Tuesday, August 28, 2012

Tapeworms


This week at infection landscapes we enter into the second group of flatworms, and the last group of helminths that we will be considering in this extended series. These are the cestodes or, as they are more commonly known, tapeworms. The tapeworm species that most commonly infect humans are Taenia solium (pork tapeworm), T. saginata (beef tapeworm), Diphyllobothrium latum (fish tapeworm), and Echinococcus granulosus (dog tapeworm). Because only T. solium causes a significant public health burden, this species will be the focus of this discussion.

The Worm. Taenia solium is the pork tapeworm.The Taenia genus is comprised of over 100 species, some of which cause human infection and disease, including T. solium and T. saginata. "Pork" and "beef" tapeworms are actually misnomers, as both T. solium and T. saginata are human tapeworms whose intermediate hosts are pigs and cows, respectively. The adult tapeworm of both species only occurs in the definitive host, which is humans for both helminths.

The Taenia genus is a member of the Taeniidae family, which is a member of the Cestoda class. Cestodes have a unique structure that is quite distinct in many ways from the trematode flatworms. The length of their body is composed of segments, called proglottids. At the anterior portion of the worm is the scolex, which the helminth uses to attach to its host's intestinal epithelium. These helminths do not have a gut tract.

Adult Taenia solium


Notice the individual proglottid segments in the picture above, as well as the scolex at the anterior tip, which appears as a small knob.

Let's consider the life cycle of T. solium. Embryonated eggs pass in gravid terminal proglottids from infected humans. When the gravid proglottids, or the eggs they contain, are ingested by pigs, porcine infection ensues. The pig is the intermediate host for this helminth.The eggs hatch in the small intestine of the pig, releasing oncospheres into the gut. These oncospheres are hooked larvae, which subsequently penetrate the epithelium of the intestine and migrate to various tissues, usually skeletal muscle tissue, by way of the blood circulation. These oncospheres encyst in the muscle tissue and develop into cysticerci (which is the stage infectious to humans), where they can remain viable for several years before calcifying. It is important to note that, while muscle tissue is the most common site for oncospheres to locate and encyst, they can potentially locate in many other tissues including liver and brain.Human infection occurs following consumption of undercooked pork products from pigs infected with cysticerci. Having reached their human definitive host, the encapsulated cysticerci lose their capsules in the stomach and subsequently enter the small intestine. In the small intestine, the juvenile cestode everts its scolex, which attaches to the intestinal epithelium using four suckers and a crown of small hooks known as the rostellum:


The juvenile grows into an adult as developing proglottids extend down the length of the small intestine. As described above these proglottids are the individual segments of the helminth:


Cestodes do not have a digestive tract, so T. solium transport nutrients obtained from the host's meals across the surface of the tegument. As they progress toward the terminal end of the helminth, the proglottids mature. The terminal proglottids are gravid with hundreds of embryonated eggs, which are infectious to the intermediate host (i.e. pig) and, in aberrant infections, they are also infectious to the definitive host (i.e. humans). These gravid proglottids can pass from the human host as single segments or as segment chains. Moreover, they can be expunged passively with feces or they can actively migrate out of the host:



The adult tapeworm will only develop in humans, not pigs. As described, humans are the definitive hosts, for whom normal transmission of infection occurs following consumption of infectious cysticerci in infected pigs. The adult tapeworms then develop in their definitive hosts following the standard life cycle of normal infections. 

However, humans can acquire aberrant infections outside the normal life cycle. While only the intermediate developmental pathway can proceed in the intermediate pig host:. 

eggs → oncospheres  cysticerci 

both the definitive and intermediate developmental pathways can proceed in humans: 

cysticerci  juvenile  adult  eggs

and 

eggs → oncospheres  cysticerci 

Humans acquire intermediate host infection by consuming water or food that has been contaminated by embryonated eggs from another infected human, or by autoinfection from the adult tapeworm already harbored in the definitive host. Ordinarily, the ingested eggs would simply pass out of the gut of the definitive host and not cause infection, as is the case when humans consume the eggs of the beef tapeworm, T. saginata. However, the oncospheres of T. solium can frequently mistake the human gut for the pig gut because of their similarity, and subsequently these larvae penetrate the gut and migrate to peripheral tissues as if the definitive host were the intermediate host. These aberrant infectious are the source of the major clinical disease and public health burden associated with pork tapeworms. The graphic below developed by the Centers for Disease Control and Prevention (CDC) nicely depicts the life cycle of T. solium:



For comparison, another graphic developed by the CDC depicts the life cycle of both T. solium and T. saginata under normal infection cycles: 



The Disease. Most taeniasis is asymptomatic. In normal definitive host infections, in which the adult tapeworm inhabits the small intestine, no symptomatic disease occurs, though there is histologic evidence of minor cellular damage at the site of attachment of the scolex. Taeniasis refers specifically to infection with the adult tapeworm in the gut of the definitive host. As such, taeniasis only occurs in humans. The quantity of nutrients the adult helminth takes from the definitive host is negligible. The same is true for T. saginata (beef tape worm), but not D. latum (fish tapeworm), which can deplete the host of vitamin B12 and eventually lead to megaloblastic anemia over a period of years. So, contrary to popular belief, infection with the adult tapeworm does not make you excessively hungry or cause you to lose weight.

Cysticercosis, on the other hand, is infection with the larval stage tapeworm in peripheral tissues in the intermediate host. Pigs are the normal intermediate hosts and, therefore, the hosts normally affected by cysticercosis. However, as described above, humans can be accidental intermediate hosts if they ingest eggs deposited from another human. Cysticercosis generally presents in muscle tissue, subcutaneously, or in the brain. Subcutaneous and muscle cysticercosis may present with fever and/or pain in nodules under the skin or in muscle tissue, respectively, but these infections are generally mild or asymptomatic. Below is a nice chart that summarizes the transmission cycles and differentiates between taeniasis and cysticercosis (Published in: Sumit Sinha, B.S. Sharma, Neurocysticercosis: A review of current status and management, Journal of Clinical Neuroscience, Volume 16, Issue 7, July 2009, Pages 867-876):



Cysticercosis in the brain is referred to as neurocysticercosis and constitutes the most important clinical manifestation of this infection in humans. Oncospheres can locate and encyst in brain parenchyma, in the subarachnoid space, or in the ventricles. Here is an example of extensive infection with intraparenchymal cysts:



The inflammatory response to intraparenchymal cysts, or later edema surrounding calcified lesions, is the primary mediator of symptoms. The most common clinical presentation of neurocysticercosis is seizure. When cysts grow in the subarachnoid space or the ventricles, cerebral spinal fluid can be blocked leading to hydrocephalus and/or intracranial hypertension, which are associated with greater mortality. Psychiatric disorders and neurologic deficits can also present.   

The Epidemiology and the Landscape. There are an estimated 50 million people infected with neurocysticercosis across the world, with approximately 50,000 deaths each year, though these are both likely to be underestimated, particularly the prevalence. Globally, T. solium, and cysticercosis in particular, is widely distributed across Latin America, South, Southeast, and East Asia, most of sub-Saharan Africa, and some islands of the Pacific, wherever pigs are part of the agricultural landscape and raised for food. The map below produced by the World Health Organization displays the global distribution of cysticercosis risk based on country-specific prevalence:
The landscape of Taenia infections is fundamentally one of animal husbandry. Perhaps more than any other helminth infection, human tapeworms are both culturally and evolutionarily derived from the relationship between humans and their livestock. This is the case for both human tapeworms, T. solium and T. saginata. This unique relationship between definitive and intermediate hosts, wherein the former consumes the latter, is necessary for the helminth to complete its life cycle. Infection derives from two fundamental points of intersection in the landscape: 1) the move to agricultural economies with the domestication of subsistence animals in the course of human evolution, and 2) the contamination of the human environment with human feces due to a lack of sanitation and good water infrastructure.

Control and Prevention. Given that there are multiple modes of transmission of T. solium to humans, there are also multiple potential points to block transmission. Let's discuss these in the context of the two types of human infection, 1) as definitive host, and 2) as accidental intermediate host.

1) As described above, human infection with the adult tapeworm is essential to the tapeworm's life cycle since humans are the sole definitive host. Thorough cooking or freezing of pork products destroys cysticerci and prevents infection with the adult tapeworm in humans.





This intervention, while fairly simple, is the only one which can be implemented on an individual basis at the level of the household. To block other transmission pathways, larger community-wide strategies are required.

2) As described above, humans are also capable of being infected as intermediate hosts when they ingest the eggs of T. solium (or also possibly by autoinfection following infection as the definitive host). Because only humans harbor the adult tapeworm, only humans pass eggs in their feces, which means human feces are the essential source of infectious embryonated eggs. As such, good sanitation and water infrastructure are important in blocking the transmission of the eggs to both humans and pigs, and would thus have wide impact on reducing intermediate host infection in both pigs and humans.

Western-style flush toilet

Squat toilet

Of course, maintaining vigilance in personal hygiene is also critical to stop human to human transmission of aberrant infections at the level of the household. However, while good personal hygiene will block aberrant human infections and thus prevent human cysticercosis, it will not block normal infections with the adult tapeworm, and thus cannot be expected by itself to contribute substantively to reducing the global burden of pork tapeworm infections. 

36 comments:

  1. Hello, Is there any drug available for the tape worm infection? Or we just have to maintain good hygiene to avoid Tape worm infection?
    Another question arise in my mind is that, how much damage does a tapeworm do to the human body? Is it a life threatening infection?

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    1. Hi Russel

      I read a bit about human tapeworm infections and found that there are medical treatments available. The treatments vary from prescribing medication to conducting surgery, depending on the severity and location of the infestation. According to the Mayo Clinic these are some of the popular drugs used to treat tapeworm infections: Praziquantel (Biltricide), Albendazole (Albenza), Nitazoxanide (Alinia). The drugs kill the adult tapeworms but not the eggs so there is always a chance of being reinfected. If an infected person is lucky enough, the tapeworms will find their own way out without being killed or forcibly removed.

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    2. According to the Mayo Clinic, not to mimic Rukshana, the symptoms of a tapeworm infection are dependent upon the kind of tapeworm, its location, and the tapeworm's place in its lifespan development. Many people are asymptomatic, however, others may experience nausea, weakness, loss of appetite, abdominal pain, diarrhea, and potentially, weight loss.
      Essentially a tapeworm can impede normal absorption of nutrients within the intestines, given an infection of high volume.
      If the tapeworm has migrated from the digestive tract, other symptoms can present, such as fever, cysts, allergic reactions, other comorbid infections, and even seizures.
      Interestingly, I have seen an advertisement, from either the 1920's or shortly preceding, extolling the purposeful purchase and ingestion of tapeworms as a weight loss technique.

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    3. For symptoms due to cysticercosis, treatment options are based on the number and location of cysts. Corticosteroids and an antiparasitic drug with or without surgery is a treatment option. If the cyst is in the eye or brain, the use of steroids few days before other medications is advisable to avoid problems caused by swelling during antiparasitic treatment.

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  2. http://www.weightymatters.ca/2010/03/tapeworms-new-diet-craze.html

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    1. @ Flynn. To add on to the point you made about Tapeworms being used for dieting, well in the US the use of Tapeworms for dieting is banned by the FDA, and more specifically the importing and selling of Tapeworms is banned. However, despite this ban and the side effects from ingesting Tapeworms this diet is still quite popular in the US. Simply, by just typing in Tapeworm diets in Google many websites will pop-up about this diet. My guess to why Tapeworm diets are still popular is that people do not associate the risk of death with ingesting Tapeworms, some people figure it is just an easy way to lose weight. I think more public awareness needs to be made about the dangers of recreational use of Tapeworms being that they are responsible for 50,000 deaths worldwide each year.

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    2. That’s incredible! The best thing about the ad was that tapeworms were being marketed as “sanitized” and “easy to swallow” to those who wish to banish fat because I guess those are legitimate concerns to anyone who is thinking about swallowing a parasite. It’s too bad tapeworms don’t cause significant weight-loss and would likely only cause mild malnutrition instead. I’m curious to know how popular it actually was back then.

      This reminds me, I have to go buy some snake oil.

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  3. Perhaps this is the reason why the pig is considered a 'dirty animal' by certain cultures, and eating pork is prohibited (Kosher and Halal diets, for example). Is the pork tapeworm the most common tapeworm infecting humans? Also, that image of the brain covered with cysts is pretty terrifying.

    The best ways to prevent tapeworm infection are already mentioned above (fully cooking pork and water sanitation). I suspect that sanitation for humans is a higher priority than sanitation for livestock, even though the former obviously has not progressed to a satisfactory level. Is there any way to check if pigs are infected before they are butchered or sold? Are there any symptoms in pigs infected with tapeworm?

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    1. Tamara, good point. My parents are Seventh Day Adventists and that's a huge part of the reason why they don't eat pork. Whenever I asked, they would always mention "the worms" in pigs. I was researching tapeworms more online and it does seem like the pork tapeworm is most common.

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    2. Allison GrossmanJuly 7, 2013 at 8:15 PM

      Tamara, I did a little research and couldn't find any way to tell if a pig is infected with tapeworm before it is butchered or sold. The National Health Service website says that in the UK, the meat is treated to remove tapeworms before consumption, but that it's still important to freeze or cook the meat before eating it.

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    3. I cannot imagine eating meat that was not thoroughly cooked. I can appreciate other cultures and different preferences, but being infected with tapeworms is just one of the many adverse outcomes from ingesting food that is not cooked properly. I think people develop habits and neglect to acknowledge the risks because they have had the "good luck" of not getting ill, so they continue to take these risks (whether or not they want to see them as such). As for those who knowingly ingest tapeworms solely for the purpose of losing weight, now that's a whole other realm of lack recklessness..

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  4. To think that tapeworms used to be advertised as a weight loss tool...People were obviously not aware of the dangers associated with said consumption. I wonder how much of the disease is attributed to the meat not being cooked or frozen properly in industrialized areas. It is understandable that this is a little more difficult in some parts of the world that do not have the means the adequately store the prepare their food.

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    1. I find it hard to believe as well but a better understanding of the microbiology and epidemiology of tapeworms have really cleared up any confusion. I found it interesting to see the relationship between the intermediate host and humans. Improved hygiene and sanitation need to be improved in underdeveloped areas in order to counteract the ramifications of expansive agricultural economies that rely on pigs and cows. On an unrelated note I wonder, do tapeworms act in a similar way to the pathogen that causes mad cow disease?

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  5. Dr. Walsh, I would like to know what you meant by "actively migrate out of the host". Also, do we know what is the approximate impact on public health...? In other words, among the helminthic infections, what percentage is attributable to T. Solium? I came across some information during the week: one of the main treatments for helminthic infection, Vermectin (Mebendazole) is discontinued in the US. Unfortunately, the other treatments are quite expensive (Stromectol (Ivermectin) can cost $120 for a full course, and 2 tablets of Albenza costs more than $200). Considering the epidemiology of the disease, and it's major impact on areas with agricultural economies, poor sanitation and poor or no water infrastructure, it would be interesting to know what interventions are being employed especially to prevent transmission (especially from pigs to humans and vice-versa).

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    1. Gravid proglottids are motile and can actively move out through the rectum.

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  6. As it was mentioned above, I have heard about the use of beef tapeworms in diet pills. From what I learned in a previous microbiology course, the pork tapeworm is the major source of tapeworm sickness, while the beef tapeworm is considered relatively harmless. I noticed fish tapeworm was mentioned in passing. I wonder how common infection due to fish tapeworm is as opposed to infection by pork tapeworm, especially in regions where seafood is a predominant component of the local diet.

    The post mentions that neurocysticercosis is the most important clinical presentation of pork tapeworm infection. In order for someone to present with hydrocephalus, seizure, etc., it seems as thought the infection would have occurred long ago or the person is being continuously exposed to pork tapeworm. Based on this, it seems that an initial tapeworm infection can actually become a chronic health issue.

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    1. Sophia, as you mentioned fish tapeworm, I tried to get more information. The official name is Diphyllobothrium latum. It can grow up to 30 feet tall – (imagine that) and is found to be the largest tapeworm to affect humans. Although in most cases, infected people are asymptomatic, there can be some severe consequences such as intestinal obstruction and possible perforation.
      I was not able to find any solid information as to whether Pork or Fish tapeworm is prevalent over each other. If I have to take a wild guess, I would go with Pork tapeworm. According to Medline Plus, humans become infected upon eating undercooked or raw freshwater fish that contain the tapeworm cyst. Given the limit to freshwater, the geography becomes narrow. Pork is more universal and is found in almost every country; based on this assumptions, I think the Pork tapeworm is most common in humans, than the other tapeworms.
      Although I don’t eat raw or rare meat, reading all this information and about these worms gives me more reasons to only eat cooked fish and meat.

      Reference: http://www.cdc.gov/parasites/diphyllobothrium/ and http://www.nlm.nih.gov/medlineplus/ency/article/001375.htm

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  7. I thought to highlight the modes of transmission and prevention of tapeworm infection: (through searching different online sources)

    Modes of infection:
    1- larvae cysts: by ingestion of raw or undercooked meat (muscle tissue) of infected animals/fish
    2- eggs: by ingestion of food, water or soil contaminated with human or animal feces, mainly through poor hygiene.

    Prevention: (mainly by preparing food properly and looking after personal hygiene particularly around animals.)
    1-Cooking pork, beef, fish, lamb and other meats to greater than 140 degrees F for 5 minutes (10 minutes in other sources) kills any tapeworm eggs or larvae.
    2-Freezing meat and fish at temperatures below -10C (14F) for at least 24 hours (48 hours in other sources) kills tapeworm eggs and larvae.
    3-Pickling may also kill tapeworm eggs and larvae, such as pickling fish in brine (salt water).
    4-Smoking or drying meat or fish are not considered reliable ways of killing tapeworm eggs or larvae.
    4-Wash raw vegetables and fruits before you eat them. Cleaning work surfaces and kitchen equipment thoroughly.
    5- wash your hands thoroughly with soap and water: before and after preparing or handling any food, including raw meat or fish, before eating, and after using the toilet.
    6- if you are visiting or traveling to an area that have poor hygiene and tapeworm infection is more frequent, make sure to cook meat and fish properly, drink clean water, use clean (safe) water to wash all fruits and vegetables before you eat them, and most importantly have a fantastic trip☺

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    1. In addition to this post about transmission and prevention of tapeworm infection, reading from the entry that cooking or freezing pork products eliminate cysticerci and prevents adult tapeworm infection in humans and that personal hygiene can prevent the spread of embryonated eggs from person to person led me to think about my experience in a third world country years ago. The area where I stayed had poor sanitation. It was okay to urinate in a corner and there was no flushing after defecating. It is not like likely that people wash their hands immediately after using the bathroom. There was also no clean flowing water, like what we are familiar with coming from a faucet. Clean water was taken from a water well and stored in large buckets. I am not sure how much has improved since I have been there. I am assuming that most tapeworm infection cases are found in poorer regions of the areas the entry mentions. Also considering the statement that “wherever pigs are part of the agricultural landscapes and raised for food tape worm infection is found” reminds me of looking at animals in the field one day and then the animals being slaughtered the next day. In areas where there is a lack of electricity and other resource it is difficult to prevent infection because the meat is not frozen and it is not guaranteed that the meat is properly handled.

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  8. Towards the end of the post, two types of toilet and sanitation systems are mentioned - Western versus Eastern. I'm curious to know whether this could be a reason for human to human transmission. While the squat toilet is better for preventing some physical health conditions, it may make it easier for the eggs to spread from person to person.

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    1. Interesting question, Rich. The style of toilet is unlikely to make a difference. The main sanitation function of either toilet is to remove waste, thus preventing the contamination of sources ingested by humans (i.e water and food). Both toilets perform this function equally well. The spread of embryonated eggs from person to person results from a lack of personal hygiene, i.e. failing to wash your hands after using the toilet. Since this kind of transmission is due to the failure of the individual to wash their hands, it is equally likely regardless of the style of the toilet.

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  9. As shown in the map above, India, China, latin America and parts of Africa are areas where Tape worms are epidemic and that goes to a lot of other parasitic infections, lately in the news the newly elected Prime Minster of India make it a campaign promise to raise the sanitation level of the country "Modi's promise of toilets before temples", now I wonder how that is going to affect the load of all the parasitic infections and other infectious disease in the country, and would there be scientific research studies done in india while this process is happening to measure the success of this campaign, how much it cost and the value of it to the public from all aspects social, economical and health. and if that program can be applied to other epidemic areas in the world?

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    1. Currently, it is estimated that 220 million children between the age of 1-14 in India are at risk of infection from parasitic worms. It seems that India, while making some progress, is still a long way away from being able to provide sanitary conditions for most of the population. However, they are now beginning a massive large-scale deworming campaign along with the World Health Organization to help affected children. Hopefully this will help to lower rates of human-to-human transmission as well.

      http://www.cbsnews.com/news/india-begins-massive-campaign-for-deworming-millions-of-children/

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  10. I know that there are medications for treating tapeworm infections, heck, there are some crazy home remedies floating around out there on the internet. I have no idea why someone would use home remedies to treat something so serious. I am, however, curious to know if the time elapsed between infection and treatment contributes to the effectiveness of clinical treatment. It is absolutely scary to know how long these cestodes can get and that they can harm the definitive hosts (humans) through autoinfection.

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    1. All bacteria, viruses and parasite infections are scary and sometimes difficult to manage. Treating tapeworm infections today is very difficult because of people migrating from the poor countries to the developed countries. I just found a very interesting thing online that shows tapeworms as a positive thing in treating different allergies in humans. Also, people use home remedies because they believe they are not toxic to their bodies and promote a faster healing to their bodies.

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  11. To know that something can grow up to 10m inside of my body is quite disgusting if I may say so. I wanted to know more about the side effects associated with tapeworm infections and I found an interesting article out of BBC on Dr. Michael Mosley who willingly ingested three tapeworm cyst eggs removed from a cow in Kenya. Dr. Mosley swallowed a pill camera which produced some pretty interesting images of the worms in his gut (see here: http://www.bbc.com/news/science-environment-25968755). What was interesting to learn is that some preliminary studies have shown that once inside a host the worms release a sugar based anti-inflammatory molecule that may help in treating metabolic disorders (more information on that here: (http://www.sciencedaily.com/releases/2013/01/130108112451.htm).

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    1. Having a parasite inside of your body that can potentially occupy the length of your small intestine is, at the very least, creepy and unsettling. As the blog suggests, like many others, I too was under the impression that an adult tapeworm infection could cause severe digestive and metabolic issues. It was slightly relieving to see that the T. solium and T. saginata have negligible effects on human health in its adult form. However it is a bit unnerving to know the dangers of humans becoming a intermediate host of the cysticerci. Dr. Walsh, I was curious as to how likely autoinfection takes place within people who are already infected with the adult tapeworm.
      I have looked at both of the articles that Elle posted, and I must say they are very fascinating, especially the second one. The possibly beneficial nature of some of the anti-inflammatory glycans produced by these tapeworms are contrary to what most people would normally think. Also another really interesting assertion the article makes is the fact that tapeworms have actually evolved alongside mammals to be symbiotic instead of parasitic.

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    2. Thank you for posting about Dr. Mosley, Elle. It was truly interesting to read about how he purposefully infected himself with parasites in an effort to understand how they affect the human body. Talk about dedication to acquiring knowledge.....Dr. Mosley takes it to a whole other level! It was also captivating to learn about the anti-inflammatory molecules released by worms once inside a host.

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  12. If I may be trite for a moment, I'm a bit of a food enthusiast. I've been to several high end restaurants where the pork chop was recommended to be cooked medium with a hint of pink inside instead of well done as conventional wisdom and history/modern medicine recommends. I did question each waiter about the chef's choice to under cook the pork and was similarly told be each that the pork of today is not what it used to be. They further went on to say that "heritage pork" comes from well cared for pigs that live in superior conditions far removed from the filthy conditions of regular pig farms. Would any of you eat pork that was under cooked vis-a-vis what we've read here and what modern farming claims to be better pork? Is it responsible to the public health for chefs/restaurants to serve under cooked pork regardless of flavor and texture?

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    1. This comment has been removed by the author.

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    2. I am also a food enthusiast and have been in restaurants where the pork is somewhat pink and not fully cooked. However, as you explained, I do believe that it has a lot to do with where the pork comes from and how it is handled prior to being served. Nowadays, people have become obsessed with food being organic, farm raised, etc., but looking back, how many years did people survive from just eating what was available? The main problem now is that big corporations (i.e. meat distributors) aim at mass production and forget to value quality over quantity; thus, leading to sanitary issues, which in this case, can lead to infected pigs (http://www.cfs.gov.hk/english/import/import_smi.html). I think that it is more our choice than the chef’s or the restaurant’s because, for example, when a person goes to a sushi place he or she should know that many of the food they serve is raw or that in a well known meat place, the meat will probably not be served well-done (it’s just wrong, in my opinion). But what we should expect is that these restaurants are well monitored by public health officials that enforce the importance of cleanliness and fresh products. A good restaurant that serves meat not fully cooked, should know the products they sell, but in the end, as I said before, it is up to us to decide what we eat. Personally, I don’t think I could ever stop eating raw fish or medium cooked meat (it’s just too good), but I always try to read about the cleanliness and quality of the restaurants I want to visit beforehand.

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    3. I hardly eat pork (although I do indulge with bacon every now and again), but when I do eat pork, it must be cooked thoroughly. Often times, I refuse to eat it unless it is completely white inside. Karla, your point about people in the past eating what was available is true, but lifespan was much shorter back then. How can we say with any certainty that people didn't get ill from the foods they ate? Of course they got sick, and maybe they even had tapeworms. However, it's the actions of cultures in the past making under cooked meat and pork specifically a delicacy. While we should respect cultures and their customs, we must be able to work alongside cultures and teach them that under cooked meat can prove to be life-threatening. In terms of high-end restaurants serving under cooked meat, it's allowed because most menus provide disclaimers: "The consumption of raw or undercooked eggs, meat, poultry, seafood or shellfish may increase your risk of food borne illness." This places most of the initial responsibility on customers which is an act of self-preservation on the side of the restaurants. I enjoy ordering a rare steak or a medium rare burger, and I would be very upset if a waiter told me that I couldn't have it. It's a strange, slippery slope that I don't think there's an obvious solution for.

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    4. http://www.animalplanet.com/tv-shows/monsters-inside-me/videos/pork-tapeworm/

      It's a good practice to cook the meat well (I don't mean well done!). I believe that most restaurants refuse to serve a rare/ medium rare burger or pork chops for fear of liability.

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  13. What a clever evolution of Taenia solium (pork tapeworm), which forces humans to battle infection on the three fronts of its life-cycle: 1) from the developmental stage in the pig host from eggs to cysticerci 2) to the adult life-cycle in humans, in which infectious cysticerci are consumed from infected pigs and 3) the aberrant self inoculation via fecal-oral contamination causing the most serious aspect of this infectious agent, cysticercosis. If it hadn’t been for human self inoculation, the tapeworm may have remained “under the radar”. While, using hand hygiene and proper cooking of pork to 145° F (in whole cuts of meat) will prevent infection ( http://www.cdc.gov/parasites/taeniasis/prevent.html); it is reassuring to know that despite best efforts, if taeniasis occurs, praziquantel can treat an individual for $15 per dose, single dose therapy. (http://www.uptodate.com. praziquantel-drug- information?source =see_link &utdPopup=true) For neurocysticercosis, more complicated due to the hazards involved in intracranial pathologies, albendazole can treat for $309/day for 8-30 days. (http://www.uptodate.com.albendazole-drug-information?source= search_result&search= albendazole &selectedTitle=1~44)
    There is one pearl of wisdom that I thought was critical to be aware of: after treatment of taeniasis, the worm dies but the gravid proglottids can continue to release eggs! Don’t let your guard down; you are at risk for auto-inoculation!

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  14. It seems interesting that there still exists such a tremendous prevalence of this problem when the solution is so simple. If this is such a widespread issue, it would seem that people would be more concerned with thoroughly cooking their pork. However, it would be pertinent for the local public health officials in the areas where this is problematic to spread information and education about the prevention of this. According to the WHO, vaccination of the livestock is also a good intermediary prevention strategy that does not depend on individual action.

    http://www.who.int/mediacentre/factsheets/fs376/en/

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