Bosmana fem: Created page with "== Zoonosis == '''Zoonosis''' (plural: '''zoonoses''') refers to any infectious disease that naturally transmits from animals to humans. The term derives from the Greek words ''zoon'' (animal) and ''nosos'' (disease). Zoonotic diseases represent a major public health burden globally, with approximately 75% of emerging infectious diseases being zoonotic in origin.Jones, K. E., Patel, N. G., Levy, M. A., et al. (2008). Global trends in emerging infectious diseases. N..."

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Created page with "== Zoonosis == '''Zoonosis''' (plural: '''zoonoses''') refers to any infectious disease that naturally transmits from animals to humans. The term derives from the Greek words ''zoon'' (animal) and ''nosos'' (disease). Zoonotic diseases represent a major public health burden globally, with approximately 75% of emerging infectious diseases being zoonotic in origin.<ref>Jones, K. E., Patel, N. G., Levy, M. A., et al. (2008). Global trends in emerging infectious diseases. N..."

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== Zoonosis ==

'''Zoonosis''' (plural: '''zoonoses''') refers to any infectious disease that naturally transmits from animals to humans. The term derives from the Greek words ''zoon'' (animal) and ''nosos'' (disease). Zoonotic diseases represent a major public health burden globally, with approximately 75% of emerging infectious diseases being zoonotic in origin.<ref>Jones, K. E., Patel, N. G., Levy, M. A., et al. (2008). Global trends in emerging infectious diseases. Nature, 451(7181), 990-993.</ref>

== Definition and Terminology ==

A '''zoonotic disease''' is defined as any disease or infection that is naturally transmissible from animals to humans. The term encompasses:

* '''Direct zoonoses''': Diseases that transmit directly from infected animals to humans
* '''Cyclozoonoses''': Diseases requiring both animals and humans for completion of the parasite lifecycle
* '''Metazoonoses''': Diseases transmitted to humans via insect or animal vectors

The '''zoonotic agent''' (the pathogen causing the disease) may originate from:
* Vertebrate animals (mammals, birds, reptiles, amphibians, fish)
* Invertebrate animals (insects, arachnids, mollusks)
* Environmental sources associated with animal populations

Humans in this context are considered ''accidental hosts'' or ''dead-end hosts'' for many zoonotic pathogens, meaning the pathogen cannot complete its lifecycle in humans alone and typically does not transmit person-to-person.

== Historical Context ==

Zoonotic diseases have shaped human history and civilization:

* '''Ancient period''': Plague, leprosy, and tuberculosis recognized as animal-associated diseases
* '''18th-19th centuries''': Edward Jenner's 1796 vaccination using cowpox (a zoonotic virus) demonstrated the principle of cross-species pathogen use for medical benefit
* '''20th century''': Recognition of zoonotic origins of influenza (1918 pandemic), HIV/AIDS (from non-human primates), and many others
* '''21st century''': High-profile zoonotic pandemics including SARS (2003), H1N1 influenza (2009), Ebola (2014-2016), Zika (2015-2016), and COVID-19 (2019-present)

The study of zoonoses became formalized with the concept of ''One Health'', recognizing the interconnection between animal health, human health, and environmental health.

== Classification ==

=== By Transmission Route ===

'''Direct transmission'''
* Bites and scratches (rabies from bats, raccoons)
* Contact with bodily fluids (Ebola, Marburg)
* Inhalation of aerosolized particles (tuberculosis from cattle, Q fever)
* Ingestion of contaminated food or water (salmonellosis, brucellosis)
* Skin contact (anthrax, ringworm)

'''Vector-mediated transmission'''
* Arthropod vectors: mosquitoes (dengue, yellow fever, Zika), ticks (Lyme disease, tick-borne encephalitis), fleas (plague), flies (sleeping sickness)
* Animal intermediate hosts: snails (schistosomiasis), crustaceans (paragonimiasis)

'''Environmental transmission'''
* Spores from soil or animal excreta (coccidioidomycosis, histoplasmosis)
* Contaminated environmental surfaces

=== By Epidemiological Pattern ===

'''Sporadic zoonoses'''
* Occur irregularly and unpredictably
* Examples: rabies, anthrax, most vector-borne diseases in non-endemic areas

'''Endemic zoonoses'''
* Maintained in animal populations with consistent human cases
* Examples: brucellosis in livestock regions, toxoplasmosis worldwide

'''Epidemic zoonoses'''
* Sudden increase in cases, often following animal-human contact changes or environmental disruption
* Examples: SARS, COVID-19, Nipah virus outbreaks

== Examples of Important Zoonotic Diseases ==

{| class="wikitable sortable"
|-
! Disease !! Zoonotic Agent !! Primary Animal Source !! Transmission Route !! Geographic Distribution
|-
| [[Rabies]] || Lyssavirus || Bats, dogs, raccoons, skunks || Bite wounds, saliva contact || Worldwide
|-
| [[Influenza]] || Influenza A virus || Birds, pigs || Respiratory droplets || Worldwide, seasonal
|-
| [[Tuberculosis]] || ''Mycobacterium bovis'' || Cattle, wildlife || Respiratory, ingestion || Worldwide
|-
| [[Brucellosis]] || ''Brucella'' species || Cattle, sheep, goats, pigs || Contact with tissues, unpasteurized dairy || Mediterranean, Middle East, parts of Asia
|-
| [[Plague]] || ''Yersinia pestis'' || Rodents || Flea bites || Central Asia, parts of Africa
|-
| [[Salmonellosis]] || ''Salmonella'' species || Poultry, reptiles, amphibians || Ingestion of contaminated food || Worldwide
|-
| [[Lyme disease]] || ''Borrelia burgdorferi'' || Deer, small mammals || Tick bite || Northern Hemisphere temperate regions
|-
| [[Dengue fever]] || Dengue virus || Monkeys, mosquitoes || Mosquito bite (''Aedes'' species) || Tropical/subtropical regions
|-
| [[Ebola virus disease]] || Ebola virus || Fruit bats, primates || Contact with blood/body fluids || Sub-Saharan Africa
|-
| [[Toxoplasmosis]] || ''Toxoplasma gondii'' || Cats, other animals || Ingestion of oocysts || Worldwide
|-
| [[Avian influenza]] || Influenza A virus (H5N1, H7N9, etc.) || Birds || Contact with infected birds || Worldwide in wild birds
|-
| [[Nipah virus infection]] || Nipah virus || Fruit bats, pigs || Contact with secretions, respiratory || Southeast Asia
|-
| [[HIV/AIDS]] || HIV || Non-human primates (SIV) || Contact with blood/body fluids || Worldwide, originated in Central Africa
|-
| [[SARS]] || SARS-CoV || Civets, bats || Respiratory droplets || Primarily East/Southeast Asia
|-
| [[COVID-19]] || SARS-CoV-2 || Bats (proposed), possibly intermediate hosts || Respiratory droplets || Worldwide pandemic
|}

== Risk Factors for Zoonotic Disease Transmission ==

=== Animal-Related Factors ===

* '''Pathogen prevalence in animal populations''': Higher infection rates in reservoir species increase transmission risk
* '''Animal reservoir size''': Larger populations support sustained pathogen maintenance
* '''Animal behavior''': Nocturnal animals reduce incidental human contact; animals entering human habitats increase risk
* '''Wildlife-livestock interface''': Contact between wild and domestic animals facilitates spillover
* '''Animal trade and transport''': Movement of infected animals to new geographic areas

=== Human Behavioral Factors ===

* '''Occupational exposure''': Hunters, farmers, veterinarians, laboratory workers, wildlife handlers
* '''Food practices''': Hunting and consuming bushmeat, consuming raw/undercooked meat, consuming unpasteurized dairy
* '''Pet ownership''': Close contact with companion animals
* '''Ecological practices''': Deforestation, habitat destruction that brings humans and wildlife into contact
* '''Travel and trade''': Movement to regions with endemic zoonoses or importation of infected animals/products

=== Environmental and Social Factors ===

* '''Ecological disruption''': Land-use changes, deforestation increase wildlife contact
* '''Climate change''': Alters animal distributions and breeding cycles, expanding vector ranges
* '''Socioeconomic status''': Limited access to healthcare, sanitation, and preventive measures
* '''Urbanization''': Dense human populations in proximity to wildlife reservoirs
* '''Armed conflict''': Disrupts disease surveillance and containment systems

== Mechanisms of Spillover ==

Zoonotic disease emergence typically involves several steps:

# '''Exposure''': Humans contact infected animals or contaminated environments
# '''Infection''': Pathogen infects human host cells
# '''Establishment''': Pathogen replicates and establishes infection
# '''Transmission''': Infected human transmits to other humans (not required for all zoonoses)
# '''Adaptation''': Pathogen evolves to become more suited to human hosts (occurs over multiple generations)

The [[basic reproduction number]] (R₀) in animals versus humans determines whether a zoonotic disease can sustain human-to-human transmission chains and cause epidemics.

== Public Health Significance ==

=== Disease Burden ===

* Approximately 60% of known human infectious diseases are zoonotic
* Approximately 75% of emerging infectious diseases have animal origins
* Annual economic losses from zoonotic disease and zoonotic animal disease exceed $220 billion USD globally<ref>Burns, A., van Panhuis, W., & Sazawal, S. (2016). The hidden pandemic of animal diseases. Chatham House Review.</ref>

=== Pandemic Risk ===

Zoonotic pathogens account for most pandemic threats:
* 1918 H1N1 influenza pandemic: ~50-100 million deaths
* 2009 H1N1 influenza pandemic: ~100,000-400,000 deaths
* HIV/AIDS pandemic: >40 million deaths to date
* COVID-19 pandemic: >7 million deaths (official count, likely underestimated)

=== Healthcare Burden ===

* Increased hospitalizations and healthcare costs
* Potential for rapid spread in healthcare settings
* Challenges to diagnostic and treatment infrastructure

== Prevention and Control ==

=== Individual-Level Measures ===

* '''Hand hygiene''': Regular handwashing, especially after animal contact
* '''Food safety''': Thorough cooking of meat, pasteurization of dairy
* '''Protective equipment''': Appropriate use of gloves, masks, and clothing in occupational settings
* '''Vaccination''': Where available (rabies post-exposure prophylaxis, avian influenza vaccines)
* '''Vector control''': Insect repellents, bed nets, permethrin-treated clothing against arthropods
* '''Animal precautions''': Avoiding wild animals, safe handling of pets

=== Community-Level Measures ===

* '''Disease surveillance''': Early detection of zoonotic disease cases and animal disease outbreaks
* '''Contact tracing''': Identification of exposed individuals
* '''Isolation and quarantine''': Separating infected individuals
* '''Vector control programs''': Mosquito spraying, tick control in endemic areas
* '''Public education''': Communication about zoonotic risks and prevention

=== Population-Level Measures ===

* '''One Health approach''': Coordinated efforts across human health, animal health, and environmental sectors
* '''Wildlife management''': Population control of reservoir species where appropriate
* '''Habitat modification''': Environmental management to reduce human-wildlife contact
* '''Biosecurity''': Controls on animal movement and trade
* '''Regulatory frameworks''': Laws governing bushmeat trade, pet trade, animal agriculture practices
* '''Climate adaptation''': Strategies to address climate-driven changes in disease distribution

=== Healthcare System Preparedness ===

* '''Diagnostic capacity''': Ability to rapidly identify zoonotic pathogens
* '''Infection control''': Protocols for managing zoonotic disease patients
* '''Supply stockpiles''': Maintenance of personal protective equipment and medical countermeasures
* '''Healthcare worker training''': Recognition and management of zoonotic diseases
* '''Research and development''': Investment in vaccines, therapeutics, and diagnostics

== Emerging Zoonotic Diseases ==

=== Factors Driving Emergence ===

* '''Ecological changes''': Habitat loss, climate change, agricultural intensification
* '''Demographic change''': Growing human population, urbanization
* '''Behavioral change''': Consumption of novel animal foods, increased wildlife trade
* '''Technological change''': Increased travel and connectivity facilitates spread
* '''Pathogen evolution''': Natural mutation and selection of viral and bacterial populations

=== Notable Emerging Zoonoses ===

* '''Henipavirus infections''' (Nipah, Hendra): Spillover from fruit bats through intermediate animal hosts
* '''Filovirus infections''' (Ebola, Marburg): Fruit bat-to-human spillover with secondary transmission
* '''SARS and COVID-19''': Suspected bat coronavirus origin with potential intermediate hosts
* '''Antimicrobial-resistant bacteria''': Including methicillin-resistant ''Staphylococcus aureus'' (MRSA) from livestock
* '''Novel arboviruses''': Zika, chikungunya expanding into new regions due to vector range expansion

== The One Health Approach ==

The '''One Health''' framework recognizes that human health, animal health, plant health, and environmental health are interconnected. This integrated approach to zoonotic disease:

* Involves collaboration between human medicine, veterinary medicine, and environmental sciences
* Addresses shared infectious disease threats at the human-animal-environment interface
* Promotes cross-sector communication and coordinated surveillance
* Advocates for sustainable food production and wildlife management
* Seeks to balance economic development with disease prevention

Organizations implementing One Health include [[World Health Organization|WHO]], [[Food and Agriculture Organization|FAO]], [[World Organisation for Animal Health|OIE]], [[United Nations Environment Programme|UNEP]], and national governments.

== Controversies and Debates ==

=== Origins of Pandemic Pathogens ===

The animal origin of certain pathogens, particularly SARS-CoV-2, remains contested. Key debates include:

* Evidence for and against animal spillover origins
* The role of intermediate hosts in spillover events
* The potential for laboratory accidents in pathogen transmission
* Geographic location of initial spillover events

=== Balancing Wildlife Conservation and Disease Control ===

* Tension between protection of endangered species and disease control measures
* Questions about when and how to manage wildlife populations
* Ethics of culling animals to prevent disease spillover

=== Animal Agriculture and Zoonotic Disease ===

* Factory farming practices and antimicrobial resistance
* Regulation of livestock production systems
* Trade-offs between food security and disease prevention

== See Also ==

* [[Pandemic|Pandemics]]
* [[Emerging infectious disease]]
* [[Vector-borne disease]]
* [[Reservoir (epidemiology)]]
* [[One Health]]
* [[Spillover (disease)]]
* [[Wildlife disease]]
* [[Antimicrobial resistance]]
* [[Food safety]]
* [[Public health]]

== References ==

<references />

== Further Reading ==

* Jones, B. A., Grace, D., Kock, R., et al. (2013). Zoonosis emergence linked to agricultural intensification and environmental change. ''Proceedings of the National Academy of Sciences'', 110(21), 8399-8404.
* Morse, S. S., Mazet, J. A., Woolhouse, M., et al. (2012). Prediction and prevention of the next pandemic zoonosis. ''The Lancet'', 380(9857), 1956-1965.
* Woolhouse, M. E., & Gowtage-Sequeria, S. (2005). Host range and emerging and reemerging pathogens. ''Emerging Infectious Diseases'', 11(12), 1842-1847.
* World Health Organization. (2020). Antimicrobial resistance: Global Report on Surveillance. WHO Publications.

== External Links ==

* [https://www.who.int/news-room/fact-sheets/detail/zoonoses WHO Fact Sheet on Zoonoses]
* [https://www.cdc.gov/onehealth/index.html CDC One Health Page]
* [https://www.oie.int/ World Organisation for Animal Health]

{{Categories|Epidemiology|Infectious diseases|Public health|Zoonosis|One Health}}

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