SARS-CoV-2 in animals

Updated on March 2, 2021

Since the initial outbreak of SARS-CoV-2 and COVID-19, there have been reports of animals becoming infected with the virus. So, which animals are at risk of infection?

  • Under natural conditions—meaning, when the virus is transmitted via close contact with a COVID-19-positive person—the primary domestic animals that have been diagnosed with SARS-CoV-2 are dogs and cats. It should be noted that these species are not easily infected under natural conditions, and there is no evidence that infected cats or dogs spread the virus to other animals or to people.
  • Under experimental conditions, animals that appear to be susceptible to the virus include cats, dogs, and ferrets, but not horses, pigs, or poultry. Results of experimental studies in cattle are conflicting, but it doesn’t appear that cattle can easily be infected.
  • Non-domestic animal species have been diagnosed with SARS-CoV-2 as well. To get more details about all reported cases of naturally acquired SARS-CoV-2 infections in animals, read our summary.

As veterinarians, we have responsibilities to care for the health and welfare of animals while also mitigating the risk to ourselves, our teams, and our clients. The following resources can help not only answer questions about SARS-CoV-2 infection in animals but also reduce your team’s risk of infection:

For pet owners, preparing in advance is key. The following resources can help pet owners plan for their pet’s care in the event that the owner or the pet is infected with SARS-CoV-2:

It is important to remember that there is no evidence at this time that animals play a significant role in spreading SARS-CoV-2. Accordingly, there is no reason to remove pets from homes where COVID-19 has been identified in members of the household, unless there is risk that the pet itself is not able to be cared for appropriately. In this pandemic emergency, pets and people each need the support of the other and veterinarians are there to support the good health of both.  

SARS-CoV-2 infections in animals

 

SARS-CoV-2 in pets and other domestic animals

COVID-19—or coronavirus disease 2019—is the disease that people get from being infected with the severe acute respiratory syndrome coronavirus 2 (or SARS-CoV-2). Domestic animals do not get COVID-19 like humans do, but under natural conditions, pet cats—and, to a lesser extent, pet dogs—may, albeit rarely, become infected with SARS-CoV-2 after close and prolonged contact with a COVID-19-positive person. In other words, a person with COVID-19 might transmit the virus that causes this disease to pet cats and dogs (and perhaps pet ferrets) in the same way we might transmit it to another person.

However, there is no compelling evidence to date that any domestic animal, including cats, dogs, and ferrets, readily transmits SARS-CoV-2 to other animals, including humans, under natural conditions. Further, the global number of naturally infected animals is far, far less than the number of people with COVID-19, indicating that animals, including pets, are not a driver of the COVID-19 pandemic—the pandemic continues to be driven by human-to-human transmission.

Clinical signs of SARS-CoV-2 infection in cats and dogs

Although cats and dogs with naturally acquired SARS-CoV-2 infections are often asymptomatic, there are several clinical signs compatible with infection, including a combination of any of the following:

  • Fever
  • Coughing
  • Difficulty breathing or shortness of breath
  • Lethargy
  • Sneezing
  • Nasal discharge
  • Ocular discharge
  • Vomiting
  • Diarrhea
Testing pets for SARS-CoV-2

Because these are non-specific clinical signs, testing a sick pet for SARS-CoV-2 should ideally be performed only after more common causes of illness have been ruled out. Further, a decision on whether to test an animal for SARS-CoV-2 should be made collaboratively by the pet’s veterinarian in consultation with the owner and in coordination with local, state, and/or federal public health and animal health officials. The CDC has more detailed guidance for state public health veterinarians and state animal health officials regarding testing animals for SARS-CoV-2 infection. And, see more information and resources from the AVMA, including a testing decision flowchart and client handout.

Experimental conditions

In multiple studies conducted in different laboratories since the start of the pandemic, ferrets—as well as cats—can be readily infected with SARS-CoV-2 after experimental inoculation. Ferrets and cats infected this way may also develop transient mild to moderate abnormal respiratory or gastrointestinal signs and transmit the virus to naïve animals of the same species under controlled conditions. 

Dogs, too, can be infected in a laboratory setting, albeit less efficiently and reliably than ferrets or cats. Experimentally infected dogs do not typically develop abnormal clinical signs, nor do they readily transmit SARS-CoV-2 to naïve dogs in these controlled environments. Data regarding experimental infection of other animals are non-existent (e.g., horses), sparse (e.g., cattle, pigs, poultry, rabbits), and at times inconsistent (e.g., pigs, rabbits). 

However, we emphasize caution in not overinterpreting the results from only a small number of experimental infection and transmission studies, because:

  • Experimentally induced infections do not mirror naturally induced infections. Just because an animal can be experimentally infected via direct intranasal or intratracheal inoculation with high concentrations of purified tissue-cultured virus does not mean that it will easily be infected with that same virus under natural conditions.
  • Experimental transmission studies are typically done under ideal conditions that may include use of negative pressure test chambers and unidirectional flow of HEPA-filtered air from the infected to the naïve animal. Such highly controlled conditions do not reflect conditions found outside a laboratory setting. As such, results should not be used as conclusive evidence that an experimentally infected animal can readily transmit COVID-19 under natural conditions.
  • The numbers of animals used in these types of experiments is typically small, with conclusions drawn based on data points that are in some cases collected from as few as two animals, making it challenging to draw definitive conclusions regarding all animals of a given species from results of only a few—and in some cases a single—study.

Links to published reports of experimental infection and transmission studies can be found in our compilation of key research articles related to SARS-CoV-2 in non-human animals.

SARS-CoV-2 in farmed, captive, and free-ranging wildlife species

SARS-CoV-2 infection in farmed mink

Mink, including those farmed commercially for fur, are in the same mammalian family (Mustelidae) as ferrets, which are susceptible to experimental inoculation with SARS-CoV-2. As such it was perhaps not surprising when, in late April 2020, government officials in the Netherlands reported the first case of SARS-CoV-2 infection in commercially farmed mink.

Additional reports of SARS-CoV-2 infected farmed mink came later in 2020 from Denmark (June), Spain (July), the U.S. (August), Italy (August), Sweden (October), France (November), Greece (November), Lithuania (November), and Canada (December).

The course of infection in mink varied, with some animals remaining asymptomatic, others developing mild to moderate respiratory or gastrointestinal illness from which they recovered, while still others developed severe illness and died or were euthanized.

In all countries that have reported SARS-CoV-2 infections on commercial mink farms, country- or state-specific surveillance programs and control measures were quickly implemented to control or stop viral transmission. Control measures have ranged from strict on-farm biosecurity and disease reporting requirements only, to depopulation orders for either infected farms or all farms, regardless of infection status.

As surveillance programs continue, both the global number of infected farms and the number of countries with infected farms will no doubt increase. We will update the number of infected mink farms in our summary of naturally occurring SARS-CoV-2 infections in animals.

SARS-CoV-2 transmission between humans and farmed mink

In almost all reports of SARS-CoV-2 infection in farmed mink, the source of infection could be definitively linked to one or more farm employees with COVID-19 who had worked closely with the animals in closed barns. Following an initial human-to-mink transmission event, SARS-CoV-2 was then readily transmitted from mink to mink throughout an affected barn.

In May 2020, results of a study from the Netherlands raised concern that mink-to-human transmission of SARS-CoV-2 may be possible. However, this was only a preliminary study investigating transmission dynamics on a few of the first infected Dutch mink farms. Analyses conducted by Dutch government agencies at that time indicated that the risk for people contracting COVID-19 from infected mink was low.

We are still learning about SARS-CoV-2 in animals, but there is currently no evidence that animals, including mink or other mustelids, play a significant role in spreading the virus to humans. Based on the limited information available to date, the risk of animals spreading SARS-CoV-2 to people is considered to be low. 

– U.S. Department of Agriculture (USDA), Interim SARS-CoV-2 Guidance and Recommendations for Farmed Mink and Other Mustelids

Reports from the Netherlands and Denmark later in 2020 suggested that, as SARS-CoV-2 circulated among mink on infected farms, clusters of unique mink variant viral sequences arose. These variant viral sequences were initially detected in a few workers at some of the farms but rarely or not at all in the general human population. Additional reports from Denmark, though, indicated that mink variant viral sequences could be detected in more people with COVID-19 than originally thought, including people with no known direct or indirect contact to an infected mink farm.

Mink variant viral sequences have not been widely detected in other countries. Additionally, only a fraction of all viruses infecting people or farmed mink in either the Netherlands or Denmark have been sequenced. As such, it is possible that the viral variants seen more commonly in infected mink arose in people before being transmitted to mink by farm workers with COVID-19. Additional studies are ongoing to help clarify SARS-CoV-2 mink-to-human transmission dynamics.

See these and other published studies of infections in farmed mink in our compilation of key research articles related to SARS-CoV-2 in non-human animals.

SARS-CoV-2 risk mitigation on mink farms

In late 2020, the World Health Organization (WHO) issued advice regarding the role that farmed mink populations might play in the ongoing transmission of SARS-CoV-2, and urged all countries to:

  • Increase the sequencing of SARS-CoV-2 from both infected humans and animals where possible and freely share sequence data internationally.
  • Enhance surveillance for SARS-CoV-2 infection at the animal-human interface.
  • Strengthen farming biosafety and biosecurity measures around potential animal reservoirs of SARS-CoV-2 in order to limit the risk of zoonotic events associated with the virus.

Likewise, the World Organisation for Animal Health (OIE) acknowledged that detection of potential mink variants of SARS-CoV-2 that may be transmissible from mink to humans “could have important public health implications.” However, the OIE also noted that “the full consequences remain unknown, and further investigation is needed to fully understand the impact of these [mink variant] mutations.”

To mitigate any potential risk of farmed mink becoming a reservoir for human infection with SARS-CoV-2, both the Dutch and Danish governments instituted depopulation measures on mink farms. In the Netherlands, all mink farms will be depopulated by early 2021 leading to the permanent cessation of the Dutch commercial mink farming business thereafter.

In Denmark, which is one of the top two mink producing countries in the world, mink farms were depopulated immediately after they were confirmed to be infected. Other mink farms within a certain radius of an infected farm were also depopulated regardless of SARS-CoV-2 status. By the end of 2020, more than 15 million mink had been culled in Denmark, and the Danish government passed a bill banning further mink farming until 2022.

Transmission dynamics between farmed mink and other animals

Studies are ongoing in multiple countries to better understand transmission dynamics between infected farmed mink and other animal species, both wild and domestic, living on or near mink farms. By the end of December 2020, only a single, free-ranging wild mink trapped near an infected mink farm in Utah had been confirmed infected with SARS-CoV-2. This animal was tested as part of a surveillance study conducted by the USDA in September and October 2020 to determine whether any of the common wild mammalian species living near infected mink farms in Utah, Michigan, or Wisconsin were infected with SARS-CoV-2. During that time, 16 escaped farmed mink, three free-ranging wild mink, and several other animals from different wildlife species were trapped and tested, with only the one wild mink in Utah testing positive for the virus.

The affected animal was asymptomatic when trapped, and the genetic makeup of the virus identified was virtually identical to that of the virus circulating on the nearby infected farm. Although it is not clear how the wild mink became infected, two hypotheses were proposed: indirect contact with infectious waste material on the infected farm or direct contact with an infected escaped farmed mink.

Similar surveillance studies have been done around infected mink farms in the Netherlands and Denmark with no trapped animals testing positive for SARS-CoV-2 infection. Surveillance studies of wildlife are ongoing, but to date, there is no evidence that SARS-CoV-2 is circulating or established in wild animal populations—even those surrounding infected mink farms.

See reports of infections in free-ranging wildlife in our summary of naturally occurring SARS-CoV-2 infections in animals.

Captive wildlife species

Captive wildlife species are also susceptible to infection with SARS-CoV-2, albeit rarely. For example, in several cases, captive big cats (e.g., lions, tigers, pumas, snow leopards) and non-human primates (e.g., western lowland gorillas) from individual zoos or wildlife refuges in the U.S. and other countries were confirmed infected with SARS-CoV-2. In each case, animals were tested after one or more developed mild to moderate clinical signs of respiratory disease with, in some cases, mild lethargy and loss of appetite.

Based on the similarities between the genomic sequences of the virus infecting these big cats and gorillas and those of the virus circulating in nearby human populations, these captive wild animals likely became infected following contact with one or more animal caretakers with suspected or confirmed COVID-19. However, subsequent transmission of SARS-CoV-2 from the first infected animal to other animals housed together or in close proximity cannot be ruled out.

See reports of infections in captive wildlife in our summary of naturally occurring SARS-CoV-2 infections in animals.

AVMA recommendations regarding SARS-CoV-2 and animals

AVMA maintains its recommendations regarding SARS-CoV-2 and animals:

Woman petting husky

  • Animal owners without symptoms of COVID-19 should continue to practice good hygiene during interactions with animals. This includes washing hands before and after such interactions and when handling animal food, waste, or supplies.
  • Do not let pets interact with people or other animals outside the household.
  • Keep cats indoors, when possible, to prevent them from interacting with other animals or people.
  • Walk dogs on a leash, maintaining at least 6 feet from other people and animals. Avoid dog parks or public places where a large number of people and dogs gather.
  • Those ill with COVID-19 should restrict contact with pets and other animals, just as you would restrict your contact with other people. Have another member of your household or business take care of feeding and otherwise caring for any animals, including pets.  If you have a service animal or you must care for your animals, including pets, then wear a cloth face covering; don’t share food, kiss, or hug them, and wash your hands before and after any contact with them.
  • At this point in time, there is no evidence to suggest that domestic animals, including pets and livestock, that may be incidentally infected by humans play a substantive role in the spread of COVID-19.
  • Routine testing of animals for SARS-CoV-2 is NOT recommended. Veterinarians are strongly encouraged to rule out other, more common causes of illness in animals before considering testing for SARS-CoV-2.
  • Human outbreaks are driven by person-to-person transmission and, based on the limited information available to date, the risk of animals spreading COVID-19 to people is considered to be low. Accordingly, there is no reason to remove pets from homes, even if COVID-19 has been identified in members of the household, unless there is risk that the pet itself is not able to be cared for appropriately.