Coronaviruses in Animals

Laurie Anne Walden, DVM

Colorized transmission electron microscopy image of avian infectious bronchitis virus. Credit: CDC/Dr Fred Murphy; Sylvia Whitfield.

Coronaviruses cause disease in many animal species. Most coronaviruses affect either the respiratory tract or the digestive system. Some coronaviruses cause no symptoms or only mild illnesses like the common cold. Others cause serious disease.
 
New information continues to emerge about SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19). At this time (early March 2020), there is no evidence that this virus can spread between humans and companion animals like dogs and cats.
 
For updated information about COVID-19, see these resources:

• Centers for Disease Control and Prevention: https://www.cdc.gov/coronavirus/2019-ncov/index.html
• World Health Organization: https://www.who.int/emergencies/diseases/novel-coronavirus-2019
• World Organisation for Animal Health: https://www.oie.int/en/scientific-expertise/specific-information-and-recommendations/questions-and-answers-on-2019novel-coronavirus/

 
Coronaviruses got their name from spike proteins that cover the surface of the virus particles and look like a crown (corona in Latin) on electron microscopy images. Coronavirus spike proteins bind to receptors on the host animal’s cells and allow the virus particles to fuse with the cells. Spike proteins and the receptors they target vary according to the type of coronavirus.
 
Because animal species don’t all have the same molecular receptors and different coronaviruses have different surface proteins, coronaviruses tend to be species specific. A coronavirus that causes disease in cows, for example, doesn’t normally cause disease in cats. This is also why your dogs don’t catch your cold even if you sneeze in their faces.
 
Some coronaviruses are zoonotic, meaning they can be transmitted between animals and humans. Coronaviruses jump to a new host species through genetic mutation. Mutation changes the virus proteins and creates a genetically different coronavirus that can infect a different host. Jumping to a new species might also be easier if the molecular receptors in the new host species are similar to those of the original host species.
 
Coronavirus infections in livestock and companion animals can be severe. However, until 2002, coronaviruses usually caused only mild disease in people with fully functioning immune systems. In 2002, an outbreak of severe acute respiratory syndrome (SARS) occurred in China, and in 2012, Middle East respiratory syndrome (MERS) emerged. Both of these outbreaks were caused by coronaviruses thought to have begun as bat viruses. Bats and people don’t have much contact, so the viruses that caused SARS and MERS spread to people through intermediate hosts: civets for SARS and camels for MERS.[1] COVID-19 is the third coronavirus disease to cause serious outcomes in humans.[2]
 
Animal Diseases Caused by Coronaviruses
Diseases caused by coronaviruses have been identified in many mammal and bird species. Some examples of coronaviruses that cause serious disease in livestock are transmissible gastroenteritis virus and porcine epidemic diarrhea virus in piglets, infectious bronchitis virus in chickens, and bovine coronavirus in cows.[3]
 
The coronaviruses of most concern in cats and dogs are feline coronavirus, canine coronavirus, and canine respiratory coronavirus. Feline coronavirus usually causes such mild symptoms they aren’t noticed at all. In some cats, though, infection leads to feline infectious peritonitis, a devastating disease that is nearly always fatal. (Feline infectious peritonitis will be covered in more detail in another article.) Canine coronavirus is passed through the feces and causes vomiting and diarrhea, especially in groups of dogs in kennels and animal shelters. Infection usually carries a low risk of death, but a more severe strain of canine coronavirus can be fatal to dogs.[4] Canine respiratory coronavirus is one of the causes of canine infectious respiratory disease (kennel cough).
 
The emergence of SARS and MERS in humans prompted more research into coronaviruses, so new therapies for coronavirus diseases may be available in the future.
 
References
1. Cui J, Li F, Shi ZL. Origin and evolution of pathogenic coronaviruses. Nat Rev Microbiol. 2019;17(3):181-192.
2. Coronaviruses. National Institute of Allergy and Infectious Diseases website. Updated March 2, 2020. Accessed March 5, 2020. https://www.niaid.nih.gov/diseases-conditions/coronaviruses
3. Fehr AR, Perlman S. Coronaviruses: an overview of their replication and pathogenesis. Methods Mol Biol. 2015;1282:1-23.
4. Decaro N, Buonavoglia C. Canine coronavirus: not only an enteric pathogen. Vet Clin North Am Small Anim Pract. 2011;41(6):1121-1132.

Image source: https://phil.cdc.gov/Details.aspx?pid=15523

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