-Vedrenne et al. (2017). Trematodes with a reproductive division of labour: heterophyids also have a soldier caste and early infections reveal how colonies become structured. International Journal for Parasitology.

What am I forgetting?

Zebra-eating plants spread anthrax

Carnivorous plants have always fascinated me. So when I saw this link on Facebook a few years ago, I was quite excited! The link (and this video) claim that the bromeliad Puya chilensis eats sheep. That’s right. A plant that eats sheep! The sheep are ensnared in the plant’s thorns until they succumb to exhaustion and die, and then their rotting carcasses feed the plant. We don’t actually know that the plants have evolved to “catch” and eat mammals, of course. An alternative explanation is that sheep are just rather unintelligent. But the idea is fascinating.

Whether some plants intentionally kill mammals or not is up for debate, but plants do eat mammals. Kind of. For instance, in Namibia, zebra carcasses increase soil nutrient concentrations for at least a year after the animal dies (Turner et al. 2014), and during that initial year, grass biomass near carcasses is higher than randomly-selected carcass-free sites (Turner et al. 2014).

The higher grass biomass near carcasses causes zebra and other ungulates to be attracted to carcass sites to forage (Turner et al. 2014). You might be thinking that foraging near a dead zebra body might be a bad idea for a zebra, and you’d be right. Namibia is one location where anthrax (caused by the bacterial pathogen Bacillus anthracis) naturally infects wildlife, so contacting a carcass could mean contacting anthrax spores. And zebras should worry about more than just the carcasses; the soil, grass roots, and grass at carcass sites all harbor anthrax spores, at least for the first year after the carcass appears (Turner et al. 2014).

If visiting carcass sites exposes zebras to a potentially lethal pathogen, why don’t zebras avoid carcasses? Well, they do, but only a little bit. When a carcass is relatively fresh, zebras are less likely to visit carcass sites than control sites, but that avoidance doesn’t last until all of the anthrax has left the grass. Therefore, sexy, delicious grass may facilitate anthrax infections in zebra.

Reference:

Turner WC et al. 2014 Fatal attraction: vegetation responses to nutrient inputs attract herbivores to infectious anthrax carcass sites. Proc. R. Soc. B 281: 20141785. http://dx.doi.org/10.1098/rspb.2014.1785

Parasites in the News – January 2017

If you haven’t voted on the best 2016 Parasite Ecology cartoon yet, please do! If you did, thanks! Have some links!

Not Up for Debate: The Science Behind Vaccination (New York Times)

We are resurfacing this article in light of the news that Robert Kennedy Jr., an anti-vaccine crusader, has said he has been asked by President-elect Trump to lead an immunization safety committee.

Relatedly, it looks like the measles vaccine protects children from more than measles.

“A research crew went on a quest for the ‘Lost City of the Monkey God.’ They nearly lost their faces for it.”

And finally, the prawns-eat-snails-to-reduce-Schistosoma-transmission project in Senegal was covered by BBC news, reminding me of that one time I tried to draw a motorcycle.

Yikes. That prawn terminator, though.

Have a good weekend!

Best parasite ecology cartoon of 2016?

It’s the first week of the new year, which means that you get to vote on the best parasite ecology cartoon from last year! In 2013, the winner was “Social Networking in Lemurs,” a cartoon about this study that painted lice on lemurs to infer lemur contacts. In 2014, the winner was “Oldest Trick in the Book,” a romantic cartoon about a snail who was castrated by trematodes. And in 2015, the winner was “Bring out yer dead (prairie dogs),” a Monty Python reference tied to a cool prairie dog plague paper. So which 2016 cartoon was best? I’m opening up the voting for these candidates:

(1) The case of the not-so-boring isopods

(2) A sworm of soldier trematodes

(3) Slugs. Ruin. Everything.

(4) The Curse of the Magical Seed Dispenser

(5) Frogald Stump bans immigration and destroys frog metapopulation stability

(6) “Parasite” fashion show

(7) House cats out of the dog house after Toxoplasma accusations 

(8) Overly-frequent arousal can kill you

(9) Weird vibrations

(10) Survival of the fattest

(11) May the force of infection be with you

Let the voting begin! You can pick your top three favorites using this poll:

 

 

 

 

 

2016 Parasite Ecology #260papers

Happy New Year!

I started blogging roughly four years ago with several goals in mind, one of which was to spend more time reading the literature. There is no question that blogging caused me to read more. But last January, Meg Duffy posted about her progress on her goal to read 260 papers in 2015,* and that made me wonder: how many papers do I actually read in a year?

I’m a big fan of tracking my personal productivity by keeping a time journal, so Meg’s idea for keeping an academic reading journal was instantly appealing. And thus I wrote down every paper that I read in 2016. I learned a lot about my work habits by doing this, so I decided to write a post about the experience, in case some of you are also interested in giving it a go in 2017.

Like Meg, I only recorded the papers that I read thoroughly (i.e., to the level that I would read a paper for a lab meeting). I must have skimmed at least three times as many papers as I actually read, especially during periods where I was reading to prepare to write grant proposals and manuscripts. To get an idea of how consistently I read thoroughly, I made this plot of my paper-reading timeline for 2016. I made an Excel spreadsheet that automatically updated this plot every time I added a paper, which helped me to track my progress.

My goal was to stay above the orange line all year, and I pretty much succeeded! As I write this post on 28 December, I have read 245 papers, leaving me 5 papers/day if I really want to reach my #260paper goal by December 31^st. That’s not too bad! I would have surpassed my goal if it wasn’t for fall field season. Unsurprisingly, I gave up reading (and regular showers and normal eating habits) for a few weeks of intense data collection, as I do every year. I wish I had kept up with reading during that time, but oh well.

You might be wondering which journals are most frequented by a self-proclaimed parasite ecologist. Of the 245 papers that I read, there were only 12 journals that showed up five or more times: Conservation Biology, Ecological Applications, Ecology, Ecology Letters, Journal of Animal Ecology, Journal of Parasitology, Philosophical Transactions of the Royal Society B, PNAS, Proceedings of the Royal Society B, Science, TREE, and Trends in Parasitology. There weren’t any huge surprises there, except maybe Philosophical Transactions of the Royal Society B, which had some excellent and recent special issues that I dug into.

Also unsurprisingly, most papers were recent, with ~16% of papers published in 2016. I did read some older papers, but I want to do a better job of digging into the older literature in 2017 – partially because I think it’s important, and partially because it’s fun! (The bin sizes on this figure are purposefully uneven.)

I also kept track of why I read each paper, though I don’t think most of those data would be interesting to people besides me. I was somewhat surprised to find that only 19 (8%) of the papers that I read in 2016 were specifically for blogging purposes. It seemed like blogging increased my reading by so much more! But an additional 20 papers were stuck under the heading of “other reading,” and many of those could have ended up on the blog, but for whatever reason I decided not to write about them. Finally, I was not surprised to find that the most common reason for reading a paper was preparing for grant writing. Because it was a busy grant year, grant preparation accounted for a whopping 42% of the papers that I read.

So there you have it! I’d be interested to hear your suggestions on how best to spend my reading time in 2017. Anyone have some neat “old” parasite ecology papers to suggest?

*#365papers was co-founded by Jacquelyn Gill.

(Not) North Pole Parasites: Mistletoe

I meant to continue blogging about North Pole Parasites today, moving on to talk about Trichinella in polar bears, but this article by Tommy Leung reminded me that mistletoe is really the ultimate Christmas parasite. So instead, I wrote you guys a poem. Happy Holidays!

EDIT: Oh, and for cool footage, check out this video!