Its summer, off to the races!

The spring semester has ended again and its time for the summer, when those of us who teach during the school year get the majority of our work done. It is also time for summer traveling, sometimes for fun but definitely for work.

I am attending the Ecology and Evolution of Infectious Disease conference and workshop this year in Ann Arbor, MI and am excited to geek-out about parasites and disease ecology. Because I am the only person studying disease ecology in mammals and ticks at IU right now, these meetings are always fun because I get to talk to other researchers who work on similar systems. This meeting is also relatively small, which means you can get face-time with “famous” professors, and get to meet a lot of really awesome students from all over.

This summer’s meetings have a bit more pressure than usual. I am hoping to graduate next spring or summer, so this summer my job is to talk to possible post-doc advisors and give people a face to put with my name if I show up on any of their job searches. I hope I can wow them with what I have been doing for the last few years and talk about possible future collaborations and projects.

I will be mobile-blogging while I am away, mainly through Tumblr I think, but I will try to have posts copy to my blog here as well. Also, International Towel Day is in a week and will happen while at the meeting, so I hope to post some Douglas Adams homages while away.

Happy spring!

We are history!

I haven’t been able to write the blog for a good while now, research and other things keep getting in the way even when I think about topics I’d like to discuss and write about. But, I have something I don’t really think needs a lot of up-front writing or analysis from me, just maybe some prompting to muse and think.

I have been listening (for the 3^rd time or so) to the audiobook of Terry Pratchett’s book A Hat Full of Sky, the second book in the Tiffany Aching series. These may be my favorite books that he’s written and I love them every time I hear/read them. I have been thinking about the excerpt below quite a bit lately. I’ve been teaching a vertebrate zoology lab this semester, so I have been thinking about phylogeny and evolution more than usual, so I’m sure that’s one reason. But also I was just thinking about how beautifully this section describes what is means to be human in a greater biological context, considering the remarkable history of life on earth and the ways that humans are different from other animals. And while we are always being reminded about how much trouble and damage humans cause the world and the other organisms we share the earth with (as being something that really does set humans apart from other living things), this is one of those passages that reminds me of the why humans are special, in spite of how extremely similar we are to other living things, there are some vastly important differences that have led to us being who we are.

So, take a minute to read this passage and see what it makes you think about. After Douglas Adams in Dirk Gently’s Holistic Detective Agency, writing about Bach being the music of the world and the “fundamental interconnectedness of all things,” this is one of my favorite excerpts about the wonder of the natural world. Let me know what your thoughts are, I would love to hear them! And pick up one, or I would recommend many, of Terry Pratchett’s books if you haven’t already done so!

(a bit of context: Tiffany is talking to a “hiver,” which is an entity that takes over the bodies of animals or people, and then “becomes” everything its ever taken over, and almost always kills whatever it is embodying. So, the hiver has all the memories and experiences of every animal or person it has ever been. It cannot think of itself as “I” or one living thing, because it is everything all at once. It cannot figure out how to die, to stop killing things, because it doesn’t know what it is.)

“Here is a story to believe,” she said. “Once we were blobs in the sea, and then fishes, and then lizards and rats, and then monkeys, and hundreds of things in between. This hand was once a fin, this hand once had claws! In my human mouth I have the pointy teeth of a wolf and the chisel teeth of a rabbit and the grinding teeth of a cow! Our blood is as salty as the sea we used to live in! When we’re frightened, the hair on our skins stands up, just like when we had fur. We are history! Everything we’ve ever been on the way to becoming us, we still are…I’m made up of the memories of my parents and grandparents, all my ancestors. They’re in the way I look, in the color of my hair. And I’m made up of everyone I’ve ever met who’s chanced the way I think. So who is ‘me’?”

“The piece that just told us that story,” said the hiver. “The piece that’s truly you.”

“Well…yes. But you must have that too. You know you say you’re ‘us’—who is saying that? Who is saying you’re not you? You’re not different from us, we’re just much better at forgetting. And we know when not to listen to the monkey.”

“You just puzzled us,” said the hiver.

“The old bit of our brains that wants to be head monkey, and attacks when its surprised,” said Tiffany. “It reacts. It doesn’t think. Being human is know when not to be the monkey or the lizard or any of those other old echoes. But when you take people over, you silence the human part. You listen to the monkey. The monkey doesn’t know what it needs, only what it wants.”

-Terry Pratchett, A Hat Full of Sky, p. 240-241

(http://books.google.com/books/about/A_hat_full_of_sky.html?id=dmc3CVG-aqgC)

I *heart* Data

PhD comics never fails to have an appropriate image. (http://www.phdcomics.com/store/mojostore.php?_=view&ProductID=12631)

 A while back I said I would discuss what “comes next” after all the field work. Well, I have started the next big project: identifying all the ticks I collected from the mice and voles we trapped over the summer. This is a big project because I collected over 670 ticks, and these are larvae and nymphs, the younger life-stages of the tick, and are really small and can only be identified under a dissecting microscope. It is important to identify all these ticks to species and life-stage because there are different assumptions about previous host interactions and possible infections for each group. To catch everyone up, here is some background before we get too deep into things.

This is a diagram of the Ixodes scapularis lifecycle. It is a "cool season" tick because its adults are active in the fall. Most of the ticks in Indaina have all life-stages active in the spring and summer.

To review, ticks are ectoparasites of vertebrates that have a 4-stage life cycle: egg, larva, nymph, and adult. These parasites need to bite a host and obtain a blood meal in order to molt and transition to the next life-stage. This is somewhat unique because other common vectors like fleas and mosquitoes only feed on a host directly in the adult stage. This means ticks can have many interactions with host over their lifetime and have the opportunity to become infected or pass on infection many times. The larvae emerge from eggs uninfected, besides obligate bacterial symbionts, so the larva can pick up a pathogen infection during their first blood meal. When these larvae molt into nymphs they become infected with whatever bacteria was picked up during the previous blood meal and can transmit to an uninfected host. This same thing can happen with adult ticks, but they have had two possible times to pick up an infection. The adult female ticks then feed to produce eggs, the males mate with the females during this blood meal and they rarely feed themselves. Then the females drop of the host and lay thousands of eggs in a “mass”. The larvae then emerge in the spring and the cycle starts all over again.

Mouse with a lot of engorged nymphs on its back.

The rodent hosts that I am interested can be hosts to the larval and nymphal stages. In the part of southern Indiana where I conducted these surveys have three main species of tick, but only two have been found using rodents as hosts, Ixodes scapularis (blacklegged deer tick) and Dermacentor variabilis (American dog tick). The main character that differentiates larvae from nymphs is that larvae have 6 legs while nymphs have 8 legs (as well as the adults). Each species has some unique features that I use to discern between the two.

My lab bench

The tools I use when identifying ticks are a dissecting microscope, this is a microscope that doesn’t need a specimen to be prepared on a slide. It used an external light source to illuminate a whole sample. I manipulate the ticks mainly with a paintbrush. This is a common tool for people who handle fragile invertebrates in the lab because it can move and stick to the specimen but won’t accidentally damage it like a normal pair of forceps. There are also “soft” forceps that are made from a flexible metal that are useful for samples that are too heavy for the paintbrush to grab on to. I covered my whole bench in white bench paper. This helps keep my workspace clean, and if any ticks fall or get dropped they will show up better on the light background. My scope to chair hight ratio is still off a bit, the chair is too high so I have to hunch to look into the dissecting scope, which can be a little painful after a long time. I’m going to have to figure out the best solution to this problem (a shorter chair or raising up the scope on a platform or something).

Dermacentor is the most common tick we’ve found on the rodents, from our previous surveys and from the data I’ve collected from this past year so far. Its mouthparts are somewhat rounded, the body and legs are a light brown color, and the shield on the back (dorsal) side comes away from the body in a straight line.

Ixodes seems to be somewhat less common on these hosts, but still very present. This is of particular interest to many because this species can carry Borrelia burgdorferi, the bacteria that causes Lyme disease. These ticks have longer, straighter mouthparts, are usually darker, blacker in color (the legs in particular, especially in the larvae), and the shield is rounded all the way around. The picture I have below compares a nymph from each species. See if you can see some of the differences I listed.

These little rodents are kind of teeming with parasites, and ticks are the only ectoparasites I collected from them. Fleas and mites were fairly common, but are harder to collect because they don’t attach to the host so they are freely moving through the host’s hair and around the body while you are trying to grab them with forceps. These parasites are important because they can also carry pathogens that can infect wildlife and humans (remember theplague post?). Analyzing the blood samples we collected in 2009 showed that many hosts are infected with Bartonella, a flea-borne pathogen, so fleas may be really important in this disease community.

Flea from a mouse, most likely Orchopeas leucopus.

Fleas and mites look really different from ticks and each other. I know fewer details about these creatures, but I do know they look pretty nasty. Fleas are covered in these little hairs which make them really sticky to the host fur (and hard to handle with the paintbrush, my usual tool for this). They look like they're "swimming" through the hair when you see them on a host, its pretty crazy.

I couldn't get the whole mite in focus at once. The left picture shows its arms in focus, while the right picture shows the little hairs that cover its back.

I think mites look like little monsters with their front set of legs reaching above their head. I’m sure many of you think these guys all look like monsters, but I get so used to looking at ticks I’m not phased by them anymore (what a strange state to be in, huh?).

If I haven't completely grossed you out with this post, stay tuned for more on parasites!