This coming Wednesday, April 11, I'll be speaking at Nerd Nite about so-called "tropical" diseases in the United States. Nerd Nite basically is a forum for individuals to share their nerdy interests with the rest of the community in a laid back setting. It started nine years ago in Boston and eventually spread around the world. Now there are Nerd Nites all over the globe!

I'm excited to have a platform where I can share disease ecology and my own research with non-scientists. I think diseases are fascinating (obviously), and I figure if others were exposed to them in a fun non-infectious intellectual way...they might think so too! A lot of people are just really turned off (or perhaps scared is a better word) by biology. The study of diseases, especially local ones, is a good way to pique interest because it gives them a reason to care, it might actually affect their health one day. Of course, I don't want to be an alarmist scientist in any way. 

I have to thank Dan Warren, another writer on the blog,  for the name of this talk: "Hot, Wet, and Infectious: Tropical Diseases in the United States."  The theme  for this month is Hidden Structures. The organizers must have thought that there are patterns in disease occurrence, which there clearly are! The other speakers will be discussing Austin traffic and the origin and creation of words. For more information about this week's Nerd Nite check out the website: http://austin.nerdnite.com/

I hope to see you there!

Author
Stavana Strutz is a doctoral candidate in the Parmesan Lab who studies disease ecology and evolution.

Tuberculosis isn't a disease you often hear about in the United States, however, if you live in Texas you might be familiar with it. Texas is one of four states (California, Florida, New York) that accounts for half of all TB cases diagnosed in the US.  Recently north Texas experienced a string of 5 outbreaks in high schools and colleges. The latest campus is Tarrant County College, which is only about 6 miles away from the house I grew up in and where I took calculus during my first summer off from UT as an undergrad.   The Centers for Disease Control reports that cases in the US are at the lowest they've ever been since TB was first nationally tracked in 1953 although some areas like Bexar county continue to see TB cases on the rise.

According to the World Health Organization:
"World TB Day raises awareness about the global epidemic of tuberculosis (TB) and efforts to eliminate the disease. One-third of the world's population is currently infected with TB. The Stop TB Partnership, a network of organizations and countries fighting TB, organizes the Day to highlight the scope of the disease and how to prevent and cure it.

The annual event on 24 March marks the day in 1882 when Dr Robert Koch detected the cause of tuberculosis, the TB bacillus. This was a first step towards diagnosing and curing tuberculosis. WHO is working to cut TB prevalence rates and deaths by half by 2015."

For more information on TB, check out the CDC page:  http://www.cdc.gov/tb/default.htm 

Author
Stavana Strutz is a doctoral candidate in the Parmesan lab at the University of Texas at Austin studying disease ecology and evolution.

I'm posting a more optimistic post this week, rejoicing in the fact that malaria has still not returned to the United States!  Malaria used to be endemic throughout portions of what is now the US in the 19th and first half of the 20th century. Occasionally,  mysterious infections are contracted here but are extremely rare. The CDC MMWR Surveillance Summary for 2010 just came out and only 2 out of 1,691 cases were "cryptic" in origin within the United States. Autochthonous cases still pop up, at least 76 cases from 1957-1994, so it isn't necessarily gone but has yet to reestablish itself.

Malaria is thought to have entered North America via European colonists and African slaves in the 16th and 17th centuries. From 1946 to 1951 the Centers for Disease Control sprayed DDT and eliminated the parasite. Since then, cases of locally acquired malaria have been documented in legal immigrants, the homeless [in Houston, Texas], and migrant workers from endemic areas living in substandard housing. Anopheline mosquitoes, the primary vectors, prefer to feed in the evening and night when the host is most likely sleeping and not slapping them. Good housing in the US is thought to greatly decrease all sorts of vector-borne diseases that otherwise would be much more rampant.

And no Parasaturdays post would be complete without a little background on the biology of the organism:

Monsters Inside Me was an Animal Planet series that ran from 2009-2010. It's a little dramatic but there are some cool computer generated animations of parasite life cycles. More videos can be found on the Animal Planet website if you feel like being very disturbed:  
http://animal.discovery.com/videos/monsters-inside-me/
More information on malaria can be found at the CDC website:  http://www.cdc.gov/malaria/about/history/ 

Zucker, J. (1996). Changing patterns of autochthonous malaria transmission in the United States: a review of recent outbreaks. Emerg Infect Dis, 2, 37–43.

Author
Stavana Strutz is a doctoral candidate in the Parmesan lab studying disease ecology and evolution.

Can I use tap water in my neti pot?

That was the interesting question I received yesterday at a birthday BBQ. Apparently and unbeknownst to me two different American individuals died after irrigating their sinuses due to the brain crawling and eating amoeba, Naegleria fowleri.  One case was reported in a 51 year old De Soto woman in northern Louisiana near the eastern Texas border and the other in a 20 year old St. Bernard man on the coast. Multiple agencies from the CDC to state health departments are issuing warnings to neti pot users to only use distilled, sterilized, or previously boiled water (1-3 minutes depending on altitude). Cases arising in Southern Australia from tap water nasal aspirations  and Arizona from tap water filled play pools have also been reported in the recent past.

Generally, N. fowleri is a free-living, freshwater, bacteria consuming amoeboid that transforms into cysts when it gets too hot or dry. However, it also feasts on central nervous tissue if given the chance, unlike 29 other Naegleria species. People tend to get infected when swimming in freshwater bodies of water when water gets inhaled into the nose. The mobile double flagellated stage can be induced to form if the trophozoite stage is washed with dilute salt solution or placed in distilled water. I suspect that this is the evolutionary escape stage triggered by inhospitable environmental conditions. I also wonder how this phenomenon would play out with neti pot use since the nasal wash is generally a mild saline. Does transformation into a more mobile stage make it more likely to migrate further into your sinuses? Or is the trophozoite stage simply being phagocytosed by structural cells lining the nasal epithelium called sustentacular cells as suggested by Visvesvara thus allowing the amoeba to travel even further inside your head? A further complication is that the amoeba has been found living in the throats and noses of healthy individuals. What makes it pathogenic? 

N. fowleri infection becomes a threat when temperatures increase and water levels decrease. Right now, we are still in the middle of a drought…and this summer will be prime time for increased brain eating amoeba caused meningitis. Normally, individuals come down with the disease after swimming in poorly chlorinated pools and freshwater bodies of water. The cyst stage can survive temperatures of 51-65°C or 123-149°F while the amoeboid stages can tolerate 10-50°C. Additionally, amoeba cultured at 30°C and 37°C were more pathogenic than those grown at 23°C and 44°C [in mice]. And just in case you didn’t know, 37°C equals 98.6°F. It makes sense from an ecological viewpoint that an organism grown and adapted to temperatures similar to mammalian host temperatures will be more pathogenic. When the water is the same temperature as your body, beware.

Yesterday at the party I didn’t know what to tell my friend, I assumed that effective water sterilization took place at water treatment plants and the chlorine concentration used was enough to kill the cyst, flagellated, and trophozoite life stages. In fact according to Jonckheere’s 1975 paper, “viable Naegleria cysts are not to be found in clean water where low concentrations of chlorine are constantly maintained.” Visvesvara also reports that chlorine levels at 1 ppm are enough to kill the amoeba. It seems that either the water treatment plants aren’t doing their job or the water is getting contaminated after leaving the plant. The Louisiana State Department of Health has already attributed these deaths to “improper use of neti pots” as opposed to the failure of local water treatment plants to insure safe water. They have also stated that tap water is safe for drinking but not for nose irrigation. I didn’t know that the only safe use of tap water was for drinking, I would have thought it safe for other hygienic purposes as well. This more or less seems like a legal move to me, a way to shift the blame away from themselves and to neti pot users.

Until this question yesterday, I never would have second guessed using tap water for nose irrigation. Should we also not rinse contact lenses or eyes when they come in contact with chemicals with tap water for fear of Acanthamoeba spp. infecting our corneas? I would be concerned if my water treatment plants were unable to kill N. fowleri, what other pathogens are slipping by and into the water supply?

But back to the question at hand? Should my friend use tap water in her neti pot? I would say definitely yes if it has been boiled or passed through a filter with an absolute pore size of 1 micron or smaller (not nominal pore size). I would also say yes if the weather has been cool and wet. However, I can’t say yes if both a drought and high temperatures are co-occurring. So the safest course of action is to follow the CDC guidelines (http://www.cdc.gov/parasites/naegleria/faqs.html). And hey, it might be worth it to buy a fancy water filter, you’ll not only be protecting yourself from amoeboid meningoencephalitis but also Giardia, Cryptosporidium, lead, and many other contaminants. 

John, D.T. (1982). Primary Amebic Meningoencephalitis and the Biology of Naegleria Fowleri. Annual Review of Microbiology, 36, 101–123.

De Jonckheere, J. & van de Voorde, H. (1976). Differences in destruction of cysts of pathogenic and nonpathogenic Naegleria and Acanthamoeba by  chlorine. Applied and Environmental Microbiology, 31, 294–297.

Visvesvara, G.S., Moura, H. & Schuster, F.L. (2007). Pathogenic and opportunistic free-living amoebae: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea. FEMS Immunology & Medical Microbiology, 50, 1–26.

Author
Stavana Strutz is a doctoral candidate studying disease ecology and evolution  in the Parmesan lab at the University of Texas at Austin. 

Let’s talk about dengue fever! No, not the band fronted by Cambodian transplant Chhom Nimol started in LA but the fever causing RNA flavivirus that likes to invade your white blood cells! 

This virus belongs to the same family of viruses as those that cause West Nile and yellow fever (there is also a band named Yellow Fever). Unfortunately, there is no vaccine for dengue like there is for yellow fever. When I traveled to Brazil in 2007 I received the yellow fever vaccine. 

So why am I discussing dengue fever today? I recently stumbled across Google dengue trends: http://www.google.org/denguetrends/  

I couldn't help but notice the close proximity of dengue cases in northern Mexico to southern Texas. This is a whole new means of disease surveillance being termed "webidemiology." While the Google trends do not represent medically diagnosed cases, they do fit medical data well, at least in the case of Flu. 

This reminded me that, yes, we have dengue in the United States which may be surprising to most people. Dengue has been found in Texas since 1980 and recently emerged again in Florida in 2011. Public health experts in Florida are already wondering when it will show up again this year, many think dengue will rear its ugly flaviviral head in March. Dengue has been found in 5 southern Texas counties which isn’t surprising since northern Mexico does seem to be somewhat endemic for the pathogen. 

For a long time I was under the impression that tropical diseases didn't happen in the USA, either because we were too far north and/or too "clean" and too developed. But tropical diseases have showed up in what is presently the United States for quite some time. Yellow fever actually made a large proportion of Philadelphia sick in a raging epidemic back in 1793, then our nation’s capital, while West Nile has spread across the country ever since its introduction in New York in 1999. I think there are tons of interesting and more-or-less unknown parasites here that may or may not be on the rise.

But I digress, back to dengue! It is a vector-borne virus spread by mosquitoes, primarily vectored by Aedes aegypti, the yellow fever mosquito. Notice the lyre shape on its thorax and white banded joints. It will fly inside to bite you and is sneakier than the next mosquito I'm going to tell you about, Aedes albopictus, the extremely invasive Asian tiger mosquito.  

A. albopictus was introduced to the United States via tires at a port in Houston in 1985 and will swarm you to get some blood. They also prefer to feed with their hind legs raised, which always reminds me of the elitist pinky finger raising affectation that occurs while drinking tea. There is a solid white stripe running down their thoraxes as opposed to the whimsical lyre on the thoraxes of A. aegypti.

Basically, if a black and white striped mosquito lands on you, you should kill it as quickly as possible! Also, now that we are finally receiving rain, make sure to empty out containers holding standing water. This not only decreases your already nearly zero risk of catching dengue [in the US] but also lowers your risk of contracting the recently introduced West Nile Virus and any other strange pathogens spread by mosquitoes. Remember that mosquitoes are more or less syringes with wings.  

And on a final note, it's pronounced "den-ghee" not "den-gay" or the lazy "dheng."

Author
Stavana Strutz is a doctoral candidate in the Parmesan lab at the University of Texas studying disease ecology and evolution.

Is this why scientists are constantly "socializing"?  

The following articles details how fruit flies besieged with parasite wasp eggs will selectively seek out alcoholic food. Alcohol consumption greatly decreases wasp larvae survival by causing their guts to shoot out of their anuses, this was nicely phrased by Carl Zimmer over at the NY Times.

http://www.nytimes.com/2012/02/21/science/tipsy-fruit-flies-on-a-mission-to-kill-parasites.html

I again apologize for the abrupt nature of this post. I, myself, am besieged with grading immunology exams. Next week I promise to write something meaty about parasites and distributions!

Author
Stavana Strutz is a doctoral candidate in the Parmesan lab studying disease ecology and evolution.

I've got a nasty cold which is why this post is a day late. I was going to write a comprehensive post about Heterobilharzia americana, aka canine schistosomiasis in America but instead I'm going to post this awesome story from The Atlantic about Toxoplasmosis gondii.
http://www.theatlantic.com/magazine/archive/2012/03/how-your-cat-is-making-you-crazy/8873/2/?single_page=true

So while I was familiar with Toxo's links to schizophrenia and "feline fatal attraction," I was unaware of this strange effect:
"The neurobiologist Ajai Vyas, after working with Sapolsky on this study as a postdoctoral student, decided to inspect infected rats’ testicles for signs of cysts. Sure enough, he found them there—as well as in the animals’ semen. And when the rat copulates, Vyas discovered, the protozoan moves into the female’s womb, typically infecting 60 percent of her pups, before traveling on up to her own brain—creating still more vehicles for ferrying the parasite back into the belly of a cat. "

Happy reading!

Author
Stavana Strutz is a doctoral candidate in the Parmesan Lab at the University of Texas studying disease ecology. 

I love bats and considered studying bat parasites back when I was trying to make up my mind about what to focus on for my dissertation. They are amazing spreaders of mammal pathogens and parasites, things like Nipah, Hendra, rabies, SARS and potentially Ebola. Our own human parasite, the bedbug, Cimex lectularius, is thought to have evolved from bat bugs!

But bats are not all bad from an anthropocentric viewpoint, they also provide important ecological services like pollination and pest control. Plus, I love watching them fly around the steeples in Austin at night and I hear they also fly out from under the Congress bridge, photo from Talke Photography. I'm a bad Austinite, I haven't actually been to see them yet!

Our furry flying friends are in danger! A highly fatal disease known as White Nose Syndrome or WNS is killing them off in droves.  WNS was first discovered in hibernacula in New York state in February 2006. Since that initial finding it has spread more than 2,000 kilometers into western Oklahoma.  A Nature paper published in December 2011 demonstrates that the fungus, Geomyces destructans, causes WNS: http://www.nature.com/nature/journal/v480/n7377/full/nature10590.html

WNS disrupts the hibernation schedule of bats and causes "abnormal arousals." Infected bats will fly at daytime in winter when they should be hibernating and also tend to cluster near the colder front portion of their caves. Many of the bats found with the parasite are emaciated [from using up their winter fat] and have fungal lesions on their muzzles and wings. I, of course, wonder if there is some way that this behavior might be beneficial for parasite dispersal. I don't want to make an adaptationist assumption, the behavioral changes could also just be a terrible side-effect with no fitness benefit for the pathogen. However, the parasite does prefer cold temperatures.

Thus far WNS has killed somewhere around 6.5 million bats and 80-97% of the bats in some caves and mines the northeast. I could ramble on and on about the damning statistics but instead I will present a link for you from USGS about the fungus: http://www.fort.usgs.gov/wns/ and a very well written article found here:  http://www.examiner.com/biology-in-hartford/geomycosis-the-cause-of-white-nose-syndrome-bats 

The big question on my mind is will it spread to Texas and what can we do about it?
The parasite seems to favor hibernating Myotis species as opposed to our migrating Mexican Free-tails, Tadarida brasiliensis. However, Texas is home to 32 species of bats and is located at a central overlapping position of migrating and hibernating species. One concern is that species not prone to infection will still transport the pathogen to susceptible and naive hosts far beyond northeastern North America. My hope is that because it is hot here and our winters are mild we will be spared the bat plague due G. destructans preference for cold temperatures. However, portions of the Panhandle might be at higher risk climatologically because of the colder temperatures experienced there. Colorado is apparently on high alert and has already taken precautionary measures such as closing public caves the year after WNS was found in Oklahoma. Luckily it hasn't spread further than OK since 2010.

So what can we do to minimize risk of spreading the pathogen? First, if you are a spelunker, wash your clothing and gear when caving in different caves. There is some evidence that humans have introduced the pathogen to virgin caves. Also, if you've seen it, report it to USGS National Wildlife Health Center and follow these guidelines: http://www.nwhc.usgs.gov/disease_information/white-nose_syndrome/USGS_NWHC_Bat_WNS_submission_protocol.pdf 

After conducting a Google Scholar search for "Geomyces destructans"/"white nose syndrome" and "ecological niche model"/"species distribution model" I found no hits. Perhaps some SDMs on the parasite's potential distribution are needed? Also, perhaps climate change will actually help our bat species out in Texas!

Author
Stavana Strutz is a doctoral candidate in the Parmesan Lab at the University of Texas studying disease ecology.
 

This is a combination Fish Friday and Parasaturday post. Basically, I was looking up recent news of parasites and this little gem popped up in the San Marcos Mercury:
http://smmercury.com/53183/invasive-snail-parasite-threaten-central-texas-fish-stocks/ 

An invasive snail species, Melanoides tuberculatus, from Asia is invading central Texas waterways. The species was originally adapted to warmer temperature water (above 64 degrees Fahrenheit) which had constrained its ability to spread from warm springs at the head of the Comal River to other cooler surface waters. Alas, as evolution would have it, or fortunately from the snail's point of view, the snail began to adapt to its new climate.

"In 2009, Huffman began finding snails thriving in the much colder waters of the Guadalupe River, and by 2011 they’d moved upstream as far as Gruene Crossing and downstream through Lake Dunlap and as far as one mile into Lake McQueeny. In January 2012, Huffman found hundreds of snails seemingly thriving near Dunlap Dam in water that had been between 11-13°C (51-55°F) for weeks—temperatures that should’ve killed the snails within two or three days."

I find this next part the most interesting though:
 "Because of the continuous, wild temperature swings at the confluence of the Comal and Guadalupe rivers in New Braunfels, Huffman predicted as far back as 2000 that if the snail were to ever make an evolutionary adaptation to colder temperatures, that’s where it would happen—and that prediction now seems to have been borne out." 

I also wonder how much the mild winter, hotter temperatures and drought has contributed to the invasive expansion of this snail. Shallower streams caused by drought would most likely be warmer as well, right? Huffman goes on to say that there aren't as many mature fish appearing in the Comal anymore, he attributes this to the trematode parasite carried by the snail which he doesn't name but I'm assuming is Centrocestus formosanus based on another paper he published, "Egg predation and parasite prevalence in the invasive freshwater snail, Melanoides tuberculata (Müller, 1774) in a west Texas spring system":
http://www.aquaticinvasions.net/2011/ACCEPTED/AI_2011_accepted_Ladd_Rogowski_correctedproof.pdf

The parasite actually damages the host's fitness in the following way:"Because the flatworm encysts on the gills of fish, it interferes with the fish’s ability to oxygenate the blood. With enough parasites, the effect would be like a person trying to run a race during an asthma attack. For fish, such infections would make them slow and sluggish, easy picking for predators long before the parasites killed them outright." 

The parasite has been found in west Texas springs but I don't see any evidence that is in central Texas from this paper or news article. Readers, is this parasite in our region? 

Does anyone want to build an SDM for this invasive species and its parasite, wink, wink, nudge, nudge? It could be fun!

Author

Stavana Strutz is a doctoral candidate studying disease ecology in the Parmesan lab at UT Austin.

Luckily, these biologically iced sugar cookies were not cookies of death. I baked these for my preliminary examinations in the Ecology, Evolution, and Behavior PhD program at the University of Texas. Of course, had I not passed...they might have been. I kid, I kid!

Like all cookies, these cookies underwent a baking metamorphosis. These cookies were once a much more delicious product: dough. Eating raw dough is my favorite part of cookie consumption! However, raw dough also poses one of the greatest risks to one's health when it comes to the entire process of cookie production/gourmandization besides exploded stomachs. Raw dough has raw eggs and these raw eggs sometimes have parasites that can kill you.

I'm a bit of a germaphobe but I like to tell myself that probabilistically there isn't that great of a chance of me contracting a horrible disease from dough because a) there is a low prevalence of germy eggs and b) my immune system could eradicate the pathogens. This post aims to investigate the first of these two justifications.

If you’re like me, you’ve no doubt been warned to not eat raw dough but then ignored the advice. There are several different salmonella species and they infect various animals such as cattle, chickens, amphibians and occasionally people. The species, subspecies and serotype we are interested in is Salmonella enterica enterica enteritidis or S. enteritidis (a discussion of the complication and controversies surrounding taxonomic classification of pathogens will undoubtedly ensue at a later date).  Before the 1970s most cases came from feces on the egg shell surface but now egg shells are sanitized. In the 1980s a new strain appeared that actually infects the ovaries of the hens and is passed down vertically within the egg itself. This is the strain we are worried about.

Most of the publications I found on the topic of S. enteritidis prevalence were from the 1990s. In the northeastern region of the United States, 45% of hen houses were contaminated with S. enteritidis while central and southeastern regions were lower, 17% and 3% contamination respectively.  This information made me feel a little better about my raw egg eating ways since the south has a lower prevalence rate but I was still concerned. The sampling was done on the ceca and not the ovaries. Would this detection method be sensitive enough to detect infection inside the eggs? I also found out that salmonella of some type was detected in 80% of egg-laying houses.  So then of course, I wondered if competitive exclusion took place between the different salmonella species and if infection with “good” salmonella prevented infection with “bad” types. (Ebel et al. 1992)

Hogue et al. also found the northern region of the US to have the highest prevalence of S. enteritidis in unpasteurized egg product and slaughtered hens, 40%. Other regions ranged between 10-12% (Hogue et al. 1997).  Another paper, however, only detected S. enteritidis in 1 out of 42 flocks from the southeast and Pennsylvania when sampling directly from ovaries, a 2.4% prevalence rate (Barnhart et al. 1991).  Aha, I thought, here is my vindication finally!   

And because this is a blog post and not a research paper, I’m going to wrap up the post now. Basically, it seems like if you live in the northern region of the United States, don’t eat raw eggs.  Nearly half the flocks/hen houses are contaminated with pathogenic salmonella. Other areas face a risk but depending on the sampling method, the prevalence will vary.  The real question is what prevalence rate are YOU willing to risk eating cookie dough for? Is 17% too high? Is 2.4% too high? And remember, these studies are dated, what is the actual prevalence now? I would also say that if you are immunocompromised or a young child you should definitely not eat raw dough. I don’t have an answer yet as to whether this information will change my behavior, most likely it will not. Maybe if I move to the east coast it will.

So as the holiday season reaches its apex, remember that not only must you beware of cookie dough but also beware of homemade egg nog, sunny side up eggs, bean sprouts, and frogs. Nothing says Christmas like a holiday tree frog. And apparently, even if your eggs are pasteurized and you buy dough from the store, you may still get sick…from E. coli contaminated flour! (http://well.blogs.nytimes.com/2011/12/12/beware-of-raw-cookie-dough/) 

Here is a great link from the CDC on how to reduce your exposure to salmonella: http://www.cdc.gov/Features/VitalSigns/FoodSafety/ 

Barnhart, H.M., Dreesen, D.W., Bastien, R. & Pancorbo, O.C. (1991). Prevalence of Salmonella enteritidis and other serovars in ovaries of layer hens at time of slaughter. Journal of food protection, 54, 488-491.

Ebel, E.D., David, M.J. & Mason, J. (1992). Occurrence of Salmonella enteritidis in the U.S. Commercial Egg Industry: Report on a National Spent Hen Survey. Avian Diseases, 36, 646-654.

Hogue, A.T., Ebel, E.D., Thomas, L.A., Schlosser, W., Bufano, N. & Ferris, K. (1997). Surveys of Salmonella enteritidis in unpasteurized liquid egg and spent hens at slaughter. Journal of food protection, 60, 1194-1200.
   

Author

Stavana Strutz is a doctoral candidate studying disease ecology in the Parmesan lab at UT Austin.