Animal Health at the Crossroads Preventing, Detecting, and Diagnosing Animal Diseases (2005) / Chapter Skim
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3 Assessment of Current Framework: Case Studies
3 Assessment of Current Framework: Case Studies
Pages 76-117
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From page 76... ...
Instead, the animal diseases or disease scenarios described here, from acute to chronic, endemic to exotic, naturally occurring to intentionally introduced, were selected to consider the breadth of issues that must be addressed by an inclusive infrastructure capable of detecting, diagnosing, and preventing a wide variety of events affecting animal and human health. The diseases selected involve each of the major animal types, namely food-animals, wildlife, and companion animals.
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From page 77... ...
. END is classified as a foreign animal disease in the United States, historically causing severe economic losses when commercial poultry industries become infected, as occurred in a major outbreak of END in southern California in 1971.
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From page 78... ...
Foreign animal diseases dis cussed in this chapter include: · Exotic Newcastle disease (END) · Foot-and-mouth disease (FMD)
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From page 79... ...
Examples addressed here include: · Avian influenza · Chronic wasting disease · West Nile virus While the committee recognizes that at one time these agents may have been considered as newly emergent, each of them has now become firmly established in North America and is considered endemic for the purposes of this report. Novel Naturally Occurring Pathogens.
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From page 80... ...
for developing rapid diagnostics for the high-risk agricultural pathogens was $2.8 million for two poultry pathogens included in the list: highly pathogenic avian influenza (AI) virus and END virus (USDA, 2002f; USDA ARS, 2002)
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From page 81... ...
· The lack of adequate surveillance for END, a foreign animal disease already known to enter the country periodically, allowed the virus to
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From page 82... ...
Federal efforts trace origin of birds to Southern California. September 25 · Index case END outbreak game fowl submitted to state diagnostic laboratory by private practitioner.
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From page 83... ...
Final · 19,146 premises quarantined totals · 932 confirmed infected premises identified · 3.21 million birds depopulated in four states · $160 million in control costs · 7670 state and federal employees on the END task force spread and become established in a relatively large animal population before detection. In the absence of available rapid detection and diagnostic assays for END, the USDA and the state diagnostic laboratory, in a largely uncoordinated effort, initiated development of a molecular-based diagnostic ap
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From page 84... ...
. The committee found the following: · Private industry, local and regional resources, and the willingness to capitalize on expertise located outside the centralized federal animal health system allowed a more timely, cost-effective, and reliable assay to be developed, validated, and implemented for disease detection and control.
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From page 85... ...
The committee found that: · FMD prevention, and disease prevention in general, through exclusion of infected animals and animal products cannot be relied on as infallible and would require a significantly more effective infrastructure than currently exists at U.S. borders and ports of entry.
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From page 86... ...
86 ANIMAL HEALTH AT THE CROSSROADS BOX 3-2 Foot-and-Mouth Disease Epidemic in Great Britain in 2001 On February 19, 2001, a routine inspection at an abattoir near London revealed "highly suspicious" signs of foot-and-mouth disease in 27 pigs. The Ministry of Agriculture confirmed the outbreak and the next day set up a 5-mile exclusion zone around the abattoir.
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From page 87... ...
control effort, and therefore was not consistently accepted. The policy, developed in large part based on computer model simulations of hypothetical disease transmission, has in retrospect been credited with the large number of noninfected animals destroyed during the 2001 epidemic and with the public's negative response to the highly visible control efforts (Haydon et al., 2004)
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From page 88... ...
exist for other animal diseases but are not yet developed or readily available for FMD control. The lessons reported from the 2001 U.K.
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From page 89... ...
Who had responsibility for surveillance, identification, and re sponse to this foreign zoonotic agent in exotic companion animals? These were some questions the committee asked while studying the monkeypox outbreak.
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From page 90... ...
However, it does not ban the importation of all exotic animals. The monkeypox outbreak revealed that: · The infrastructure that exists for preventing animal disease outbreaks is focused primarily on livestock, including poultry and farmed
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From page 91... ...
Good laboratory practice includes training and proficiency testing of laboratory staff in use of equipment and specific protocols, but neither the Laboratory Response Network for bioterrorism nor the National Animal Health Laboratory Network currently has responsibility for ensuring that these tenets of a quality system are in place in veterinary diagnostic laboratories. In summary, the monkeypox outbreak revealed significant gaps in prevention, problems with responsibilities, and coordination of response and in laboratory capacity, especially concerning delays in the development and validation of diagnostic assays.
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From page 92... ...
Establishing countrywide disease-free status once a case is diagnosed can be extremely difficult. According to a panel of experts from the European Association for Animal Production, the estimated total cost of BSE in Europe is 92 billion, nearly $115 billion dollars (EAAP, 2003)
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From page 93... ...
Lessons identified from the BSE experience included the following: · The U.S. animal health community realized that BSE can no longer be considered a problem only for other nations.
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From page 94... ...
from the human food chain; prohibition of a meat label for dorsal root ganglia that might be present in products obtained through advanced meat recovery processes; prohibition of air injection stunning of cattle at slaughter; prohibition of mechanically separated meat in human food; holding product from BSE-tested animals until a final diagnosis has been made; and immediate implementation of a national animal identification system. These new rules were published in the Federal Register on January 12, 2004.
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From page 95... ...
Immunohistochemistry, in which the presence of the abnormal prion is visualized under the microscope in a section of brain by a trained pathologist, and Western blots, in which the abnormal prion in the brain can be visualized and its approximate molecular weight determined after separation from other proteins in the brain based on its size and resistance to enzymes, are widely considered gold standard tests. Immunohistochemistry, however, cannot be used for high throughput testing, in which rapid turnaround is required, as results typically are not available for 24 days, leading to this lesson learned: · There is no available method for diagnosing BSE in young calves, when infection first occurs, or in live animals.
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From page 96... ...
Current research on diagnostics focuses on the development of a sensitive live animal test. Unfortunately, this is a challenge in BSE, since experimental data suggest that the abnormal BSE prion is either not present or is rarely and inconsistently present in blood and lymphoid tissue, unlike scrapie which is present in both blood and lymphoid tissue or chronic wasting disease (CWD)
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From page 97... ...
is a virtual network of 11 leading, well-equipped, and high biosecurity infectious disease labs in nine countries established primarily to address influenza outbreaks. GOARN was instrumental in spearheading laboratory efforts: these labs were connected by secure web sites and daily teleconferences to identify the causative agent of SARS, develop diagnostic tests, and collect and analyze clinical and epidemiological data on SARS.
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From page 98... ...
The unsani tary conditions in live animal markets in China (and elsewhere) foster an envi ronment conducive to the emergence of new zoonotic and animal diseases and likely played a role in SARS transmission from animals to humans (Peiris et al., 2004; Xu et al., 2004)
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From page 99... ...
. Recent data based on serology suggest that some SARS antibody seropositives occurred in Hong Kong in 2001 before the documented SARS outbreaks, suggesting that low numbers of subclinical SARS infections likely occur (Zheng et al., 2004)
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From page 100... ...
, fosters an environment conducive to the emergence of new zoonotic and animal diseases and likely played a role in the putative transmission of SARS from animals to humans. The published evidence and epidemiological data suggest that SARS was a probable zoonosis (Guan et al., 2003; Peiris et al., 2004; Xu et al., 2004; Wu et al., 2005)
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From page 101... ...
In the case of SARS, research ties and interagency funding and cooperation are lacking to promote collaborative infectious and zoonotic disease research between biomedical and veterinary scientists and to provide trained biomedical and veterinary public health personnel. Furthermore, funds are lacking to study disease pathogenesis in the appropriate animal host and to investigate zoonotic diseases including identifying animal reservoirs and the mechanisms and chain of interspecies transmission.
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From page 102... ...
ENDEMIC DISEASES: AVIAN INFLUENZA, CHRONIC WASTING DISEASE, AND WEST NILE VIRUS A large array of indigenous diseases could serve as case studies in the category of endemic disease. The committee selected three diseases, including avian influenza (AI)
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From page 103... ...
. Nature of the Pathogen Avian influenza viruses are endemic in wild bird and migratory waterfowl populations and can be transmitted to domestic poultry.
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From page 104... ...
. The majority of avian influenza viruses have low pathogenicity, typically causing little or no clinical disease in infected birds, particularly migratory waterfowl, which serve as a reservoir of the virus.
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From page 105... ...
· Thijs Kuiken and colleagues at the Erasmus Medical Centre in the Netherlands found that cats could become infected and spread the avian influenza virus H5N1 (Kuiken et al., 2004)
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From page 106... ...
As the 19841985, 1992, and 2001 outbreaks in poultry illustrate, influenza viruses of low pathogenicity have the capacity to mutate into highly pathogenic strains, sometimes after very short periods of circulation in poultry populations. Aggressive surveillance, detection, and disease control, generally including total depopulation of poultry in the area, are considered critical to minimize transmission, control economic losses, and eliminate the public health risks associated with human exposure to highly pathogenic avian influenza viruses.
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From page 107... ...
Globally, public health as well as animal health agencies have closely followed the appearance and movement in 2004 of H5 avian influenza viruses in poultry and are particularly concerned about its rapid spread through Asia, where acceptance or compliance with slaughter-based control efforts is considered not economically feasible or socially acceptable. The millions of affected birds, commingling of different avian and mammalian species, difficulty in protecting poultry workers from respiratory exposure, and the recognition of bird-to-human transmission have placed the global community on high alert for the potential evolution of a pandemic influenza virus.
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From page 108... ...
. Since 2002, the wider application of testing of hunter-killed or other animals has uncovered endemic loci of infected animals in western Colorado, Nebraska, New Mexico, South Dakota, Utah, Wyoming, Wisconsin, Illinois, and New York, and in Saskatchewan, Canada.
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From page 109... ...
The national response to CWD has been guided since 2002 by a Plan for Assisting State and Federal Agencies and Tribes in Managing CWD in Wild and Captive Cervids (USDA APHIS, 2002) , developed by a task force of federal and state wildlife management agencies.
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From page 110... ...
As of June 2004, 24 state wildlife management agencies adopted a policy set out in Multi-state Guidelines for Chronic Wasting Disease Management in Free-ranging White-tailed Deer, Mule Deer and Elk. The APHIS-proposed rule, Chronic Wasting Disease (CWD)
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From page 111... ...
. Through an examination of CWD, the committee learned that: · The infrastructure to detect, diagnose, and prevent wildlife diseases is an essential element in the nation's framework for dealing with animal diseases and its consequences.
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From page 112... ...
West Nile virus has an extremely broad host range replicating in birds, reptiles, amphibians, mammals, and numerous mosquito vectors. While WNV is primarily a vector-borne zoonotic disease that is maintained through a bird-to-bird transmission cycle via mosquito vectors, new information has also revealed that this flavivirus can be transmitted by other means: for example, contaminated blood products, organ transplantation, maternal transmission via breast milk and intrauterine, percutaneous exposure in a lab setting, and, at least experimentally, direct horizontal transmission between and among birds due to exposures via fecal shedding.
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From page 113... ...
Ecology, wildlife dynamics, and epidemiology are among the scientific disciplines that need to be addressed by the animal health framework in the future. · WNV offers further evidence that the veterinary profession and animal health organizations must develop the expertise, knowledge, and skills needed to address the implications of zoonotic diseases.
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From page 114... ...
In this respect, emergent RNA viruses are notorious because of the presence of quasispecies or "swarms of virus within a viral population," high mutation rates due to lack of proofreading mechanisms for RNA polymerases, and the ability to generate genetic recombinant or reassortant viruses. Recent examples include the emergence of several RNA viruses in swine such as: · The porcine respiratory and reproductive syndrome virus (PRRSV)
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From page 115... ...
will remain important tools in disease diagnosis. However, rapid and unambiguous diagnostic tools are needed for early intervention in the event of a bioterrorism-related national crisis or for identifying novel pathogens.
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From page 116... ...
INTENTIONALLY INTRODUCED PATHOGENS AND DISEASES OF TOXICOLOGICAL ORIGIN Of course, an act of bioterrorism need not involve a bioengineered pathogen. The intentional spread of known microorganisms or microbial toxins can be accomplished using the same routes as accidental introductions, which occur when disease agents are brought to new areas via the movement of air and water, fomites, vectors, infected animals, or animal products.
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From page 117... ...
SUMMARY The lessons of past disease outbreaks and the prospects of future epidemics suggest that the animal health framework faces a formidable challenge in preventing, detecting, and diagnosing the spectrum of animal diseases, some of which have direct consequences for humans as well as animals. The challenge is multifaceted and includes planning for outbreaks; conducting multidisciplinary research across species; developing new vaccines and rapid diagnostic tools; effectively using the broad capabilities of university, industry, state veterinary diagnostic laboratories; and ensuring that an appropriate and state-of-the-art infrastructure exists to accomplish diagnosis.
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