Bird Flu, Avian Superhighways, and the Perils of Messing with Mother Nature
What you need to know
"It's just the flu," you say. Although you get a shot every fall, you know that vaccinations don't cover every strain. But if you've been following recent news reports, you might wonder if the next time you roll up your sleeve, you should see a veterinarian or a physician!
Last month for the first time, bird flu, also known as Avian influenza, was detected in dairy cattle in Texas and Kansas. Outbreaks in Michigan, Idaho, and New Mexico dairy herds have followed. Now this week, there's more startling news: a dairy worker suffering from pink eye at a Texas operation was diagnosed with the virus causing avian influenza after exposure to infected cows.
This case, confirmed by the Centers for Disease Control and Prevention (CDC), is only the second human case of avian influenza in the U.S. In 2022, the first human case of avian influenza was reported after a Colorado farmer who worked with poultry complained of fatigue. The CDC warns that anyone with exposure to infected birds or livestock has a greater risk, since they're exposed to high levels of the virus.
Public health officials have hastened to downplay the human risk of bird flu from consuming milk. Infected cows are taken out of milk production, and pasteurization also kills the virus. (People should avoid unpasteurized milk and raw cheese.) The bird flu is not deadly to cows.
Bird flu takes flight again
Unfortunately, Iowans are all too aware of the impact of avian influenza in poultry. Off-and-on, over the past nine years, millions of chickens and turkeys have been destroyed after being infected with this highly pathogenic virus typically spread by wild waterfowl shedding it as they pass over Iowa during their spring and fall migrations.
Fortunately, the H5N1 bird flu doesn't easily affect the human upper respiratory tract. However, there's some evidence it could bind to receptors in the lower respiratory tract. According to the CDC, the U.S. has a limited stockpile of vaccines for H5N1 and related bird flu viruses, in case of a human outbreak. But it would need to ramp up quickly.
What else should we know about emerging diseases like the bird flu and their interface with human health?
Human-Animal Interactions
Zoonotic diseases are diseases that pass from animal to human. In the past four decades, more than 40 of these infectious diseases have emerged. Here are a few of the most well-known:
· AIDS (acquired immunodeficiency syndrome), caused by the HIV virus carried by a nonhuman primate
· SARS (severe acute respiratory syndrome) caused by a novel coronavirus in small Asian wildlife
· Hantavirus pulmonary syndrome, carried by the deer mouse
· Monkeypox, known as mpox, caused by African rodents
· Ebola hemorrhagic fever in central Africa, most likely originated in fruit bats
· West Nile virus encephalitis carried by birds and transmitted by mosquito bites
· Lyme disease caused by deer ticks
· H1N1 swine influenza virus (2009), contains gene segments of humans, birds, and pigs
· Covid-19, a novel coronavirus with more than three different variants (animal source: bats)
What's triggering these outbreaks? Scientists have identified environmental, economic, social, and scientific factors. This includes greater movement of people, animals, and plants across national boundaries, as well as population overgrowth. The Institute of Medicine, a research arm of the federal government, cites the following 13 factors:
1. Microbial adaptation and change
2. Human susceptibility to infection
3. Climate and weather
4. Changing ecosystems
5. Human demographics and behavior
6. Economic development, land use
7. International travel and commerce
8. Technology and industry
9. Breakdown of health measures
10. Poverty and social inequality
11. War and famine
12. Lack of political will
13. Bioterrorism
Remember that guy, Anthony Fauci, from the Covid-19 outbreak? As you'll recall the first human cases were linked to human contact with wild animals infected by bats in China. Looking back to a 2003 column I wrote in Successful Farming about the factors causing emerging infectious diseases, I found this quote: "A substantial proportion relates to man's manipulation of ecology," Fauci said. In other words, beware of humans messing with Mother Nature.
Reducing Pandemic Potential
Agriculture plays a key role in emerging infectious disease outbreaks and their Intersection with public health. Most cases of influenza jumping species involve hog and poultry confinements. In Asia and China, proximity to people, pigs, and waterbirds is a common link.
The Hong Kong flu (H5N1) in 1997 was spread by poultry: 1.6 million chickens were culled. SARS, linked to small Asian animals considered culinary delicacies, multiplied to 8,000 cases in 2003, resulting in 700 deaths in 29 countries.
Concentrated livestock operations in tropical, underdeveloped counties without public health safeguards are especially vulnerable. The Nipah virus jumped species in 1998 after a 15,000 head hog confinement replaced fruit orchards in a Malaysian mountain valley. Fruit bats shed the virus, infecting the hogs, and the hogs infected the workers. A total of 265 people were infected; 105 died. A total of 1.1 million pigs were culled.
Confined animal agriculture, including the dairy cattle in Texas and other states infected with bird flu, can be a breeding ground. This week, Cal-Maine in Parmer County, Texas, the largest U. S. egg producer reported it had detected bird flu and was culling about 1.6 million hens and 337,000 young hens. Backyard chicken flocks also are vulnerable, but the spread and the financial impact are limited.
So far, Avian influenza hasn't been confirmed in beef cattle. In the Texas Panhandle, dairies are commonly located near huge outdoor beef feedlots. However, in many Midwestern states, small beef herds aren't confined.
Animal husbandry practices also can be a factor. When agriculture changes, pathogens adapt. BSE (bovine spongiform encephalopathy) came from the practice of feeding meat and bonemeal to cattle in a misguided effort to increase efficiency. It was linked in 1996 to the rare variant Creutzfeldt-Jakob disease in humans.
Failure to protect natural landscapes is a critical fault line. Extensive land clearing of rainforests across the globe allows pathogens to hitch a ride with vectors. New dams and irrigation systems provide new pools of stagnant water in different places. In 1977, standing water behind Egypt's Aswan Dam produced swarms of mosquitoes. A total of 200,000 people were infected with Rift Valley Fever; 498 died.
As suburban development encroaches onto farmland, humans encounter animal vectors for disease transmissions: ticks, mosquitoes, bats, birds, and rodents.
Global warming, also exacerbated by humans, is raising the risks of emerging infectious diseases, as animal vectors expand into new regions with milder winters, warmer summer, and fewer days of frost.
Mother Nature vs. Human Nature
Wild birds have been migrating across North American flyways for millenniums. No doubt Avian influenza has winged its way in tandem. What has changed? Human interactions with the natural world.
Avian influenza in mammals is a source of concern. Last month, in Minnesota, a young goat on the same farm as infected chickens tested positive for bird flu. In August 2023, it was detected in marine mammals in South America; it invaded a mink farm in Spain in October 2022. Bird flu was found in red foxes in seven U.S. states in 2021, including Iowa, as well as in bobcats in Wisconsin.
There's no reason to expect the threat of similar emerging infectious diseases to diminish. Humans are likely to continue flirting with the risks of potential pandemics as long as they are turning a profit. Looming beyond the unintended consequences of a pandemic, however, emerging infectious diseases are a national security threat when weaponized by hostile countries.
I'm not an infectious disease expert. But we need more stoplights at the intersections of human, livestock, and wildlife health. The evolution of infectious diseases is a numbers game. Eventually, over time, animal pathogens adapt, increasing human risks.
There's no doubt that manipulating our ecology and environment has improved our human lives. Yet we've lost respect for Mother Nature and for the critical role of healthy ecosystems in reducing zoonotic disease spillover into humans.
Twenty three years ago, I wrote this in a Successful Farming column:
"I believe human arrogance is a driving force behind new threats to public health. The problem of looking at disease from a human standpoint alone is that we're all in this together. These outbreaks demonstrate we're part of an intricate ecological chain.
"Animal and human health are intertwined. If we ignore our interconnectedness, agriculture risks becoming a detriment to public health. A dose of humility would be good for our health."
One World, One Health initiative: http://www.onehealthinitiative.com
Thank you once again for your insights Cheryl. I know about the interconnection of all species but you have opened up a whole new perspective for me.