|
THE NEED TO IMPROVE ANTIMICROBIAL
USE IN AGRICULTURE
Ecological and Human Health Consequences
EXECUTIVE SUMMARY
OVERVIEW
- Exposure
to antimicrobials fundamentally alters microbial
ecosystems of humans, animals and the environment,
which may lead to the development of antimicrobial
resistance.
- Increasing
antimicrobial resistance limits treatment options,
raises health care costs, and increases the number,
severity and duration of infections.
- Antimicrobial
use is a major cause of antimicrobial resistance.
- It
is estimated that, in the United States, the amount
of antimicrobials administered to food animals is
comparable to that used in humans. These antimicrobials
are utilized largely to promote growth and prevent
disease, thereby reducing production costs. A substantial
amount of them are sold over-the-counter and do
not require a veterinarian's prescription.
- Most
antimicrobials used in food animal production are
the same as, or closely related to, drugs used in
human medicine.
- Current
antimicrobial use policy for animals in the US differs
from policy enacted in the European Union, which
has banned the use of some antimicrobials for growth
promotion on the farm.
- Also
of concern is the farm use of antimicrobials of
critical importance in human medicine, such as fluoroquinolones
and third (or higher) generation cephalosporins.
- Once
the prevalence of antimicrobial resistance in a
population reaches a certain level, reversal of
the problem becomes extremely difficult.
EXECUTIVE
SUMMARY
The
APUA "FAAIR Report," entitled "The Need to Improve Antimicrobial
Use in Agriculture: Ecological and Human Health Consequences,"
is published in full as Vol 34, Supplement 3, June 1,
2002 of the journal Clinical Infectious Diseases.
The
Risk to Human Health
Since
the 1940s, antimicrobials have been considered the gold
standard for treatment of bacterial infections in both
animals and humans. Taken properly, these medications
may destroy or disable the bacterial pathogens that
cause infections. In recent years, however, we have
witnessed a rapid increase in drug-resistant bacteria
leading to failure in the treatment of infectious diseases.
The overuse of antimicrobials in food animal production
is an under-appreciated problem. In both human and veterinary
medicine, the risk of developing resistance rises each
time bacteria are exposed to antimicrobials. Resistance
opens the door to treatment failure for even the most
common pathogens and leads to an increasing number of
infections. The mounting evidence of the relationship
between antimicrobial use in animal husbandry and the
increase in bacterial resistance in humans has prompted
several reviews of agricultural practices by scientific
authorities in a number of countries, including the
US.
The
APUA "FAAIR Report"
The
Alliance for the Prudent Use of Antibiotics (APUA) is
a non-profit organization whose mission is to improve
control of infectious disease worldwide through promoting
appropriate use of antimicrobials and reduction of antimicrobial
resistance. To help inform the policy debate surrounding
antimicrobial use in animal husbandry, APUA initiated
the FAAIR (Facts about Antibiotic Use in Animals and
its Impact on Resistance) Project in early 2000. Since
then, a Scientific Advisory Panel of medical and scientific
experts, coordinated by APUA, met over the course of
two years in order to analyze the evidence and develop
consensus recommendations.
The APUA "FAAIR Report" is based on a review of approximately
500 published studies on the topic of antimicrobial
use in agriculture. The report is the first of its kind
to evaluate the risk to human health from: (1) direct
and indirect transfer of resistance through the food
chain and ecosystems, as well as (2) the cumulative
effects of the dissemination of antimicrobial resistance
in the environment.
Selected
Report Findings
- Most
food animals in the US are exposed to antimicrobials
in feed, water, or by injection at some point during
their lives.
- Fecal
waste from food animals treated with antimicrobials,
which is often composted and spread as fertilizer,
is implicated in environmental contamination with
resistant bacteria.
- Several
lines of evidence may link antimicrobial use in
food animal production to resistant infections in
humans. These include: (i) direct studies tracing
resistant infections in humans to specific meat
and poultry operations; (ii) temporal evidence (i.e.
the emergence of resistance in animal-associated
bacteria prior to its emergence in human pathogens);
(iii) circumstantial evidence linking human disease
to trends in resistance among common bacterial pathogens
such as Salmonella, Campylobacterand E. coli; (iv) studies
suggesting that farmers and family members may be
more likely than the general public to harbor antimicrobial-resistant
intestinal bacteria; and (v) studies of the transfer
of resistance in commensal bacteria.
- Published
risk assessments of antimicrobial use in agriculture
likely underestimate the risk to human health because
they tend to ignore future cumulative effects, ecological
impact and potential transfer of resistance from
one bacterium to another and from one animal species
to another.
Selected
Conclusions
- All
uses of antimicrobials in animals, agriculture and
humans contribute to the global pool of antimicrobial
resistance genes in the environment.
- Use
of antimicrobials in food animals contributes to
the growing problem of antimicrobial resistance
in human infections. Transfer of bacteria from food
animals to humans is a common occurrence.
- The
amount of antimicrobials administered to animals
is comparable to that used in humans. Unlike use
in humans, however, much of the antimicrobial administration
to food animals is to large groups at low doses,
for non-therapeutic purposes such as growth promotion
and disease prevention.
- The
elimination of non-therapeutic use of antimicrobials
in food animals and agriculture will lower the burden
of antimicrobial resistance in the environment with
consequent benefits to human and animal health.
Selected
Recommendations
Based
on its assessment of the scientific evidence, the Scientific
Advisory Panel strongly urges implementation of policy
reforms in a timely fashion. Specific changes called
for are:
- Antimicrobial
agents should not be used in agriculture in the
absence of disease.
- Use
of antimicrobials in food animal production should
be limited to therapy for diseased animals or prevention
of disease when it has been documented in a herd
or flock.
- Use
of antimicrobials for economic purposes such as
growth promotion or to enhance feed efficiency should
be discontinued (with the exception of ionophores
and coccidiostats, because current evidence indicates
that use of these antimicrobials does not affect
resistance in human pathogens).
- Because
of their critical importance to treat human disease,
fluoroquinolones and third generation (or higher)
cephalosporins should not be used in agriculture
except to treat refractory infections in individual
animals.
- Antimicrobials
should be administered to animals only when prescribed
by a veterinarian.
- In
many cases, legislation by Congress or direct changes
in policy by the US Food and Drug Administration,
US Department of Agriculture, US Environmental Protection
Agency, or other government agencies will be necessary
to implement the recommendations of the Panel. The
ecology of antibiotic resistance should be considered
by regulatory agencies in assessing human health
risk associated with antibiotic use in agriculture.
|