anthroponotic
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OR:

A reverse
zoonosis A zoonosis (; plural zoonoses) or zoonotic disease is an infectious disease of humans caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that has jumped from a non-human (usually a vertebrate) to a human. ...
, also known as a zooanthroponosis (Greek "animal", "man", ''"''disease") or anthroponosis, is 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 ...
reservoired in
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, cultu ...
s that is capable of being transmitted to non-human
animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
s.


Terminology

Anthroponosis refers to pathogens sourced from humans and can include human to non-human animal transmission but also human to human transmission. The term zoonosis technically refers to disease transferred between any animal and another animal, human or non-human, without discretion, and also been defined as disease transmitted from animals to humans ''and vice versa''. Yet because of human-centered medical biases, zoonosis tends to be used in the same manner as anthropozoonosis which specifically refers to pathogens reservoired in non-human animals that are transmissible to humans. Additional confusion due to frequency of scientists using "anthropozoonosis" and "zooanthroponosis" interchangeably was resolved during a 1967 Joint Food and Agriculture and
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...
committee meeting that recommended the use of "zoonosis" to describe the bidirectional interchange of infectious pathogens between animals and humans. Furthermore, because humans are rarely in direct contact with wild animals and introduce pathogens through "soft contact", the term "sapronotic agents" must be introduced. Sapronoses (Greek "decaying") refers to human diseases that harbor the capacity to grow and replicate (not just survive or contaminate) in
abiotic In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them under ...
environments such as soil, water, decaying plants, animal corpses,
excreta Excretion is a process in which metabolic waste is eliminated from an organism. In vertebrates this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific tasks after lea ...
, and other substrata. Additionally, sapro-zoonoses can be characterized as having both a live host and a non-animal developmental site of organic matter, soil, or plants. Obligate intracellular parasites that cannot replicate outside of cells and are entirely reproductively reliant on entering the cell to use intracellular resources such as viruses, rickettsiae, chlamydiae, and Cryptosporidium parvum cannot be sapronotic agents.


Etymological pitfalls

Categorizing of disease into epidemiologic classes by the infection's supposed source or the direction of transmission raises a number of contradictions that could be resolved by the use of cyclical models. See the following scenarios:


''Zoonosis'' vs ''reverse zoonosis'' vs ''anthroponosis''

In the case of diseases transferred from
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
vectors such as urban
yellow fever Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains – particularly in the back – and headaches. Symptoms typically improve within five days. ...
,
dengue Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. These may include a high fever, headache, vomiting, muscle and joint pains, and a characteristic ...
, epidemic typhus, tickborne relapsing fever,
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 ...
, and
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
, the differentiation between terms becomes ever more hazy. For example, a human infected with malaria is bitten by a mosquito that is subsequently infected as well. This is a case of reverse zoonosis (human to animal). However, the newly infected mosquito then infects another human. This could be a case of zoonosis (animal to human) if the mosquito is considered the original source, or anthroponosis (human to human) if the human is considered the original source. If this infected mosquito instead infected a non-human primate, it could be considered a case of reverse zoonosis/zooanthroponosis (human to animal) if the human is considered the primary source, or simply zoonosis (animal to animal) if the mosquito is considered the primary source.


''Zoonosis'' vs ''anthroponosis''

Similarly,
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 ...
originating in simians (crossover due to humans consuming wild chimpanzee bushmeat) and
influenza A '' A virus'' (''IAV'') causes influenza in birds and some mammals, and is the only species of the genus ''Alphainfluenzavirus'' of the virus family ''Orthomyxoviridae''. Strains of all subtypes of influenza A virus have been isolated from wild ...
viruses originating in avians (crossover due to an antigenic shift) could have initially been considered a zoonotic transference as the infections first came from vertebrate animals, but could currently be regarded as an anthroponosis because of its potential to transfer between human to human.


''Sapronosis'' vs ''sapro-zoonosis''

Typical examples of sapronotic agents are fungal such as
coccidioidomycosis Coccidioidomycosis (, ), commonly known as cocci, Valley fever, as well as California fever, desert rheumatism, or San Joaquin Valley fever, is a mammalian fungal disease caused by '' Coccidioides immitis'' or ''Coccidioides posadasii''. Coccid ...
,
histoplasmosis Histoplasmosis is a fungal infection caused by '' Histoplasma capsulatum''. Symptoms of this infection vary greatly, but the disease affects primarily the lungs. Occasionally, other organs are affected; called disseminated histoplasmosis, it can ...
,
aspergillosis Aspergillosis is a fungal infection of usually the lungs, caused by the genus ''Aspergillus'', a common mould that is breathed in frequently from the air around, but does not usually affect most people. It generally occurs in people with lung di ...
,
cryptococcosis Cryptococcosis is a potentially fatal fungal infection of mainly the lungs, presenting as a pneumonia, and brain, where it appears as a meningitis. Cough, difficulty breathing, chest pain and fever are seen when the lungs are infected. When the ...
, ''Microsporum gypseum''. Some can be bacterial from the
sporulating In biology, a spore is a unit of sexual reproduction, sexual or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of ...
clostridium and bacillus to ''Rhodococcus equi, Burkholderia pseudomallei, Listeria'', ''Erysipelothrix'', ''Yersinia pseudotuberculosis,'' legionellosis, Pontiac fever, ''and'' nontuberculous mycobacterioses. Other sapronotic agents are amebic as in primary amebic meningoencephalitis. Yet again, difficulties in classification arise in the case of sporulating bacteria whose infectious spores are only produced after a significant period of inactive vegetative growth within an abiotic environment, yet this is still considered a case of sapronoses. However, cases of zoo-sapronoses involving ''
Listeria ''Listeria'' is a genus of bacteria that acts as an intracellular parasite in mammals. Until 1992, 17 species were known, each containing two subspecies. By 2020, 21 species had been identified. The genus is named in honour of the British pio ...
'', '' Erysipelothrix'', '' Yersinia pseudotuberculosis'', ''Burkholderia pseudomallei'', and ''Rhodococcus equi'' can be transferred by an animal or an abiotic substrate but usually occur via a fecal-oral route between humans and other animals.


Cases with modes of transmission


Arthropod vectors


Malaria

Malaria involves the cyclical infection of animals (human and non-human) and
mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...
es from the genus
Anopheles ''Anopheles'' () is a genus of mosquito first described and named by J. W. Meigen in 1818. About 460 species are recognised; while over 100 can transmit human malaria, only 30–40 commonly transmit parasites of the genus ''Plasmodium'', which ...
with a number of
Plasmodium ''Plasmodium'' is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of ''Plasmodium'' species involve development in a blood-feeding insect host which then injects parasites into a ver ...
species. The Plasmodium parasite is transferred to the mosquito as it feeds on the blood of the infected animal whereupon it begins a sporogenic cycle in the gut of the mosquito that will infect another animal at the next blood meal. There does not seem to be any deleterious effects to the mosquito as a result of the parasitic infection. The
Plasmodium brasilianum ''Plasmodium brasilianum'' is a parasite that infects many species of platyrrhine monkeys in South and Central America. Description Sequence analysis of circumsporozoite protein, merozoite surface protein-1, and small subunit ribosomal RNA of ...
parasite normally found in primates is morphologically similar to the malarial inducing Plasmodium malariae that is more commonly found in humans and it is contested as to whether the two are actually different species. Nevertheless, 12 reports of malaria in the remotely located indigenous
Yanomami The Yanomami, also spelled Yąnomamö or Yanomama, are a group of approximately 35,000 indigenous people who live in some 200–250 villages in the Amazon rainforest on the border between Venezuela and Brazil. Etymology The ethnonym ''Yanomami' ...
communities of the Venezuelan
Amazon Amazon most often refers to: * Amazons, a tribe of female warriors in Greek mythology * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon River, in South America * Amazon (company), an American multinational technolog ...
arose where it was surprisingly found to be caused by a strain of P. brasilianum with 100% identical to sequences found in Alouatta seniculus monkeys. This suggests a definite zoonosis and high possibility of spillback back into non-human primate bands as reverse zoonoses.


African sleeping sickness

''
Trypanosoma brucei gambiense ''Trypanosoma brucei'' is a species of parasitic kinetoplastid belonging to the genus ''Trypanosoma'' that is present in sub-Saharan Africa. Unlike other protozoan parasites that normally infect blood and tissue cells, it is exclusively extracellu ...
(T. b. gambiense) is a species of'' African
trypanosomes Trypanosomatida is a group of kinetoplastid excavates distinguished by having only a single flagellum. The name is derived from the Greek ''trypano'' (borer) and ''soma'' (body) because of the corkscrew-like motion of some trypanosomatid species. ...
which are protozoahemoflagellates responsible for
trypanosomiasis Trypanosomiasis or trypanosomosis is the name of several diseases in vertebrates caused by parasitic protozoan trypanosomes of the genus ''Trypanosoma''. In humans this includes African trypanosomiasis and Chagas disease. A number of other diseas ...
(more commonly known as African sleeping sickness) in humans and other animals. The protozoa are transferred via
Tsetse flies Tsetse ( , or ) (sometimes spelled tzetze; also known as tik-tik flies), are large, biting flies that inhabit much of tropical Africa. Tsetse flies include all the species in the genus ''Glossina'', which are placed in their own family, Glos ...
where they multiply and can be transferred to yet another animal host during the fly's blood meal feeding. Outbreaks of sleeping sickness in certain human communities have been eliminated but only temporarily as constant re-introduction from unknown sources statistically suggests the presence of a non-human reservoir where spillback of the pathogen is maintained in a sylvatic cycle and re-introduced into the urban cycle. The presence of T. b. gambiense has been found separately in humans and livestock. This spurred a molecular study comparing serum reactivity of
pig The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous, domesticated, even-toed, hoofed mammal. It is variously considered a subspecies of ''Sus ...
s,
goat The goat or domestic goat (''Capra hircus'') is a domesticated species of goat-antelope typically kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the a ...
s, and
cows Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult mal ...
to human serum where notable similarities in all samples but especially in pig samples. Combined, these findings implicate a reverse zoonotic human to animal transmission.


Arboviruses

Yellow fever viruses, Dengue fever viruses, and Zika viruses are of the
Flavivirus ''Flavivirus'' is a genus of positive-strand RNA viruses in the family ''Flaviviridae''. The genus includes the West Nile virus, dengue virus, tick-borne encephalitis virus, yellow fever virus, Zika virus and several other viruses which may cau ...
genera and
Chikungunya Chikungunya is an infection caused by the ''Chikungunya virus'' (CHIKV). Symptoms include fever and joint pains. These typically occur two to twelve days after exposure. Other symptoms may include headache, muscle pain, joint swelling, and a ra ...
virus is of the
Alphavirus ''Alphavirus'' is a genus of RNA viruses, the sole genus in the ''Togaviridae'' family. Alphaviruses belong to group IV of the Baltimore classification of viruses, with a positive-sense, single-stranded RNA genome. There are 32 alphaviruses ...
genera. All of them are considered
arbovirus Arbovirus is an informal name for any virus that is transmitted by arthropod vectors. The term ''arbovirus'' is a portmanteau word (''ar''thropod-''bo''rne ''virus''). ''Tibovirus'' (''ti''ck-''bo''rne ''virus'') is sometimes used to more sp ...
es denoting their ability to be transmitted through arthropod vectors. Sylvatic transmission cycles for arboviruses within non-human primate communities have the potential to spillover into an urban cycle within humans where humans could be dead-end hosts in scenarios where further intermingling is eliminated but much more probable is a reemergence of these viruses into either cycle due to spillback. Apparently the maintenance of an arboviral urban cycle between humans requires a rare or understudied conjunction of factors to occur. One of the following situations occurs: * An infected human in an urban environment feeds a sylvatic (typically remotely located) mosquito such as Haemogogus (which has a relatively long lifespan compared to other mosquitoes and can transmit the virus for extended periods) that infects another human or non-human animal that will serve as a reservoir. * An urban
Aedes ''Aedes'' is a genus of mosquitoes originally found in tropical and subtropical zones, but now found on all continents except perhaps Antarctica. Some species have been spread by human activity: '' Aedes albopictus'', a particularly invasive sp ...
(more commonly found in urban areas feeds and transmits the virus to another human or non-human animal that will serve as a reservoir. * Sufficient numbers of sylvatic vector mosquito and the animal reservoir inhabit the same ecologic niche in close contact to promote and sustain the zoonotic cycle of the virus. * The animal reservoir of the virus maintains a suitable virus level in the blood to allow the infection of a vector mosquito. * A bridge-vector mosquito such as
Aedes albopictus ''Aedes albopictus'' (''Stegomyia albopicta''), from the mosquito (Culicidae) family, also known as the (Asian) tiger mosquito or forest mosquito, is a mosquito native to the tropical and subtropical areas of Southeast Asia. In the past few cen ...
, which can survive in an urban area and spread to rural, semi-rural, and forest areas could carry the virus to a sylvatic environment. * Zika fever: The Zika virus is caused by the single stranded RNA Flavivirus that uses the Aedes mosquito as a vector to infect other human and animal hosts. A 2015 zika virus strain isolated from a human in
Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
was used to infect pregnant
rhesus macaque The rhesus macaque (''Macaca mulatta''), colloquially rhesus monkey, is a species of Old World monkey. There are between six and nine recognised subspecies that are split between two groups, the Chinese-derived and the Indian-derived. Generally ...
s
intravenously Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...
and intra amniotically. Both the dams and the
placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...
s were infected with Zika positive tissue samples being recorded for up to 105 days. This confirms a reverse zoonotic transference potential between humans and non-human primates. * Yellow fever: Yellow fever virus also transmitted by the bite of an infected Aedes or Haemagogus species of mosquitoes that feed off an infected animal. The historical course of the American slave trade is a prime example of introduction of a pathogen to create a completely new sylvatic cycle. Previous hypotheses of a "
New World The term ''New World'' is often used to mean the majority of Earth's Western Hemisphere, specifically the Americas."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: Oxford University Press, p. ...
YFV" were laid to rest in a 2007 study that examined rates of nucleotide substitution and divergence to determine that yellow fever was introduced into the Americas approximately 400 years ago from
West Africa West Africa or Western Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali, M ...
. It was also around the 17th century that yellow fever was documented by Europeans complicit in slave trafficking. The actual mode of introduction could have played out in a number of scenarios whether a viremic Old World human, infected Old World mosquito, eggs laid by an Old World infected mosquito, or all three were transported to the Americas seeing that yellow fever transmission was not uncommon on sailing vessels. Amidst more recent yellow fever outbreaks in southeastern Brazil, the spillback potential was highly indicated. Molecular comparisons of non-human primate outbreak strains proved to be more closely related to human strains than strains derived from other non-human primates thus suggesting a continuing reverse zoonosis. * Chikungunya: The Chikungunya virus is a single stranded RNA alphavirus typically transmitted by the Aedes mosquitoes to another animal host. There is no evidence to suggest a barrier to Chikungunya switching hosts between humans and non-human primates because it has no preferences in any given primate species. It has a high potential to spill-over or spill-back into sylvatic cycles as was the case with the similar arbovirus that was imported to the Americas during the slave trade. Studies have proven chikungunya's potential to orally infect sylvatic types of mosquitoes including ''Haemagogus leucocelaenus'' and ''Aedes terrens''. Moreover, in a
serologic Serology is the scientific study of serum and other body fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum. Such antibodies are typically formed in response to an infection (against a given mic ...
survey carried out in non-human primates of urban and peri-urban areas of Bahia State, 11 animals showed chikungunya
neutralizing antibodies A neutralizing antibody (NAb) is an antibody that defends a cell from a pathogen or infectious particle by neutralizing any effect it has biologically. Neutralization renders the particle no longer infectious or pathogenic. Neutralizing antibod ...
. * Dengue fever: The Dengue virus is a flavivirus also transmissible by ''Aedes'' mosquito vectors to other animal hosts. Dengue was also introduced to the Americas by the slave trade along with ''Aedes'' aegypti. A 2009 study in
French Guiana French Guiana ( or ; french: link=no, Guyane ; gcr, label=French Guianese Creole, Lagwiyann ) is an overseas department/region and single territorial collectivity of France on the northern Atlantic coast of South America in the Guianas. ...
found that infections of dengue viruses types 1 through 4 were present in various different types of
neotropical The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In bioge ...
forest mammals other than primates such as
rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...
s,
marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a ...
s, and
bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most ...
s. After sequence analyses, it was revealed that the 4 non-human mammalian strains had an 89% to 99% similarity index to human strains circulating at the same time. This confirms that other mammals in the vicinity have the potential to be infected by human sources and indicates presence of an urban cycle. A case to prove the arthropod vectors are capable of being infected comes from Brazil where ''Aedes albopictus'' (which frequents the backyards of human houses but easily spreads into rural, semi-rural, and wild environments) was found infected with dengue virus 3 in
São Paulo São Paulo (, ; Portuguese for ' Saint Paul') is the most populous city in Brazil, and is the capital of the state of São Paulo, the most populous and wealthiest Brazilian state, located in the country's Southeast Region. Listed by the Ga ...
State. Meanwhile, in the State of Bahia, the sylvatic vector ''Haemogogus leucocelaenus'' was found to be infected with dengue virus 1. In another study carried out in the Atlantic Forest of Bahia, primates ('' Leontopithecus chrysomelas'' and '' Sapajus xanthosternos'') were found with antibodies dengue viruses 1 and 2 while sloths ( Bradypus torquatus) had antibodies for dengue virus 3 therefore suggesting the possible presence of an established sylvatic cycle.


Wild animals

A large number of wild animals with habitats that have yet to be encroached upon by humans are still affected by sapronotic agents through contaminated water.


Giardia

* Beavers: Giardia was introduced to beavers through
runoff Runoff, run-off or RUNOFF may refer to: * RUNOFF, the first computer text-formatting program * Runoff or run-off, another name for bleed, printing that lies beyond the edges to which a printed sheet is trimmed * Runoff or run-off, a stock marke ...
of human sewage upstream of a beaver colony.


Influenza A virus subtype H1N1

* Seals: In 1999, wild seals were admitted into a Dutch seal rehabilitation center with
flu-like symptoms Influenza-like illness (ILI), also known as flu-like syndrome or flu-like symptoms, is a medical diagnosis of possible influenza or other illness causing a set of common symptoms. These include fever, shivering, chills, malaise, dry cough, loss ...
and it was found that they were in fact infected with a human influenza B like virus that had circulated in humans in 1995 and had undergone an antigenic shift since adaptation to its new seal host.


Tuberculosis

*
Red deer The red deer (''Cervus elaphus'') is one of the largest deer species. A male red deer is called a stag or hart, and a female is called a hind. The red deer inhabits most of Europe, the Caucasus Mountains region, Anatolia, Iran, and parts of we ...
,
wild boar The wild boar (''Sus scrofa''), also known as the wild swine, common wild pig, Eurasian wild pig, or simply wild pig, is a suid native to much of Eurasia and North Africa, and has been introduced to the Americas and Oceania. The species is ...
: In areas of intensive game management that included big game fencing, supplementary feeding locations, and grazing livestock, cases of
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, i ...
lesions in wild red deer and wild boars appeared. Some boars and deer shared the same strains of tuberculosis which were similar to those found in livestock and humans suggesting a possible sapronotic or sapro-zoonotic contamination of shared water sources, supplemental feed, direct contact with humans or livestock, or their excretions.


Domesticated companionship animals


E. coli

*
Dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
s,
horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...
s: Evidence of infection by human E. coli strains in several dogs and horses across Europe was found, thus implicating the possibility of zoonotic inter-special transmission of multiresistant strains from humans to companion animals and vice versa.


Tuberculosis

* Dog: A
Yorkshire terrier The Yorkshire Terrier (often shortened as Yorkie) is one of the smallest dog breeds of the terrier type and indeed of any dog breed. The breed developed during the 19th century in Yorkshire, England.euthanized because of a
urethral obstruction Urinary tract obstruction is a urologic disease consisting of a decrease in the free passage of urine through one or both ureters and/or the urethra. It is a cause of urinary retention. Complete obstruction of the urinary tract requires prompt tr ...
. A necroscopy was performed where
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
and tracheobronchial lymph node samples in fact tested positive for the exact same strain of tuberculosis the owner had previously. This is a very clear case of reverse zoonosis.


Influenza A virus subtype H1N1

* Ferrets: Ferrets are often used in human
clinical studies Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, dieta ...
thus the potential for human influenza to infect them was previously confirmed. However confirmation of natural transference of a human H1N1 strain from the 2009 outbreak in household pet ferrets further implicates human to animal transference.


COVID-19

Amidst the 2020 global pandemic of
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease quickly ...
, susceptibility of cats, ferrets, dogs,
chicken The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adu ...
s, pigs, and ducks to the
SARS-CoV-2 Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) is a strain of coronavirus that causes COVID-19 (coronavirus disease 2019), the respiratory illness responsible for the ongoing COVID-19 pandemic. The virus previously had a ...
coronavirus was examined and it was found that it can be replicated in cats and ferrets with lethal results. *
Cat The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s: The virus can be transmitted in the air between cats. Viral RNA was detected in feces within 3–5 days of infection and pathological studies detected viral RNA in the
soft palate The soft palate (also known as the velum, palatal velum, or muscular palate) is, in mammals, the soft tissue constituting the back of the roof of the mouth. The soft palate is part of the palate of the mouth; the other part is the hard palate. ...
,
tonsil The tonsils are a set of lymphoid organs facing into the aerodigestive tract, which is known as Waldeyer's tonsillar ring and consists of the adenoid tonsil, two tubal tonsils, two palatine tonsils, and the lingual tonsils. These organs play ...
s, and
trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from the ...
. Kittens acquired massive lesions in the lungs, nasal and tracheal mucosa epitheliums. Surveillance for SARS-CoV-2 in cats should be considered as an adjunct to elimination of COVID-19 in humans. * Ferrets: Ferrets were inoculated with viral strains from the environment of the Huanan Seafood Market in Wuhan, China as well as human isolates from Wuhan. It was found that with both isolates, that the virus can replicate in the upper respiratory tract of ferrets for up to 8 days without causing disease or death and viral RNA was detected in
rectal The rectum is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction (the end of the sigmoid colon) at the le ...
swabs.
Pathological Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in th ...
studies performed after 13 days of infection revealed mild peribronchitis in the lungs, severe lymphoplasmacytic perivasculitis and
vasculitis Vasculitis is a group of disorders that destroy blood vessels by inflammation. Both arteries and veins are affected. Lymphangitis (inflammation of lymphatic vessels) is sometimes considered a type of vasculitis. Vasculitis is primarily caused ...
amongst other ailments with
antibody 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 ...
production against SARS-CoV-2 detected in all ferrets. The fact that SARS-CoV-2 replicates efficiently in the
upper respiratory tract The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa. Air is breathed in through the nose to t ...
of ferrets makes them a candidate animal model for evaluating antiviral drugs or vaccine candidates against COVID-19. * Dogs: Of the
Beagle The beagle is a breed of small scent hound, similar in appearance to the much larger foxhound. The beagle was developed primarily for hunting hare, known as beagling. Possessing a great sense of smell and superior tracking instincts, th ...
dogs tested, viral RNA was detected in fecal matter and 50% of the Beagles that were inoculated seroconverted after 14 days while the other 50% remained seronegative demonstrating a low susceptibility to SARS-CoV-2 in dogs. * Chicken, duck, pig: There was no evidence of susceptibility in chickens, ducks, or pigs with all viral RNA swabs returning negative results and seronegative after 14 days post inoculation.


Domesticated livestock animals


Influenza A virus subtype H1N1

*
Turkeys The turkey is a large bird in the genus ''Meleagris'', native to North America. There are two extant turkey species: the wild turkey (''Meleagris gallopavo'') of eastern and central North America and the ocellated turkey (''Meleagris ocellat ...
: A
Norwegian Norwegian, Norwayan, or Norsk may refer to: *Something of, from, or related to Norway, a country in northwestern Europe * Norwegians, both a nation and an ethnic group native to Norway * Demographics of Norway *The Norwegian language, including ...
turkey breeder's flock exhibited a decrease in egg production with no other clinical signs after a farm hand reported having
H1N1 In virology, influenza A virus subtype H1N1 (A/H1N1) is a subtype of influenza A virus. Major outbreaks of H1N1 strains in humans include the Spanish flu, the 1977 Russian flu pandemic and the 2009 swine flu pandemic. It is an orthomyxoviru ...
. A study revealed that the turkeys also had H1N1 and were seropositive to its antigens. Maternally derived H1N1 antibodies were detected in egg yolks and further genetic analyses revealed an identical H1N1 strain in the turkeys as the farm worker who likely infected the turkeys during
artificial insemination Artificial insemination is the deliberate introduction of sperm into a female's cervix or uterine cavity for the purpose of achieving a pregnancy through in vivo fertilization by means other than sexual intercourse. It is a fertility treatment ...
. * Pigs: Human to pig H1N1 transmission was reported in Canada, Korea, and eventually came to include every continent save Antarctica during the 2009 outbreak. It has also been known to spread during seasonal epidemics in
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...
between humans and pigs.


Methicillin-resistant ''Staphylococcus'' ''aureus''

* Horses: 11
equine Equinae is a subfamily of the family Equidae, which have lived worldwide (except Indonesia and Australia) from the Hemingfordian stage of the Early Miocene (16 million years ago) onwards. They are thought to be a monophyletic grouping.B. J. Ma ...
patients admitted into a veterinary hospital for various reasons from different farms over the span of approximately one year exhibited
MRSA Methicillin-resistant ''Staphylococcus aureus'' (MRSA) is a group of Gram-positive bacteria that are genetically distinct from other strains of ''Staphylococcus aureus''. MRSA is responsible for several difficult-to-treat infections in humans. ...
infections later. Considering that MRSA isolates are extremely rare in horses, it was suggested that the MRSA outbreak was due to
nosocomial A hospital-acquired infection, also known as a nosocomial infection (from the Greek , meaning "hospital"), is an infection that is acquired in a hospital or other health care facility. To emphasize both hospital and nonhospital settings, it is ...
infection derived from a human during the horse's stay at the hospital. * Cows, turkeys, pigs: A case of reverse zoonosis was proposed to explain how a particular human
Methicillin Methicillin ( USAN), also known as meticillin ( INN), is a narrow-spectrum β-lactam antibiotic of the penicillin class. Methicillin was discovered in 1960. Medical uses Compared to other penicillins that face antimicrobial resistance ...
Sensitive Streptococcus Aureus strain was found in livestock (pigs, turkeys, cows) with not only a loss of human virulence genes (which could decrease zoonotic potential for human colonization) but also the addition of methicillin resistance and a
tetracycline Tetracycline, sold under various brand names, is an oral antibiotic in the tetracyclines family of medications, used to treat a number of infections, including acne, cholera, brucellosis, plague, malaria, and syphilis. Common side effects in ...
(which will increase occurrence of MRSA infections). The concern here being that excessive antibiotic usage in livestock productions exacerbate the creation of novel
antibiotic resistant Antimicrobial resistance (AMR) occurs when microbes evolve mechanisms that protect them from the effects of antimicrobials. All classes of microbes can evolve resistance. Fungi evolve antifungal resistance. Viruses evolve antiviral resistance. ...
zoonotic
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 ...
s.


Wild animals in captivity


Tuberculosis

*
Elephant Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantidae ...
s: In 1996, The Hawthorne
Circus A circus is a company of performers who put on diverse entertainment shows that may include clowns, acrobats, trained animals, trapeze acts, musicians, dancers, hoopers, tightrope walkers, jugglers, magicians, ventriloquists, and unicyclis ...
Corporation reported 4 of their elephants and 11 of their keepers harboring ''M. tuberculosis'' infections. Unfortunately, these elephants had been sub-leased out to different circus acts and zoological gardens all over America. This spurred a nation-wide
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 ...
, but because tuberculosis isn't a disease that's typically transmitted from animals to humans, it was suggested that the epidemic was because of transference from a human handler to a captive elephant.


Coronavirus

*
Alpaca The alpaca (''Lama pacos'') is a species of South American camelid mammal. It is similar to, and often confused with, the llama. However, alpacas are often noticeably smaller than llamas. The two animals are closely related and can success ...
s: A 2007 outbreak of alpaca coronavirus because of the intermingling happening at a national alpaca exhibition led to a comparison between human and alpaca coronaviruses in an attempt to deduce the source of the outbreak. It was found that the alpaca coronavirus is most evolutionarily similar to a human coronavirus strain that was isolated in the 1960s suggesting that an alpaca coronavirus could have very well been circulating for decades causing
respiratory illness Respiratory diseases, or lung diseases, are pathological conditions affecting the organs and tissues that make gas exchange difficult in air-breathing animals. They include conditions of the respiratory tract including the trachea, bronchi, bron ...
in herds undetected for lack of diagnostic capabilities. It also suggests a human to alpaca mode of transmission.


Helminths and protozoans

*
Primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians ( monkeys and apes, the latter including ...
s: At the
University of Ibadan The University of Ibadan (UI) is a public research university in Ibadan, Nigeria. The university was founded in 1948 as University College Ibadan, one of many colleges within the University of London. It became an independent university in 19 ...
Zoological Garden in
Nigeria Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf o ...
,
fecal Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...
samples of
zookeeper A zookeeper, sometimes referred as animal keeper, is a person who manages zoo animals that are kept in captivity for conservation or to be displayed to the public.Hurwitz, Jane. Choosing a Career in Animal Care (World of Work). New York: Rosen Gr ...
s tested positive for
helminths Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as ...
('' Ancylostoma duodenale'', ''
Ascaris lumbricoides ''Ascaris lumbricoides'' is a large parasitic worm that causes ascariasis in humans. A roundworm of genus '' Ascaris'', it is the most common parasitic worm in humans. An estimated one-sixth of the human population is at some point infected by ...
'' and ''
Trichuris trichiura ''Trichuris trichiura, Trichocephalus trichiuris'' or whipworm, is a parasitic roundworm (a type of helminth) that causes trichuriasis (a type of helminthiasis which is one of the neglected tropical diseases) when it infects a human large intes ...
'') and protozoan cysts (''
Giardia lamblia ''Giardia duodenalis'', also known as ''Giardia intestinalis'' and ''Giardia lamblia'', is a flagellated parasitic microorganism of the genus '' Giardia'' that colonizes the small intestine, causing a diarrheal condition known as giardiasis. ...
'' and ''
Entamoeba histolytica ''Entamoeba histolytica'' is an anaerobic parasitic amoebozoan, part of the genus ''Entamoeba''. Predominantly infecting humans and other primates causing amoebiasis, ''E. histolytica'' is estimated to infect about 35-50 million people worldwid ...
''). The exact same strain of helminths and protozoan cysts were found in the zoo's non-human primates thus implicating a zoonosis between the two.


Measles

* Non-human primates: In 1996, a measles outbreak occurred in a sanctuary in 94 non-human primates. Although the source of the outbreak was never determined, serum and
urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellular ...
testing proved that the virus was definitely associated with recent human cases of measles in the U.S.


''Helicobacter pylori''

*
Marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a ...
s: The stripe-face dunnart is an Australian marsupial that has faced multiple outbreaks of ''
Helicobacter pylori ''Helicobacter pylori'', previously known as ''Campylobacter pylori'', is a gram-negative, microaerophilic, spiral (helical) bacterium usually found in the stomach. Its helical shape (from which the genus name, helicobacter, derives) is thoug ...
'' in captivity.
Stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...
sampling from the marsupial revealed that the ''H. pylori'' strain responsible for the outbreaks aligned 100% with a strain originating from the human intestinal tract. Thus, it can be assumed that the outbreak was caused by the handlers.


Wild animals in conservation areas


Coronaviruses

* Chimpanzees: The transmission of the human coronavirus HCoV-OC43 to wild chimpanzees ('' Pan troglodytes verus'') living in the
Taï National Park Taï National Park () is a national park in Côte d'Ivoire that contains one of the last areas of primary rainforest in West Africa. It was inscribed as a World Heritage Site in 1982 due to the diversity of its flora and fauna. Five mammal sp ...
, Côte d'Ivoire was reported in 2016 to 2017. These chimpanzees were accustomed to human presence that had been studying these particular communities since the 1980s The HCoV-OC43, belonging to the species ''
Betacoronavirus 1 ''Betacoronavirus 1'' is a species of coronavirus which infects humans and cattle. The infecting virus is an enveloped, positive-sense, single-stranded RNA virus and is a member of the genus ''Betacoronavirus'' and subgenus ''Embecovirus.'' Li ...
'' (BetaCoV1), normally causes episodes of common cold in humans (this excludes
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, ''seve ...
and MERS), but has also been detected in
ungulate Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, ...
s,
carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other s ...
s, and lagomorphs. Therefore, it is completely plausible that researchers or
poachers Poaching has been defined as the illegal hunting or capturing of wild animals, usually associated with land use rights. Poaching was once performed by impoverished peasants for subsistence purposes and to supplement meager diets. It was set a ...
could have inadvertently spread the virus to the chimpanzees thus revealing yet another interface in coronavirus host switching.


Rhinovirus C

* Chimpanzees: Though previously considered a uniquely human pathogen, human Rhinovirus C was determined to be the cause of a 2013 outbreak of respiratory infections in chimpanzees in
Uganda }), is a landlocked country in East Africa. The country is bordered to the east by Kenya, to the north by South Sudan, to the west by the Democratic Republic of the Congo, to the south-west by Rwanda, and to the south by Tanzania. The sou ...
. Examination of chimpanzees from all over Africa found that they show a universal
homozygosity Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. ...
for the 3 CDHR3-Y529
allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...
( cadherin related family member) which is a receptor that drastically increases susceptibility to rhinovirus C infection and
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, co ...
in humans. If respiratory viruses of human origin are capable of maintaining circulation in non-human primates, this would prove to be harmful should the infection spillback into human communities.


Tuberculosis

* Elephants: A necroscopy of a free-ranging African elephant (''Loxodonta africana'') in Kruger National Park in
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
found significant lung damage due to a human strain of ''M. tuberculosis.'' Elephants explore their environment with their trunks therefore it was very likely that
aerosolized Aerosolization is the process or act of converting some physical substance into the form of particles small and light enough to be carried on the air i.e. into an aerosol. Aerosolization refers to a process of intentionally oxidatively converting a ...
pathogens from domestic waste, contaminated water from a human community upstream, human excrement, or contaminated food from tourists was the source of the infection.


Pneumoviruses

* Chimpanzees: In Uganda, reports of respiratory viruses of human origination infected two chimpanzee (Pan troglodytes schweinfurthii) communities in the same forest. It was later discovered to be caused by a human metapneumovirus (also known as MPV,
Pneumoviridae ''Pneumoviridae'' (from Greek pneumo-, lung, -viridae, virus from Latin, poison, slimy liquid) is a family of negative-strand RNA viruses in the order '' Mononegavirales''. Humans, cattle, and rodents serve as natural hosts. Respiratory tract in ...
, Metapneumovirus) and a human respirovirus 3 (also known as HRV3,
Paramyxoviridae ''Paramyxoviridae'' (from Greek ''para-'' “by the side of” and ''myxa'' “mucus”) is a family of negative-strand RNA viruses in the order '' Mononegavirales''. Vertebrates serve as natural hosts. Diseases associated with this family inclu ...
, Respirovirus, or formerly known as parainfluenza virus 3).


Reverse zoonosis in gorillas

*
Gorilla Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four or fi ...
s: Conservational areas subject to ecotourism in Uganda, Rwanda, and the
Democratic Republic of the Congo The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
, free-ranging gorillas have become increasingly accustomed to the presence of humans whether that be in the form of ranger guides, tourists, trackers, veterinarians, poachers, or researchers. '' Iodamoeba buetschlii'', ''Giardia lamblia'', ''
Chilomastix ''Chilomastix'' is a genus of pyriform excavates within the family Retortamonadidae All species within this genus are flagellated, structured with three flagella pointing anteriorly and a fourth contained within the feeding groove. ''Chilomastix ...
sp.'', ''Endolimax nana'', ''
Entamoeba coli ''Entamoeba coli'' is a non-pathogenic species of ''Entamoeba'' that frequently exists as a commensal parasite in the human gastrointestinal tract. ''E. coli'' (not to be confused with the bacterium ''Escherichia coli'') is important in medicin ...
'', and ''
Entamoeba histolytica ''Entamoeba histolytica'' is an anaerobic parasitic amoebozoan, part of the genus ''Entamoeba''. Predominantly infecting humans and other primates causing amoebiasis, ''E. histolytica'' is estimated to infect about 35-50 million people worldwid ...
'' have been found in the feces of gorillas and promiscuous defecations left behind by humans encroaching on the habitat. Additionally, increased numbers of '' Cryptosporidium sp.'' and capillaria infections were found in gorillas that maintained more frequent contact with humans than those that did not. Together these findings suggest the occurrence of reverse zoonoses.


See also

*
Cross-species transmission Cross-species transmission (CST), also called interspecies transmission, host jump, or spillover, is the transmission of an infectious pathogen, such as a virus, between hosts belonging to different species. Once introduced into an individual of a ...
*
Spillover infection Spillover infection, also known as pathogen spillover and spillover event, occurs when a reservoir population with a high pathogen prevalence comes into contact with a novel host population. The pathogen is transmitted from the reservoir population ...
*
Zoonosis A zoonosis (; plural zoonoses) or zoonotic disease is an infectious disease of humans caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that has jumped from a non-human (usually a vertebrate) to a human. ...


References

{{Authority control Animal diseases Infectious diseases et:Antroponoos fr:Anthropozoonose