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A zoonosis (; plural zoonoses) or zoonotic disease is an
infectious disease An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dis ...
of humans caused by a pathogen (an infectious agent, such as a
bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
,
virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's ...
, parasite or
prion Prions are misfolded proteins that have the ability to transmit their misfolded shape onto normal variants of the same protein. They characterize several fatal and transmissible neurodegenerative diseases in humans and many other animals. It i ...
) that has jumped from a non-human (usually a
vertebrate Vertebrates () comprise all animal taxon, taxa within the subphylum Vertebrata () (chordates with vertebral column, backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the ...
) to a
human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, an ...
. Typically, the first infected human transmits the infectious agent to at least one other human, who, in turn, infects others. Major modern diseases such as
Ebola virus disease Ebola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a viral hemorrhagic fever in humans and other primates, caused by ebolaviruses. Symptoms typically start anywhere between two days and three weeks after becom ...
and
salmonellosis Salmonellosis, more commonly known as food poisoning is a symptomatic infection caused by bacteria of the ''Salmonella'' type. It is also a food-borne disease and are defined as diseases, usually either infectious or toxic in nature, caused by ...
are zoonoses.
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...
was a zoonotic disease transmitted to humans in the early part of the 20th century, though it has now evolved into a separate human-only disease. Most strains of
influenza Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms ...
that infect humans are human diseases, although many strains of bird flu and
swine flu Swine influenza is an infection caused by any of several types of swine influenza viruses. Swine influenza virus (SIV) or swine-origin influenza virus (S-OIV) refers to any strain of the influenza family of viruses that is endemic in pigs. As o ...
are zoonoses; these viruses occasionally recombine with human strains of the flu and can cause
pandemic A pandemic () is an epidemic of an infectious disease that has spread across a large region, for instance multiple continents or worldwide, affecting a substantial number of individuals. A widespread endemic disease with a stable number of in ...
s such as the
1918 Spanish flu The 1918–1920 influenza pandemic, commonly known by the misnomer Spanish flu or as the Great Influenza epidemic, was an exceptionally deadly global influenza pandemic caused by the H1N1 influenza A virus. The earliest documented case was ...
or the
2009 swine flu The 2009 swine flu pandemic, caused by the H1N1 influenza virus and declared by the World Health Organization (WHO) from June 2009 to August 2010, is the third recent flu pandemic involving the H1N1 virus (the first being the 1918–1920 Span ...
. ''
Taenia solium ''Taenia solium'', the pork tapeworm, belongs to the cyclophyllid cestode family Taeniidae. It is found throughout the world and is most common in countries where pork is eaten. It is a tapeworm that uses humans as its definitive host and pig ...
'' infection is one of the neglected
tropical disease Tropical diseases are diseases that are prevalent in or unique to tropical and subtropical regions. The diseases are less prevalent in temperate climates, due in part to the occurrence of a cold season, which controls the insect population by forci ...
s with public health and veterinary concern in
endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...
regions. Zoonoses can be caused by a range of disease pathogens such as
emergent virus An emergent virus (or emerging virus) is a virus that is either newly appeared, notably increasing in incidence/ geographic range or has the potential to increase in the near future. Emergent viruses are a leading cause of emerging infectious dis ...
es, bacteria, fungi and parasites; of 1,415 pathogens known to infect humans, 61% were zoonotic. Most human diseases originated in non-humans; however, only diseases that routinely involve non-human to human transmission, such as
rabies Rabies is a viral disease that causes encephalitis in humans and other mammals. Early symptoms can include fever and tingling at the site of exposure. These symptoms are followed by one or more of the following symptoms: nausea, vomiting, vi ...
, are considered direct zoonoses. Zoonoses have different modes of transmission. In direct zoonosis the disease is directly transmitted from non-humans to humans through media such as air (
influenza Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms ...
) or through bites and saliva (
rabies Rabies is a viral disease that causes encephalitis in humans and other mammals. Early symptoms can include fever and tingling at the site of exposure. These symptoms are followed by one or more of the following symptoms: nausea, vomiting, vi ...
). In contrast, transmission can also occur via an intermediate species (referred to as a
vector Vector most often refers to: *Euclidean vector, a quantity with a magnitude and a direction *Vector (epidemiology), an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematic ...
), which carry the disease pathogen without getting sick. When humans infect non-humans, it is called
reverse zoonosis A reverse zoonosis, also known as a zooanthroponosis (Greek "animal", "man", ''"''disease") or anthroponosis, is a pathogen reservoired in humans that is capable of being transmitted to non-human animals. Terminology Anthroponosis refers to ...
or anthroponosis. The term is from
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
: ζῷον ''zoon'' "animal" and νόσος ''nosos'' "sickness". Host genetics plays an important role in determining which non-human viruses will be able to make copies of themselves in the human body. Dangerous non-human viruses are those that require few mutations to begin replicating themselves in human cells. These viruses are dangerous since the required combinations of mutations might randomly arise in the
natural reservoir In infectious disease ecology and epidemiology, a natural reservoir, also known as a disease reservoir or a reservoir of infection, is the population of organisms or the specific environment in which an infectious pathogen naturally lives and ...
.


Causes

The emergence of zoonotic diseases originated with the
domestication Domestication is a sustained multi-generational relationship in which humans assume a significant degree of control over the reproduction and care of another group of organisms to secure a more predictable supply of resources from that group. A ...
of animals. Zoonotic transmission can occur in any context in which there is contact with or consumption of animals, animal products, or animal derivatives. This can occur in a companionistic (pets), economic (farming, trade, butchering, etc.), predatory (hunting, butchering or consuming wild game) or research context. Recently, there has been a rise in frequency of appearance of new zoonotic diseases. "Approximately 1.67 million undescribed viruses are thought to exist in
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s and birds, up to half of which are estimated to have the potential to spill over into humans," says a study led by researchers at the
University of California, Davis The University of California, Davis (UC Davis, UCD, or Davis) is a public land-grant research university near Davis, California. Named a Public Ivy, it is the northernmost of the ten campuses of the University of California system. The institu ...
. According to a report from the
United Nations Environment Programme The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on ...
and International Livestock Research Institute large part of the causes are environmental like climate change, unsustainable agriculture, exploitation of wildlife, land use change. Others are linked to changes in human society like more mobility. The organizations propose a set of measures to stop the rise.


Contamination of food or water supply

The most significant zoonotic pathogens causing foodborne diseases are ''Escherichia coli'' O157:H7, ''
Campylobacter ''Campylobacter'' (meaning "curved bacteria") is a genus of Gram-negative bacteria. ''Campylobacter'' typically appear comma- or s-shaped, and are motile. Some ''Campylobacter'' species can infect humans, sometimes causing campylobacteriosis, a d ...
'', '' Caliciviridae'', and ''
Salmonella ''Salmonella'' is a genus of rod-shaped (bacillus) Gram-negative bacteria of the family Enterobacteriaceae. The two species of ''Salmonella'' are ''Salmonella enterica'' and ''Salmonella bongori''. ''S. enterica'' is the type species and is furt ...
''. In 2006 a conference held in Berlin focused on the issue of zoonotic pathogen effects on
food safety Food safety (or food hygiene) is used as a scientific method/discipline describing handling, preparation, and storage of food in ways that prevent food-borne illness. The occurrence of two or more cases of a similar illness resulting from t ...
, urging government intervention and public vigilance against the risks of catching food-borne diseases from
farm-to-table Farm-to-table (or farm-to-fork, and in some cases farm-to-school) is a social movement which promotes serving local food at restaurants and school cafeterias, preferably through direct acquisition from the producer (which might be a winery, brewer ...
dining. Many food-borne outbreaks can be linked to zoonotic pathogens. Many different types of food that have an animal origin can become contaminated. Some common food items linked to zoonotic contaminations include eggs, seafood, meat, dairy, and even some vegetables. Outbreaks involving contaminated food should be handled in preparedness plans to prevent widespread outbreaks and to efficiently and effectively contain outbreaks.


Farming, ranching and animal husbandry

Contact with farm animals can lead to disease in farmers or others that come into contact with infected farm animals.
Glanders Glanders is a contagious zoonotic infectious disease that occurs primarily in horses, mules, and donkeys. It can be contracted by other animals, such as dogs, cats, pigs, goats, and humans. It is caused by infection with the bacterium ''Burkhold ...
primarily affects those who work closely with horses and donkeys. Close contact with cattle can lead to cutaneous anthrax infection, whereas inhalation anthrax infection is more common for workers in
slaughterhouse A slaughterhouse, also called abattoir (), is a facility where animals are slaughtered to provide food. Slaughterhouses supply meat, which then becomes the responsibility of a packaging facility. Slaughterhouses that produce meat that is no ...
s,
tanneries Tanning may refer to: *Tanning (leather), treating animal skins to produce leather *Sun tanning, using the sun to darken pale skin ** Indoor tanning, the use of artificial light in place of the sun **Sunless tanning, application of a stain or dye ...
and wool mills. Close contact with sheep who have recently given birth can lead to infection with the bacterium ''
Chlamydia psittaci ''Chlamydia psittaci'' is a lethal intracellular bacterial species that may cause endemic avian chlamydiosis, epizootic outbreaks in mammals, and respiratory psittacosis in humans. Potential hosts include feral birds and domesticated poultry, ...
,'' causing chlamydiosis (and enzootic abortion in pregnant women), as well as increase the risk of
Q fever Q fever or query fever is a disease caused by infection with '' Coxiella burnetii'', a bacterium that affects humans and other animals. This organism is uncommon, but may be found in cattle, sheep, goats, and other domestic mammals, includin ...
, toxoplasmosis, and
listeriosis Listeriosis is a bacterial infection most commonly caused by ''Listeria monocytogenes'', although '' L. ivanovii'' and '' L. grayi'' have been reported in certain cases. Listeriosis can cause severe illness, including severe sepsis, meni ...
, in the pregnant or otherwise
immunocompromised Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that a ...
.
Echinococcosis Echinococcosis is a parasitic disease of tapeworms of the ''Echinococcus'' type. The two main types of the disease are ''cystic echinococcosis'' and '' alveolar echinococcosis''. Less common forms include ''polycystic echinococcosis'' and ''uni ...
is caused by a tapeworm, which can spread from infected sheep by food or water contaminated by feces or wool. Bird flu is common in chickens and, while rare in humans, the main public health worry is that a strain of bird flu will recombine with a human flu virus and cause a pandemic like the
1918 Spanish flu The 1918–1920 influenza pandemic, commonly known by the misnomer Spanish flu or as the Great Influenza epidemic, was an exceptionally deadly global influenza pandemic caused by the H1N1 influenza A virus. The earliest documented case was ...
. In 2017,
free-range Free range denotes a method of farming husbandry where the animals, for at least part of the day, can roam freely outdoors, rather than being confined in an enclosure for 24 hours each day. On many farms, the outdoors ranging area is fenced, ...
chickens in the UK were temporarily ordered to remain inside due to the threat of bird flu. Cattle are an important reservoir of
cryptosporidiosis Cryptosporidiosis, sometimes informally called crypto, is a parasitic disease caused by ''Cryptosporidium'', a genus of protozoan parasites in the phylum Apicomplexa. It affects the distal small intestine and can affect the respiratory tract i ...
, which mainly affects the immunocompromised. Reports have shown
mink Mink are dark-colored, semiaquatic, carnivorous mammals of the genera ''Neogale'' and '' Mustela'' and part of the family Mustelidae, which also includes weasels, otters, and ferrets. There are two extant species referred to as "mink": the A ...
can also become infected. In Western countries,
Hepatitis E Hepatitis E is inflammation of the liver caused by infection with the hepatitis E virus (HEV); it is a type of viral hepatitis. Hepatitis E has mainly a fecal-oral transmission route that is similar to hepatitis A, although the viruses are un ...
burden is largely dependent on exposure to animal products, and pork is a significant source of infection, in this respect.
Veterinarians A veterinarian (vet), also known as a veterinary surgeon or veterinary physician, is a medical professional who practices veterinary medicine. They manage a wide range of health conditions and injuries in non-human animals. Along with this, vet ...
are exposed to unique
occupational hazard An occupational hazard is a hazard experienced in the workplace. This encompasses many types of hazards, including chemical hazards, biological hazards (biohazards), psychosocial hazards, and physical hazards. In the United States, the Natio ...
s when it comes to zoonotic disease. In the US, studies have highlighted an increased risk of injuries and lack of veterinary awareness of these hazards. Research has proved the importance for continued clinical veterinarian education on occupational risks associated with
musculoskeletal The human musculoskeletal system (also known as the human locomotor system, and previously the activity system) is an organ system that gives humans the ability to move using their muscular and skeletal systems. The musculoskeletal system provid ...
injuries, animal bites, needle-sticks, and cuts. A July 2020 report by the
United Nations Environment Programme The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on ...
stated that the increase in zoonotic pandemics is directly attributable to anthropogenic destruction of nature and the increased global demand for meat, and that the industrial farming of pigs and chickens in particular will be a primary risk factor for the spillover of zoonotic diseases in the future.


Wildlife trade or animal attacks

The wildlife trade may increase spillover risk because it directly increases the number of interactions across animal species, sometimes in small spaces. The origin of the ongoing COVID-19 pandemic is traced to the wet markets in China. *
Rabies Rabies is a viral disease that causes encephalitis in humans and other mammals. Early symptoms can include fever and tingling at the site of exposure. These symptoms are followed by one or more of the following symptoms: nausea, vomiting, vi ...


Insect vectors

*
African sleeping sickness African trypanosomiasis, also known as African sleeping sickness or simply sleeping sickness, is an insect-borne parasitic infection of humans and other animals. It is caused by the species ''Trypanosoma brucei''. Humans are infected by two typ ...
*
Dirofilariasis Dirofilariasis is an infection by parasites of the genus ''Dirofilaria''. It is transmitted through a mosquito bite; its main hosts include dogs and wild canids. These can give rise to granulomas in the pulmonary artery. Some common symptoms inclu ...
* Eastern equine encephalitis *
Japanese encephalitis Japanese encephalitis (JE) is an infection of the brain caused by the Japanese encephalitis virus (JEV). While most infections result in little or no symptoms, occasional inflammation of the brain occurs. In these cases, symptoms may include he ...
*
Saint Louis encephalitis Saint Louis encephalitis is a disease caused by the mosquito-borne Saint Louis encephalitis virus. Saint Louis encephalitis virus is related to Japanese encephalitis virus and is a member of the family ''Flaviviridae''. This disease mainly aff ...
*
Scrub typhus Scrub typhus or bush typhus is a form of typhus caused by the intracellular parasite ''Orientia tsutsugamushi'', a Gram-negative α-proteobacterium of family Rickettsiaceae first isolated and identified in 1930 in Japan.Tularemia Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium ''Francisella tularensis''. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. Occasionally, a form that results in pneumonia or a throat infe ...
*
Venezuelan equine encephalitis Venezuelan equine encephalitis virus is a mosquito-borne viral pathogen that causes Venezuelan equine encephalitis or encephalomyelitis (VEE). VEE can affect all equine species, such as horses, donkeys, and zebras. After infection, equines may ...
*
West Nile fever West Nile fever is an infection by the West Nile virus, which is typically spread by mosquitoes. In about 80% of infections people have few or no symptoms. About 20% of people develop a fever, headache, vomiting, or a rash. In less than 1% of ...
*
Western equine encephalitis The Western equine encephalomyelitis virus is the causative agent of relatively uncommon viral disease ''Western equine encephalomyelitis'' (WEE). An alphavirus of the family ''Togaviridae'', the WEE virus is an arbovirus (arthropod-borne virus) ...
*
Zika fever Zika fever, also known as Zika virus disease or simply Zika, is an infectious disease caused by the Zika virus. Most cases have no symptoms, but when present they are usually mild and can resemble dengue fever. Symptoms may include fever, red ...


Pets

Pets can transmit a number of diseases. Dogs and cats are routinely vaccinated against
rabies Rabies is a viral disease that causes encephalitis in humans and other mammals. Early symptoms can include fever and tingling at the site of exposure. These symptoms are followed by one or more of the following symptoms: nausea, vomiting, vi ...
. Pets can also transmit
ringworm Dermatophytosis, also known as ringworm, is a fungal infection of the skin. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area affected. Symptoms begin four to fourteen days after exposure. Multiple ar ...
and ''
Giardia ''Giardia'' ( or ) is a genus of anaerobic flagellated protozoan parasites of the phylum Metamonada that colonise and reproduce in the small intestines of several vertebrates, causing the disease giardiasis. Their life cycle alternates between ...
'', which are endemic in both animal and human populations. Toxoplasmosis is a common infection of cats; in humans it is a mild disease although it can be dangerous to pregnant women.
Dirofilariasis Dirofilariasis is an infection by parasites of the genus ''Dirofilaria''. It is transmitted through a mosquito bite; its main hosts include dogs and wild canids. These can give rise to granulomas in the pulmonary artery. Some common symptoms inclu ...
is caused by ''
Dirofilaria immitis ''Dirofilaria immitis'', also known as heartworm or dog heartworm, is a parasitic roundworm that is a type of filarial worm, a small thread-like worm, that causes dirofilariasis. It is spread from host to host through the bites of mosquitoe ...
'' through mosquitoes infected by mammals like dogs and cats. Cat-scratch disease is caused by ''
Bartonella henselae ''Bartonella henselae'', formerly ''Rochalimæa henselae'', is a bacterium that is the causative agent of cat-scratch disease ( bartonellosis). ''Bartonella henselae'' is a member of the genus ''Bartonella'', one of the most common types of bact ...
'' and ''
Bartonella quintana ''Bartonella quintana'', originally known as ''Rochalimaea quintana'', and "''Rickettsia quintana''", is a bacterium transmitted by the human body louse that causes trench fever. This bacterial species caused outbreaks of trench fever affecting ...
'', which are transmitted by fleas that are endemic to cats. Toxocariasis is the infection of humans by any of species of
roundworm The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a broa ...
, including species specific to dogs (''
Toxocara canis ''Toxocara canis'' (also known as dog roundworm) is a worldwide-distributed helminth parasite of dogs and other canids. The name is derived from the Greek word "," meaning bow or quiver, and the Latin word "caro," meaning flesh.Bassert , J., & T ...
)'' or cats ('' Toxocara cati'').
Cryptosporidiosis Cryptosporidiosis, sometimes informally called crypto, is a parasitic disease caused by ''Cryptosporidium'', a genus of protozoan parasites in the phylum Apicomplexa. It affects the distal small intestine and can affect the respiratory tract i ...
 can be spread to humans from pet lizards, such as the
leopard gecko The leopard gecko or common leopard gecko (''Eublepharis macularius'') is a ground-dwelling lizard native to the rocky dry grassland and desert regions of Afghanistan, Iran, Pakistan, India, and Nepal. The leopard gecko has become a popular pet, ...
. ''
Encephalitozoon cuniculi ''Encephalitozoon cuniculi'' (''E. cuniculi'') is a mammalian microsporidial pathogen with world-wide distribution. An important cause of neurologic and renal disease in rabbits, ''E. cuniculi'' can also cause disease in immunocompromised peopl ...
'' is a
microsporidia Microsporidia are a group of spore-forming unicellular parasites. These spores contain an extrusion apparatus that has a coiled polar tube ending in an anchoring disc at the apical part of the spore. They were once considered protozoans or prot ...
l parasite carried by many mammals, including rabbits, and is an important
opportunistic pathogen An opportunistic infection is an infection caused by pathogens (bacteria, fungi, parasites or viruses) that take advantage of an opportunity not normally available. These opportunities can stem from a variety of sources, such as a weakened immune ...
in people
immunocompromised Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that a ...
by
HIV/AIDS Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual ma ...
,
organ transplantation Organ transplantation is a medical procedure in which an organ is removed from one body and placed in the body of a recipient, to replace a damaged or missing organ. The donor and recipient may be at the same location, or organs may be transpo ...
, or CD4+ T-lymphocyte deficiency. Pets may also serve as a reservoir of viral disease and contribute to the chronic presence of certain viral diseases in the human population. For instance, approximately 20% of domestic dogs, cats and horses carry anti-Hepatitis E virus
antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
and thus these animals probably contribute to human Hepatitis E burden as well. For non-vulnerable populations (people who are not immunocompromised) the associated disease burden is, however, small.


Exhibition

Outbreak In epidemiology, an outbreak is a sudden increase in occurrences of a disease when cases are in excess of normal expectancy for the location or season. It may affect a small and localized group or impact upon thousands of people across an entire ...
s of zoonoses have been traced to human interaction with, and exposure to, other animals at fairs, live animal markets,
petting zoo A petting zoo (also called a children's zoo, children's farm, or petting farm) features a combination of domesticated animals and some wild species that are docile enough to touch and feed. In addition to independent petting zoos, many general ...
s, and other settings. In 2005, the
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georg ...
(CDC) issued an updated list of recommendations for preventing zoonosis transmission in public settings. The recommendations, developed in conjunction with the National Association of State Public Health Veterinarians, include educational responsibilities of venue operators, limiting public animal contact, and animal care and management.


Hunting and bushmeat

* HIV *
SARS Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the severe acute respiratory syndrome coronavirus (SARS-CoV or SARS-CoV-1), the first identified strain of the SARS coronavirus species, ''sever ...


Deforestation, biodiversity loss and environmental degradation

Kate Jones Kate Jennifer Jones (born 10 April 1979) is an Australian former politician from Queensland. She served as a Labor Party Member of Parliament in the Legislative Assembly of Queensland from 2006 to 2012, and again from 2015 to 2020. Jones firs ...
, Chair of Ecology and Biodiversity at
University College London , mottoeng = Let all come who by merit deserve the most reward , established = , type = Public research university , endowment = £143 million (2020) , budget = � ...
, says zoonotic diseases are increasingly linked to environmental change and human behaviour. The disruption of pristine forests driven by logging, mining, road building through remote places, rapid urbanisation and population growth is bringing people into closer contact with animal species they may never have been near before. The resulting transmission of disease from wildlife to humans, she says, is now "a hidden cost of human economic development". In a guest article, published by
IPBES The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) is an intergovernmental organization established to improve the interface between science and policy on issues of biodiversity and ecosystem services. It ...
, President of the
EcoHealth Alliance EcoHealth Alliance is a US-based non-governmental organization with a stated mission of protecting people, animals, and the environment from emerging infectious diseases. The nonprofit is focused on research that aims to prevent pandemics and p ...
and zoologist Peter Daszak, along with three co-chairs of the 2019 ''
Global Assessment Report on Biodiversity and Ecosystem Services Global means of or referring to a globe and may also refer to: Entertainment * ''Global'' (Paul van Dyk album), 2003 * ''Global'' (Bunji Garlin album), 2007 * ''Global'' (Humanoid album), 1989 * ''Global'' (Todd Rundgren album), 2015 * Bruno ...
'', Josef Settele, Sandra Díaz, and Eduardo Brondizio, wrote that "rampant deforestation, uncontrolled expansion of agriculture, intensive farming, mining and infrastructure development, as well as the exploitation of wild species have created a 'perfect storm' for the spillover of diseases from wildlife to people." Joshua Moon, Clare Wenham and Sophie Harman said that there is evidence that decreased biodiversity has an effect on the diversity of hosts and frequency of human-animal interactions with potential for pathogenic spillover. An April 2020 study, published in the ''
Proceedings of the Royal Society ''Proceedings of the Royal Society'' is the main research journal of the Royal Society. The journal began in 1831 and was split into two series in 1905: * Series A: for papers in physical sciences and mathematics. * Series B: for papers in life ...
'' Part B journal, found that increased virus spillover events from animals to humans can be linked to
biodiversity loss Biodiversity loss includes the worldwide extinction of different species, as well as the local reduction or loss of species in a certain habitat, resulting in a loss of biological diversity. The latter phenomenon can be temporary or permanent, de ...
and
environmental degradation Environmental degradation is the deterioration of the environment through depletion of resources such as quality of air, water and soil; the destruction of ecosystems; habitat destruction; the extinction of wildlife; and pollution. It is define ...
, as humans further encroach on wildlands to engage in agriculture, hunting and resource extraction they become exposed to pathogens which normally would remain in these areas. Such spillover events have been tripling every decade since 1980. An August 2020 study, published in ''
Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are p ...
'', concludes that the
anthropogenic Anthropogenic ("human" + "generating") is an adjective that may refer to: * Anthropogeny, the study of the origins of humanity Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows: * Human im ...
destruction of ecosystems for the purpose of expanding agriculture and human settlements reduces biodiversity and allows for smaller animals such as bats and rats, who are more adaptable to human pressures and also carry the most zoonotic diseases, to proliferate. This in turn can result in more pandemics. In October 2020, the
Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) is an intergovernmental organization established to improve the interface between science and policy on issues of biodiversity and ecosystem services. It ...
published its report on the 'era of pandemics' by 22 experts in a variety of fields, and concluded that anthropogenic destruction of
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') le ...
is paving the way to the pandemic era, and could result in as many as 850,000 viruses being transmitted from animals – in particular birds and mammals – to humans. The increased pressure on ecosystems is being driven by the "exponential rise" in consumption and trade of commodities such as meat, palm oil, and metals, largely facilitated by developed nations, and by a growing human population. According to Peter Daszak, the chair of the group who produced the report, "there is no great mystery about the cause of the Covid-19 pandemic, or of any modern pandemic. The same human activities that drive
climate change and biodiversity loss Climate change has adversely affected both terrestrial and marine ecosystems, and is expected to further affect many ecosystems, including tundra, mangroves, coral reefs, caves etc. Increasing global temperature, more frequent occurrence of ext ...
also drive pandemic risk through their impacts on our environment."


Climate change

According to a report from the
United Nations Environment Programme The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on ...
and International Livestock Research Institute, entitled "Preventing the next pandemic – Zoonotic diseases and how to break the chain of transmission," climate change is one of the 7 human-related causes of the increase in the number of zoonotic diseases. The University of Sydney issued a study, in March 2021, that examines factors increasing the likelihood of
epidemic An epidemic (from Greek ἐπί ''epi'' "upon or above" and δῆμος ''demos'' "people") is the rapid spread of disease to a large number of patients among a given population within an area in a short period of time. Epidemics of infectious d ...
s and pandemics like the COVID-19 pandemic. The researchers found that "pressure on ecosystems, climate change and economic development are key factors" in doing so. More zoonotic diseases were found in high-income countries. In 2022, a big study dedicated to the link between climate change and Zoonosis was published. The study found a strong link between climate change and the epidemic emergence in the last 15 years, as it caused a massive migration of species to new areas, and consequently contact between species which do not normally come in contact with one another. Even in a scenario with weak climatic changes, there will be 15,000 spillover of viruses to new hosts in the next decades. The areas with the most possibilities for spillover are the mountainous tropical regions of Africa and southeast Asia. Southeast Asia is especially vulnerable as it has a large number of bat species that generally do not mix, but could easily if climate change forced them to begin migrating. A 2021 study found possible links between climate change and transmission of COVID-19 through bats. The authors suggest that climate-driven changes in the distribution and robustness of bat species harboring coronaviruses may have occurred in eastern Asian hotspots (southern China, Myanmar and Laos), constituting a driver behind the evolution and spread of the virus.


Secondary transmission

* Ebola and
Marburg Marburg ( or ) is a university town in the German federal state (''Bundesland'') of Hesse, capital of the Marburg-Biedenkopf district (''Landkreis''). The town area spreads along the valley of the river Lahn and has a population of approximate ...
are examples of viral hemorrhagic disease.


History

During most of human
prehistory Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use of ...
groups of
hunter-gatherers A traditional hunter-gatherer or forager is a human living an ancestrally derived lifestyle in which most or all food is obtained by foraging, that is, by gathering food from local sources, especially edible wild plants but also insects, fungi ...
were probably very small. Such groups probably made contact with other such bands only rarely. Such isolation would have caused epidemic diseases to be restricted to any given local population, because propagation and expansion of epidemics depend on frequent contact with other individuals who have not yet developed an adequate
immune response An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of different microorganisms including viruses, bacteria, parasites, and fungi which could ...
. To persist in such a population, a pathogen either had to be a chronic infection, staying present and potentially infectious in the infected host for long periods, or it had to have other additional species as
reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including control ...
where it can maintain itself until further susceptible hosts are contacted and infected. In fact, for many "human" diseases, the human is actually better viewed as an accidental or incidental victim and a dead-end host. Examples include
rabies Rabies is a viral disease that causes encephalitis in humans and other mammals. Early symptoms can include fever and tingling at the site of exposure. These symptoms are followed by one or more of the following symptoms: nausea, vomiting, vi ...
,
anthrax Anthrax is an infection caused by the bacterium '' Bacillus anthracis''. It can occur in four forms: skin, lungs, intestinal, and injection. Symptom onset occurs between one day and more than two months after the infection is contracted. The s ...
,
tularemia Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium ''Francisella tularensis''. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. Occasionally, a form that results in pneumonia or a throat infe ...
and
West Nile virus West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family ''Flaviviridae'', from the genus ''Flavivirus'', which also contains the Zika virus, dengue virus, and yellow fever virus. The virus ...
. Thus, much of human exposure to infectious disease has been zoonotic. Many diseases, even epidemic ones, have zoonotic origin and
measles Measles is a highly contagious infectious disease caused by measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often greater than , cough, ...
,
smallpox Smallpox was an infectious disease caused by variola virus (often called smallpox virus) which belongs to the genus Orthopoxvirus. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) cer ...
,
influenza Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms ...
, HIV, and
diphtheria Diphtheria is an infection caused by the bacterium ''Corynebacterium diphtheriae''. Most infections are asymptomatic or have a mild clinical course, but in some outbreaks more than 10% of those diagnosed with the disease may die. Signs and s ...
are particular examples. Various forms of the
common cold The common cold or the cold is a viral infectious disease of the upper respiratory tract that primarily affects the respiratory mucosa of the nose, throat, sinuses, and larynx. Signs and symptoms may appear fewer than two days after exposur ...
and
tuberculosis Tuberculosis (TB) is an infectious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in w ...
also are adaptations of strains originating in other species. Some experts have suggested that all human viral infections were originally zoonotic. Zoonoses are of interest because they are often previously unrecognized diseases or have increased virulence in populations lacking immunity. The West Nile virus first appeared in the United States in 1999, in the New York City area.
Bubonic plague Bubonic plague is one of three types of plague caused by the plague bacterium (''Yersinia pestis''). One to seven days after exposure to the bacteria, flu-like symptoms develop. These symptoms include fever, headaches, and vomiting, as well ...
is a zoonotic disease, as are
salmonellosis Salmonellosis, more commonly known as food poisoning is a symptomatic infection caused by bacteria of the ''Salmonella'' type. It is also a food-borne disease and are defined as diseases, usually either infectious or toxic in nature, caused by ...
,
Rocky Mountain spotted fever Rocky Mountain spotted fever (RMSF) is a bacterial disease spread by ticks. It typically begins with a fever and headache, which is followed a few days later with the development of a rash. The rash is generally made up of small spots of bleedin ...
, and
Lyme disease Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the ''Borrelia'' bacterium, which is spread by ticks in the genus ''Ixodes''. The most common sign of infection is an expanding red rash, known as erythema migran ...
. A major factor contributing to the appearance of new zoonotic pathogens in human populations is increased contact between humans and wildlife. This can be caused either by encroachment of human activity into wilderness areas or by movement of wild animals into areas of human activity. An example of this is the outbreak of
Nipah virus Nipah virus, scientific name ''Nipah henipavirus'', is a bat-borne virus that causes Nipah virus infection in humans and other animals, a disease with a high mortality rate. Numerous disease outbreaks caused by Nipah virus have occurred in Sout ...
in peninsular Malaysia, in 1999, when
intensive pig farming Intensive pig farming, also known as pig factory farming, is the primary method of pig production, in which grower pigs are housed indoors in group-housing or straw-lined sheds, whilst pregnant sows are housed in gestation crates or pens and g ...
began within the habitat of infected fruit bats. The unidentified infection of these pigs amplified the force of infection, transmitting the virus to farmers, and eventually causing 105 human deaths. Similarly, in recent times
avian influenza Avian influenza, known informally as avian flu or bird flu, is a variety of influenza caused by viruses adapted to birds.spilled over into human populations probably due to interactions between the carrier host and domestic animals. Highly mobile animals, such as bats and birds, may present a greater risk of zoonotic transmission than other animals due to the ease with which they can move into areas of human habitation. Because they depend on the human host for part of their life-cycle, diseases such as African
schistosomiasis Schistosomiasis, also known as snail fever, bilharzia, and Katayama fever, is a disease caused by parasitic flatworms called schistosomes. The urinary tract or the intestines may be infected. Symptoms include abdominal pain, diarrhea, bloody ...
, river blindness, and
elephantiasis Elephantiasis is the enlargement and hardening of limbs or body parts due to tissue swelling. It is characterised by edema, hypertrophy, and fibrosis of skin and subcutaneous tissues, due to obstruction of lymphatic vessels. It may affect the genit ...
are ''not'' defined as zoonotic, even though they may depend on transmission by insects or other vectors.


Use in vaccines

The first vaccine against smallpox by
Edward Jenner Edward Jenner, (17 May 1749 – 26 January 1823) was a British physician and scientist who pioneered the concept of vaccines, and created the smallpox vaccine, the world's first vaccine. The terms ''vaccine'' and ''vaccination'' are derived f ...
in 1800 was by infection of a zoonotic bovine virus which caused a disease called cowpox. Jenner had noticed that milkmaids were resistant to smallpox. Milkmaids contracted a milder version of the disease from infected cows that conferred cross immunity to the human disease. Jenner abstracted an infectious preparation of 'cowpox' and subsequently used it to inoculate persons against smallpox. As a result, smallpox has been eradicated globally, and mass vaccination against this disease ceased in 1981. There are a variety of vaccine varieties, including traditional inactivated pathogen vaccines,
Subunit vaccine A subunit vaccine is a vaccine that contains purified parts of the pathogen that are antigenic, or necessary to elicit a protective immune response. A "subunit" vaccine doesn't contain the whole pathogen, unlike live attenuated or inactivated vac ...
s, live attenuated vaccines. There are also new vaccine technologies such as viral vector vaccines and DNA/RNA Vaccines, which includes the SARS-CoV-2 Coronavirus vaccines.


Lists of diseases


See also

* * * * * * * * * *


References


Bibliography

* . * * * * H. Krauss, A. Weber, M. Appel, B. Enders, A. v. Graevenitz, H. D. Isenberg, H. G. Schiefer, W. Slenczka, H. Zahner: Zoonoses. Infectious Diseases Transmissible from Animals to Humans. 3rd Edition, 456 pages. ASM Press. American Society for Microbiology, Washington, D.C., 2003. . * *


External links


AVMA Collections: Zoonosis Updates

WHO tropical diseases and zoonoses

Detection and Forensic Analysis of Wildlife and Zoonotic Disease

Publications in Zoonotics and Wildlife Disease

A message from nature: coronavirus
United Nations Environment Programme The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on ...
{{Authority control Animal diseases Disease ecology Infectious diseases