New Parasite Ecology Papers – January 2018

If you set a New Year’s resolution to read #260papers this year, you might want to check out some of these recent gems. (I’m not providing all of the citation info, in an attempt to prevent accidental inflation of Google Scholar citation indices. So you’ll need to click through for full info.) And if you’re interested in what I’m reading in 2018, you can check my #260papers Twitter thread.

Rabies elimination research: juxtaposing optimism, pragmatism and realism

Corals hosting symbiotic hydrozoans are less susceptible to predation and disease

Disease implications of animal social network structure: a synthesis across social systems

Wildlife disease ecology from the individual to the population: Insights from a long-term study of a naturally infected European badger population

Parasites at Risk – Insights from an Endangered Marsupial

To Reduce the Global Burden of Human Schistosomiasis, Use ‘Old Fashioned’ Snail Control

Contact networks structured by sex underpin sex-specific epidemiology of infection

Best parasite ecology cartoon of 2017?

Happy New Year!

Before we leave 2017 behind us, let’s take a walk down memory lane, and re-visit some of the blog’s best parasite ecology cartoons. At the end, you can vote on your favorite 2017 cartoon.

If you want to delve even further into the past, you can also check out some of the previous best-of-the-best winners: 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. In 2015, the winner was “Bring out yer dead (prairie dogs),” a Monty Python reference tied to a cool prairie dog plague paper. And in 2016, the winner was my cartoon rendering of Frogald Trump.

Here are the cartoons that I’ll open the voting for this year:

(1) Ticks suck moose dry


(2) Parasite valentine


(3) Orange amphipod zombie apocalypse


(4) Parasites and de-extinction


(5) This terrifying clown isopod


Here’s the poll! You can only vote for one cartoon.


12 Days of Parasite Ecology Christmas

Happy Holidays, Everyone! I already spread some parasite love this season by giving Parasite Rex and a mistletoe ornament as a white elephant gift, but I feel like I have even more to give. So here’s my first and best take on a parasite ecology Christmas carol. You can click through the links to learn more about each system, should you so choose.

On the 12th day of Parasite Ecology Christmas, my true love sent to me:

12 nematomorph-infected crickets leaping


11 male crabs doing ladies’ dancing


10 Indian pipe plants piping


9 parasitoid wasps a-drumming (photo from here)


8 ants a-milking (I snuck in a mutualism! Deal with it!)

7 leeches a-swimminghippoassleech

6 cuckoos a-laying


(One hundred and) 4 Galapagos lice on birds

3 French T. gondii infections (cartoon from here)

2 turtle acanthocephalans

And a partridge that was covered in fleas!

If you’re looking for more Christmas-themed parasite topics, you can check out my mistletoe-themed version of Twas the Night Before Christmas or my take on Santa’s bizarre roof top behaviors. See y’all next year!

Forest conservation and restoration to reduce human diarrheal disease

In the NCEAS SNAPP Ecological Levers for Health working group, we’re collecting examples of local or regional interventions that can have direct, measurable benefits for human health (via reduced infectious disease) AND the environment – win–win solutions. The case studies that we’ve collected thus far are so cool that we just can’t wait to share them! In September, I shared a story about vulture conservation and rabies. This week, I’ll tell you about plants and diarrheal disease.

Two years ago, I adopted a tiny blue Aussie puppy: a wild, brilliant beast with a thirst for adventure… and water. I mean he really likes water – jumping in it, biting it, blowing bubbles in it, fishing sticks out of it, etc. And the dirtier that water is, the better. So I set my puppy loose at the duck pond at our local gem of a dog park, where I had seen my previous dog and dozens of other dogs safely drink the water. Days later, my precious puppy developed severe diarrhea, and just hours after the onset of his symptoms, he became terrifyingly lethargic. The enteric pathogens that he had guzzled in the pond water might have killed him if we had not immediately sought out veterinary care. But fortunately, antibiotics and rehydration allowed Carrot to make a full recovery, and he grew up to be the healthy mud monster pictured below. From that experience, I re-learned an important lesson from disease ecology: pathogens often have minimal effects on adult animals, which have developed resistance/immunity during prior exposure, but the same pathogens can be deadly for juveniles during their first exposure.


This principle doesn’t just apply to puppies: diarrheal disease is the second leading cause of global childhood mortality for children under five years old. That’s hundreds of thousands of children dying every year because they did normal childhood things – like eating, drinking, and playing outside – and became infected by waterborne or foodborne pathogens like rotaviruses, Vibrio cholerae, and Salmonella. Many more children become infected by these pathogens and survive their illnesses, only to experience lasting physiological impacts. For instance, diarrhea leads to malnourishment, and malnourishment increases a child’s risk of future infection and diarrhea, creating a vicious cycle of ill health that can retard physical and mental development.

How can we remedy this huge global burden of childhood morbidity and mortality? The good news is that we already have substantially reduced the global impacts of childhood diarrheal disease by (1) improving hygiene and sanitation to reduce peoples’ exposure to the pathogens and (2) using oral rehydration therapy to treat children who are suffering from diarrhea, so that they do not die from dehydration. However, millions of people still lack access to clean water resources and quality healthcare, and an unthinkable number of children are still dying each year, and thus there is still much to do. Today, I want to broaden the scope of potential solutions: are there ecological solutions that can help reduce human exposure to enteric pathogens as a complement to current public health efforts?

But before we discuss specific ecological solutions, it’s worth discussing how these pathogens enter and persist in water sources in the first place. In some cases, the pathogens are pumped into public water sources directly from sewage pipes or human bodies (e.g., people swimming and defecating at water access points). In other cases, the pathogens reach public water sources via runoff from the environment after they’ve been excreted by humans and/or animals. When these pathogens reach a waterbody, they do not necessarily find and infect a human. For instance, if the pathogen is buried under the sediment in a stream, degraded by sunlight, consumed by microorganisms, or destroyed by plant biocides, it will never reach a human host. So ideally, ecological solutions will reduce the number of pathogens reaching waterbodies and/or increase pathogen death rates in those waterbodies. With this in mind, let’s talk about one class of ecological solutions for waterborne enteric pathogens: can plants be a win–win solution for conservation and human health?


In my freshmen year as an undergrad, my favorite professor made us “draw and describe, in excruciating detail, the difference between an urban and rural hydrograph.” I received full marks, so let’s assume I’m an expert: in urbanized areas with lots of buildings and paved, impervious surfaces, stormwater reaches streams and rivers quickly, whereas in rural areas with lots of trees and permeable soil, stormwater reaches streams and rivers relatively slowly (see below). And of course, it isn’t just water that reaches those streams and rivers. In urban environments, pollutants and pathogens within the stormwater also make it to downstream waterbodies faster, meaning that fewer pathogens die before reaching water sources where they can encounter and infect people. Therefore, human-caused hydrological changes should affect human disease burdens.


And we’re seeing that. For instance, in a massive study of 300,000 children in 35 nations, deforestation upstream from a child’s house was found to be strong predictor of whether the child had high risk of diarrheal disease, presumably because many pathogens were entering the waterbodies upstream (Herrera et al. 2017). (But this was only true for the poor children – the wealthier children living in cities probably had better access to sanitation infrastructure.) Similarly, in Brazil, children living near protected forests were less likely to experience diarrheal disease (Bauch et al. 2015). These large-scale correlational studies suggest that protecting forests might be a win–win solution for conserving biodiversity and reducing childhood diarrhea!

Of course, many forests have already been cut down, so it’s too late to preserve them for human health. In those cases, reforestation/restoration might be a win–win solution. For instance, Herrera et al. (2017) predicted that increasing upstream forest cover by 30% would reduce childhood diarrheal risk as much as improved sanitation and hygiene!

5 RickettsFig

But re-forestation is a big undertaking, and as far as I know, no one has experimentally evaluated the effects of re-forestation on human disease yet. An easier/faster intervention to slow the rate that pathogens and other pollutants reach streams and rivers might be replanting vegetation just within riparian buffers. It’s still unclear whether replanting riparian vegetation can reduce human infection, but in some studies, the number of enteric pathogens and/or fecal indicator bacteria within streams has decreased after riparian buffers were restored, which suggests that human infectious risk would be reduced by stream-side vegetation. This remains an important avenue for future research.

So, preserving or restoring forests and/or riparian buffers can reduce the number of pathogens reaching waterbodies and potentially reduce human infection, but can plants also reduce the number of pathogens that reach human hosts after reaching waterbodies? Potentially! For instance, at Indonesian islands without wastewater treatment systems, there are fewer human bacterial pathogens in seagrass meadows than in nearshore waters that lack seagrass meadows (Lamb et al. 2017). Furthermore, disease burdens in corals are lower near seagrass meadows, too, suggesting that preserving or restoring seagrass meadows could be a win–win for human health and conservation. This is a great correlational study, but is there any experimental evidence that aquatic/marine plants reduce environmental pathogen loads or human disease burdens?

Yep! You may have seen something similar to the photograph below in a town near you. It’s a constructed wetland. Specifically, it’s the Dominguez Gap Wetland, which was created to treat stormwater before it reached the LA River and then the Pacific Ocean. Constructed wetlands like this one are typically designed to filter heavy metals, excess nitrogen and phosphorous, and other chemical pollutants from stormwater. But they can also remove viruses, bacteria, protozoans, and other pathogens from runoff waters. For instance, by forcing viruses to hang out in the slow-flowing water for a while, the wetlands ensure that many viruses die from UV exposure long before they reach downstream waterbodies. Several studies have shown that constructed wetlands successfully reduce environmental pathogen loads, and now we need studies that link constructed wetlands and human disease risk.


However, there are many varieties of constructed wetlands – they vary in retention time, turbidity, whether they contain plants or not, whether there is subsurface or surface water flow, etc. And some designs are better at removing pathogens from stormwater than others. Furthermore, even really efficient constructed wetlands might fail to reduce pathogen loads to levels that are safe for human use, depending on how many pathogens are entering the environment. Therefore, if we want to use constructed wetlands to reduce human exposure to enteric pathogens, we need to design them carefully.

So there you have it! “Plants” – or environmental characteristics associated with plants – can reduce the number of human pathogens that reach waterbodies and pathogen survival time within waterbodies. And lower pathogen loads in waterbodies presumably reduce human disease, especially childhood diarrheal risk. As far as I can tell, no one is currently using forest protection/restoration or constructed wetlands on a large scale to try to prevent childhood diarrhea, but “plants” could be “ecological levers for health” that advance both conservation and human health goals.

If you know of any existing, planned, or in-progress forest protection, reforestation, or constructed wetland interventions aimed at reducing human diarrheal diseases, please let me know! And if you can think of any other win–win solutions for conservation and human health, we’d love to hear about them.


Bauch, Simone C., Anna M. Birkenbach, Subhrendu K. Pattanayak, and Erin O. Sills. “Public Health Impacts of Ecosystem Change in the Brazilian Amazon.” Proceedings of the National Academy of Sciences 112, no. 24 (June 16, 2015): 7414–19.

Collins, Rob, Malcolm Mcleod, Mike Hedley, Andrea Donnison, Murray Close, James Hanly, Dave Horne, et al. “Best Management Practices to Mitigate Faecal Contamination by Livestock of New Zealand Waters.” New Zealand Journal of Agricultural Research 50, no. 2 (June 1, 2007): 267–78.

Daigneault, Adam J., Florian V. Eppink, and William G. Lee. “A National Riparian Restoration Programme in New Zealand: Is It Value for Money?” Journal of Environmental Management 187 (February 1, 2017): 166–77.

Falabi, J. A., C. P. Gerba, and M. M. Karpiscak. “Giardia and Cryptosporidium Removal from Waste-Water by a Duckweed (Lemna Gibba L.) Covered Pond.” Letters in Applied Microbiology 34, no. 5 (2002): 384–87.

Graczyk, Thaddeus K., Frances E. Lucy, Leena Tamang, Yessika Mashinski, Michael A. Broaders, Michelle Connolly, and Hui-Wen A. Cheng. “Propagation of Human Enteropathogens in Constructed Horizontal Wetlands Used for Tertiary Wastewater Treatment.” Applied and Environmental Microbiology 75, no. 13 (July 1, 2009): 4531–38.

Hench, Keith R., Gary K. Bissonnette, Alan J. Sexstone, Jerry G. Coleman, Keith Garbutt, and Jeffrey G. Skousen. “Fate of Physical, Chemical, and Microbial Contaminants in Domestic Wastewater Following Treatment by Small Constructed Wetlands.” Water Research 37, no. 4 (February 1, 2003): 921–27.

Herrera, Diego, Alicia Ellis, Brendan Fisher, Christopher D. Golden, Kiersten Johnson, Mark Mulligan, Alexander Pfaff, Timothy Treuer, and Taylor H. Ricketts. “Upstream Watershed Condition Predicts Rural Children’s Health across 35 Developing Countries.” Nature Communications 8, no. 1 (October 9, 2017): 811.

Johnson, Kiersten B., Anila Jacob, and Molly E. Brown. “Forest Cover Associated with Improved Child Health and Nutrition: Evidence from the Malawi Demographic and Health Survey and Satellite Data.” Global Health, Science and Practice 1, no. 2 (August 2013): 237–48.

Lamb, Joleah B., Jeroen A. J. M. van de Water, David G. Bourne, Craig Altier, Margaux Y. Hein, Evan A. Fiorenza, Nur Abu, Jamaluddin Jompa, and C. Drew Harvell. “Seagrass Ecosystems Reduce Exposure to Bacterial Pathogens of Humans, Fishes, and Invertebrates.” Science 355, no. 6326 (February 17, 2017): 731–33.

Maseyk, Fleur J. F., Estelle J. Dominati, Toni White, and Alec D. Mackay. “Farmer Perspectives of the On-Farm and off-Farm Pros and Cons of Planted Multifunctional Riparian Margins.” Land Use Policy 61 (February 1, 2017): 160–70.

Pattanayak, Subhrendu K., and Kelly J. Wendland. “Nature’s Care: Diarrhea, Watershed Protection, and Biodiversity Conservation in Flores, Indonesia.” Biodiversity and Conservation 16, no. 10 (September 1, 2007): 2801–19.

Quiñónez-Díaz, M. J., M. M. Karpiscak, E. D. Ellman, and C. P. Gerba. “Removal of Pathogenic and Indicator Microorganisms by a Constructed Wetland Receiving Untreated Domestic Wastewater.” Journal of Environmental Science and Health. Part A, Toxic/Hazardous Substances & Environmental Engineering 36, no. 7 (2001): 1311–20.

Russell, Richard C. “Constructed Wetlands and Mosquitoes: Health Hazards and Management Options—An Australian Perspective.” Ecological Engineering 12, no. 1 (January 1, 1999): 107–24.

Vymazal, Jan. “Removal of Enteric Bacteria in Constructed Treatment Wetlands with Emergent Macrophytes: A Review.” Journal of Environmental Science and Health. Part A, Toxic/Hazardous Substances & Environmental Engineering 40, no. 6–7 (2005): 1355–67.

Wu, Shubiao, Pedro N. Carvalho, Jochen A. Müller, Valsa Remony Manoj, and Renjie Dong. “Sanitation in Constructed Wetlands: A Review on the Removal of Human Pathogens and Fecal Indicators.” The Science of the Total Environment 541 (January 15, 2016): 8–22.

Other photo credits from our Tweets:

  1. Universal Children’s Day
  2. Water use art

What is parasite ecology?

Since you’re reading a blog called Parasite Ecology, you probably already know what a “parasite ecologist” studies. If you do, you’re a member of a global minority – congratulations! Your membership ID card will be arriving in the mail any day now.

If I had a nickel for every time someone asked me what “parasite ecologists” study, or came to the blog after Googling “what is parasite ecology?”, I could buy another pumpkin latte today. In some ways, it’s weird that I’m asked this so often, because I don’t go around introducing myself as a parasite ecologist. (I think my job prospects are better if I sell myself more broadly to other scientists, and I think my communication with non-scientists is more effective if I say that I study “infectious diseases in wildlife and sometimes people, like rabies.”) But because I have a Parasite Ecology blog – maybe even The Parasite Ecology Blog? – I suppose I am The Chosen Answerer of This Question. So, here it is:

Parasite ecologists study the ecology of parasites: the interactions between parasites (or pathogens), hosts, and their (abiotic and biotic) environments.

If you’re looking for something more specific, I also made you this word cloud to illustrate the terms that parasite ecologists used the most in 2017 publications.* Like other types of ecologists, parasite ecologists want to understand the distribution and abundance of individual species, as well as the processes that affect species diversity. To do that, we study individuals, populations, and communities. Sometimes we study the effects of parasites on ecosystems and/or the effects of ecosystems on parasites, but ecosystem-level studies aren’t as common in this subfield, as is corroborated by the fact that ecosystems didn’t make it into the word cloud.


So there you have it! But perhaps you’re thinking, “Wait, that sounds like disease ecology. What’s the difference?” The answer is that parasite ecology = disease ecology. But I think that parasite ecology is a better term, because not all infected hosts are diseased.

If you want to complicate matters further, have you seen my old post about the difference between disease ecology and parasitology? 😛

*To make the word cloud, I performed an ISI Web of Knowledge search for all papers published in 2017 that contained the terms parasit* AND ecology. I performed the search on 28 October 2017, and it picked up several papers from November journal issues. I used the titles and abstracts from all 410 papers to create the word cloud. (I didn’t filter the papers at all, so there are probably a few papers in the dataset that aren’t highly relevant.) If you would like to make your own word cloud, you can access the data and the R code on my GitHub.

Parasite Ecology Tricks and Treats

Happy Halloween!

Reading excellent parasite ecology papers is always a treat. So to celebrate Halloween, I have some recent gems for you here. But there are also some tricks mixed in, so proceed with caution…if you dare. 

Paper 1

Paper 2

Paper 3

Paper 4

Paper 5

Paper 6

Paper 7

Paper 8

Paper 9

Paper 10

Paper 11

Paper 12

And here’s a gratuitous cartoon of a clown isopod, because I needed a reason to procrastinate coding.