Who Ate the Dinosaurs? Part II: More on Arthropods

       At the recommendation of a well-known parasitologist, I began reading about the parasites that plagued everyone’s favorite prehistoric animals: the dinosaurs. I found lots of information on various forms of dino-parasites…everything from protists, to helminths, to insects. Today, let’s continue talking about things living on the outside of our beloved reptiles and make a transition into their upper respiratory tracts for a look at some nifty little arthropods. Then we will discuss some of the possible parasite vectors and their roles in the extinction of dinosaur populations.

Dino-Mites

A piece of Canadian Cretaceous amber with a
preserved feather and associated mite.

            It appears that mites were some of the first animals to walk on land some 400 million years ago. They would later give rise to the group of animals we now call ticks, but that wouldn’t come along until much later. In 1998, eggs from a type of feather mite were found on feathers belonging to a Cretaceous (120 million years ago) dinosaur from modern-day northeast Brazil. Later researchers claimed these eggs to be more similar to mites in the family Cheyletoidea (these guys cause a form of dermatitis known as “walking dandruff” in modern mammals and birds).

T-Rex Ticks?

            Ticks were once thought to have originated about 42 million years ago on the modern continent of South America. However, a recent discovery of a tick stuck in amber from New Jersey pushes tick origins back to about 90 million years ago. This fossilized larval tick was named Carios jerseyi and was a type of soft tick. Unlike most soft ticks, this species had dozens of tiny hairs aligned in two rows along its back. Because this is the only known specimen from this time period so far, its gut contents can not be examined for the blood of dinosaurs. However, because it lived at the same time, and because we know that ticks today feed on everything from birds, to mammals, to lizards and snakes, we can assume that this species probably did feed on dinosaurs. 

Carios jerseyi

Tongue Worms in Dino-Lungs?

           Pentastomids are a group of crustaceans that date back to 500 million years ago! These little guys live in the respiratory tracts of terrestrial vertebrates. Close to 85% of modern pentastomids are found in the lungs of reptiles. Being present so early in the fossil record indicates that these animals have had associations with vertebrates for a very long time. Given what we know about these arthropods, it wouldn’t be too much of a stretch to assume that they may have been present in dinosaurs. From what little bit I’ve read, it seems that many scientists are convinced that dinosaurs played host to tongue worms….however, I have not found any studies confirming this. The problem is that soft-bodied invertebrates, as well as dinosaur lung-tissue, does not preserve well over millions of years. Will we ever know if these guys parasitized dinosaurs for sure? Maybe…we are learning more and more as technology progresses…but for now, suffice it to say that they were probably a common dino-parasite.

A modern-day pentastomid
(Armillifer agkistrodontis)
from a snake.

Insects
            Insect populations exploded during the time of the dinosaurs. We are talking, like dragonflies with two-foot wing spans exploded. This was because the environment was right for them, the world being covered in warm-temperate, subtropical, and tropical biomes. Naturally, many of those species were blood-feeders, such as everyone’s least favorite little blood-sucker, the mosquito.  In addition, there existed many other species of biting flies, and the lice and fleas I mentioned in a previous post. With the arrival of blood-feeding insects, it was only natural that these animals would become choice candidates as vectors for disease transmission.

            Many forms of diseases we know about today are blood-borne. For the sake of brevity, which is as we all know the soul of wit, I will say that the insects that lived with, and probably feed upon, the dinosaurs were probably carrying various infectious agents. These could have been viral, bacterial, or parasitological (as in protists or intestinal worms, perhaps). There have been instances of finding sand flies preserved in amber, which we know to be the vectors of Leishmania today. Dr. Poinar, author of “What Bugged the Dinosaurs?”, has spent much of his time looking at specimens from amber such as the one mentioned above. He was quoted as saying this in an interview I found online: 

“Our research with amber shows that there were evolving, disease-carrying vectors in the Cretaceous, and that at least some of the pathogens they carried infected reptiles.”

            He went on to discuss how big of a role insects played in the gradual downfall and eventual extinction of our archosaurian predecessors as best I could understand from reviews about the book. Needless to say, this one is definitely makings my “must-read-someday” list. Apparently he also co-authored another book called "The Quest for Life in Amber", which may have also made said list.

 Moral of the Story

            When a conversation turns to dinosaurs, we don’t often think about how arthropods may have annoyed them as much as they sometimes annoy us. It is pretty amazing to think of all that we have learned about dino-parasites, but even more amazing is that which we have yet to learn or what information has been lost to evolutionary history. So at the next party you attend, you should casually mention how far back into the fossil record you have to reach to find the presumed origins of arthropods like mites and pentastomes.  Maybe you will start up a vibrant conversation with someone worth talking to. If so, you should most certainly ask them to join you for a cup of coffee sometime and the two of you can contemplate the role of parasitism in the extinction of the dinosaurs. You could make a new friend just because you read my blog. You are welcome. ;)

Who Ate the Dinosaurs? Part I: Ectoparasites

An artist's rendition of a Jurassic flea.

        At the recommendation of a well-known parasitologist, I began reading about the parasites that plagued everyone’s favorite prehistoric animals: the dinosaurs. I found lots of information on various forms of dino-parasites…everything from protists, to helminths, to insects. I’ve decided to break up this topic into a series of posts over the next few weeks. Today, let’s talk about things living on the outside of our beloved reptiles. In doing so, we will also mention a little about how these creatures probably feasted on the blood of ancient birds and mammals as well. You will also have the pleasure of reading a bit about ectoparasite evolution, and how studying these little guys helps us to paint a more accurate picture of life over a 100 million years ago.

Dino-Lice

            Lice are thought to have evolved over 65 million years ago according to a new study using modern lice DNA. That time frame places their ancestors in the same place as dinosaurs. One study is even showing that lice began diversifying on mammals and birds before the dinosaurs went extinct! (Which means that mammals and birds may have been diversifying at this time as well?!) How interesting is it that these little guys could be proxy indicators of bird and mammal radiations preceding what has been conventionally accepted as post-dinosaurian diversification of these types of creatures!!?!?!!  Here’s an awesome quote from Dr. Vincent Smith, a researcher who has been working on dino-lice at the Natural History Museum in London:

Fossilized lice remains from 44 million years ago (left) next to
a modern-day louse from an aquatic bird (right).

“Lice are like living fossils. The record of our past is written in these parasites, and by reconstructing their evolutionary history we can use lice as markers to investigate the evolutionary history of their hosts. …  It was thought that after the dinosaurs went extinct that's when these birds or mammals diversified into these different niches, but based on the evidence from lice, the radiation of birds and mammals was already under way before the dinosaurs went extinct.”

            

           Pretty cool huh? Some researchers believe that louse-lineages may even go back as far at 115-130 million years ago! It’s thought that these ancient lice may have fed on feathered dinosaurs such as China’s Sinornithosaurus. The most recent numbers I could find in the literature regarding lice stated that the first instances of parasitic lice occurred between 100 million and 125 million years ago. The same study suggested that these little guys didn’t become parasites until animals began to develop fur or feathers. It seems that modern birds may have gotten their modern louse-burdens from feathered versions of their dino-brethren. 

Dino-Fleas

Fossilized flea from the Jurassic period.

            Okay, so maybe some dinosaurs had lice…but what about another exciting group of ectoparasites…fleas? There are fossils of fleas that date back to the Jurassic, some 100 million years ago. They were anywhere from twice to ten times the size of modern fleas and lack the jumping potential that our familiar forms possess. They also donned elongated sucking mouthparts that were serrated…presumably for piercing hides that were much thicker than the hosts’ hides that contemporary fleas must penetrate. They were dorso-ventrally flattened rather than laterally compressed. (For those who aren’t biologists, this means that the bodies are flattened from front to back rather than from the sides. Fish, for example, are laterally compressed.) They also had spiny bodies and claws that helped them to cling to prehistoric feathers and fur. It is most likely that these guys fed on pterosaurs and early rodent-like mammals. 

Jurassic flea fossils from China.
(Note size compared to the human hand.)

A recent examination for fossilized fleas from China found that some fleas existed 165 million years ago! Two species have been named from these Chinese fossils. They were given the names Pseudopulex jurassicus and Pseudopulex magnus based on compression fossils, which provide much more detail of the fossil’s anatomy as opposed to impression fossils. P. jurassicus is smaller in size than P. magnus. It is believed that these fleas fed on feathered dinosaurs, such as Epidexipteryx hui and Pedopenna daohugouenis, during the mid-Jurassic period. I read a few articles that mentioned other types of dinosaur fleas, but I have yet to uncover the scientific names of those fleas.

Moral of the Story

            When a conversation turns to dinosaurs, we don’t often think about how these massive creatures may have played host to ectoparasites in the same way that animals like corgis do today. We think of the astounding size of these animals and about how they ruled the planet so long ago. As interesting as they are, I think it’s even more fascinating to know that they were not exempt from the most efficient form of symbiosis found in any ecosystem. In my head, I can’t help but picture a pissed off velociraptor rubbing up against a tree to sooth the itch of a group of 2cm long fleas feasting on his back. (For the record, that’s purely a figment of my imagination, there’s no evidence to support that fleas actually fed on velociraptors.) Anyway, the next time you are at a party, you should throw around the name Pseudopulex jurrassicus. If this attracts a woman, she’s a keeper. If it doesn’t, then no woman at that party is worth your time anyway! :p

On the Tip of Everyone's Tongue!

It has recently come to my attention that there are lots of new ways to talk about parasites and connect with others interested in parasites. Yay technology! So, as an almost-Halloween treat I have put together some of these sources I've just discovered for you to peruse at your leisure. You can also check out the "Links" tab for more parasitophiliac websites. Anyway, the following is a list of my new favorite parasite-related thing-a-mo-bobs!

1) First and foremost, if you haven't heard this, do it! Now! Okay, maybe not right now, but as soon as you have an hour to kill. This podcast was recommended to me by a friend and I just heard the parasite episode for the first time last night. Can I just say....AWESOME! This actually has an interview with THE Carl Zimmer! (See "Must-Read" tab.) He gave them three parasites as examples for why we should be in awe and have admiration for parasites rather than be disgusted by them. It went on to interview other important parasitophiliacs and gave you a chance to hear about hookworms from a historical perspective as well as from a medical perspective. They ended up talking about using hookworms for therapeutic purposes. If you haven't heard of this, you should check out my last blog post, and of course listen to this amazing podcast. Enough rambling...check it out already!!!

http://www.radiolab.org/popup_player/#

If the popup isn't working, try this link: http://www.radiolab.org/2009/sep/07/

2) While you are getting into podcasts, head over to Dr. Vincent Raciniello's site and check out This Week in Parasitism (TWiP). This virologist from Columbia University also has an awesome podcast known as This Week in Virology (TWiV). I learned about his podcast at a Virology Symposium that I attended for funzies a few weeks ago. I got to sit in on a recording of a TWiV podcast at that symposium and I was delighted to learn that he also had a podcast about parasites! (He also have TWiM for all you microbiology-lovers out there!) This podcast doesn't have all the fun sound effects and flair of radiolab, but it does get into more in-depth issues regarding parasitology. You should definitely check it out! This week he and his co-host Dr. Dickson Despommier interviewed a few post-docs who are working with the dreaded Plasmodium falciparum (a very virulent little protist that causes malaria...the worst strain of malaria, in fact). The great thing about this is that it is an on-going show, not just a single episode as the above link. I've been trying to download these to my iPod to listen to as a ride my bike to school, but I've been having technical difficulties. But enough about me, let's talk about you! And about how you should be listening to this:

http://www.microbeworld.org/index.php?option=com_content&view=category&layout=blog&id=99&Itemid=259

3) Here's a fun talk given by Carl Zimmer that I ran across. :) Enjoy!

http://magazine.storycollider.org/2012/features/interview-carl-zimmer-stories-from-the-parasite-hole/

4) While we are talking about Carl Zimmer....here's another great podcast called "Meet the Scientist". It's not specific to parasites, but I thought it was really cool, so I'm posting it anyway. :)

http://www.microbeworld.org/index.php?option=com_content&view=category&layout=blog&id=37&Itemid=155

Here's an episode about malaria from the same podcast:

http://www.microbeworld.org/index.php?option=com_content&view=article&id=640:mts49-irwin-sherman-the-quest-for-a-malaria-vaccine&catid=37:meet-the-scientist&Itemid=155

5) Even the CDC is jumping on the podcast bandwagon...worthy of a mention here.

http://www.cdc.gov/parasites/podcasts.html

I hope I have helped you all to kill some time learning about these wondrous creatures that we know as parasites! I'd love to hear any comments about parasite podcasting or any other topic related to parasites!

 

Helminthic Therapy

For this week’s post, I decided to cover a subject rather than a particular parasite. This is the subject of Helminthic Therapy.  So what is helminthic therapy you ask? Great question! Let’s delve in and explore this somewhat counter-intuitive idea.  Perhaps in the end you won’t think it’s quite so counter-intuitive after all!

The word “helminth” comes from the Greek word “hélmins”, which is a kind of worm.  For parasitologists, this term refers to any type of parasitic worm, be it a flat worm, roundworm, hairworm, etc.  The study of parasitic worms and how they effect their hosts is called “helminthology”.  Helminthic therapy is a type of treatment that utilizes helminthes or their eggs (a.k.a. “ova”) to heal patients with immune disorders or autoimmune diseases. This is a form of “immunotherapy”, a type of treatment that involves inducing, suppressing, or even enhancing an immune response in order to treat a disease. In this case, parasitic worms or their ova are introduced intentionally into a patient.

So, why would anyone think this was a good idea? 

Research has shown that people in well-developed, industrialized countries are at greater risk for autoimmune diseases and allergies than people living in less developed countries. Over time, epidemiologists (people who study the spread of diseases) have begun to link parasitic infestations to lower instances of autoimmune diseases.  Sure, you might be genetically predisposed to certain types of autoimmune diseases, but the rate of increased numbers of people afflicted with autoimmune diseases is not a result of genetic changes.  If this were the case, the emergence of autoimmune diseases would be able to be traced back much further. Since these diseases have a relatively recent emergence, environmental changes (rather than genetic changes) seem to be far more likely explanations.

Environmental factors that could induce such an emergence may include exposure to different medicines, foods (or food preparations), industrial chemicals, etc.  These factors are great for subduing particular diseases such as those associated with infection by bacteria, viruses, and yes, parasites.  However, because there is a lack of exposure to these diseases, human bodies may be likely to develop the antibodies needed to fight off a major infection by the aforementioned disease-causing agents. Therefore, by not ever being exposed to naturally occurring pathogens/parasites, you may be at a greater risk for developing autoimmune diseases and allergies.

This idea is consistent with what epidemiologists call “the hygiene hypothesis”. This hypothesis states that by not exposing people to infectious agents during childhood, the development of the immune system is naturally suppressed. This leads to increased susceptibility to allergic diseases.  Immunologists (people who study the immune system in all of its mind-boggling complexity) have shown that many types of bacteria and viruses elicit an immune response that is mediated by T_h1 cells. These cells cause a down-regulation of responses by T_h2 cells. If a human is not exposed to pathogens that induce a response mediated by the T_h1 cells, then that human’s body does not have a way of initiating the down-regulation of response by T_h2 cells.  The result is that the T_h2 cells respond excessively. When these cells respond to a harmless antigen inappropriately, you have an allergic reaction. When it comes to more complex issues, such as full-blown autoimmune diseases, it is hypothesized that immune systems that were never exposed to stimuli from infectious agents or parasites do not develop regulatory T cells adequately. Since these regulatory T cells don’t develop properly, they are not sufficient at repressing T_h1 or T_h2 immune responses, and therefore the immune system is more susceptible to autoimmune diseases. This second hypothesis regarding more complex issues is endearingly called the “old friends hypothesis”. The hypothesis is aptly named as such because it relies on the idea that exposure to microorganisms and parasites at low levels of pathogenicity instigate the development of regulatory T cells. It further implies that these organisms have evolved alongside humans throughout our own evolutionary history.

I rarely take quotes directly from sources, but this was much better than the way that I put it. So, for your reading pleasure I present a quote about the hygiene hypothesis from a paper titled “Helminths and Harmony” that was published by Gut in January of 2004 (authored by JV Weinstock, R Summers, and DE Elliott….53(1): 7-9):

“The development of vaccines, hygienic practices, and effective medical care have diminished or eliminated the prevalence and impact of many parasitic organisms, as well as bacterial and viral infections. This has been of obvious benefit with the effective eradication of many diseases that have plagued human beings. However, while many severe diseases have been eradicated, humans' exposure to benign and apparently beneficial parasites has also been reduced commensurately. The central thrust of the theory is, therefore, that correct development of T regulator cells in individuals may depend on exposure to organisms such as lactobacilli, various mycobacteria, and helminths.”

I have to muse at the fact that I’ve also heard the “old friends hypothesis” referred to as the “lost friends theory” or the “depleted biome theory” in various papers. This is just such a novel and interesting way of thinking about human evolution with regard to parasitism! But, I digress…back to helminthic therapy!

Researchers have established a link between parasitic infections and how these infections play a protective role against the development of autoimmune diseases! Geneticists have found that helminths have helped to shape part of the evolution of the human immune system based on a subset of interleukin (IL) genes. The immune system is highly dependent upon these particular genes. In fact, deficiencies in some of the IL genes seem to be the cause for autoimmune diseases. A lack of helminth exposure can be associated with deficiencies in the IL genes associated with Crohn’s disease, celiac disease, and ulcerative colitis. 

What types of diseases might helminthic therapy be useful for treating?

I’ve already mentioned a few here, but just to reiterate and to add in a few others:
-Asthma
-Celiac Disease 
-Crohn’s Disease                             
-Eczema
-Dermatitis        
-Hayfever
-Inflammatory Bowel Disease
-Multiple Sclerosis
-Ulcerative Colitis

Whipworm Ova

-Various Food Allergies 

So what types of helminths are used for this therapy? 

I’m glad you asked! As of now, the only organisms used have been hookworms (Necator americanus) and both pig and human whipworms (Trichuris suis and Trichuris trichiura respectively). From what little I know about the subject, adult hookworms are used while it is the ova of whipworms that are used.

How effective is helminthic therapy?

From some of the papers and forums I have run across researching this topic, I have found that this has a great success rate. Use of Trichuris suis ova have Crohn’s disease and ulcerative colitis remission rates of 55%. Use of Necator americanus has Crohn’s disease remission rates of 85%! Use of Trichuris trichiura has Crohn’s disease and ulcerative colitis remission rates of 85%. Remission rates for a combined use of hookworms and whipworms (while taking vitamin D supplements) are over 90%!!!

How do you introduce the parasites into a patient’s body? 

Vial containing 15 adult hookworms.
Photo from http://coloncomrades.wordpress.com/

Most people are a little creeped out by the idea of parasites living within their bodies. (Though some of us parasitophiliacs may like the thought of contracting a parasite just long enough to remove it and save it as a testament to our strengths as a biologist…) The medical world takes this fear into consideration. Apparently, the whipworm eggs come in a liquid suspension (eggs are in a buffer solution). The patient is to drink half a cup or so of this suspension, which, from forum posts, should taste no different than drinking a glass of water.  Administration of the hookworms is a little more involved. Patients pour a small vial of hookworms in a liquid medium onto a piece of gauze and apply the gauze to the inside of the arm. They secure the gauze with either medical tape or a band-aid for a little bit. The only symptoms associated were some minor itching and little red dots from where the worms burrowed into the patients. The hookworms don’t have to be reapplied for 3-5 years when the parasites will start to die off.

Application of Adult Hookworms
Photo from http://coloncomrades.wordpress.com/

So a treatment regime that can have anywhere from 55%-90% remission rates MUST be expensive, right? 

WRONG! True, some of the companies that sell the pig whipworms charge a pretty penny, but from what I understand, purchasing the hookworms or human whipworms is extremely inexpensive. (And those species have better remission rates anyway!) Some estimates show that you can be treated for less than $3 a day using hookworms!  The lump sum is fairly high, but when you take into account that you only have to dose once every 3-5 years and that most people are relieved of allergies to foods and to allergic reactions such as hay-fever, you are actually saving money in the long run. (No more medications like Zyrtec or Claritin and you can often eat foods you love once more without going into anaphylactic shock! Talk about a bonus!!!) 

Keep in mind that helminthic therapy is NOT FDA approved. From what I understand, you cannot patent a biological organism (though some companies patent the production of media for administration of these parasites). If it did become FDA approved, it would be something that anyone could produce for very little money. On average, it takes about 10 years and millions of dollars to get a drug approved, so most companies wouldn’t be able to recoup their costs from hookworm media production due to how cheaply it can be produced, and theoretically sold. Thus, big pharmaceutical companies don’t have an interest in funding drugs that can’t be patented and won’t have a big return on their investment. While we are on the subject, you should check out this link to a DIY for growing hookworms and whipworms at home. Just keep in mind that this is a “at your own risk” sort of thing. You don’t want to infect anyone too heavily as these ARE parasites we are working with here, and heavy infestations can have some nasty clinical manifestations. As you might have guessed, you are really better off having a doctor monitor your intentional infections.