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How eating animals comes back to bite us: from Antibiotic resistance to Zoonotic diseases


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This presentation begins with a brief review of UN and other studies showing that global animal agriculture is a major contributor to greenhouse gases and climate change. Less widely appreciated are the various ways that exploitation of animals for food is an increasingly important contributor to antimicrobial drug resistance. Furthermore, both “local” and factory farming of animals, as well as the consumption of wild “bush meat”, contribute to and exacerbate “emerging” and established infectious diseases, including HIV, Ebola and influenza.
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Prof. Ethan Will Taylor
Dept. of Chemistry and Biochemistry,
University of North Carolina at Greensboro
Director, Biosafety Level 3 Lab,
Joint School of Nanoscience and Nanoengineering
1. Brief review of UN and other studies showing that
global animal agriculture is a major contributor to
greenhouse gases and climate change
Less widely appreciated:
2. How exploitation of animals for food is an
increasingly important contributor to antimicrobial
drug resistance
3. How both “local” and factory farming of animals,
as well as the consumption of wild “bush meat”,
contribute to and exacerbate “emerging” and
established infectious diseases
Concluded that 18 percent of
annual worldwide greenhouse
gas (GHG) emissions are
attributable to livestock
Quote from report:
"the livestock sector is a major
stressor on many ecosystems
and on the planet as a whole.
Globally it is one of the largest
sources of greenhouse gases and
one of the leading causal factors
in the loss of biodiversity, while in
developed and emerging
countries it is perhaps the leading
source of water pollution."
Livestock and their byproducts
actually account for at least 32.6
billion tons of carbon dioxide eq.
per year, or 51 percent of annual
worldwide GHG emissions
“Total GHG emissions from
livestock supply chains are
estimated at 7.1 gigatonnes
CO2-eq per annum for the
2005 reference period. They
represent 14.5 percent of all
human-induced emissions
Gerber, P.J., et al. 2013. Tackling climate
change through livestock – A global
assessment of emissions and mitigation
opportunities. Food and Agriculture
Organization of the United Nations, Rome
“The livestock sector is a major emitter
of GHGs and its contribution to climate
change is set to grow as global demand
for animal products rises.”
“… it is unlikely that global temperature
rises can be kept below two degrees
Celsius in the absence of a radical shift
in meat and dairy consumption.”
This report addresses the general lack of
awareness about this issue, but concludes:
“… consumers with a higher level of
understanding of the links between
livestock production and climate change
are more likely to indicate willingness to
reduce their meat and dairy consumption.”
Significance: “We project that health and climate change
benefits will both be greater the lower the fraction of animal-
sourced foods in our diets.”
“Transitioning toward more plant-based diets … could reduce
global mortality by 6–10% and food-related greenhouse gas
emissions by 29–70% compared with a reference scenario in
2050… we estimate the economic benefits of improving diets
to be 1–31 trillion US dollars, which is equivalent to 0.4–13%
of global gross domestic product (GDP) in 2050.”
PNAS (2016) Vol. 113 no. 15, 4146–4151, doi: 10.1073/pnas.1523119113
Perhaps the most worrisome
impact of industrial meat
production, analyzed and
discussed in many scientific
publications in recent years, is the
role of livestock in climate change.”
Note massive recent increase in meat supply in China and Asia
The WAY they treat their animals will have an
effect on us, even half a world away…
Due to their use of antibiotics in animal feed,
even if banned in the US or Europe, leading to
Antibiotic resistant bacteria spreading worldwide
and, independent of antibiotics,
The evolution of new strains of viruses with the
potential to trigger global epidemics (e.g. swine or
bird flu), or local outbreaks (e.g. SARS)
Antibiotic resistance is one type of antimicrobial resistance (AMR)
Can occur with antibiotic, antiviral, antifungal and antiprotozoal drugs
(Figure from CDC Antibiotic Resistance Threats 2013, public domain)
Antimicrobial resistance
More likely to develop when
sub-optimal drug doses are
used, or with prolonged
Leads to exhaustion of
treatment options for
serious infectons
Resistant microbes can
have names like “Methicillin-
Resistant Staph Aureus”
“Salmonella spreads from animals
to people mostly through food.
Antibiotic use in food animals can
result in resistant Salmonella, and
people get sick when they eat foods
contaminated with Salmonella.”
CDC Antibiotic Resistance Threats 2013
“Campylobacter spreads from animals to people through contaminated food, particularly raw or
undercooked chicken and unpasteurized milk. Infections may also be acquired through contact with
animals and by drinking contaminated water. Antibiotic use in food animals can result in resistant
Campylobacter that can spread to humans.” CDC Antibiotic Resistance Threats 2013 p. 62
“Recent research suggests that
bidirectional transmission of
strains of S. aureus between
humans and livestock is not a
rare occurrence. In addition to
the movement of CC398
between animals and humans,
studies have suggested that
a human pandemic clone,
CC97, had its origin in cattle
Additionally, antibiotic
resistance genes,
including mecA and mecC
have been suggested to have
an animal origin.”
Cited in: Smith TC (2015) Livestock-Associated Staphylococcus aureus: The United
States Experience. PLoS Pathog 11(2): e1004564. doi:10.1371/journal.ppat.1004564
Moono et al. Clostridium difficile infection in production animals and
avian species: a review. Foodborne Pathog Dis. 2016 Sept 7 [Epub]
DR Knight et al. Contamination of Australian newborn calf carcasses at
slaughter with Clostridium difficile. Clin Microbiol Infect. 2016,
22:266.e1-7. " further confirm that Australian neonatal veal calf
carcasses are contaminated with potentially significant strains of C.
difficile at slaughter
Peláez et al. Characterization of swine isolates of Clostridium difficile
in Spain: a potential source of epidemic multidrug resistant strains?
Anaerobe. 2013, 22:45-9. “All isolates were resistant to the
fluoroquinolone ciprofloxacin.. Resistance to clindamycin, ertapenem,
erythromycin and moxifloxacin was common”
Thitaram et al. Antimicrobial susceptibility of Clostridium difficile
isolated from food animals on farms. Int J Food Microbiol. 2016,
16;227:1-5. "almost all isolates (98.1%) were resistant to levofloxacin”
“Emerging infectious diseases” are defined loosely as those
whose occurrence in humans has increased in the last few
decades or threatens to increase in the near future
After decades of global spread, some, like HIV/AIDS,
can turn into chronic human diseases
Some, like Zika, may have had little impact at first but later
re-emerge in other locations and populations
Others, like Ebola, keep popping up and then burning out in
different times and places, with outbreaks often triggered by
contact with or consumption of wild animals (“bush meat”)
HIV evolved in humans from primate (simian)
SIVs, very likely due to the practice of hunting
wild monkeys and chimpanzees as bush meat
Because of this…
The world has this…
Patient zero in the 1976 Ebola outbreak in DR Congo was
a teacher who almost certainly contracted it by eating meat
of a wild antelope or monkey
Patient zero in the 2013-2015 Ebola outbreak was a child
in Guinea who was infected by a fruit bat, a common meat
source in the area
The SARS coronavirus entered the
human population in China in 2003
via infected “Civet cats” and/or infected
bats captured and sold as food in the
same wild meat markets in Guangzhou
“Direct adaptation”
From: Watanabe et al. The changing nature of avian influenza A virus (H5N1). Trends in Microbiology 2012, 20:11-20
The 1918 H1N1 flu pandemic killed 20 - 40 million people worldwide.
The 2009 H1N1 flu pandemic began in Mexico early in 2009. By May
2010 one billion people were infected in 200 countries; 200,000 died.
K.F. Shortridge et al. (2003) The next influenza pandemic: lessons from Hong
Kong. J Appl Microbiol. 94 Suppl:70S-79S. Regarding 1997 H5N1 bird flu infection
of humans, they conclude "The 1997 incident upheld the hypothesis that southern
China is an epicentre for the emergence of pandemic influenza viruses. However,
the intensification of the poultry (chicken) industry worldwide coupled with the
spread of viruses such as the Eurasian lineage of H9N2 suggest that the genesis
of a pandemic could take place elsewhere in the world"
Bravo-Vasquez et al. Presence of influenza viruses in backyard poultry and swine
in El Yali wetland, Chile. Prev Vet Med. 2016 Oct 6. pii: S0167-5877(16)30432-9.
Mena et al. (2016) Origins of the 2009 H1N1 influenza pandemic in swine in
Mexico. Elife, Jun 28;5. pii:e16777. Results "establish that the swine virus
responsible for the 2009 pandemic evolved in central Mexico. This finding
highlights how the 2009 pandemic arose from a region not considered a pandemic
risk, owing to an expansion of IAV diversity in swine resulting from long-
distance live swine trade."
G. C. Buehring et al. (2015) Exposure to Bovine Leukemia Virus Is Associated
with Breast Cancer: A Case-Control Study. PLoS ONE 10(9): e0134304
Presence of BLV in mammary epithelium
Odds of having breast cancer if BLV+
is 3.1 times greater than if BLV-
Higher than any of the frequently
publicized risk factors for breast cancer,
e.g. obesity, alcohol consumption and
use of post-menopausal hormones
BLV is likely to be acquired via consumption of dairy products:
100% of dairy operations with large herds of 500 or more cows tested positive for
BLV antibodies in pooled milk tanks
83% of operations with small herds of fewer than 100 cows tested positive for BLV
Existential threat from increasing livestock production: it is unlikely that
global temperature rise can be kept below two degrees Celsius in the
absence of a radical decrease in meat and dairy consumption
Food borne illnesses like Salmonella are increasingly drug resistant
MRSA and antibiotic resistant C. diff. are becoming more widespread
and dangerous due to evolution in livestock
Bushmeat is the origin of outbreaks of many infectious diseases like
Ebola, with the potential to become global pandemics like HIV-AIDS
Both local backyard farming of pigs and poultry, as well as mass
factory farming practices, put us at increased risk of global influenza
pandemics, which can kill millions.
Risk of breast cancer increases >3-fold if exposed to Bovine Leukemia
Virus, which may come from diary or beef consumption.
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