Reverse zoonosis

Yellow fever viruses, Dengue fever viruses, and Zika viruses are of the

• 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 (more commonly found in urban areas ^[14] 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, which can survive in an urban area and spread to rural, semi-rural, and forest areas could carry the virus to a sylvatic environment.^[15]

• Zika fever: The Zika virus is caused by the
  non-human primates.^[17]
• 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 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. 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.^[18] Amidst more recent yellow fever outbreaks in southeastern Brazil, the spillback potential was highly indicated.^[19] 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.^[20]
• 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.^[21] Studies have proven chikungunya's potential to orally infect sylvatic types of mosquitoes including Haemagogus leucocelaenus and Aedes terrens. Moreover, in a serologic survey carried out in non-human primates of urban and peri-urban areas of Bahia State, 11 animals showed chikungunya neutralizing antibodies.^[13]
• 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.^[22] A 2009 study in French Guiana found that infections of dengue viruses types 1 through 4 were present in various different types of neotropical forest mammals other than primates such as rodents, marsupials, and bats. 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.^[23][24] 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 State. Meanwhile, in the State of Bahia, the sylvatic vector Haemogogus leucocelaenus was found to be infected with dengue virus 1.^[25] 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.^{[citation needed]}

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.^{[citation needed]}

Giardia

• Beavers: Giardia was introduced to beavers through runoff of human sewage upstream of a beaver colony.^[26]

Influenza A virus subtype H1N1

• Seals: In 1999, wild seals were admitted into a Dutch seal rehabilitation center with flu-like symptoms 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.^[27]

Tuberculosis

• Red deer, wild boar: In areas of intensive game management that included big game fencing, supplementary feeding locations, and grazing livestock, cases of tuberculosis 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.^[28]

Domesticated companionship animals

E. coli

• Dogs, horses: 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.^[29]

Tuberculosis

• Dog: A
  urethral obstruction. A necroscopy was performed where liver 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.^[30]

• Ferrets: Ferrets are often used in human clinical studies 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.^[31]

COVID-19

Amidst the 2020 global

• Cats: 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, tonsils, and trachea. 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.^[32]
• 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 swabs. Pathological studies performed after 13 days of infection revealed mild peribronchitis in the lungs, severe lymphoplasmacytic perivasculitis and vasculitis amongst other ailments with antibody production against SARS-CoV-2 detected in all ferrets. The fact that SARS-CoV-2 replicates efficiently in the upper respiratory tract of ferrets makes them a candidate animal model for evaluating antiviral drugs or vaccine candidates against COVID-19.^[32]
• Dogs: Of the
  seronegative demonstrating a low susceptibility to SARS-CoV-2 in dogs.^[32]
• 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.[32]

Domesticated livestock animals

Influenza A virus subtype H1N1

• clinical signs after a farm hand reported having H1N1. 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.^[33]
• Pigs: Human to pig H1N1 transmission was reported in Canada,[34] Korea,^[35] and eventually came to include every continent save Antarctica during the 2009 outbreak.^[36] It has also been known to spread during seasonal epidemics in France between humans and pigs.^[37]