Interview on dunnbooks.com

Adam Dunn, author of Rivers of Gold and The Big Dogs, has posted an interview with me on his website, dunnbooks.com. Dunn's latest book deals with a different kind of "parasite:" the less than saintly financial gurus of Wall Street. My favourite review of The Big Dogs (for obvious reasons) is "Dunn's writing is like the candiru fish. It squirms its way into one's cerebral cortex & is quite difficult to dislodge." (Col. Lee T. Guzofski, Chief Executive Officer, G2G Enterprises, Inc.)

It was a pleasure corresponding with Adam Dunn.

Drinking Surface Water

While discussing a relatively low coliform and E. coli count in well water recently, a water treatment professional told me that he didn’t think drinking this water would be any worse than drinking from a stream.

[caption id="attachment_331" align="alignleft" width="300" caption="Don't drink surface water"][/caption]

What?

My initial response to this is that one must understand it’s not the E. coli and coliforms that we need to worry about. These organisms are markers for fecal contamination of water. Your guts and my guts are already full of them. It’s the other things that come with feces that make it imperative we take a low count seriously—viruses such as Hepatitis A, and parasites, such as Giardia, Cryptosporidium, and Toxoplasma. If E. coli and coliforms are in your water, these other things might be there too. Boil.

And furthermore, the days when we could safely drink from streams or other surface water are long gone. Yes, it may look crystal clear. It may be flowing through “pristine” woodland (is there such a thing any more?), but beavers and other mammals living near water carry Giardia; migrating birds carry Cryptosporidium, and wild cats can contaminate water with Toxoplasma. A lot of other things could be there too. Maybe you’ll get away with drinking from a stream, and maybe you won’t—all surface waters are contaminated.

There are seven billion people on Earth now, all defecating daily (and millions don’t have toilets). There are still municipalities that discharge untreated sewage into surface water—rivers, lakes, and coastal marine water. There are millions of cows living in feedlots, and millions of feral cats – their wastes often wash off land into surface water. There are millions of migrating Canada geese in North America, visiting surface water all along their migration route.

It has been said that if feces were fluorescent, the tropics would glow at night. Let’s face it, if we include animal feces, the entire temperate region and much of the arctic/antarctic would glow as well. Boil.

Naegleria fowleri, Terror of Swimmers

It’s two thirds of the way through a long hot summer (in some places) and numerous swimming holes have had lots of time to warm up to temperatures well above average. Tragically, this sometimes results in deaths due to infection with Naegleria fowleri, especially in warmer regions such as the southern United States. Naegleria, sometimes referred to as the “brain-eating parasite,” is an environmental amoeba that can, given the opportunity, gain access to the human brain through the back of the nose.

Naegleria Thrives Where Water is Warm

Naegleria does not habitually parasitize humans, but it does multiply in warm waters, and if swimmers draw water up the nose, infection can follow. (This year, one victim reportedly infected himself using a neti pot – a device used to rinse the sinuses.) Once infected, very few people survive the dreadful illness that Naegleria causes. Victims, of course, are typically those who enjoy water sports and games – the young, fit, and healthy.

Deaths due to N. fowleri are often widely reported, especially now that we have the internet. After such a death, people call for disclosure of the bodies of water involved, more public education, and surveillance. This is entirely understandable, but these demands really do miss the point. Naegleria is an environmental organism, widely distributed in nature, and well known for multiplying in warm bodies of water. It could be in any warm water, even the stuff in your hot water tank (as in the neti pot story). We can’t eradicate it, or even pinpoint where it will turn up next except in the most general terms.

If you really want to avoid this risk (and it is a small small risk) don’t swim in water warmer than 80F (26.7C). Never draw warm water up your nose unless it has been sterilized. If there is a risk of drawing water up the nose, use nose plugs or a nose clip.

Naegleria Deaths in Perspective

The reality is that any activity carries a certain risk, even sitting at home. For comparison, the number of fatalities from N. fowleri in the United States in the decade from 2001 to 2010 is thought to be about 30, an average of three per year:

• In that same time period, National Geographic reports that more than 400 people were killed by lightening.


• In 2004, an average of nine people accidentally drowned per day in the United States (Poseidon).


• In 2004, almost 4000 people died in fires, mostly residential.


• Each year, more than 33,000 people are killed in automobile accidents in the United States (NHTSA).

Deaths due to N. fowleri are quick, horrifying, and tragic, but this disease shouldn’t be blown out of proportion. It’s rare. Exercise reasonable caution while swimming (submerged hazards, drowning, pathogens, dangerous aquatic animals etc.) and enjoy the summer.

Is Babesia Spreading or Not?

Babesia microti was first recognized as a potential cause of human infection in New England in 1969. Before this, human cases of babesiosis involving other Babesia species were recognized in other places, chiefly Europe. The appearance and persistence of Babesia microti have been associated with high deer populations, increased human contact with the deer tick, Ixodes scapularis, and the presence of Lyme disease.

[caption id="attachment_316" align="alignleft" width="300" caption="Ixodes scapularis, image by Stuart Meek"][/caption]

In 2003, a paper published in the American Journal of Tropical Medicine and Hygiene noted “Human babesiosis generally is detected in sites where Ixodes ticks are endemic only after Lyme disease has become well established” (Krause et al, “Increasing Health Burden of Human Babesiosis in Endemic Sites," 68(4)). Why?

It’s tempting to explain away the late appearance of babesiosis by saying, well, physicians aren’t familiar with it, no one is looking for it, and most cases are mild anyway, so it’s simply being missed. As well, no one’s collecting data on diagnosed cases, so the incidence is unknown.

A current article published on SouthCoastTODAY.com discusses the work of Stephen Rich at the University of Massachusetts Amherst's Laboratory of Medical Zoology (Clark, “Much to Learn About Babesia’s Spread”). Rich’s research on Ixodes scapularis suggests that Babesia microti is spreading inland at a much slower rate than Borrelia burgdorferi, the organism that causes Lyme disease.

Rich’s work tells us that the organism truly is not well established in new locales – there’s not as much of it there. This likely explains why cases of babesiosis lag behind cases of Lyme disease, but it still raises a big question mark. If ticks and Lyme are spreading, why is Babesia not spreading just as quickly? The answer isn’t clear, but it appears that something is slowing down transmission of Babesia from host to host.

Rich doesn’t say that Babesia is absent in places where ticks and Lyme have appeared, he says there is a “much lower incidence” (qtd. in Clark). I suspect that incidence will rise over time – it may take years – and eventually make babesiosis a significant health concern over a much larger geographical area. I hope surveillance and medical knowledge stay ahead of it. If nothing else, the risk of contamination of the blood supply should fuel increased interest in this organism.

Where Did Toxoplasma gondii Come From?

Toxoplasma gondii, one assumes, evolved as a parasite of cats. Is this a safe assumption? All the texts tell us that the cat is the only animal in which T. gondii completes the sexual phase of its life cycle, which is strong evidence for the cat being the original host. It is possible that there are other hosts in which T. gondii can produce gametocytes and reproduce sexually – maybe we just haven’t found them yet. Maybe we haven’t looked exhaustively either. Nonetheless, in the absence of evidence to the contrary, I’ll stick with the assumption that T. gondii evolved in cats.

T. gondii was first discovered in Tunisia in 1908. By coincidence, Northern Africa is also one of the places where the cat is thought to have been domesticated (there or present day Iraq) and this explains my somewhat illogical but long held assumption that T. gondii probably evolved in Africa. There is actually no reason why the parasite couldn’t have evolved in some other feline species and spread to domestic cats later.

One theory has it that T. gondii evolved in South America.

[caption id="attachment_309" align="alignleft" width="162" caption="Did prehistoric jaguars have T. gondii?"][/caption]

The paper “Globalization and the Population Structure of Toxoplasma gondii,” reports an odd distribution of genotypes: one is found worldwide, one is found everywhere but South America, and several more are found only in South America. The authors' (Lehmann et al, PNAS July 25, 2006) interpretation is that there was an early split, originating in South America and leaving two populations to evolve in isolation from each other. One evolved in the “old world” and today is found everywhere but South America. The other is found everywhere, but apparently only spread very recently from its origins. Several more never left South America.

So maybe Toxoplasma gondii came from a prehistoric cat species in South America. It's a place to start.

(Image by Simon Burchell. Creative Commons)

Must We Hate Worms?

Is the revulsion we feel toward intestinal worms (in fact, anything called a parasite) innate or learned? If we hadn’t been surrounded by the “yuck factor” all our lives, grossed out by anything that wriggles or crawls, would we view them with disgust or curiosity? I think it would be more in the realm of curiosity.

In his book Parasites and Parasitic Infections in Early Medicine and Science, R. Hoeppli describes early attitudes toward parasites. Even within the last few hundred years, many people believed they arose spontaneously from intestinal contents, blood, even dust and ashes. And “in China,” he writes, “there existed from ancient times the widespread belief that one should have at least three worms in order to remain in good health” (p. 164).

Robin M. Overstreet has investigated the deliberate ingestion of parasites for various reasons by humans and found that parasites are often deliberately eaten and sometimes even regarded as delicacies (“Flavor Bugs and other Delights,” Journal of Parasitology: 89(6)). Overstreet describes a boy “open[ing] the intestine (of a possum) where a lump existed to allow the tapewoms to squirt out, remov[ing] the feces from the worms, and drop[ping] each writhing organism straight into his mouth.”

A former co-worker described an encounter with a small boy who was playing with a rather large roundworm, whirling it around while holding on to one end. When asked where he got it, he calmly indicated that it had come out of his nose.

These things suggest that a horror of worms is not a natural characteristic of humans. Similarly, Hans Zinsser writes that “as wise a man as Linnaeus suggested that children were protected by their lice from a number of diseases” (Rats, Lice and History, p. 139).

[caption id="attachment_301" align="alignleft" width="249" caption="Portrait of Carolus Linnaeus by Alexander Roslin, 1775"][/caption]

I’ve often suggested that if it were possible to keep mosquitoes out of your back yard, it would be socially unacceptable to have any there. I believe that’s what’s happened to parasites. If they were unavoidable, we’d accept them as part of life, like mosquitoes and mud puddles. In the handful of decades since we’ve been able to avoid having parasites in developed countries, we’ve also learned to abhor them.

Getting Parasites from Animals

An article by Peter Michael on couriermail.com.au (“Dingo Poo Spreading Deadly Parasites to Humans,” July 13) interests me for several reasons. First, the “deadly parasite” involved is Ecinococcus granulosus, which is by no means a new parasite for people in many parts of the world. It was once a big problem anywhere sheep were raised because sheep dogs could pass the worm’s eggs to people. Today, mostly because sheep dogs typically get better preventative care, the parasite is slowly losing ground.

It’s a bitter twist, then, that wild canines that have lost their fear of humans and come into human communities are now a source of infection. Therein lies the other thing that interests me. A few of the people who commented on that article have it right: it’s not that these wild animals are “encroaching” on us; it’s that we have encroached on them, and we’ve been doing that ever since the first human settlements with the beginning of agriculture and domestic animals.

[caption id="attachment_296" align="alignleft" width="200" caption="Dingos by Joshposh, Creative Commons 3.0"][/caption]

Before we grew our own food and raised animals, how often would we have come in close enough contact with an animal to catch a disease? Sporadically: when an animal was killed for food, when we shared the same cave perhaps, and by accident. Now we breed them and invite them in by carelessly providing food: cattle, pigs, birds, dogs, cats, fish, raccoons, dingos, rats, mice, and lots more. Meanwhile, we destroy their habitat and oblige them to adjust. Civilization is bad for our health: so many devastating diseases would be rare if we had not settled down and brought animals, and their parasites, into our space, one way or another.

Of course, without civilization, people would be rare as well. Most of us wouldn’t be here, I wouldn’t be writing this, and there wouldn’t be an internet. So one wonders, was it all worth it, and where does it stop?