1. Texas A&M University - https://vetmed.tamu.edu/hamer-lab/covid-19-pets-research/ and https://krld.radio.com/articles/news/study-makes-link-between-people-and-pets-who-test-positive

2. University of Pennsylvania - https://www.sciencemag.org/news/2020/03/quarantine-cat-disinfect-dog-latest-advice-about-coronavirus-and-your-pets


References of Human-to-Animal 
Transmission

- Frequently Asked Questions COVID-19 and Feline Health. (2020, May 14). Retrieved January 05, 2021, from https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/coronavirus-update/frequently-asked-questions-covid-19-and-feline-health

- Penn State News. (2020, October 10). Veterinary experts offer advice after pet cat tests positive for COVID-19 in Pa. Retrieved January 31, 2021, from https://news.psu.edu/story/636163/2020/10/20/research/veterinary-experts-offer-advice-after-pet-cat-tests-positive-covid

References for COVID-19 and Domestic Cats 

AKC Staff. (2020, September 17). Can Dogs Get Coronavirus? Retrieved January 19, 2021, from https://www.akc.org/expert-advice/news/can-dogs-get-coronavirus/ 

References for Dogs and COVID-19

- It is believed that although dogs can test positive for COVID-19, it does not pose a health risk to them.
- Findings have indicated that it is not easy for dogs to contract the virus.

Dogs and COVID-19

- Singla, R., Mishra, A., Joshi, R., Jha, S., Sharma, A. R., Upadhyay, S., Sarma, P., Prakash, A., & Medhi, B. (2020). Human animal interface of SARS-CoV-2 (COVID-19) transmission: a critical appraisal of scientific evidence. Veterinary research communications, 44(3-4), 119–130. https://doi.org/10.1007/s11259-020-09781-0
- Frequently Asked Questions COVID-19 and Feline Health. (2020, May 14). Retrieved January 05, 2021, from https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/coronavirus-update/frequently-asked-questions-covid-19-and-feline-health
- Penn State News. (2020, October 10). Veterinary experts offer advice after pet cat tests positive for COVID-19 in Pa. Retrieved January 31, 2021, from https://news.psu.edu/story/636163/2020/10/20/research/veterinary-experts-offer-advice-after-pet-cat-tests-positive-covid

Human-to-Animal Transmission References

Human-to-Animal-Transmission Visual

A tiger at the Bronx Zoo in New York City tested positive for COVID-19 after it showed respiratory symptoms such as dry cough. It is believed that the tiger got the infection from an asymptomatic zookeeper who was in contact with the tiger. This was the first documented case of a COVID-19 positive tiger in the world. 

COVID-19 in Tigers

There is evidence that minks can also contract COVID-19 from humans as seen in the Netherlands. After an increase in mink mortalities at a farm following respiratory symptoms, post-mortem testing showed positive COVID-19 results. Several of those who worked at the farm showed respiratory illness and tested positive for COVID-19 after the testing. 

COVID-19 in Minks

In late April 2020, the CDC confirmed the first COVID-19 cases among cats in the USA. Two cats in New York tested positive, with at least one presumed to be infected by an owner who had COVID-19. In early June 2020, the first dog in the USA to test positive was a German Shepherd in New York, infected after its owner tested positive. The dog later died, although its concurrent lymphoma leaves questions about the exact cause of death.

First COVID-19 Cases in Cats and Dogs in the USA

Domestic cats are susceptible to SARS-CoV-2, the virus that causes COVID-19, although they are not considered highly susceptible. This conclusion is supported by the identification of naturally occurring infections, the presence of COVID-19 antibodies in domestic felines, and findings from experimentally infected cats.

COVID-19 in Domestic Cats

Early results from a study led by Dr Sarah Hamer, an associate professor of epidemiology at Texas A&M University, shows a connection between households with positive cases in Texas and their pets carrying the virus.

Shelly Rankin, a microbiologist at the University of Pennsylvania’s School of Veterinary Medicine, states that humans can infect animals with the virus. They have many of the same types of receptors on their cells that we do where the virus could attach itself.


University of California, Santa Cruz

Michigan State University

Though it has been confirmed that pets can be infected by COVID-19, as proven by many worldwide cases and lab trials, it is important to take note of the subjects of transmission.


Modes and Subjects of Transmission

Transmission of COVID-19 between two animals, specifically household pets of the same species, has been proven to be quite common.

A study conducted by the Harbin Veterinary Research Institute in China researched transmission of the virus between animals by administering a high dose of the virus to a group of cats and dogs and placing some of the infected animals next to uninfected control animals.

The study accomplished four major findings:

1) Immunity Increases by Age: Older animals had a stronger immune response to fight off the infection. The kittens who were administered the virus all became seriously ill, resulting in the death of two kittens. Meanwhile, the older cats were able to fight off the infection without becoming seriously ill.

2) Feline Susceptibility: Just after a week, one-third of the control cats were found positive for the virus, proving that the virus can replicate in cats and can transfer through respiratory droplets to other cats

3) Greater Resistance from Dogs: The dogs in the study were much resistant to the virus and did not transmit the virus to the other animals.

4) Unlikeliness of Transmission Across Species: The study found no evidence that would prove the inoculated dogs infected the control cats or the inoculated cats infected the control dogs. 


Animal-to-Animal Transmission

Though there have been no cases of animal-to-human transmission and no evidence, according to Mayo Clinic and the CDC, that viruses can spread to people from a pet's skin, fur or hair, this does not excuse its possibility and the likely transmission through respiratory droplets.

In a letter, which was composed by a vast number of established doctors, in the New England Journal of Medicine, it is stated that the confirmation of cats transmitting the virus to other cats calls for more study at the possibility of animal to human transmission. In particular, they state "cats may be a silent intermediate host of SARS-CoV-2, because infected cats may not show any appreciable symptoms that might be recognized by their owners.”


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