Category: Zoonotic Diseases

Oy Vey!: Pig Tapeworm in the Orthodox Jewish Community

By Rebecca Kreston | August 19, 2012 5:00 pm

A few months back, Carl Zimmer published a short article on the startling widespread prevalence of neurocysticercosis; the larval infective form of the pig tapeworm Taenia solium that just so happens to infect the human brain. Check it out, but beware!, you will be learning about a parasite that gives unwelcome deep tissue massages in your gray matter and you will see photographic evidence of it.

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An Update on Baylisascariasis: Benign Infection in an Elderly Woman

By Rebecca Kreston | April 13, 2012 11:23 am

A timely letter was published in the Emerging Infectious Diseases journal shortly after my article on Baylisascaris procyonis was posted two weeks ago. It describes a quite unusual case of the infection in a recently deceased elderly woman that had lived in British Columbia, Canada. I wanted to write a quick note about this because it changes the dimensions of our understanding of this parasitic infection, challenging the notion of this disease as typically only afflicting infants and toddlers. Additionally, this letter nicely demonstrates how essential autopsies are to the ongoing pursuit of medical knowledge.

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Baylisascariasis! The Tragic Parasitic Implications of Raccoons In Your Backyard

By Rebecca Kreston | March 29, 2012 1:46 pm

This article was published as a guest post on the blog of the Parents of Kids with Infectious Diseases (PKIDs) nonprofit on April 2, 2012. It can be visited here in an edited, shorter form. You can find out more about this great organization and their public health mission here.

The re-wilding or “greening” of urban and suburban spaces has been an indefatigable, faddy trend in urban planning for the past two decades. Urbanites like accessible parks and community gardens and food forests and stately trees and along with our car-filled cities. Hell, we name our streets after trees – spruce, elm, oak, pine and so on. These are the things we do to justify our shoddy recycling habits and not giving due care to our carbon footprint. Sustainability is the new mantra, screen-printed on our reusable grocery totes. So it can be troubling when we see the repercussions when we bring nature into the neighborhood and blur the line between urban comforts and rural charms. One of those manifestations can be rodents, coyotes, foxes, opossums, and raccoons joining the ‘hood.

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Chronicle of a Death Foretold: Human Sentinels for Disease Outbreaks

By Rebecca Kreston | March 23, 2012 8:47 pm

The bodies of dead crows were found littered through back yards, overgrown meadows, and public parks. We like to attach meanings to events, to craft symbols out of the mysterious and unknown. Birds, in particular, are favorite auguries of ours. These mass crow die-offs were an ugly, sinister sign – what could this mean, mass deaths of creatures customarily seen as living omens of death and the plague?

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Man’s Best Friend, the Turkana Tribe & a Gruesome Parasite

By Rebecca Kreston | January 26, 2012 2:00 pm

Dogs are dirty, dirty animals. I know because I’ve had several, which currently includes a mud-loving, cockroach-catching, drooly mess of a boxer who enjoys nothing more than sleeping her way over every soft surface in my house. The fact that dogs also transmit diseases, and an incredible variety of them at that, does not help matters! Parasites, viruses, bacterial and fungal infections! To their owners! To me, maybe you, maybe your friends! Your relationship with your pet is, in short, a lot richer than you could ever imagine. In light of this, I have a real doozy of a story about the relationship between pet dogs and a miserable little parasite set in the barren desert of northwest Kenya.

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Behind Enemy Lines: Cutaneous Leishmaniasis in Returning US Troops from the Middle East

By Rebecca Kreston | November 4, 2011 1:25 pm

The Soviet invasion of Afghanistan from 1979 to 1988, by all accounts, did not go as well as they had anticipated. The locals were unsupportive of their efforts against the Mujahideen, the notoriously craggy terrain regularly chewed through soldiers’ boots, the Soviet army was frequently unable to provide suitable equipment, food and water to its own troops, and so on.

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

By Rebecca Kreston | October 17, 2011 1:10 am

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.

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Consider the Carpaccio: Looking at Toxoplasmosis

By Rebecca Kreston | April 28, 2011 11:38 pm

A parasite that infects the human brain, subtly changing its personality and social behavior, and capable of passing from mother to infect an infant in utero? That is the essence of a body horror, but this little rascal isn’t fiction. And it gets better: this parasite is considered to be one of the most successful parasites in the world due to its widespread, global distribution as well as its capacity to infect nearly every type of body tissue in all warm-blooded vertebrates (a). Schedule a phone conference with Spielberg and Cruise ASAP, guys, we’ve got the next sci-fi-action blockbuster on our hands (brains?). We’re looking at the ubiquitous protozoa Toxoplasma gondii and research on its capacity to modulate human personality and behavior.

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The Congo, the Crimea & an Eight-Legged Arthropod

By Rebecca Kreston | April 5, 2011 2:06 am

I love this picture of a female lone start tick and her enormous egg mass not just because of the striking imagery, but because it confronts the viewer with a major difficulty commonly encountered in tick and tick-borne disease control – reducing the dangers of a relatively small but fast reproducing species capable of stealthy and lethal infection. Many public health and entomology initiatives focus on mosquitoes but I’ve always found ticks to be the more fascinating arthropod. They’ve got that essential “creepy” factor but they’re also prodigious reproducers and can transmit a slew of truly nasty diseases. Renewed interest for public health practitioners in these creatures stems from the growing problem of habitat change that is resulting in increasing numbers of habitats and climates well-suited to ticks.

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Beating around the Bush: Bushmeat & Emerging Diseases

By Rebecca Kreston | March 18, 2011 3:36 am

Many diseases so familiar to those of us in the study of infectious disease (ID) are of zoonotic, or animal, origin. It’s a long, chilling list – AIDs, SARs, Ebola, West Nile Virus, and dengue hemorrhagic fever are just a few well-known examples. What’s worse is that those just listed have only emerged in the past two decades (1). Frightening stuff. Here’s another alarming statistic: a staggering 75% of novel emerging diseases are of zoonotic origin (2).

One of the most exciting work in the studies of emerging infectious diseases (EID) and, in particular, zoonotic diseases is the work of Nathan Wolfe and his team at the Global Viral Forecasting Initiative. Their pioneering research has primarily focused on the origin and evolution of major IDs amongst mankind, many of which can be traced to originating with animals of different species. The wild animal and human interface seems to be a very rich source of new travel destinations for microbes.

As such, the best place for examining the “who, what, how and why” of novel EIDs, this so-called “viral chatter”, is to venture into regions where this real-life experiment is on-going. For Wolfe and his team, that means examining communities in African forests that rely on the bushmeat trade as a livelihood. By looking at anthropoid primates and their homegrown diseases, Wolfe’s team may give us greater insight into the latest zoonotic disease that may visit a closely related primate, the human. If you’re into gambling, maybe we could even predict a disease that’ll make a lasting jump from a previously wild reservoir into human civilization.

Wolfe’s most seminal research looks at a virus  endemic in most Old World primates native to Africa and Asia. The virus, simian foamy virus (SFV), is a blood-borne, non-fatal virus that is genetically similar to HIV. Wolfe and his team have looked at the presence SFV of in humans as a transmission marker to examine the potential of other such similar viral transmission events between humans and primates. As expected, the more contact people have with primates, especially that of blood and bodily fluids as a result of meat butchering, the greater the likelihood is that they have antibodies to SFV, an indication of immunological exposure to the virus (3).

Previous research examining the phylogenies of HIV-1 and HIV-2, as well as the closely related simian immunodeficiency viruses (SIVs), indicate that the viruses had on the order of eight separate transmission between African monkeys and apes (3). Wolfe’s research gives as a bit of an idea of what the plot background was with those eight separate transmissions, in which these viruses were metaphorically hopscotching between primates and humans and prior to their permanent entry into mankind.

A bushmeat hunter & his kill: a still from Wolfes TED talk

Wolfe’s team is also engaged in viral monitoring in which they track zoonotic viruses with the assistance of bushmeat hunters in Cameroon. Trained hunters take blood samples from their kill by dripping small drops of blood into prepared filter papers that will later serve as samples for their fantastic investigate work into the transmission history between retroviruses (4). Blood samples are also taken from the hunters themselves so as to monitor any evidence of cross-species viral infection with their prey. This surveillance research complements their molecular and phylogenetic based work in that they can monitor the current catalog of viruses in the wild and any potential real-time transmissions between wild animals and bushmeat hunters. Already they have discovered several new retroviruses genetically similar to HIV (5). You can check out his genuinely inspiring talk on TED and get a better idea of the project.

Asking just these kinds of questions is of the utmost importance in the public health field. ID’s already account for 16% of global deaths as is and there are more lurking in the jungles just waiting for some human-wild animal interface (2). Remember the SARS pandemic in 2002? That’s a great example of the sticky, tangled interactions between zoonoses, the bushmeat trade and international travel. An unfamiliar member of the coronavirus family (the common cold is also a member), Severe Acute Respiratory Syndrome (SARS-CoV) virus had never been seen before in humans and it was quite the introduction. In the span of over six months, the extraordinarily infectious virus had infected more than 8,000 people and killed 774 people around the world, 347 of those on the Chinese mainland (6). The virus has the ignoble title of initiating the first pandemic of the 21st century.

As the virus swept China and started appearing in nearby countries, blame focused upon the civet cat, whose meat is considered a great delicacy in Southern China. Many of the earliest cases of SARS were professionals with heavy involved in the bushmeat trade in the Guangdong Province, ranging from breeding, butchering, selling and even preparing and serving civet cat meat (7). Immediate culling of the carnivores, along with two other suspects, the raccoon dog and Chinese ferret badger, commenced in the hope that with the elimination of the primary source, transmission rates would plummet and end the pandemic (8). However, recent research has implicated bats of the genus Rhinolophus as the natural, unaffected reservoir of the SARS virus, not the civet cat (7). Indeed, the SARS pandemic showcased just how rapidly viral evolution can occur. A mutation in the receptor-binding domain (RBD) of a gene known as the spike protein appears to have enhanced the virus’ ability to infect humans (7); indeed this very gene has been implicated before in the ability of viruses to adopt to novel hosts. In the case of this virus, the civet cat was an unwitting intermediate host of a viral spillover from bats that made the transition to humans.

From MSNBC: A civet cat at a wild-game market in Guangzhou, capital of the Guangdong province

It seems like a random fluke, just an evolutionary anomaly in the viral world. A small mutation and a viral protein is suddenly able to bind just a little bit better to a human cell receptor and slink into our cells. And perhaps it would remain just a stroke of bad luck in the viral immunology world except that this isn’t the first time it’s happened. And if the history of infectious diseases is anything to go by, nor will it be the first – just last year we were introduced to influenza H5N1, the ignominiously named “swine flu”. Probably best to stick with a street-meat hot dog as opposed to bushmeat wild dog for the time being.

There is a lot of really fantastic research exploring this issue and much more, including how man-made problems such as deforestation, climate-change, logging, agriculture and even civil conflict have increased contact between humans and wild life. Indeed, bushmeat plays just a small role in zoonotic EIDs. There are complex ecological, biological and social factors involved in disease transmission beyond simply human-animal contact; the host, vector and the pathogen itself are at the whim of the environment, the diversity of human cultures and behaviors, and, as previously mentioned, sheer luck.

Check out these great reviews for more info if you’re interested!

Wild Primate Populations in Emerging Infectious Disease Research:  The Missing Link?

Nathan Wolfe’s talk on his research at TED in 2009

References

(1) Wolfe ND et al. (1998) Wild Primate Populations in Emerging Infectious Disease Research:  The Missing Link? Emerging Infectious Diseases. 4(2): 149-58.
(2) Karesh, WB & Noble, E. (2009) The Bushmeat Trade: Increased Opportunities for Transmission of Zoonotic Disease. Mount Sinai Journal of Medicine. 76(5):429–434.
(3) Wolfe ND. (2004) Naturally acquired simian retrovirus infections in central African hunters. Lancet. 363(9413): 932-7.
(4) Wolfe ND. “Nathan Wolfe’s jungle search for viruses” (video). TED Conference Website. http://www.ted.com/talks/nathan_wolfe_hunts_for_the_next_aids.html. Accessed February 25, 2011
(5) Svoboda, E. “Deep in the Rain Forest, Stalking the Next Pandemic.” New York Times, October 20, 2008. Accessed February 25, 2011.? http://www.nytimes.com/2008/10/21/health/research/21prof.html?_r=2&ref=science&oref=slogin.
(6) “Civet cat crackdown reported in China.” International Herald Tribune, February 19, 2007. Accessed February 25, 2011. http://www.nytimes.com/2007/02/19/world/asia/19iht-sars.4644110.html
(7) Wang L and Eaton B. (2007) Bats, Civets and the Emergence of SARS. Wildlife and Emerging Zoonotic Diseases: The Biology, Circumstances and Consequences of Cross-Species Transmission. Current Topics in Microbiology and Immunology. 315: 325-344.
(8) Childs JE. (2007) Pre-spillover Prevention of Emerging Zoonotic Diseases: What Are the Targets and What Are the Tools? Wildlife and Emerging Zoonotic Diseases: The Biology, Circumstances and Consequences of Cross-Species Transmission. Current Topics in Microbiology and Immunology315: 389-443
ResearchBlogging.org
Wolfe, N. (1998). Wild Primate Populations in Emerging Infectious Disease Research: The Missing Link? Emerging Infectious Diseases, 4 (2), 149-158 DOI: 10.3201/eid0402.980202

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