![Rabid dog](https://upload.wikimedia.org/wikipedia/commons/9/90/Rabid_dog.jpg)
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 dise ...
of humans caused by a
pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
(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 1 ...
,
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
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 ...
) that has
jumped from a non-human (usually a
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
) 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, ...
.
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 a ...
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
"Bird Flu" is an urumee melam-dance song by recording artist M.I.A. on her second studio album '' Kala'' (2007). It was released as a digital download in 2006 through XL Recordings under exclusive license to Interscope Records in the US. Cr ...
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 (epidemiology), endemic disease wi ...
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 influenza A virus subtype H1N1, 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 f ...
. ''
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 pigs ...
'' infection is one of the neglected
tropical disease
Tropical diseases are Infectious disease, diseases that are prevalent in or unique to tropics, tropical and subtropics, subtropical regions. The diseases are less prevalent in temperate climates, due in part to the occurrence of a cold season, whic ...
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 elsew ...
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 Viral evolution, appeared, notably increasing in incidence (epidemiology), incidence/geographic range limit, geographic range or has the potential to increase in the near future. ...
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 p ...
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 rep ...
.
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. ...
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 institut ...
. 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 th ...
and
International Livestock Research Institute
The International Livestock Research Institute or ILRI is an international agricultural research institute within the CGIAR – formerly the Consultative Group for International Agricultural Research. It was established in 1994 by merger of t ...
large part of the causes are environmental like
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
, 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'', ''
Caliciviridae
The ''Caliciviridae'' are a family of "small round structured" viruses, members of Class IV of the Baltimore scheme. Caliciviridae bear resemblance to enlarged picornavirus and was formerly a separate genus within the picornaviridae. They are p ...
'', 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 fur ...
''.
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 ''Burkhol ...
primarily affects those who work closely with horses and donkeys. Close contact with cattle can lead to
cutaneous anthrax infection, whereas
inhalation 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 ...
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 t ...
and
wool mill
Textile Manufacturing or Textile Engineering is a major industry. It is largely based on the conversion of fibre into yarn, then yarn into fabric. These are then dyed or printed, fabricated into cloth which is then converted into useful goods ...
s. Close contact with sheep who have recently given birth can lead to infection with the bacterium ''
Chlamydia psittaci
''Chlamydia psittaci'' is a lethal intracellular parasite, intracellular bacterial species that may cause Endemism, endemic Bird, avian chlamydiosis, epizootic outbreaks in mammals, and respiratory psittacosis in humans. Potential hosts include ...
,'' causing chlamydiosis (and
enzootic abortion
''Chlamydia abortus'' is a species in Chlamydiota that causes abortion and fetal death in mammals, including humans. ''Chlamydia abortus'' was renamed in 1999 as ''Chlamydophila psittaci'' along with all Chlamydiota except ''Chlamydia trachomat ...
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, including ...
,
toxoplasmosis
Toxoplasmosis is a parasitic disease caused by ''Toxoplasma gondii'', an apicomplexan. Infections with toxoplasmosis are associated with a variety of neuropsychiatric and behavioral conditions. Occasionally, people may have a few weeks or months ...
, 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, men ...
, 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 ''unic ...
is caused by a tapeworm, which can spread from infected sheep by food or water contaminated by feces or wool.
Bird flu
"Bird Flu" is an urumee melam-dance song by recording artist M.I.A. on her second studio album '' Kala'' (2007). It was released as a digital download in 2006 through XL Recordings under exclusive license to Interscope Records in the US. Cr ...
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 in ...
, 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 unrel ...
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 Nation ...
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 prov ...
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 th ...
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
Industrial agriculture is a form of modern farming that refers to the industrialized production of crops and animals and animal products like eggs or milk. The methods of industrial agriculture include innovation in agricultural machinery and far ...
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
The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identif ...
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 ty ...
*
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 incl ...
*
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 affe ...
*
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 ...
*
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 vir ...
*
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 a ...
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
Toxoplasmosis is a parasitic disease caused by ''Toxoplasma gondii'', an apicomplexan. Infections with toxoplasmosis are associated with a variety of neuropsychiatric and behavioral conditions. Occasionally, people may have a few weeks or months ...
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 incl ...
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 mosquitoes ...
'' through mosquitoes infected by mammals like dogs and cats.
Cat-scratch disease
Cat-scratch disease (CSD) or felinosis is an infectious disease that most often results from a scratch or bite of a cat. Symptoms typically include a non-painful bump or blister at the site of injury and painful and swollen lymph nodes. People m ...
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 bacte ...
'' 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 1 ...
'', which are transmitted by fleas that are endemic to cats.
Toxocariasis
Toxocariasis is an illness of humans caused by the dog roundworm ('' Toxocara canis'') and, less frequently, the cat roundworm (''Toxocara cati'').https://academic.oup.com/ajcp/article/142/suppl_1/A104/1771175 Eosinophilic Pseudoleukemia Due to T ...
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
''Toxocara cati'', also known as the feline roundworm, is a parasite of cats and other felids. It is one of the most common nematodes of cats, infecting both wild and domestic felids worldwide. Adult worms are localised in the gut of the host. I ...
'').
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 in ...
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 people ...
'' 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 ...
,
organ transplantation
Organ transplantation is a medical procedure in which an organ (anatomy), 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 organ ...
, 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
fair
A fair (archaic: faire or fayre) is a gathering of people for a variety of entertainment or commercial activities. Fairs are typically temporary with scheduled times lasting from an afternoon to several weeks.
Types
Variations of fairs incl ...
s,
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, Georgi ...
(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
The National Association of State Public Health Veterinarians (NASPHV) develops and publishes uniform public health procedures involving zoonotic disease (diseases transmitted from animals to people) in the United States and its territories. These ...
, 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 ''
'', 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 s ...
''
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 (biophysical), environment through depletion of resources such as quality of air, water and soil; the destruction of ecosystems; habitat destruction; the extinction of wildlife; an ...
, 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 physics, physical world or universe. "Nature" can refer to the phenomenon, 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. ...
'', 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
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'') l ...
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 th ...
and
International Livestock Research Institute
The International Livestock Research Institute or ILRI is an international agricultural research institute within the CGIAR – formerly the Consultative Group for International Agricultural Research. It was established in 1994 by merger of t ...
, 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 Ancient Greek, 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 ...
s and pandemics like the
COVID-19 pandemic
The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identif ...
. 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
A high-income economy is defined by the World Bank as a nation with a gross national income per capita of US$12,696 or more in 2020, calculated using the Atlas method. While the term "high-income" is often used interchangeably with "First World" a ...
.
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 contro ...
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 sk ...
,
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) c ...
,
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 exposu ...
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 ...
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 a ...
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 a ...
,
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. and West Nile virus have
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 s ...
,
river blindness
Onchocerciasis, also known as river blindness, is a disease caused by infection with the parasitic worm ''Onchocerca volvulus''. Symptoms include severe itching, bumps under the skin, and blindness. It is the second-most common cause of blindne ...
, 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
Cowpox is an infectious disease caused by the ''cowpox virus'' (CPXV). It presents with large blisters in the skin, a fever and swollen glands, historically typically following contact with an infected cow, though in the last several decades more ...
. 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 va ...
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
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References
Bibliography
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* 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. .
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External links
AVMA Collections: Zoonosis UpdatesWHO tropical diseases and zoonosesDetection and Forensic Analysis of Wildlife and Zoonotic DiseasePublications 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 th ...
{{Authority control
Animal diseases
Disease ecology
Infectious diseases