Everything You Didn’t Want to Know About Cockroaches

Amongst its many epicurean, architectural and otherwise louche charms, New Orleans has another infamous, uncelebrated one: a problematically vibrant cockroach population. Every summer (oh, let’s be honest here: they’re here spring, summer and fall), the German brown cockroach can be seen snatching its way around your house, flitting on sidewalks at dusk, and intimidating the locals.

They fly down here in the Deep South, did you know?

One Saturday night back in August, one such creature dive-bombed into my cleavage. After one spilled G&T (Oh God, not my drink!) and many sputtered expletives, the critter was ousted and a friend graciously stomped it into a unrecognizable smear into the pavement.

And so with the impending cockroach population explosion coming any summer day now, I figure why not have a chat about what diseases they can harbor and spread on your tabletops. Hmmm? And lest you think that this article is a paean extolling their overlooked virtues – alas! – they really are as filthy as everyone thinks they are.

A colored scanning electron micrograph of Periplanta americana, the American cockroach, one of the smallest known species. Note the ubiquitous hairs covering the insect, allowing for microbes to be picked up during its feedings. Image: Dr. Biology, Arizona Board of Regents. Click for source.

I’ll try to make this as painless as possible.

Out of the 4000 species of cockroach that exist, there are three major species that plague humanity – Periplaneta americana, Blattella germanica and Blattella orientalis. They feed on just about anything, even their deceased brethren, but they do have a sweet tooth and prefer to eat sugary and starchy items such as sweets, cardboard and book-bindings (1). Included in their rather diverse diet is their consumption of human detritus such as feces, sputum, toe nails, and bodily residue on surgical swabs. These unseemly dietary choices lead to their contamination of food, utensils and surfaces for food prep and have direct consequences on human health in three interrelated ways – their arbitrary feeding habits, eating both human excrement and human food; their indiscriminate defecation habits; and the fact that they regurgitate digestive fluids in the process of eating (2). Endearing, no?

Roaches also serve as an important source of infectious pathogens. They serve as a sort of public transit for the busy microbiological world, a bus ferrying bacteria, viruses, fungi and parasites between filth and human comestibles; really, every buggy imaginable rides on this double-decker of an arthropod. Bacteria and viruses settle into the crevices and cracks between thorax and head, and begin to multiply. There are so many fissures and clefts and crannies on a cockroach. Everywhere there are hairs, but especially on the six legs that escort these scuttling creatures from one dark, humid hideaway to another. Microbes snatch a ride on these hairs or are accidentally consumed by the cockroach only to pass into the alimentary canal where they may multiple in number. In one study, the bacterium Pseudomonas aeruginosa was found to have increased multiple-fold over the course of 114 days in the gut of a cockroach (3).

Colored scanning electron micrograph (SEM) of Blattella germanica, the German cockroach, one of the smallest known species. This roach’s long antennae can be seen protruding from its head and its wings (blue) can be seen at lower left. The anatomy of the cockroach provides several areas for bacteria, viruses and parasitic eggs/cysts to settle into. Image: Volker Steger, Science Photo Library. Click for source.

In this regard, roaches are not so much vectors as they are reservoirs; a mosquito will squelch its proboscis in your ankle, inoculating you with malaria in their quest for blood but a cockroach indiscriminately contaminates anything lying around. Entomologists describe this process as “mechanical transmission”, indirectly transmitting disease to humans. It’s not personal, it’s just business. 

All types of passengers are welcome on this cockroach bus. Over 30 species of bacteria have been found on the cuticle and gut of roaches, including those of serious medical import such as E. coli, various species of Salmonella and Staphylcoccous, Pseudomonas aeruginosa and Klebsiella pneumoniae (4). These bacteria cause diseases such as urinary tract infections, dysentery, diarrhea, pneumonia, cholera, polio, septicemia and wound infections (5). One study that trapped cockroaches in order to measure their bacterial load found that number was as high as 14 million microbes found on the exterior of the bodies, and 7 million in their fecal droppings (5).

Viable eggs and dormant cysts of parasites also hitch a ride; the culprits include the ova of Ascaris lumbricoides (giant roundworm), Anchylostoma deodunale (hookworm), Trichuris trichura (whipworm), Enterobius vermicularis (pinworm) and Strongyloides stercoralis (threadworm), and the cysts of Entomoeba hystolitica, Balantidium coli, C. parvum, C. cayetenensis and Isospora belli (4). Even the virus that causes polio, poliomyelitis, has been found within the guts of cockroaches (6).

There are several documented cases of small outbreaks that pinpoint to cockroaches playing an indirect but prominent role in disease transmission. In one county in Northern Ireland in the late 1970s, fifteen food-handlers in various establishments fell ill to dysentery caused by the Shigella bacterium over the course of eight weeks (2). These restaurants had serious infestations, particularly in the kitchen and dining areas, and the stomach contents of trapped roaches showed viable Shigella dysenteriae serotype 7 bacteria, incriminating the arthropods in the spread of the disease.

Cockroaches were also suspected to be the cause of a hepatitis A outbreak in a Los Angeles housing project in the late 1950s. From 1956 to 1959, the Carmelitos Housing Project represented 39% of all cases of hepatitis A in Los Angeles County with numbers of the infected steadily increasing through the years (7). It was only until a full-scale cockroach control program employing a newly developed insecticide, the industrial silica aerogel Dri-Die 67, was the outbreak halted. Two years following the program, incidences of hepatitis A from the Housing Project dropped to 0.0% and cockroaches traversing between the sewage system and the Project were pinpointed as the source of the epidemic.

A colored scanning electron micrograph close-up of Periplaneta americana, the American cockroach, which can be found around the world. Image: Stephen Gschmeissner. Click for source.

Typhoid patients in Italy were found to have cockroaches harboring S. typhi in their homes in a study conducted in 1943 (2). Similarly, the same organism was found in cockroaches infesting a Belgian hospital’s children’s ward undergoing an epidemic of gastroenteritis in 1950 (2). Most recently, outbreaks of Klebsiella pneumoniae in neonatal units have been tied to cockroach infestations in hospitals in Ethiopia and South Africa (8)(9). These studies indicate that cockroaches may play an unappreciated role in the epidemiology of infections in both the home and hospital.

Though it’s difficult to say what part roaches play in small disease outbreaks, they are capable of harboring antibiotic-resistant bacteria. A 2012 study in Ethiopia looked at cockroaches trapped in a neonatal intensive care unit and found widespread multi-drug resistance among individual species of bacteria residing in the roaches. Reading the lists of antibiotics these bacteria were found to be resistant to is like a “who’s who” of the antibiotic world – ampicillin, augmentin, tetracycline, chloramphenicol, amoxicillin, doxycycline, and ciprofloxacin (8). An earlier study in South Korea found that cockroaches trapped in homes located 3 miles from a hospital harbored bacteria that were resistant to anywhere from 6 to 12 commonly used antibiotics (3). These medications are the mainstay for treating bacterial infections and the discovery that cockroaches in hospitals harbor bacteria no longer susceptible to them is discomfiting to say the least.

Bugs are such an inescapable component of our day-to-day living, whether we care to acknowledge them or not. They live their own buggy lives, spinning webs, squirming through our compost or draining picoliters of our blood. We pay little attention to them until they inconvenience us and spoil our clean, bleached perception of the world.

Cockroaches are especially gifted at this. They are the boldest creepy-crawlies, not only daring to openly traverse our homes and personal spaces but thriving in those environments. They need us for the waste and shelter we provide, and for that we despise them. And, sadly, the public opinion of them isn’t wrong. They really are gross – they serve as an efficient means for microbes of all kinds to traverse between sites of human waste and food preparation and consumption. Their traipsing through family dwellings, food establishments and hospitals compromises public health and may also contribute to the ongoing antibiotic-resistance in bacteria worldwide.

Check out the Resources below to see how you can prevent buggies and bacteria from getting a free ride into your kitchen. In the meantime, happy hunting!

Resources

The most recent cockroach-related outbreaks of disease have happened in developing countries that may lack adequate municipal sanitation and regular garbage disposal. Hospitals and multi-family dwellings that rely on old buildings may also suffer cockroach infestations due to shoddy construction or inevitable decay (3)(10). The WHO has a very helpful, fact-filled PDF here on how to protect your home from these little invaders.

Really wanna get in deep with Blattella germanica, the German cockroach? For only $326, this book could be yours. What a deal!  If you’re just into skimming, then you can check it out on Google here.

Cockroaches can dirty up human spaces but at least they have little friends that can keep their own bodies clean – mites!

From the ignominious Daily Mail, a collection of scanning electron micrograph images of the buggies that live in your home with you. More images can be found here but they’re sadly unlabeled.

References
(1) Rozendaal JA. October 1997. “Cockroaches.” Vector control: Methods for use by individuals and communities. World Health Organization. PDF of chapter is accessible here. Click here for access to the entire resource.
(2) Burgess NR & Chetwyn KN. (1981) Association of cockroaches with an outbreak of dysentery. Trans R Soc Trop Med Hyg. 75(2): 332-3
(3) Hsiu-Hua P et al. (2005) Isolation of bacteria with antibiotic resistance from household cockroaches (Periplaneta americana and Blattella germanica) Acta Tropica 93: 259–265  T
(4) Tatfeng YM et al. (2005) Mechanical transmission of pathogenic organisms: the role of cockroaches. J Vect Borne Dis. 42: 129–134
(5) Chaichanawongsaroj et al. (2004) Isolation of gram-negative bacteria from cockroaches trapped from urban environment. Southeast Asian J Trop Med Public Health. 35(3): 681-4
(6) Healing TD. (1993) Arthropod Pests as Disease Vectors. Proceedings of the First International Conference on Urban Pests. Accessible here.
(7) Tarshis IB. (1962) The cockroach–a new suspect in the spread of infectious hepatitis. Am J Trop Med Hyg 11: 705-11
(8) Tilahun et al. (2012) High load of multi-drug resistant nosocomial neonatal pathogens carried by cockroaches in a neonatal intensive care unit at Tikur Anbessa specialized hospital, Addis Ababa, Ethiopia. Antimicrobial Resistance and Infection Control. 1: 12
(9) Cotton MF et al. (2000) Invasive disease due to extended spectrum beta-lactamase-producing Klebsiella pneumoniae in a neonatal unit: the possible role of cockroaches. J Hosp Infect. 44(1): 13-7
(10) Fakoorziba MR et al. (2010) Cockroaches (Periplaneta americana and Blattella germanica) as potential vectors of the pathogenic bacteria found in nosocomial infections. Ann Trop Med Parasitol. 104(6): 521-8

Pai, H., Chen, W., & Peng, C. (2005). Isolation of bacteria with antibiotic resistance from household cockroaches (Periplaneta americana and Blattella germanica) Acta Tropica, 93 (3), 259-265 DOI: 10.1016/j.actatropica.2004.11.006

Of Warts & Men: Meat-Handlers Infected with Human Papillomavirus 7

Every profession seems to have its own tailor-made occupational hazard. Veterinarians suffer bites and scratches, office workers struggle with carpal tunnel syndrome, anxiety torments professional graduate students and so on. A few years ago, I was stunned to hear that butchers, fish-mongers and those intimately involved in the meat-handling trade (please don’t read into that any more than is necessary) are more likely to be infected with a certain strain of Human Papillomavirus (HPV). Odd, huh? And kind of gross.

A scanning electron micrograph of a negatively-stained HPV virion. Image: Unknown. Source: Laboratory of Tumor Virus Biology. Click for source.

The thriving 120-member HPV family is quite successful at infecting humans, with up to the 20% of a population infected with a HPV wart or verruca (1). This family is as familiar to the human body as the warming, joyful sensation of the sun on our skin. The viruses are real home-bodies, typically favoring one part of the body whether that be the feet, hands, anogenital region or what-have-you. The HPV family is roughly segmented into three infection subtypes: anogenital and/or mucosal, non-genital cutaneous, and epidermodysplasia verruciformis (EV), a rare, hereditary infection that can cause widespread squamous cell skin tumors (2). The papillomaviruses show strict species specificity; attempts at a Frankensteinian or “Heart of a Dog” type of cross-species viral infection have been, thankfully, unsuccessful (4).

HPV causes epithelial proliferations of the skin and mucous membranes, with a clinical expression resulting in anything from benign warts to invasive tumors. Warts are acquired by direct or indirect contact; infected individuals transmit the infection by living their life day-to-day, unknowingly smearing HPV particles on surfaces willy-nilly (5). And so we go about living our lives, blissfully unaware of such matters. Until now, that is.

The HPV family has the ignoble distinction of being the most commonly sexually transmitted disease with over 40 viruses capable of infecting the genitals, mouth and throat. It’s quite impressive, really. HPV-16 and HPV-18 are the most familiar to us, being globally ubiquitous and responsible for causing genital warts as well as the great majority of cases of cervical cancer, now easily preventable by vaccination (if people would get vaccinated, that is!).

Common warts found on the hands, palms and around the nails and plantar warts on the feet are most often caused by strains HPV-2 and HPV-4, though HPV-1 and many more may also be responsible. These verrucas  of the hands and feet typically affect children and young adults (much to the dismay of mothers). This self-limiting infection can be difficult to treat and fully eradicate – warts can either be non-responsive to or reappear after treatment. Dermatologists recommend letting them reside and proliferate benignly until the immune system kicks into high gear and eliminates them.

"Butcher's Stall" by Pieter Aertsen, 1508 - 1575. Click for source.

In 1969, a physician named Jerome Litt found that meat-handlers had a greater incidence of hand warts than the general population (3). These warts were often quite abundant, grew in a proliferative fashion and were localized to the dorsal and palmar sides of the hand (4). The warts have been described as having a cauliflower-like appearance. Hyperkeratinosis is often seen, where the outermost layer of the epidermis, the stratum corneum, has thickened and darkened. The increased prevalence of warty hands within this population remains the case today where it is estimated that up to 23% of people who frequently handle meat, fish and poultry will develop warts on their hands (5).

Initially, researchers thought the warts of those involved with the slaughtering or butchering of cows were a result of a bovine papillomavirus (BPV), seemingly infected by the virus in a direct cow-to-human transfer. It seemed reasonable enough: the warts are localized to the hands, these guys are in frequent contact with blood and flesh, ergo these verrucas are bound to be a cow wart virus. Even so, after many biopsies and running samples through PCRs, researchers have found that these viruses are all of the human variety.

In several studies of butcher’s warts, researchers have found that HPV-2, HPV-4 or HPV-7 are the most common culprits, with HPV-7 leading the pack (5). Often, several HPV subtypes have been found on one hand, throwing themselves a good ol’ warty party (7). So we have a situation in which men who work in abattoirs and retail and wholesale butcher shops were showing evidence of a profession-specific viral warty infection.

Butchers at work in 1928 at the Loch Bros. butchery in Emerald, Australia. Image: Unknown. Source: John Oxley Library. Click for source.

Even those working in the seafood industry aren’t spared. Fishmongers also can become infected with the HPV types HPV-1, HPV-2, HPV-4 and HPV-7 (8). In fact, researchers found that infection with HPV-7 was directly correlated with the length of time one had been employed as a fishmonger, a finding similar to that in the case of the abattoir and butcher workers (5). Poultry workers and farmers have also been found with infections, so this is not a bovine-specific hazard.

So why do people working exclusively in the butchering industry get this human virus while we non-meat-handling office workers and laborers are spared? The simple answer is “we don’t know”. We really don’t. The reservoir of HPV-7 and where it hides out, why meat-workers are disproportionately infected and what the role of the flesh of animals or the slaughtering environment has to do with the propagation of the virus are all frustratingly unknown.

Proliferative warts localized to the dorsal side of the hand similar to what a HPV-7 infection may look like. Image: Logical Images. Source: SkinSight. Click for source.

Some speculate that environmental conditions may well be a serious factor in HPV-7 infection (8). It has been shown that abrasions of the skin encourage penetration of the HPV virus and proliferation of common and plantar warts (5). And we know that meat-handlers typically work with a variety of animals with very sharp knives in wet and cold environmental conditions. It’s a gem of a setting: working with flailing, dying animals, surrounded by fur, blood and scales, and acquiring minor abrasions and accidental lacerations throughout. It seems quite reasonable to expect that they would get some infection or another, so why not some harmless warts?

Now the “but”: a group of British researchers have conducted extensive surveys looking at hand trauma, environmental conditions and handling of specific kinds of meat and found no association between these factors and hand wart or HPV-2 and HPV7 prevalence (6). There was also no evidence of person-to-person transmission, meaning that butchers aren’t spreading this virus to their work-mates in their working environment (7). These results suggest that HPV-7 is distributed throughout the population but only causes disease under certain environmental conditions or stimuli, and that there is some component of animal flesh that predisposes activation, infection and/or replication of HPV-7 in the epithelia (6).

In other words, there’s something in a slaughtering/butchering environment that encourages replication and growth of HPV. Does meat or blood have some sort of immunosuppressive factors that allow for HPV-7 to blossom on butchers’ hands? One study clearly seems to support this idea with the finding that lower incidences of warts are found in those working in modern slaughterhouses, with automated butchering rather than butchering by hand (5). Warts can develop within two years of working with meat, which also seems to suggest that cumulative exposure is necessary before your hands start growing some new, minor appendages (8).

Alas, the research is rather thin on HPV-7. There just isn’t that much of an academic drive for investigating this rare, benign virus that affects a sub-set of professionals. But what a good, meaty mystery, eh? Definitely something to consider when you’re deciding whether to embark on a career change as, say, the latest hipster butcher. In the meantime, take this as a cautionary tale to wash your hands frequently and especially after preparing your filet mignon for tonight’s dinner.

Resources
For more information on the molecular structure and pathogenesis of HPV, there’s a public-access PDF from 1993 that’s helpful but mostly focuses on cervical strains. This student-made page from Brown University is also insightful.

For a list of the different types of warts and the HPV strains that cause them, go to the helpful eMedicine overview.

For an catalogue of truly alarming images of warts, I reluctantly point you in the direction of the DermNet NZ site. NSFW and NSFFH (Not Safe For the Faint of Heart).

References
1) S Jabłońska, S Majewski, S Obalek, G Orth. (1997) Cutaneous Warts. Clin Dermatol. 15(3): 309-19
2) PA Gearhart. (2011) Human Papillomavirus. Medscape Reference. Retrieved: Oct 13, 2011 from http://emedicine.medscape.com/article/219110-overview
3) JJ Meffert (2001) Butcher’s Warts: Dermatological Heritage or Testable Misinformation? Arch Dermatol. 137(3): 384-5
4) W Melchers, S de Mare, E Kuitert, J Galama, J Walboomers, and AJ van den Brule. (1993) Human Papillomavirus and Cutaneous Warts in Meat Handlers. J Clin Micro. 31(9): 2547-49
5) R Rüdlinger, MH Bunney, R Grob & JA Hunter (1989) Warts in fish handlers. Br J Dermatol. 120(3):375-81
6) M Keefe, A al-Ghamdi, D Coggon, NJ Maitland, P Egger, CJ Keefe, A Carey, CM Sanders (1994) nBr J of Dermatol. (130)1: 9–14
7) M Keefe, A al-Ghamdi, D Coggon, NJ Maitland, P Egger, CJ Keefe, A Carey, CM Sanders (1994) Butchers’ warts: no evidence for person to person transmission of HPV7.  Br J of Dermatol. (130)1: 9–14
8) A Tosti & BM Pieraccini (2001) Warts of the Nail Unit: Surgical and Nonsurgical Approaches. Dermatol Surg. 27(3): 235-9

KEEFE, M., AL-GHAMDI, A., COGGON, D., MAITLAND, N., EGGER, P., KEEFE, C., CAREY, A., & SANDERS, C. (1994). Cutaneous warts in butchers British Journal of Dermatology, 130 (1), 9-14 DOI: 10.1111/j.1365-2133.1994.tb06874.x
Melchers W, de Mare S, Kuitert E, Galama J, Walboomers J, & van den Brule AJ (1993). Human papillomavirus and cutaneous warts in meat handlers. Journal of clinical microbiology, 31 (9), 2547-9 PMID: 8408588

Revenge of the Fishball: The Magnificent Fish Tapeworm

You’re complaining of having nightmares about your teeth falling out? I dream of intestinal colonization with a 30 foot tapeworm. Everyone’s got their own hang-ups and quite frankly the largest parasite of man, the freak of nature Diphyllobothrium latum, unnerves me. What’s not to dislike? The longest lifespan of any human parasite and the jaw-dropping lengths it can reach are just a few of its charms.

The fish tapeworm has long been an intestinal bedfellow of mankind. The earliest evidence of infection has been found in archaic coprolites along the Pacific coast of Chile and Peru dating from 4110 to 1950 BC (1). Tapeworm eggs have also been found at Neolithic lakeside settlements dating from 3900 BC in Germany and Switzerland and represent the earliest occurrence of the tapeworm in the Old World; diphyllobothriasis, as the infection is called, may have been one of the leading parasitic infections of Neolithic people during that period (2). It still remains a modern scourge, with an estimated 20 million people worldwide infected (3).

An unfragmented fish tapeworm excreted after injection of amidotrizoic acid. Arrow identifies the scolex. Inset shows magnification of the proglottids. Click for source.

Scandinavians brought the creature to the midwestern United States as they left their homeland and moved to the lake regions of Minnesota and Wisconsin in the 1800s (4). As the sewage of sturdy Norwegians and what-have-yous contaminated the lakes of the Midwest, tiny copepods ingested the eggs. These little crustaceans would be consumed by predatory freshwater fish such as pike, carp, salmon, perch, turbot and pickerel and the tapeworm larva would embed itself in their muscle or viscera. The larval form of the tapeworm, the plerocercoid, makes its final home in the small intestine of humans or bears when the fish is eaten in a raw or undercooked state. The tapeworm can live quite comfortably there, in relative parasitic harmony with its host for several decades.

D. latum has one the most magnificent anatomies of the helminthic family. It has two suction cup-like grooves located at its head, known as a scolex, that allow it to grip the small intestine. The scolex looks like some sort of bizarre, antique tool you’d stumble upon in your grandfather’s shed. Or a sex toy. Anyway! The body is composed of thousands of rectangular segments known as proglottids; the worm can be made of up to thousands of these guys stretching through the intestine for several feet. It’s a rapidly growing beast too – tapeworms can grow 22 cm a day or 1 cm per hour (5). The longest specimen every found was recorded at an alarming 25 m or 82 ft (6).

The scolex head of the fish tapeworm. Note the bothria "grooves" that it uses to attach to the intestinal wall. Click for source

A stained proglottid segment from the fish tapeworm showing the uterus. Image: CDC. Click for source.

Each proglottid contains all of the necessary machinery to reproduce – testes, ovaries and uterus are neatly compacted into a globular, rosette shape that churns out eggs. Most interestingly, egg production seem to be more common in the late summer and fall (7). The tapeworm continuously grows new proglottids downwards from the head and neck, shifting the older segments further down the intestines where they may be eventually lost as the tapeworm ages. If you’re infected and in great luck, you may see wildly thrashing proglottids (either singly or in a chain) upon defecation. A proglottid segment has been evocatively described as “tagliatelle” like (8). Splendid!

We can thank gefilte fish for the alarming sight of a wriggling proglottid in the toilet bowl of a Jewish housewife in Brooklyn. Gefilte fish is quite the culinary amuse bouche – a ground-up concoction of freshwater fish, eggs, matzo meal and your requisite salt, which is then smushed into a ball and promptly boiled. These balls may then be stuffed into a whole fish and served. Determining whether your gefilte fish is properly cooked depends on instinct and you and your family members’ standards of taste and “doneness” – in other words, frequent taste testing which may result in self-inoculation with the larval plerocercoid. Handling of the raw fish can also deliver the infective larva to the intestinal system. Tapeworm infection is most likely to occur in the Jewish population during Passover when gefilte fish is much in demand (9).

Bubbe's geftile fish. What could go wrong? Click for source.

Scandinavians have a similarly constructed dish, fish balls or “fiskeboller”, though it is typically served with a cream sauce instead of inhabiting the interior of another fish. The high prevalence of diphyllobothriasis due to the culinary adventures in these two communities have earned
the tapeworm the name “Jewish/Scandinavian housewife’s disease”.

This parasite is quite tolerant of other religions and eating habits – all cultures that consume freshwater fish are susceptible to infection. The Japanese may be infected by D. nihonkaiense* by eating uncooked or raw sushi or sashimi made of anodromous fish such as salmon that is used as an intermediate host by the worm. The global epidemiology of infection with this species has truly evolved as transportation and refrigeration systems have improved thus enabling the transport of fresh fish from rural, isolated regions to urban locales (10).

A fish tapeworm located in the terminal ileum and extending to the sigmoid colon discovered during a colonoscopy. Image: Jae Hak Kim. Click for source.

 D. latum has also reared its narrow scolex head in Brazil thanks to a burgeoning aquaculture industry that rears salmon in southern Chile (11). Consuming dishes of contaminated raw or smoked salmon are typically responsible for tapeworm transmission, though Japanese cuisine has also made its mark in South America where raw sushi has become quite popular. Diphyllobothriasis was also quite common in the Canadian Inuit population but has declined significantly over the past few decades due to cultural changes in eating behaviors (11).

Despite its preposterous length, tapeworm infection itself is rather benign. At the most, a person may initially suffer abdominal discomforts such as diarrhea, cramping, flatulence, vomiting, nausea, and weakness. Chronic infections may result in weight loss, fatigue and pernicious anemia. This type of anemia occurs when there are exceptionally low levels of folic acid, otherwise known as vitamin B12, a macromolecule necessary for the production of red blood cells by bone marrow. The tapeworm actively competes for the vitamin, nicking it from its human host. Scandinavians and the Finnish in particular have a genetic predisposition to B12 deficiency and are more susceptible to suffering from pernicious anemia.

For those who have no qualms about body infestation, flailing worms and colonoscopies, I highly recommend watching the Youtube video below of an accidental discovery.

Treatment is, shockingly, quite simple – administering a single dose of the anthelmintic praziquantel should expel the worm. It is important that the entire worm is removed from the intestine; if the scolex and head remain, the tapeworm will continue to quite happily grow proglottids.

Thankfully, incidence of tapeworm infection in the United States has declined due in part to the increased inspection of fish imports, improved sewage management as well as the modern convenience of cheap, cooking thermometers (7). Most sushi served in the United States is used with previously frozen fish which kills the plerocercoid. Diphyllobothriasis is still common in Europe, especially in the Baltic and Scandinavian countries (11).

For those of you who will be joining me in dreaming of tapeworm tangos in your belly, just remember that sushi, sashimi, carpaccio or ceviche that is prepared with never-frozen freshwater fish should be eaten with caution. Or gusto depending on how you live your life – who am I to say? Bon appetite!

*Note

Parasitologists are still disentangling the morphological and ecological variations between Diphyllobothrium species – much of the genus’ phylogeny needs rigorous molecular and genetic characterization. It could very well be that there is only one species of tapeworm or gazillions of them. A super cool hypothesis about the morphological differences seen in different tapeworms found throughout the world is that human hosts alter the tapeworm’s morphology. For a review, click here.

Resources

For more in-depth information on the life cycle of D. latum, the indispensable CDC is always here to help you.

A charming infestation story a few years back from the NYT. Also the great Robert Desowitz goes into a nice story about a Jewish grandmother infected with a new Scandinavian friend. Get the book here.

Looking to buy antiquated tapeworm cures and other parasitological ephemera for beloved relatives? I know just the thing!

References
(1) KJ Reinhard (1992) Parasitology as an Interpretive Tool in Archaeology. American Antiquity. 2(57): 231-45
(2) M Le Bailly, U Leuzinger, H Schlichtherele & F Bouchet. (2005) Diphyllobothrium: Neolithic Parasite? J Parasitol. 91(4): 957-9
(3) T Scholz, HH Garcia, R Kuchta, B Wicht. (2009) Update on the Human Broad Tapeworm (Genus Diphyllobothrium), Including Clinical Relevance. Clin Microbiol Rev. 22(1): 146-60
(4) Weintraub, S. The Parasite Menance. Woodland Publishing, 2000
(5) F Kuhlow (1955) Studies on the development of Diphyllobothrium latum. Z. Tropenmed. Parasitol. 6 :213–225
(6) von Bonsdorff, B. 1977. Diphyllobothriasis in Man. Academic Press, New York, NY.
(7) EJ Jenkins, JM Schurer, KM Gesy. (2011) Old problems on a new playing field: Helminth zoonoses transmitted among dogs, wildlife, and people in a changing northern climate. Vet Parasitol. Epub ahead of print
(8) Y Jackson, R Pastore, P Sudre, L Loutan, F Chappuis. (2007) Diphyllobothrium latum Outbreak from Marinated Raw Perch, Lake Geneva, Switzerland. Emerg Infect Dis. 13(12): 1957-8
(9) D Gibbs (1984) Gut feelings in the old. Brit Med J. 289: 1065
(10) N Arizono, M Yamada, F Nakamura-Uchiyama, K Ohnishi. (2009) Diphyllobothriasis Associated with eating raw pacific salmon. Emerg Infect Dis. 15(6): 866-70
(11) FC Cabello (2007) Salmon Aquaculture and Transmission of the Fish Tapeworm. Emerg Infect Dis. 13(1): 169-71

Scholz, T., Garcia, H., Kuchta, R., & Wicht, B. (2009). Update on the Human Broad Tapeworm (Genus Diphyllobothrium), Including Clinical Relevance Clinical Microbiology Reviews, 22 (1), 146-160 DOI: 10.1128/CMR.00033-08
Cabello, F. (2007). Salmon Aquaculture and Transmission of the Fish Tapeworm Emerging Infectious Diseases, 13 (1), 169-171 DOI: 10.3201/eid1301.060875