Pathogens
A large variety of bacteria, viruses, protozoa, and parasitic worms
can be transferred from hogs to people. They may be ingested via contaminated
drinking water, or inhaled as aerosols carried by wind when manure is
sprayed on fields.
The US Agriculture Dept. has cautioned that many swine pathogens can
be spread on farms by rodents and cats.
Some examples:
Yersinia is a bacterium that causes severe gastrointestinal illness.
Japan has identified Yersinia in imported Canadian pork. In Denmark,
pork has been reported to be the only source of human infection in that
country. It has been demonstrated in hog manure in Quebec.
Streptococcus suis is a meningitis that can infect hog workers
E. coli: some varieties can result in grave illness or even death
Listeria monocytogenes: a meningitis that can be lethal
Brucella: in 1992 there was an outbreak of brucellosis among the workers
in a North Carolina pork processing plant
Bacillus anthracis: there was an outbreak of anthrax in 1989 at a pig
farm in north Wales
Pfiesteria: outbreaks have occurred in various places around the world
associated with intensive swine confinement
Salmonella: pigs now harbor many antibiotic-resistant strains. In Germany
20% of human cases have been shown to originate from swine.
Toxoplasma gondii: an intracellular parasite that is particularly hazardous
to pregnant women. A 1991-92 study found that 8.6% of Canadian market-age
pigs were infected with this organism
Cryptosporidium: a protozoan that has already been found in some water
supplies in Manitoba. This organism is resistant to chlorination, and
causes a severe gastrointestinal illness.
Ascaris: a large (30 cm) roundworm that lives in the intestine. One
female worm produces 2 million eggs/day. Eggs can remain viable in water
and soil for many months.
Trichinella spiralis is a small roundworm that may be found in cysts
in pork meat. Eating undercooked pork may result in trichinosis in humans,
and can be fatal. According to the Centers for Disease Control and Prevention
in the U.S. 80% of trichinosis cases were due to pork consumption.
Taenia solium is a tapeworm that is readily transferable to humans.
Many kinds of viruses and other infectious agents: e.g. swine
influenza: the Journal of Occupational Medicine reported an occupational
hazard for pork producers, veterinarians and meat plant employees
In North Carolina, Texas, Minnesota and Iowa there have been outbreaks
of influenza-A viruses that were very similar to human genetic strains.
Swine hepatitis-E virus has been shown to be transferable to humans.
The British Medical Journal reported that BSE (mad cow disease) can
be present in pigs as well as cows
There are many health issues related to the Hog Industry Air pollution
Odor reduces quality of life. On many days people can’t go
outdoors. Hydrogen sulphide gas causes people to feel ill,
have headaches, breathing difficulties as well as experiencing increased
reaction time and mood changes
Water pollution
Nitrate in the waste gains easy access to surface and ground
water. Nitrate in drinking water may cause methemoglobinemia, a condition
where blood can no longer carry oxygen effectively. Infants are at
greatest risk.
Chronic consumption of nitrate in drinking water may be associated
with greater risk of stomach cancer
Some studies have implicated nitrate exposure in increased rate of
birth defects, particularly spina bifida
Ammonia is extremely soluble in water. It is toxic to animals.
Phosphorus tends to leach easily from fields where manure has
been spread because the nutrient proportion in manure does not match
the needs of crops, therefore phosphorus tends to be in excess
In surface water phosphorus and nitrogen feed the growth of noxious
algae that impact on the fisheries and tourism industries
Bluegreen algae may create blooms to the extent that the water
may become toxic to people, livestock and wildlife. Water containing
a bluegreen algal bloom is unsuitable for swimming because the
toxins cause skin irritation and there is the danger of swallowing
some water
Drug and vaccine residues
A
variety of antibiotics, vaccines and hormones are used because disease
can spread extremely quickly in the crowded conditions of the barns.
The massive use of antibiotics contributes to the emergence of
new antibiotic-resistant strains of disease organisms threatening
human health. A 1998 study reported in the journal Microbial Drug
Resistance showed that “E. coli from swine may represent a considerable
reservoir of antibiotic resistance genes”.
There is considerable concern about residues of antibiotics in pork.
Some (e.g. Sulfamethazine) are carcinogenic. Antibiotic residues
may be high enough in meat that sensitive individuals may get an
allergic reaction on consuming the meat. Hog farmers that use
medicated feed have been shown to harbor a higher proportion of antibiotic
resistance than the general population
Compounds that speed growth of swine, e.g. porcine somatotropin and
beta-agonists increase the leanness of meat and reduce the amount
of feed needed. Some studies suggest that hormone residues in meat
may affect young consumers. The European Union has banned the use
of hormones in meat, and no longer permits the importation of hormone-treated
meat.
Drug residues are also present in the manure and can gain access to
water. Ochratoxin A is a fungal toxin that can originate from contaminated
grain and has been demonstrated in Canadian pork products. It Is carcinogenic
and suppresses the immune system, and causes kidney damage.
Report to the State of Iowa
Department of Public Health on the Investigation of the Chemical and
Microbial Constituents of Ground and Surface Water Proximal to Large-Scale
Swine Operations
October-December 1998
For more information please contact:
Enzo R. Campagnolo, DVM, MPH
Health Studies Branch
National Center for Environmental Health
Centers for Disease Control and Prevention
tel. 770-488-3530
fax. 770-488-3505
email: ejc5@cdc.gov
Carol S. Rubin DVM, MPH
Chief, Health Studies Branch
National Center for Environmental Health
Centers for Disease Control and Prevention
tel. 770-488-7350
fax. 770-488-3506
email: chrl@cdc.gov
EXECUTIVE SUMMARY
As a direct follow-up to a Centers for Disease
Control and Prevention (CDC) workshop on public health issues related
to concentrated animal feeding operations (CAFOs), an investigation
into the chemical and microbial constituents of ground and surface
water proximal to large-scale swine operations was conducted in Iowa.
The goal of this study was to obtain a broad profile of the chemical
and microbial constituents of both ground and surface water that were
potentially hazardous to human health.
The highest levels of chemical pollutants and zoonotic pathogens were
generally found in samples collected from earthen manure lagoons,
which amass and store waste from swine barns until it is applied to
agricultural fields as crop fertilizer. The contaminants included
nutrients, common ions, trace elements, antibiotics, parasitic oocysts
of the protozoan Cryptosporidium parvum, and bacteria that demonstrated
particular resistance to several antibiotics commonly used in swine
management practice as feed supplements and therapeutics.
The results of this study also demonstrated the presence of trace
metals, common ions, nutrients. pesticides, antibiotics, bacteria.
and parasitic oocysts in samples obtained from collection points other
than earthen manure lagoons. These sites include agricultural drainage
ditches, agricultural drainage v1ells, tile line inlets, tile line
outlets, earthen lagoon monitoring wells, and a river. These findings
suggest the possibility of the movement of both chemical pollutants
and microbial pathogens through soil and away from their point of
highest concentration, the animal manure lagoons, and by overland
flow away from the site of manure application.
Although chemical pollutants and zoonotic pathogens were identified
in the environment on and proximal to large-scale swine feedding operations,
the sample collection sites did not appear to be in locations that
could pose a direct threat to human health. However, more research
is recommended to accurately determine the potential level of risk,
possible pathways of exposure, and critical control points to avoid
any potential exposure to humans.
The
rapid expansion of intensive hog production in eastern North Carolina
has been accompanied by reports of decreased health and quality of
life among persons residing in proximity to large swine operations.
To investigate these issues we enumerated households and surveyed
residents of 3 rural communities, one in the vicinity of an approximately
6000-head hog operation, one in the vicinity of two intensive cattle
operations, and a third rural agricultural area where residents lived
at least 2 miles from livestock operations that use liquid waste management
systems.
Trained interviewers were introduced to residents by members of local
community-based organizations and completed 155 interviews. The refusal
rate for this door-to-door survey was 15 percent. A short questionnaire
was used to obtain information on the number of episodes of skin and
eye irritation, respiratory and gastrointestinal problems, and reduced
quality of life during the previous six months. Community differences
in mean number of episodes were compared with adjustment for age,
gender, smoking status and participation in the labor force.
The average number of episodes of most symptoms was similar in the
three communities with the exception of elevations of certain respiratory
and gastrointestinal problems and mucous membrane irritation among
residents of the hog community. Hog community residents reported increased
occurrence of headaches, runny nose, sore throat, excessive coughing,
diarrhea, and burning eyes compared to residents of the community
with no intensive livestock operations.
Quality of life, as indicated by the number of times residents could
not open windows or go outside even in nice weather, was similar in
control and cattle communities but greatly reduced among residents
of the hog community. Respiratory and mucous membrane effects in hog
community residents are consistent with results of studies of occupational
exposures among swine confinement house workers. This study supports
previous findings that community members experience health problems
due to airborne emissions from intensive swine operations.
Long-term physical and mental health impacts of reduced quality of
life could not be investigated in this study.
Authors:
Steve Wing, PhD is Associate Professor and Susanne Wolf, MPH, RN is
Research Associate in the Department of Epidemiology, UNC School of
Public Health.
A
full copy of the report can be found at:http://www.dhhs.state.nc.us/docs/ilo.pdf
A report by Melva Okun, School
of Public Health, University of North Carolina at Chapel Hill, January,
1999.
"This paper summarizes the issues pertinent to human health that are
raised by people and pigs living in proximity to each other. Section
One includes research findings and information related to air issues.
This section contains specific concerns for the health of workers
employed in the hog industry, the effect on the physical and mental
health of neighbours to hog ILOs [intensive livestock operations],
and some preliminary concerns for asthmatics living in proximity to
such operations. Section Two covers the groundwater issues associated
with hog ILOs and the related health concerns of consuming water contaminated
with nitrates. Section Three includes some of the surface water issues
that appear to be related to high nutrient waters. Section Four contains
information about infectious disease concerns for workers and neighbours
to such hog operations. In Section Five the findings are summarized
and recommendations made."
The full report can be found here.
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