Don A. Franco, DVM, MPH, DVPM
President, Animal Protein Producers Industry
Vice President, National Renderers Association
California Department of Food and Agriculture Symposium
April 8, 2002
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.
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.
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.
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.
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 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.
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.
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.
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.
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.
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