Zoonotic Diseases: The Next Global Plague?

An in-depth overview of an evolving human health threat

An overwhelming amount of nutritional research implicates the consumption of meat, dairy and eggs as a key cause of cancer, heart disease, diabetes, and other serious illnesses. Industrialized factory farming is also one of the main drivers of environmental degradation, from pollution to global warming, pushing humanity’s very survival toward the brink of extinction. Yet there is another potentially deadly danger linked to the eating and production of animal products: zoonotic diseases that can be transmitted from domesticated farm animals to people.

According to the Centers for Disease Control and Prevention (CDC), an agency of the U.S. Department of Health and Human Services, food borne illnesses are responsible for about 325,000 hospitalizations and 5,000 deaths every year in the U.S. The CDC estimates that at least one-third of these illnesses and fatalities are directly attributable to the consumption of meat. However, this does not account for cases of food-borne illness caused by eating tainted dairy or eggs, the consumption of plant foods contaminated by bacteria originating from animals, or direct contact with infected animals.

The biological symmetries between humans and other animals enable some viruses to leap the species barrier when humans eat contaminated animal flesh, or by infecting farmers working in close proximity to livestock (who in turn become contagious and pass viruses to people with whom they come into contact). Some of these contagions are the result of complex evolutionary processes which make them so novel that the human immune system has not yet developed defenses against them. In other instances, bacteria growing inside the intestines of animals can afflict whoever ingests contaminated food with symptoms ranging from indigestion to fatal organ failure.

However they are transmitted, zoonotic diseases are clearly a grave threat to public health that some virologists say could potentially kill hundreds of millions of people worldwide should any of them grow into pandemics. Fortunately, there are many preventative measures we can take today to minimize the impact of this medical menace in years to come. With this in mind, below is an overview of the most common and emerging zoonotic diseases.

Methicillin-resistant Staphylococcus aureus (MRSA)

• Prevalence: Over 90,000 confirmed cases and 18,000 deaths in the U.S. per year
• Symptoms: Large staph infections (usually on the face, behind the knees, under the arms, and/or on the buttocks) that can turn into abscesses and lethally infect the bloodstream, bones, joints, lungs, and heart
• Transmission: Direct contact between humans and infected pigs; possibly communicable through consumption of contaminated pork products

MRSA (pronounced “mersa”) now claims more human victims in the U.S. than the AIDS virus, and poses the greatest danger to people with compromised immune systems. Scientists have established that MRSA is transmitted to people through direct physical contact with pigs. However, fears that the disease may have entered the human food chain arose in 2008 when three patients in Scotland who had no contact with pigs were diagnosed with a variant strain known as ST398.

A team of independent researchers from the University of Iowa found MRSA present in 70 percent of the 209 hogs tested on 10 different farms in two states. Despite this evidence, the U.S. Department of Agriculture has no plans to test pigs or pork products for infection. Meanwhile, the pork industry categorically opposes testing, claiming that taking such precautions is “unnecessary to protect public health”.

Variant Creutzfeldt-Jakob disease (vCJD, or Mad Cow Disease)

• Prevalence: 117 confirmed deaths worldwide since 1990
  
• Symptoms: Loss of muscle control, changes in personality, impaired memory, and degenerating vision rapidly leading to severe dementia and death
• Transmission: Consumption of beef products infected with prions (aberrant protein agents) from the brain or spinal cord tissue of cattle

For many years, farmers inexpensively fattened cattle to slaughter weight by feeding them a high-protein diet made from the detritus on the slaughterhouse floor — including the bones, entrails, brains, and spinal cords of other cattle, which is where the virtually indestructible prions that cause bovine spongiform encephalopathy (BSE) reside. BSE was nicknamed “Mad Cow Disease” because the prions damage bovine’s brains, causing them to exhibit symptoms of “madness” such as uncoordinated movement, loss of balance, and radical temperamental alterations. People who contract vCJD (the human equivalent of BSE) display similar behavioral abnormalities as the prions rapidly destroy their brains.

The disease typically gestates for a period of years in the body, but usually kills its victims within weeks or months of the onset of symptoms. The vast majority of cases in both humans and cattle have occurred in the United Kingdom, but in the U.S., three BSE-infected cattle have been found, and three humans are know to have contracted vCJD. Notably, the CDC does not require doctors and hospitals to report when patients are diagnosed with the disease (so the number of affected could be considerably higher), and the USDA scaled back its detection efforts by about 90 percent in 2006 based on its claim that there is only “a very, very low level of BSE in the United States”.

H1N1 (Swine Flu)

• Prevalence: In the 2009-2010 outbreak, over 16,455 confirmed human deaths worldwide, including 2,009 deaths in the U.S.
  
• Symptoms: Fever, cough, sore throat, runny or stuffy nose, muscle stiffness, headache, chills, fatigue, diarrhea, and vomiting
• Transmission: Humans contract H1N1 through direct contact with infected pigs (e.g., in hog barns on farms), then spread the virus to other people; there have been no documented cases of infection through consumption of pork products
  

H1N1 (commonly known as “swine flu”) gets its abbreviated name from the hemagglutinin (type 1 of 16) that binds the recombinant human-pig-bird virus to the host cell (the first of 9 types of neuraminidase). The recent H1N1 outbreak is descended from an influenza pandemic that killed more than 50 million people worldwide in 1918 and 1919, and recurred several times throughout the 20th century in different locations. Indeed, the evolutionary trajectory of the virus has been tracked by research identically matching 80 percent of the newest H1N1 strain’s gene sequences to a superbug that first emerged in 1998 from a Smithfield pig processing plant in North Carolina (the top pork-producing state in the U.S.) and ravaged the North American pig population.

While the virus had originally spread from pigs to farm employees working in close proximity to contaminated animals, the first case of a human infecting a hog herd occurred in Alberta, Canada. Soon after this discovery, the Egyptian government ordered the slaughter of the entire nation’s pig population – about 400,000 animals – ostensibly to stem the spread of H1N1 to humans. As the United Nations criticized the move as “a real mistake” that would do nothing to protect the populace, animal rights groups maintained that factory farms (rather than pigs) were responsible for the virus, and culling herds would be cruel and counterproductive.

H5N1 (Avian Flu)

• Prevalence: 486 confirmed cases and 287 human fatalities worldwide; no reported human cases in the U.S.
  
• Symptoms: Viral pneumonia, respiratory distress, and multiple organ failure
• Transmission: Most cases are the result of direct physical contact with infected birds on farms and in live markets, or surfaces contaminated with their feces; passage of the virus from person-to-person remains relatively rare
  

Like other avian flu viruses, H5N1 is naturally present in the intestines of wild birds and rarely causes them to be sick, but this disease is devastating to domestic chickens, turkeys, ducks, and geese unfortunate enough to contract it. Transmitted via saliva, mucus or feces, H5N1 is highly communicable among avian populations, and can very quickly devastate whole flocks (with an average mortality rate near 90 percent) and expand to others. Notably, while this virus does not spread as easily to humans, it is almost as deadly, killing more than half the people it has infected.

H5N1 was first found in the human population in 1997, and while most of the cases have occurred in Indonesia, the virus has also struck African and European countries. Given the relatively high fatality rate associated with H5N1, scientists are concerned about this strain mutating into a form that can pass more easily from person-to-person and cause a global pandemic that could claim hundreds of millions of lives. Laboratory research suggests that medications currently on the market could be used to effectively treat people for avian influenza, but experts also warn that the virus could quickly develop resistance to these drugs.

Salmonellosis

• Prevalence: Kills several thousand people worldwide (approximately 580 in the U.S.) every year
• Symptoms: Fever, abdominal cramps and diarrhea (which can spread infection to the bloodstream and become fatal)
• Transmission: Salmonella typically infects people who consume foods contaminated with animal feces (usually meat, milk or eggs, but salmonella-tainted manure from farms can also poison fruits and vegetables)

With more than 40,000 cases diagnosed each year in the U.S., salmonellosis is among the most common intestinal infections affecting the human population. Infants, the elderly and persons with compromised immune systems are the most vulnerable to salmonella bacteria, which comes from the digestive tract of birds, reptiles and mammals. Studies have found that about 25 percent of chickens sold in the U.S. are contaminated with salmonella.

Persons infected with salmonella typically exhibit symptoms within 6 to 48 hours of ingesting the bacterium, and recovery usually takes about a week. Antibiotics are often not an effective treatment for salmonellosis because many strains have become antibiotic-resistant, and because these compounds can slow the process of intestinal shedding necessary for recuperation. Cooking food thoroughly and washing all surfaces that come into contact with raw meat can help prevent the spread of infection.

Escherichia coli 0157:H7

• Prevalence: Causes approximately 73,480 illnesses, 2,168 hospitalizations and 61 deaths a year in the U.S.
• Symptoms: Abdominal cramps, diarrhea, fever, and vomiting; approximately 10 percent of subjects (mostly children and the elderly) develop haemolytic uraemic syndrome (HUS), a disease that causes acute renal failure in as many as 5 percent of those who contract it
  
• Transmission: Most infections are the result of physical contact with infected people or animals, or the consumption of contaminated water or food (most commonly milk or cheese that has not been pasteurized); can also be passed from person to person
  

One of the most common bacteria living in the digestive tract of humans and other animals, E. coli is usually harmless to its hosts. However, some strains make people sick, and one particular variety that has developed in the intestines of cattle (E. coli 0157:H7) has the power to kill. Research indicates that as much as 3 percent of the U.S. cattle herd may harbor this deadly contagion.

E. coli spreads very easily, as ingesting only a tiny amount of bacteria (as little as 10 microbes) can cause serious illness and even death. Food contaminated with E. coli looks, smells and tastes the same as nontoxic food, so it is impossible to tell using just one’s senses whether meat, dairy and other products (such as alfalfa sprouts and other vegetables) are safe to eat. Cooking food thoroughly and washing all surfaces that come into contact with raw meat can help prevent the spread of infection.

Campylobacteriosis

• Prevalence: Approximately 2.4 million cases and 124 deaths in the U.S. every year
• Symptoms: Diarrhea, abdominal pain, nausea, vomiting and fever; can become life-threatening to persons with compromised immune systems if it infects the bloodstream
• Transmission: Most cases are caused by eating raw or undercooked poultry, or cross-contamination of other foods by infected flesh; outbreaks are also associated with the consumption of unpasteurized milk or infected water

By far the most common cause of food-borne illness, campylobacter affects almost 1 percent of the U.S. population every year. This bacterium naturally resides in the intestinal tracts of mammals and birds, doing them no harm. However, ingesting it can cause humans to suffer severe sickness and even death.

Studies indicate that more than one-half of raw chicken carcasses sold in the U.S. contain campylobacter. However, it is a relatively fragile bacterium that can be killed by drying, exposure to oxygen, excessive heat (i.e., cooking), and the pasteurization process. Cooking food thoroughly and washing all surfaces that come into contact with raw poultry can help prevent the spread of infection.

Factory Farms: Breeding Grounds for Zoonotic Diseases

Meat-borne diseases have plagued humankind since our pre-historical hunting and gathering days, but a relatively recent (mid-20th century) agricultural innovation – factory farming – has created a “perfect storm” of conditions for the rampant development and rapid dissemination of new pathogens among the human population. Some of the profit-driven techniques steering the world toward impending disaster include:

• Overcrowding – Factory farms typically cram thousands of animals together in a single massive building where they spend most of their lives. Population density is increased through the use of intensive constriction devices, such as battery cages (for egg-laying hens) and gestation crates (for pregnant sows). Keeping animals packed together in regimented rows saves space and makes large farms easier to manage, but also greatly amplifies the spread of contagions through constant close contact.

• Environmental deprivation – The stress caused by intensive confinement, lack of exercise, unnatural diet, absence of sunlight, taking children away from mothers, and other traumatic factors impairs animals’ immune systems to the point where their bodies become dangerously susceptible to disease. The living conditions at Concentrated Animal Feeding Operations (CAFO) are so bad that many animals would not survive without the antibiotics farmers constantly feed them. In fact, the Union of Concerned Scientists estimates that about 70 percent of the antibiotics administered in the U.S. are given to farm animals, an abusive practice that is making these drugs less effective in the treatment of human diseases.

• Substandard sanitation – The average CAFO generates millions of gallons of waste a year, and animals therefore typically wind up standing and lying in their own decaying feces. As the waste putrefies on the ground, it also fouls the air with ammonia, methane, hydrogen sulfide, and other toxic gasses that diminish immunity and breed respiratory infections. Not surprisingly, microbes from animal feces are the primary source of most foodborne pathogens, often contaminating meat during the slaughter process.

Downed animals – those too sick or injured to stand or walk – are more likely to carry dangerous viruses or bacteria that can be transmitted to humans who come into contact with them or eat their flesh. In March 2009, the U.S. government announced a new rule banning the slaughter of all downed cattle, a move that will help protect the public from zoonotic diseases and prevent much unnecessary animal suffering. However, it is still legal to cruelly force other species of animals to the kill floor for processing by prodding them with electric shocks, dragging them by chains, or pushing them with forklifts.

As long as producers can make even a small amount of profit from the flesh and blood of downed animals, there will be an incentive to abuse them without regard for their suffering and endanger people’s health by processing potentially diseased animals into food. You can take a stand for human health and farm animals by going vegan and contacting Secretary of Agriculture Tom Vilsack urging him to extend the ban on slaughtering downed cattle to all animals used for food.

President Obama Announces Downed Cattle Ban

Decision is a milestone victory for animal welfare and food safety

Today, President Barack Obama announced in his weekly video address that the U.S. Department of Agriculture (USDA) will finally ban the slaughter of all downed cows for food. This is a major win for animal protection and consumer health advocates that has been in the making since the early 1990s, when organizations like Farm Sanctuary and HSUS started pushing the government to pass legislation prohibiting producers from dragging sick, crippled cattle to the killing floor for processing. Significantly, Obama took action on this important issue only 54 days into his still-young presidency, sending the message that he takes food safety and animal welfare seriously.

Elected and appointed officials must (or should) know by now that downed animals are far more likely than their ambulatory counterparts to carry diseases such as mad cow and bacteria like E. coli that can be fatal to humans who eat their meat. During one of the eight congressional hearings held last year following the largest beef recall in U.S. history, many of them would have also seen HSUS’s undercover video exposé showing workers at the Hallmark/Westland Meat Company packing plant in Chino, California abusing downed cows by ramming them with forklifts and shocking them with electric prods. Nevertheless, the USDA has allowed producers to process cattle who become downed after reaching the slaughterhouse since 2007. The ban Obama announced today will close this legal loophole by permanently prohibiting the slaughter of all downed cattle for food, no matter when they become disabled.

Animals typically become downers because of the way they are raised on factory farms: genetically bred for fast growth, crowded together or confined in cages or crates, mutilated without anesthetic, and fed garbage, the only reason that any factory farmed animals can actually walk to their own deaths is that they are routinely pumped up with non-therapeutic antibiotics. Because downed animals are already suffering greatly when they get to the slaughterhouse, current laws must be reformed to require timely euthanization of cattle deemed unfit for human consumption in order for the ban to actually prevent animals from lingering in pain. I assume that such a provision will be put in place (but cannot presently find any corroborating details), and that some kind of enforcement mechanisms will be implemented.

Political Prognostications and Appointees

In September 2008, I wrote a blog post analyzing Obama’s record on animal issues, concluding that he would be far more likely to support and promote animal causes than his opponent, Republican candidate John McCain, based on their respective legislative histories. In January, I wrote my monthly column for The Animal World magazine about Tom Vilsack, Obama’s appointee to Secretary of Agriculture, examining his public service career and speculating as to whether he would challenge Big Ag's mistreatment of animals. Well, it seems like the administration is on the right track so far: here’s hoping they keep up the momentum and accomplish even more for animals in the coming four years.

Secretary Vilsack called the downed cow ban "a step forward for both food safety and the standards for humane treatment of animals," which is a brave statement for someone in his position, given that most previous Secretaries of Agriculture have been unwilling to even acknowledge farm animal welfare as a legitimate concern for fear of blowback from powerful agribusiness interests. For his own part, President Obama also made some bold assertions in his video address. For example, after qualifying that "the United States is one of the safest places in the world to buy groceries at a supermarket," he called the nation’s food safety inspection system a "hazard to public health," noting that the annual number of contaminated food outbreaks in the U.S. today is more than triple what it was just 15 years ago.

Alerting viewers to the fact that the Food and Drug Administration (FDA) has been so underfunded that it can only inspect about 5% of the nation’s food processing facilities every year, President Obama promised that his new pick for FDA Commissioner, Margaret Hamburg, will change all that — and start by hiring more inspectors. "Dr. Hamburg brings to this vital position not only a reputation of integrity," Obama said, "but a record of achievement in making Americans safer and more secure." There’s absolutely no question about it, Hamburg's résumé is impressive, so it’s not surprising that both public health advocates and food industry groups are praising the pick. According to Obama, the work of Hamburg and her Deputy Commissioner at the FDA, Dr. Joshua Sharfstein, "will be part of a larger effort taken up by a new Food Safety Working Group" that will advise the president "on how we can upgrade our food safety laws for the 21st century; foster coordination throughout government; and ensure that we are not just designing laws that will keep the American people safe, but enforcing them."

Pigs: The Other Downed Animals

The downed animal ban announced by President Obama applies only to cattle, leaving downed pigs, sheep, goats, and other farm animals to suffer the cruelty inherent in dragging, pushing or otherwise coercing large animals onto the kill floor. Pigs are also known to carry transmissible diseases from which humans have died and approximately 100,000 downed pigs go to market each year, yet for the foreseeable future, these animals will continue to suffer cruelty while the pork-eating public remains at risk. And don’t forget that salmonella poisoning kills about 1,500 humans every year, and that approximately 15% of chickens sold in the U.S. are contaminated with salmonella.

People who eat meat must understand that as long as agribusiness corporations insist on treating animals like interchangeable biomachines instead of individual living creatures, meat will be swarming with bacteria from feces and other unsanitary substances that are part and parcel of the assembly-line factory farming system. That is, improvements in animal welfare and food safety are intimately connected — and you can’t have one without the other. So please, urge your legislators and President Obama to expand the downed animal ban so that it protects all farm animal species.

Turd Sandwich

Why are there bugs, rat hairs and feces in our supposedly "vegan" food?

Hold onto your gag reflex before reading "The Maggots in Your Mushrooms," an Op-Ed in yesterday’s New York Times which points out that insects, rodent fur, "foreign matter" like cigarette butts, and other barfworthy ingredients are all commonly present in the foods we eat — even though you won’t find them listed on the labels. That's because the USDA doesn’t especially consider these nauseating items health hazards, but rather unavoidable "aesthetic" defects, and has established standards to regulate the amounts of detritus that various foods can legally contain before being deemed unfit for human consumption. For instance, tomato juice can include 10 or more fly eggs per glass, 25 grams of curry powder can have over 100 bug fragments, and up to 2,500 plant lice may be swimming in a bottle of beer. These government-sanctioned criteria leave the average person scarfing down two to three pounds of bug-hair-crap-matter every year.

Yuck, to be sure (even though insects are considered delicacies in some cultures), but the real gross-out factor here for vegans is the fact that even many supposedly vegan foods are not really vegan because they contain parts of dead bugs and other animals (that just happened to get mixed in there during the manufacturing process). While we vegans like to think that our diet is "pure" (in the sense that we don’t eat any creature that crawls, flies or swims), there is certainly no guarantee of this, especially if we purchase packaged foods or patronize restaurants. The good news is that we can avoid most of these unsavory contaminants by preparing fresh produce, grains, beans, etc. at home from scratch.

Meat Is Murder — And Icky!

Notably, the Times piece doesn't even mention the revolting substances found in meat, milk and eggs. Of course, as a vegan, I find the idea of eating animal flesh or secretions to be just as repugnant as ingesting bugs, if not more so — which is why I can continue eating what I do, even knowing what (and who) is actually in it. I figure most meat eaters must rely on a considerable amount of cognitive dissonance just to prevent themselves from being aware that the organisms they’re devouring were once actually living, breathing creatures made up of blood, veins, intestines, and other internal organs that produce things like piss and shit…which, by the way, are far more prevalent in meat, dairy and eggs than plant-based edibles. Food-borne pathogens such as salmonella, campylobacter and E. coli can certainly wind up on tomatoes and spinach, but the primary source of these dangerous bacteria is animal feces.

According to the Centers for Disease Control, there are around 75 million cases of food-borne illness in the U.S. every year, about 5,000 of which are fatal. Food contaminated with animal feces (whether by direct contact or agricultural runoff) is the number one cause of these infections, and meat is the main agent by which they spread. That is because animal flesh is exposed to fecal matter during every step of the production process — from the crowded factory farm, where animals live in their own filth, to the slaughterhouse kill floor, where the fetid contents of their bowels can spill into the "product" when their stomachs are eviscerated from their still-warm carcasses.

A person infected with even the most miniscule amount of E. coli may, for example, suffer seizures, neurological damage or a stroke — all from eating a little bit of shit. Unfortunately, modern industrial production methods only make the problem more widespread. Hamburger meat, for instance, is processed by the ton in gigantic grinders before being shipped all over the country, meaning that a single fast food burger may contain flesh from dozens or even hundreds of different animals, and a single diseased animal can taint over 16 tons of beef. Yet the E. coli bacteria is so resilient that it can survive freezing and direct temperatures exceeding 150 degrees, so if you do still eat meat (though I’m ethically against it), definitely cook it thoroughly before consuming.

But (you may protest) the meat industry, and government regulatory agencies, are always looking out for our best interests, right? Well, let me tell ya, they have a way of dealing with this disgusting and life-threatening dilemma...but you might not like it. Their solution: irradiate meat products, which disrupts the bacteria’s DNA so they can’t reproduce but doesn’t kill them. In other words, if you eat irradiated meat, you’re still eating shit, even if the massive number of microbes feeding on it can no longer get busy. But then this leads to more shit in your food, because if producers can just blast meat with radiation to make it "safe" (forget palatable), why should they even bother trying to keep fecal matter out of it?

OK, Life Itself is Kinda Gross…

It is not possible to exist without harming or ingesting bugs, as it were, since the vast majority of them are microscopic, and live on and within us by the billions. In fact, scientists claim that our bodies are composed of about ten times as many microbes as human cells. That means that in terms of each person's biomass (i.e., the total volume of living cells in a body), approximately 10% is human, and the other 90% or so is "other" (so to speak). Just think about it: there are about three pounds of bacteria in your digestive tract alone, and many, many more microbes crawling in and around your body at any given moment than there are humans on the Earth.

These single-celled organisms are (evolutionarily speaking) about 3.5 billion years older than humans, and have a symbiotic relationship with every living creature on the planet. As a result, not so surprisingly, they basically control all of our essential biological functions, from maintaining the surface of our skin to breaking down the food we eat. If it weren’t for these tiny, virtually weightless entities, our bodies would literally just fall apart — and yet, without us, they would do just fine.

Which is precisely why the future of medical science may very well depend on a more complete knowledge of these fascinatingly mysterious life forms. David A. Relman, a microbiologist at California’s Stanford University and chief of infectious diseases at the VA hospital in Palo Alto, believes that "A better understanding of the indigenous microbiota of the human body will lead to much more prudent strategies for maintaining and restoring health." This may (or may not) be putting it mildly: in his book Tomorrow Now: Envisioning the Next Fifty Years, futurist and speculative fiction writer Bruce Sterling predicts that microbial medicine will soon become the very foundation of all health care.

...but this shit doesn't just "happen"

When the USDA says that the presence of fecal matter and other contaminants in our food is "unavoidable," what they really mean is that it would cost producers (and therefore consumers) more to ensure that our food is safe and consistent with our cultural standards. OK, so tens of millions of people get sick, and about 5,000 people (mostly children and the elderly) die every year from food-borne pathogens, while fundamentally repugnant stuff is made an inherent part of our food supply: that’s just the cost of doing business…and of making a hefty profit. Sarcastically speaking, we can’t seriously expect the multi-billion dollar food industry to uphold higher quality standards: I mean, they might make less money!

Essentially, contamination of food (whether vegan or otherwise) is not unavoidable: the USDA merely refuses to hold companies accountable for harming their customers. But there are still ways that you can help reduce the number of food-borne pathogens in our food:

- Go vegan: This will lower your own chances of contracting a meat-borne disease while also diminishing the number of animals on factory farms, thereby decreasing the volume of feces produced by livestock (and thus the incidence of food-borne illness).

- Encourage legislators to pass food safety laws: Visit the Center for Science in the Public Interest Web site to see what laws are being considered, then contact your legislators urging them to support those you agree with.