What Pathogens and Why? Answer: Zoonoses. Zoonoses: microorganisms of animal origin that can also infect humans Animal-to-human transmissionHuman-to-animalHuman-to-human by the same pathogensTransmission routes:Direct contactIndirect contactFoodWaterAirOther environmental media and routes.
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1. Overview of Pathogens Associated with AFOs: What Organisms and Why? Mark D. Sobsey
University of North Carolina
Chapel Hill, NC
Email: [email protected]
4. Animal Wastes Potentially Contain Human Pathogens at High Concentrations Agricultural animals can harbor and shed high concentrations of viruses, bacteria and parasites that are pathogenic for humans
Levels of human pathogens in animal manures can be millions to billions/gram of feces
Antibiotic use also causes high proportions of antibiotic-resistant bacteria in animal wastes
Animal waste pathogens have caused disease and death in humans via:
Farm workers and other people with animal contact
Environmental contamination: notably water and air
5. Some Known Zoonotic Pathogens Causing Infection and/or Disease Viruses: rotaviruses, reoviruses, noroviruses, SARS, hepatitis E virus, (para)myxoviruses (Swine flu, “bird flu, Nipah, etc.)
Bacteria: Salmonella, E. coli O157:H7, Yersinia enterocolitica, Campylobacter spp., Mycobacterium avium
Protozoan parasites: Cryptosporidium parvum, Giardia lamblia, and Toxoplasma gondii
Helminths: Trichuris trichuria, Taenia spp., Echinococcus spp.
Prions: Bovine spongiform encephalopathic agent (BSE); variant Creuzfeldt Jacob
Many are responsible for known cases and outbreaks of foodborne and waterborne diseases
Consequences: temporary morbidity to mortality, especially in high-risk individuals
10. Zoonotic Pathogen Issues to Address Which zoonoses are foodborne pathogens; how/where do they contaminate food?
Which zoonoses are waterborne; how/where do they contaminate water
Which zoonoses are airborne; how/where do they contaminate air
What are the principal microbes of animal (AFO) origin that can contaminate the environment and cause human disease
what are their origins and sources?
What are the pathways of exposure and transmission to people?
What is the contribution of AFOs, and pastureland systems to the total burden of infectious disease from these organisms?
What features are most important to the ability of zoonotic pathogens to survive in the environment?
11. Zoonotic Pathogen Issues to Address Can strains of zoonotic microorganisms that infect humans be differentiated from those that are not infectious to humans?
To what extent and how do animal pathogens evolve (mutate) and interact to become human pathogens?
Do current public health, animal agriculture and environmental practices protect the public from exposure to zoonotic pathogens?
What analytical methods and indicators are available to detect, quantify and identify the pathogens and monitor treatment and control processes?
What are the most effective Rx processes, management practices and systems for these pathogens to protect the environment
How can management of sources and exposure pathways control the potential for human exposure?
12. Zoonotic Pathogen Issues to Address Which pathogens fall outside the current “prevention and control envelope”?
What are the appropriate research and regulatory approaches to address this issue?
Which zoonotic pathogens are candidates for future concerns and evaluation with respect to human health risks from animal agriculture?
13. Biological Factors Contributing to Pathogen (Re-)Emergence Genetic changes due to mutation
Genetic changes due to recombination, reassortment, and other gene “swapping”
Changes in gene expression
Changes in human and animal hosts that alter pathogen properties, including host range and infectivity
Environmental changes altering pathogen-host interactions
14. Factors Influencing Zoonotic Pathogen Risks Pathogen adaptability
Increasing reservoir/routes of introduction into the environment
“Proximity” of reservoir to water/human exposure
Persistence of pathogen in the environment and resistance to control measures
Human behavior factors
Outcome factors (infectivity, severity of adverse health impacts)
Public health factors
potential contribution of an exposure route to overall burden of disease
15. Other Factors Contributing to Zoonotic Risks Human intrusion into sylvan and other undeveloped regions
Intense human exposure to animals from agriculture and other activities (e.g., pets, including exotic ones)
Increased urbanization and animal vector attraction
Growing immune compromised human and animal populations
Global climate change and other ecological alterations
Changing and severe weather
Continued use of antibiotics for therapeutic and non-therapeutic purposes
Travel, migration and importation of humans and animals
International trade in animals, foods and other and animal products
16. Practices and Systems for Animals, Food and the Environment Which management and other practices will be protective?
Current practices adequate?
New or better approaches needed to protect human health?
Can zoonotic pathogens be best managed at the source?
Prevention measures (vaccines, drugs, genetic manipulation?)
Animal health interventions
Human health interventions
Through animal husbandry and management practices?
Food safety practices: HACCP, pre-/post-harvest processes?
Waste Rx, water pollution control & environmental management.?
Waste Rx, runoff management, riparian buffers, DW water Rx
Are optimum combinations of all/some multiple barriers the best approach?
18. Some Bioaerosol Materials and Exposure Routes Animals, including fur, feathers, skin flakes, etc.
Litter and bedding
Spray irrigation of liquid wastes
Land spreading of manure solids
Waste treatment processes, especially mixing and other mechanical processes
19. Microbial Reductions by Liquid Animal Waste Treatment Processes and Management Systems Most evaluated only for fecal coliform bacteria reductions
little/no data on bacterial pathogens, viruses and parasites
Many achieve moderate (90-99%) pathogen reductions:
high pathogen levels remain in treated liquids and solids
Some achieve high (>99.99%) pathogen reductions:
high temperature (thermophilic and composting) processes
Alkaline (lime) stabilization at pH >11
Some give ineffective (<90%) microbial reductions
Overland flow; other biological systems of short residence time
Survival, transport and fate of pathogens after land application and other post-treatment management options is poorly characterized
20. Animal Solid Waste Management and Pathogens Pathogen levels decline with time in stored manure
reductions poorly characterized for different storage conditions and pathogens
Composting increases rate of pathogen reduction
Pathogen reductions of >99.99% are expected
Land application method and rate and environmental conditions will influence pathogen survival on land/in soil
Stored manure can attract vectors
pathogen recontamination by animals and other vectors (e.g., birds, mice, flies) is a concern
vectors spread pathogens to other places, animals & people
Physical handling of dry manure can increase airborne dissemination of pathogens (bioaerosols)
21. Issues and Needs to Address Animal waste management systems can cause pathogen contamination of land, air and surface and ground waters
Greater risks of pathogen contamination during/after precipitation
How can systems be further improved to reduce pathogen levels in foods, reaching off-farm environmental media or contacting humans?
Is the EPA CAFO regulation an adequate step?
Probably not for pathogens
NPDES permits, Best Practicable Control Technologies, Best Available Technologies, Best Management Practices, Effluent Guidelines and Total Maximum Daily Loads
Identifying BMPs for pathogen reduction and containment
Understand pathogen contamination and human health risks
Characterize pathogen fate in Rx processes and management systems
Assess pathogen impacts on environmental media and human health
23. Goals/Approaches to Address Pathogens from AFOs Provide guidance to stakeholders
Characterize current systems and address current issues
Anticipate and identify potential future problems:
Which present, emerging and re-emerging pathogens?
Which exposure routes?
Which management and other practices will be protective?
Disease surveillance, diagnosis and response measures
What surveillance systems are` best to detect new zoonoses?
How can new and (re-)emerging pathogens be best detected?
What disease surveillance, investigation and response systems will best detect, diagnose and contain/rid zoonotic pathogens?
How can agriculturalists, microbiologists, veterinarians, physicians, epidemiologists, biosecurity specialists and other public health and environmental specialists best work together?
24. Need for a Risk-based Approach