PREAMBLE
I commend the California Department of
Food and Agriculture (CDFA) for bringing together this forum of diverse
interests to examine the broad spectrum of complex issues associated with
animal disposal. I appreciate the opportunity to provide a perspective of the
subject, and I will emphasize principles/concepts of bio-security with
highlights on aspects of the transmission of pathogens, the challenges for
disease control, environmental health and accountability, and the attributes of
sustainable agriculture contextual to animal and human health. An overview and
comparative assessments of existing technologies for animal disposal will be
presented with profiles of the advantages and disadvantages based on current
knowledge, and the recommendation that rendering offers the best considerate
option to assure safe disposal and minimize risk, as affirmed by the principles
of bio-security.
INTRODUCTION
The safe and responsible disposal of
animals is an important element of animal agriculture and public health in all
industrialized societies of the world. It has also been an integral part of
sustainable agriculture and environmental health practice in the United States
for over 200 years. This activity, sometimes called environmental sanitation or
environmental health, is defined by the World Health Organization as “the
control of all those factors in man’s physical environment which exercise or
may exercise a deleterious effect on his physical development, health, and
survival.” This definition must be extended to incorporate factors that could
also influence animal health, since the theme, animal disposal, has important
inferences for the health and welfare of the animal population. Thus, the
significance of the topic mandates a comprehensive examination and discussion
of the varied potentials that could impact both animal and human health.
THE
RATIONALE FOR SAFE ANIMAL DISPOSAL
Thrift G. Hanks in a
literature survey summarizing the pertinence of solid wastes/disease
relationships described both the dilemma and an analogy: “The literature fails
to supply data which would permit a quantitative estimate of any solid
waste/disease relationship. The circumstantial and epidemiological information
presented does support a conclusion that, to some diseases, solid wastes bear a
definite, if not well-defined, etiologic relationship. The diseases so
implicated are infectious in nature; no relationship can be substantiated for
non-communicable disease agents associated with solid wastes, not because of
negating data, but because of lack of data.”
Although animal
disposals were not directly implicated to exemplify the solid waste disposal –
disease relationship inferred by Hanks, the nature/character and degradation of
animal tissues can serve as an ideal matrix for the transmission and
perpetuation of disease causing pathogens, many of zoonotic significance with
potentially serious consequences to exposed susceptible populations, both
animal and human.
In the United
States, livestock and poultry agriculture has historically been big business.
This is affirmed by the current average annual slaughter and processing of 100
million pigs, 35 million cattle, and approximately 8 billion chickens. This
bountiful capacity contributes to the nation’s wholesome meat and poultry
supply and is dependent on an integrated linkage from the farm to the
slaughterhouse. This interrelatedness between farm and slaughterhouse in
livestock production and processing, introduces the world to the realities of
the pertinence of animal production, environmental health, sustainable
agriculture, and the nuances and challenges of the proper disposal of animals
and their parts. This ecological balance is important to maintain the four
essentials of life – water, food, land, and air in human activities, and
affirms the importance, and indeed, the need for proper animal disposal to
attain this continuing balance.
THE
RENDERING PERSPECTIVE: AN INTRODUCTION
Rendering has been an activity closely
linked to the history of mankind, and has been an integral part of American
agriculture from the founding of the republic. In theory, it is nothing more
than a cooking and drying process that yields both edible and inedible fats of
varying grades, and animal and poultry protein meals. Most people, however, are
unaware of the relationship between the rendering industry, the livestock
sector, the environment, and public health. Without the recycling and
processing services of renderers, massive problems of disposal from
farms/feedlots, slaughterhouses, food processors, restaurants, and institutions
would result, contributing to serious challenges to disease transmission,
disease prevention and control, and environmental and public health. As a
result, the contributions of the rendering industry to the nation’s overall
effort to maintain a clean and healthy environment can be considered
monumental.
The industry makes the
most efficient use of renewable resources and enhances environmental quality
and biological cycles and controls by annually converting over 50 billion
pounds of otherwise in-edible by-products from meat and poultry production and
processing into usable commodities, predominantly as highly valued protein
supplements for livestock, poultry, and pet foods, and tallow as a source of
energy for feed rations and the manufacture of fatty acids. These cumulative
activities provide direct benefits to farmers, slaughterhouses, and the feed
manufacturing industry while serving as an active intermediary in the broad
realm of production, environmental quality, and a support mechanism for
sustainable agriculture by assisting the economic viability of farm operations
and the quality of life for farmers and society as a whole.
A major attribute of
the rendering industry contextual to animal disposal is that it is the most
professionally acceptable mechanism/technology for the processing of carcasses
and their parts. This opinion has been consistently validated globally by
various authorities on environmental quality/health, regulatory animal disease
control, microbiologists, and public health officials. Realistically, of the
available methods for disposal, the rendering industry has withstood scrutiny
for the past 200 years, with an outstanding record of safety. And, from an
interesting retrospect, it was considered the ideal of the existing
alternatives for the disposal of animal carcasses during the recent
foot-and-mouth disease (FMD) outbreak in the United Kingdom (U.K.).
Retrospectively, the different departments coordinating the disposal efforts in
the U.K. would have readily embraced rendering as the most acceptable option,
but the industry’s available capacity was determined to be limited for
addressing the needs of such a massive epidemic.
RENDERING DISPOSAL
METHODS:
AN ANALYSIS OF TWO DISEASES OF RELEVANCE
A consideration of
comparative technologies necessitates highlighting the benefits of rendering
versus other alternative methods by a comprehensive review of the literature.
This can best be accomplished by an exemplification of two major diseases with
different etiologies, and with recent relevance; foot-and-mouth disease (FMD)
caused by a virus, and anthrax, caused by bacteria that could form spores with
heat resistant properties. The use of these two pathogens with broadly
different characteristics for a study of the subject is relevant because it
provides two very interesting disease causing microorganisms that heighten the
issue perfectly. Equally relevant, they are both diseases of national and
international importance, and are widely referenced in both veterinary and
medical literature, the latter with special pertinence to anthrax.
1.
Foot-and-Mouth
Disease (FMD)
The virus causing
foot-and-mouth disease (FMD) is transmitted mainly by respiratory aerosols and
as a result easily transmitted to distant points. The disease may also be
transmitted or introduced to a susceptible herd by feeding contaminated
garbage, meat, milk, blood, glands, or bones; also, by contact with
contaminated objects, or by contaminated non-host animals, birds, arthropods,
or parasites.
The disease is also
highly communicable and affects almost exclusively cloven-footed animals, both
domesticated and wild, and has been reported in many countries, at times with
extensive epizootics and panzootics involving several different countries. The
most important hosts are cattle, swine, sheep, goats, wild pigs, wild
ruminants, hedgehogs, rats, mice, and grizzly bears. An infected animal
eliminates the virus in all secretions and excretions, especially in profuse
salivation, which contaminates the environment and leave small droplets
containing virus suspended in the air. Lesser quantities of virus are also eliminated
through the urine and feces. In an outbreak of FMD, the roles of the three
primary hosts of the disease in transmission are as follows: sheep act as
maintenance hosts; pigs as amplifiers, and cattle as indicators.
The last outbreak of
FMD in the United States was 1929, and regulatory officials at both the Federal
and State levels are conscious of the catastrophic consequences that the
disease could have on the country if another outbreak ever occurred, thus a
perfect case study for animal disposal, because of the significance – rapid
spread of the disease and the fact that multiple species could be affected. FMD
in pigs spreads very rapidly because they produce 30 to 100 times more virus in
aerosols than sheep or cattle. Thus, an infected pig can produce a hundred
million infectious doses per day. This provides evidence of the varying
behavior of the virus and the resulting dissemination by different species.
The economic
consequences to animal agriculture, dependent on the extent of the outbreak
would vary, but estimates would approximate the loss of billions of dollars,
including the resultant loss of markets, and the restructuring of regulatory
controls including surveillance programs. Use of the U.K.’s most recent
outbreak as a prototype for the assessment of costs would affirm that an
outbreak in the U.S. would “paralyze” animal agriculture.
2.
Anthrax
Anthrax, a disease
of animals and humans, is caused by an aerobic, spore-forming, Gram-positive
rod – Bacillus anthracis, first recorded in the United States in Louisiana in
1700. This was followed by the first written account in 1824, by a Kentucky
physician, J. Kercheval.
The disease is also
of historical significance as not only having been implicated with the
devastating plagues of antiquity, but of also playing the core role in the germ
theory of disease. Robert Koch, a German physician, duplicated some of the
early work done by Louis Pasteur, and transferred the disease to mice, removed
the spleens from the experimental mice, and further re-isolated the organism
from the infected spleens, thus establishing the famous Koch’s postulates, and
the pertinence of “germs” in disease causation.
Currently,
industrialized societies of the world have developed a heightened sense of
awareness of the potential relevance of anthrax, and the disease’s causative
organism, B. anthracis, as a source for a bio-terrorism attack. As a result,
the organism has now attained universal importance, over and above its disease
causing characteristics in animals. In essence, therefore, the organism causing
anthrax is diversified and holds a special niche in the development of the
science of bacteriology, the extension of knowledge of infectious diseases, and
its potential use as an agent of bio-terrorism.
All mammals appear
to be susceptible to anthrax, although cattle, sheep, horses, and goats, in
that order, are the most commonly affected animals. This wide range of
susceptible livestock creates a serious challenge for animal disease control
officials, and medical/public health authorities in regions or countries where
the disease is endemic. The problem is exacerbated by the fact that dogs and
cats, both domestic and wild, are also susceptible hosts, manifesting the
disease in a manner similar to pigs.
The disease in
animals occurs in at least three distinct forms, varying from per-acute, acute,
and sub-acute to chronic with the different clinical manifestations for each of
the syndromes.
3. Inactivation of the causative agents
of FMD and Anthrax
The virus of FMD is
completely inactivated by temperatures of 180 F and above, regardless of the
serotypes involved in an outbreak. In fact, most viral infectivity is generally
destroyed by heating at temperatures of 50 – 60 C (122 – 140 F) for 30 minutes.
Thus, the rendering process will readily inactivate the virus in the early
stages of the cooking process.
Research work
contracted by the Fats and Proteins Research Foundation (FPRF) and performed at
Iowa State University, used the pseudorabies virus (PRV) to determine whether
PRV will resist the rendering process and persist in meat and bone meal (MBM)
quickly conformed to what is known about viral susceptibility to heat. In the
study, it was concluded that 165 F (73.9 C) was effective in completely inactivating
the pseudorabies virus in as little as 10 minutes.
In spite of the
current anxiety of anthrax and its animal and human health implications, we
have known for over 70 years that the time and temperature processes used by
the rendering industry (in North America this vary from 240 F – 280 F)
inactivate both the vegetative and spore forms of Bacillus anthracis. This was
affirmed by work done by T.J. Murray of Rutgers University, and published in
1931 in the Journal of Infectious Diseases. His work demonstrated that the
effective temperatures for the destruction of anthrax spores were time
dependent. At 105 C (221 F) the time varied from 5 to 10 minutes; at 100 C (212
F) the spores of most strains were destroyed in 5 minutes; at 95 C (203 F) most
spores were destroyed in 10 to 25 minutes; and at 90 C (194 F) most spores were
destroyed in 15 – 45 minutes.
The developed
practical time – temperature guide for killing anthrax spores using moist heat
is:
221 F for at
least 8 minutes OR
212 F for at
least 10 minutes OR
203 F for at
least 25 minutes OR
194 F for at
least 45 minutes.
We, therefore, have
scientific affirmation that the wide range of time – temperature processes of
the rendering industry, varying from 240 F – 280 F, will easily inactivate
viruses like FMD, and even the most resistant strains of bacteria like the
spore formers of B. anthracis. These two diseases provide a logical matrix for
the consideration of rendering as a logical option for animal disposal based on
the science of inactivation. The only infectious agent known today that is
relevant to feed/food safety that the rendering process will likely not
completely inactivate will be the prions, considered the most plausible cause
of the transmissible spongiform encephalopathies (TSEs).
This is, however,
not applicable to our current topic, since an outbreak of BSE, a prion disease,
in any country of the world, would engender specific preventive controls that
are prescriptive, including a policy for carcass disposal that mandates
incineration. This is so because of the resistant nature of the infectious
agent, its public health inference, and the global recommendations for the
handling of these types of affected carcasses.
RENDERING ATTRIBUTES
COMPARED TO ALTERNATIVE METHODS
Animal disposal is
an inherent part of sustainable agriculture and as such has important
implications for environmental quality and animal and human health. It is a
subject that has been insufficiently studied, and definitely in need of further
re-consideration of some of the past practices, and many of the current
proposed practices. This is important as we examine two important diseases (FMD
and anthrax) as prototypes for the discussion of acceptable disposal options
that will conform to the esthetic standards of an advanced industrialized
society.
Rendering as a means
of animal disposal offers a safe and integrated system that will comply with
all the fundamental requirements of environmental quality and disease control.
The rendering industry has to abide by State laws regarding “dead stock”
disposal, which establish a time limit within which the disposal must take
place (usually 24 or 48 hours after death) to avoid the nuisances associated
with odors, and the potential transmission of disease causing pathogens from
the carcasses. The “dead stock” are picked up by specially designated and
equipped trucks to preclude any possibility of contamination of the roadways.
The trucks are also cleaned and disinfected after designated routes, are
subject to inspection, and authorized by law in facilities that are also
licensed and approved. The aforementioned processes maximize government’s
ability to monitor and regulate disposal and assure compliance with sanitation
and hygiene that are vital factors in the prevention and transmission of
infectious agents and the subsequent spread of disease.
This infrastructure
for controls at the raw material level prior to processing is heightened by on
site inspections of rendering facilities by both State and Federal regulatory
officials; the random testing of finished products for the presence of
microorganisms (Salmonella), and the presence of PCBs and dioxin in select
products. Also, all rendering facilities in the United States have been
inspected for compliance with the requirements of the ruminant to ruminant feed
prohibition promulgated by the Food and Drug Administration (FDA), and will be
subjected to this type of inspection on an on-going basis to prevent the
“transmission and amplification” of the infectious agent of bovine spongiform
encephalopathy (BSE), an important disease of zoonotic significance, not
present in the United States. In essence, several branches of both the State
and Federal governments regulate activities of the rendering industry to assure
compliance with environmental and feed ingredient safety requirements.
The time and temperature of rendering and the
inactivation of the organisms causing the two diseases prototyped for this
discussion has been addressed under separate cover, with supporting references
to validate the rendering process as a safe and logical option for the disposal
of animal carcasses and parts.
Landfills
The very nature and recommended use of landfills,
whether registered by a State or not, presents problems that should be
carefully assessed. It is a bad practice as evidence by the presence of rats,
smoke, stinks, and loose, light paper and plastic film dispersed by the winds. The
leachate from landfills of nitrogen, carbon dioxide, and methane affirms the
problem. Small amounts of poisonous and threatening gases also evolve from
landfills including hydrogen sulfides, and chemical relatives. The explosive
properties of methane and the hazards of the sulfides should be reason enough
to consider this a non-viable option with serious public health implications.
Landfill disposal methods, despite the
existing limitations, will continue to be an important and necessary method for
municipal waste disposal, but remain a poor choice for the disposal of animal
carcasses and other products (tissues) of animal origin. The purpose of a
“secure” landfill is to physically isolate the waste from the environment and
to prevent impairment of waste or air resources.
The characteristics
of the landfill involve chemical, bacteriological, and physical changes.
Generally, and dependent on the material “landfilled”, in about 4 days after
placement and at about 3 feet below the surface, temperatures rise rapidly to
130 to 150 F. They remain at this point for approximately 60 days and then fall
gradually for about 10 months to near air temperatures. In essence,
decomposition proceeds very slowly. These ranges of temperatures should be of
grave concern to disease control officials because inactivation of heat
resistant organisms and spore formers would not be realized.
There is also the
potential for ground and surface water contamination. Groundwater is contained
in a geological layer termed an aquifer. Aquifers are composed of permeable or
porous geological material called aquitards. Though they are located at greater
depths and are protected to a degree, confined aquifers can nevertheless be
contaminated when they are tapped for use or are in proximity for a long period
of time to a source of heavy contamination, with resultant public health
implications.
An industry
sponsored survey of land disposal practices examined 12, 627 landfills in the
United States; of these, only 40 were reported to operate with liners to
prevent the migration of leachate (liquids formed within the landfill) and only
26 were lined with operational leachate treatment and control systems. Thus, a
realistic threat exists for the introduction of landfill pollutants to land or
surface water.
A final report due
later this year has re-examined the safety of land-applying bio-solids.
According to the Environmental Protection Agency (EPA) Inspector General’s
Office, EPA does not have adequate resources to manage the land application of
bio-solids and is affecting regulatory oversight at both the State and Federal
levels. An excerpt from the report states: “At a time when there is public
concern about pathogens and vector attraction and allegations of human and
animal death due to bio-solids land application, EPA is providing States with
less support and assistance.” Senator Charles E. Grassley (Iowa), who farms and
has many constituents living in rural areas expressed concerns that EPA’s
regulations could put people at risk, and states in a letter to EPA: “It is
also alarming that the internal report suggests EPA’s policies and regulations
for such hazardous materials are not based upon thorough, scientific
examinations.”
The report further
alludes to a very interesting aspect of the current concerns of the safety of
landfills by observing that EPA no longer promotes land-applying bio-solids and
is neutral on the concept. The agency has less than the equivalent of 16
full-time employees at the headquarters and regional offices devoted to
bio-solids issues. Staff changes in recent years demonstrate the extent of the
problem – the number of full-time employees responsible for enforcing the
bio-solids program has been cut in half since 1998. In 1998, there were seven
employees involved in enforcement compared with less than four in 2000.
Interestingly, twenty-four States have one or fewer full-time employees devoted
to bio-solids.
Composting
During the past
three decades, considerable interest has developed in composting as a method of
waste disposal. The process has been widely used in Europe and Japan, but is
not as prevalent in the United States. Europeans basically use the technology
as a form of waste recovery, and subsequently the composted refuse as a source
of “organic additive” or fertilizer for land application.
It is an aerobic
decomposition by bacteria and fungi. The carbon to nitrogen ratio is about 30:1
to assure the nitrogen supply for the bacteria. To speed up the bacterial
action, the raw refuse is shredded prior to placement in piles, digesters, or
bins for decomposition. The optimum moisture content for aerobic composting is
40 to 60 percent, depending of the character of the material.
Effective
composting, nonetheless, is difficult to manage and depending on the system
used could result in odors during breakdowns. Also, substantial supervision of
the processes and knowledge is needed to ensure complete decomposition and a
composted material that is stable.
While the heat
developed in the composting process will kill most eggs of parasites, and many
bacteria, the lethal temperatures usually extends to within 4 to 8 inches of
the surface of the compost. If turning is not properly done and adhered to, the
destruction of pathogens cannot be assured, especially heat resistant bacteria,
and spore-formers like, B. anthracis, the cause of anthrax.
There is another
existing irony to the use of composting as a likely means of animal disposal.
The optimum temperature range in the compost varies from 122 to 158 F, with about
140 F being an ideal. Since excessively high temperatures, over 167 F, will be
injurious to bacterial action in the compost, a basic analogy will dictate that
the optimum average temperature of 140 F will not suffice to inactivate many
disease-causing pathogens.
Flies, mosquitoes,
rats, wildlife, and other vectors of disease transmission that are attracted to
compost would act as reservoirs for the spread of disease. Large bones and
hides will not compost readily and serve as definite deterrents to the
composting process. Thus, while composting appears to serve as a need for the
disposal of certain forms of solid waste, like other alternative technologies,
the process has severe limits in addressing the challenges of animal disposal
and their parts.
Incineration
Incineration is a
valuable process for its ability to stabilize and eliminate hazardous material.
It basically converts organic material into inorganic matter while destroying
pathogenic organisms through the application of high ambient temperature
conditions. The temperature within the incinerator (continuous combustion type)
is stabilized to keep it constant at 900 C (1652 F) at the exit portion of the
combustion chamber.
The incineration
process is an ideal for the disposal of carcasses in countries with BSE,
because of the known heat resistance of the infectious agent, a prion. It is
also an excellent mechanism and can be used as an adjunct with other
technologies for animal disposal for other specific disease control
initiatives, but the limited availability and concurrent capacity of
incinerators throughout the country makes this process an impractical
considerate option, and, therefore, moot.
Burial
For centuries,
burial has been an historical practice of animal disposal throughout the world.
In the past two decades, however, serious concerns about the contamination of
groundwater and, hitherto, other unforeseen environmental factors have surfaced
and forced many States to ban the practice of burying animal carcasses.
A disease like anthrax
provides a semblance of the concerns associated with potential environmental
contamination, in the process of burial, where exudates and secretions could
contaminate the soil, if proper control measures are not carefully enforced.
Regardless of the environmental and physical conditions necessary for
maintenance of anthrax contamination on a premise, the organism – susceptible
host – disease – death – dissemination of organisms from the carcasses to other
premises remain the standard cycle of transmission. The anthrax spore is
impervious to physical inactivation by environmental heat, cold, and
desiccation and highly resistant to chemical inactivation with disinfectants,
thus, the need to establish the role of soil contamination as an important
source of spread of the disease.
Burial, as already
stated, has clearly identified limits and is no longer proposed as a
responsible option for animal disposal.
Burning
Whether burning is
performed on farm or off-site in mass, the practice is not compatible with
existing environmental quality and health standards. One problem with any form
of combustion is the release of dioxin to air or water, contributing to an
unwanted contaminant with health related implications. This release also
provides ample opportunity for subsequent uptake by plants and animals, and a
potential source of contamination of the food chain.
The cancer-related
inference of dioxin by the Environmental Protection Agency (EPA) has raised
another level of serious public health concern for burning as an option for
carcass disposal. Obviously, in emergencies, governments may have to resort to
options that are unacceptable, like occurred in the United Kingdom. But,
burning as an acceptable routine/method for the disposal of animals cannot be
condoned. This does not even consider the other negative elements of burning
that contribute to the pollution of the environment in general, and the release
of other noxious gases and compounds that affect the health and well-being of
exposed populations.
ANIMAL MORTALITIES
AND DISPOSAL METHODS:
COST CONSIDERATIONS
A recent report
indicates that renderers process roughly 50% of all livestock mortalities
approximating 3 billion pounds in 2000. Of this number, beef cattle accounts
for the largest proportion of the mortalities requiring disposal, based on a by
weight analysis. The rendering industry has typically charged modest fees to
collect the on-farm/feedlot mortalities. A comparison to the operating costs
and likely fixed costs associated with other animal disposal methods, the
rendering option remains highly cost effective.
The existing (and
future) economic climate could result in increases in renderer fees for
collection. In some regions of the country, renderers have already discontinued
the service of picking up farm “deads.” It is simply a matter of cost –
benefits, a fundamental element of business. Many producers recognize that it
is still more cost effective to pay a reasonable fee to have the service of
renderers than resorting to alternative disposal methods with the possible
concurrent problems of environmental harm, disease transmission to animals and
man, and the resultant economic damage associated with these aforementioned
likely outcomes. Some producers may want to examine alternatives, regardless of
the hazards and risks associated with the selected options to obviate costs.
The challenge for
regulators is to assess the disposal methods based on the known science and
principles of bio-security today and prudently weigh the advantages and
disadvantages of rendering compared to the alternatives, including taking a
chance with unproven or ill-advised disposal methods that could result in
catastrophic consequences of environmental degradation, disease outbreaks in
animals or man, and affronts to sustainable agriculture.
DISCUSSION
This manuscript is
not meant to be either an exhaustive review of the subject, or comprehensively
all embracing. It is nothing more than a highlight of the major factors that
relates to animal disposal, animal disease control, environmental
quality/health, and some aspects/concepts that could negatively influence
public health in the process.
Despite
precautionary controls, pathogens survive in the environment and surprisingly
little is known on the quantity of a biological agent needed to produce
infection in animals or man. Anecdotal suggestions and assumptions have
predominated for years, and many persist to this day, because very little
scientific research went into the study of the likely risk factors associated
with animal disposal. We have often blindly accepted the theories and practices
of yesteryear without fully examining the impact based on the current knowledge
of disease transmission and environmental health. This effort is meant to
examine the broad issues and resort to policies that will serve the best
long-term interests of sustainable livestock agriculture, while also protecting
animal and human health, in an environmentally responsible manner.
The health effects
of the mismanagement of solid wastes are mostly indirect, but these are not
inconsequential. In essence, as referenced, no method of solid waste handling
which favors the breeding, feeding, and harborage of flies, mosquitoes, or
rodents and the possible transmission of disease-causing microbes is
hygienically acceptable.
Two diverse
diseases, FMD, caused by a virus, and anthrax, associated with spore-forming
and heat-resistant characteristics, were used to prototype the challenges
associated with carcass disposal, and the major secondary nuances of
environmental controls in the assessment and evaluation of the most
scientifically acceptable option for animal disposal. One distinct disadvantage
in using specific prototypes to posture theories is that there is a tendency to
circumvent major facets of the subject, because of the likelihood of
overlooking the major traditional diseases of importance to animal disease
control and public health e.g. rabies, tuberculosis, brucellosis, to name a few
of pertinence. This is unfortunate, but does not take away from the postulates
using only two representative diseases.
The manuscript
reviewed the rationale for safe animal disposal, the solid waste/disease
relationship, an introduction to rendering contextual to the select diseases,
FMD and anthrax, the attribution of rendering with comparisons to alternative
methods such as landfills, incineration, composting, burial and burning. No
effort was made to discuss a serious practice still in vogue in limited
geographic areas of the country, the leaving of dead livestock to the elements
of nature, and the potential for environmental and disease related
consequences. A case history exemplifies the relevance. In a game park in South
Africa, several “wild animals” had died of anthrax. Vultures fed upon the dead
animals and subsequently contaminated the water supply by bathing, drinking,
defecating, or vomiting ingested meat into the water. As the disease outbreak
spread, animals died around the waterholes, and the affected animal carcasses
were “mangled” by crocodiles, terrapins, or carnivores further increasing the
transmission of the disease related spores in and around the watering holes.
While the
aforementioned unusual case history could be described as atypical, and many
may posture not applicable to the United States, there are pertinent lessons
for disease transmission that can be learnt in the process. Flies and other
insects, mice, rats, wildlife (wild pigs, hedgehogs), dogs, and other vectors
can all serve as reservoirs of transmission of FMD and anthrax. Especially
relevant is the possible contamination of soil by the spores of anthrax.
Preventive controls,
therefore, necessitate looking at all the potential factors, albeit in a
worst-case scenario, that could contribute to risk. Regulatory guidelines and
policies must ascertain that the most scientifically validated option be
instituted to assure the continued viability of American livestock agriculture
regionally and nationally. Realistically, we are all accountable for achieving
this objective, from producers, renderers, slaughter establishments to the
State of California officials charged to examine “concerns over emerging
pathogens, by the varied geography and business climate of the state and by a
growing need for developing economically sound practices.” Circumvention of the
most scientifically affirmed method of animal disposal, rendering, could come
at a price that we may all ultimately regret.
Rendering also
offers other environmental and regulatory benefits that are not duplicated by
other forms of disposal. Unlike landfill and composting, both methods that
increase volume and contribute to ecological challenges, the rendering process
reduces mass/volume. Rendering conforms to the traceability aspect of
regulations as mandated by the Food and Drug Administration (FDA), and since
only finished rendered products are regulated e.g. in the case of BSE, these
records will not be available or required for composting or landfill
application.
SUMMARY
The two key factors
which affect the spread of infectious diseases in animals and in the human
community other than the nature of the infectious agent is ecology and
behavior. Obviously, the survival of infectious agents in a given environment
is dependent on factors that permit the “agents” to successfully maintain
themselves in said environment. In reality, then, government policies at any
level, including a State, should create an environment that will preclude
potential risks to animal or human health.
The re-emergence of
anthrax outbreaks in different regions of the country, and the fact that the
source of infection to man is always infected animals, contaminated animal
products, or environmental contamination by spores that tend to be resistant
from these sources should be reason for grave concern. In essence, our disease
control methodologies must be state of the art to maintain and sustain animal
agriculture to the optimum.
Extensive research
findings, commencing in 1931 at Cook College, Rutgers University, New Jersey,
have clearly demonstrated the time – temperature processes of rendering readily
inactivate bacteria, viruses, and other disease causing agents and have been
historically accepted by international disease control authorities as a safe
and logical adjunct to infectious disease control. Thus, rendering and
incineration (when applicable) remain the most reliable and tested mechanisms
for the safe and responsible disposal of animal carcasses and other products of
animal origin. Alternative animal disposal methods (landfill, composting,
burial, burning) were highlighted with objectivity and the known existing
disadvantages associated with each of the different methods. Policies not
affirmed by science could be catastrophic.
As a society, we
have too much to lose by resorting to unproven methods as options.
The varying impacts
were all alluded to in different segments of the manuscript. And, indeed,
animal disposal is an inherent aspect of public health protection.
