Canine Coronavirus Infection in Dogs

What is canine coronavirus disease?

Canine coronavirus disease, known as CCoV, is a highly infectious intestinal infection in dogs, especially puppies. Canine coronavirus is usually short-lived but may cause considerable abdominal discomfort for a few days in infected dogs. The virus is from the Coronaviridae family. The virus gets its name from the fact that when viewed from above under an electron microscope, the virus has a ring of projections that appear like a coronet, or a small crown made of ornaments fixed on a metal ring. There are many types of coronavirus, each affecting different animal species, including humans.

“Canine coronavirus (CCoV) is not the same virus as SARS-CoV-2 that causes the novel coronavirus (COVID-19).”

Canine coronavirus (CCoV) is not the same virus as SARS-CoV-2 that causes the novel coronavirus (COVID-19). CCoV does not affect people. CCoV causes gastrointestinal problems in dogs, as opposed to respiratory disease.

See the handout “SARS-CoV-2 (COVID-19)” for information on the disease caused by SARS-CO-V-2.

How is canine coronavirus transmitted?

Most cases of canine coronavirus are contracted by oral contact with infected fecal matter. A dog may also become infected by eating from contaminated food bowls or by direct contact with an infected dog.

“Crowding and unsanitary conditions favor transmission.”

Crowding and unsanitary conditions lead to coronavirus transmission. The incubation period from ingestion to clinical signs is one to four days. The duration of illness is two to ten days in most dogs. Secondary infections by bacteria, parasites, and other viruses may develop and prolong illness and recovery. Dogs may be carriers of the disease for up to six months (180 days) after infection.

What are the signs of canine coronavirus?

Most canine coronavirus infections are sub-clinical and produce few clinical signs in dogs. Occasionally an infection may cause more severe symptoms, particularly in young puppies. The most typical sign associated with canine coronavirus is diarrhea, typically sudden in onset, which may be accompanied by lethargy and decreased appetite. The stool is loose, with a fetid odor and orange tint. It may contain blood or mucus. If a puppy has a mixed infection, for instance both coronavirus and parvovirus (see handout “Parvovirus in Dogs”), the illness will be more severe.

Are there diseases that can be confused with canine coronavirus?

There are many causes of diarrhea in dogs. Severe cases of coronavirus can be easily confused with parvovirus, and they may occur at the same time. Be sure to see your veterinarian if your dog has diarrhea that does not resolve within twenty- four hours or is associated with significant lethargy or loss of appetite.

Is there any treatment?

There is no specific treatment for canine coronavirus.

“Antibiotics are ineffective against viruses, but may be useful in controlling secondary bacterial infections.”

Antibiotics are ineffective against viruses, but may be useful in controlling secondary bacterial infections. Withholding food for twenty-four hours after diarrhea ceases and gradually reintroducing small amounts of food may be the only required treatment. A dehydrated patient may require intravenous fluids to correct the fluid and electrolyte imbalances. Early medical intervention is the key to successful treatment of severe cases.

What about vaccines?

Canine coronavirus vaccines are available. This vaccine is not recommended for all dogs and will be administered based on your dog’s lifestyle and risk assessment. This vaccine will only work for the CCoV type of coronavirus. It is not effective for the prevention of COVID-19.

Symptoms and Types

The symptoms of a CCV infection vary. In adult dogs, the majority of infections will be inapparent, with no symptoms to show. Sometimes, a single instance of vomiting and a few days of explosive diarrhea (liquid, yellow-green or orange) may occur. Fever is typically very rare, while anorexia and depression are more common. Occasionally, an infected dog may also experience some mild respiratory problems. Puppies may exhibit protracted diarrhea and dehydration , and are most at risk of developing serious complications with this virus. Severe enteritis (inflammation of the small intestine) in puppies will occasionally result in death.

Can dogs get the new coronavirus (COVID-19)?

At this time, experts believe it is very unlikely. The World Health Organization currently advises that there is no evidence to suggest that dogs or cats can be infected with the new coronavirus. The OIE states there is no evidence that dogs play a role in the spread of this disease or that they become sick. The CDC also seconds that opinion, stating that, “At this time, there is no evidence that companion animals including pets can spread COVID-19.”

If experts believe it is unlikely for a dog to get COVID-19, how did a dog test “positive” in Hong Kong?

This canine patient was in close contact with an infected human, who was likely shedding large quantities of the virus. This led to the virus being in the dog’s nose. There is no indication that the dog is sick or showing any symptoms. Authorities say they will continue to quarantine and test the dog to evaluate if the canine patient becomes ill. In short, there was coronavirus on the dog just like there was coronavirus on the floor in the room but the dog was not infected or diseased.

LISTEN AND LEARN: PODCAST ON NEW CORONAVIRUS

Download the podcast with veterinarians Jim Lowe and Ashley Mitek. They explain terms like “pandemic” and “virulence” in language everyone can understand and provide a fascinating account of how viruses move from one species to another, occasionally with devastating effects on the human population.You’ll come away with a much better understanding of the risks of COVID-19 and how government agencies are responding to them.

March 12, 2020 update: The dog was placed under quarantine after its owner was hospitalized with COVID-19 infection on February 26. Subsequent tests revealed weak positive results for the nasal and oral samples taken on February 28 and for the nasal samples on March 2 and March 5. The weak positive result 5 and 8 days after the dog was removed from the home where the person was sick suggests the dog has a low-level infection, which was likely caused by a case of human-to-animal transmission.
The Hong Kong Health Authorities and the World Organization for Animal Health continue to investigate. All pet mammals from households with confirmed human cases of COVID-19 will be placed under quarantine and veterinary surveillance for 14 days in Hong Kong. There is still no indication that pets can shed the virus or get sick from the virus at this time.

Although pets cannot become sick from COVID-19, could they serve as a conduit of infection between people?

Yes. It is possible that a person with COVID-19 could sneeze or otherwise contaminate their pet, and then another individual could touch that animal and contract the disease. Veterinary experts believe the risk for transmission would be low. However, animals living with sick individuals should be kept away from other people and animals (quarantined at home), just as people who live with sick individuals must avoid contact with others.

Is there a COVID-19 vaccine for dogs and cats?

There is no vaccine for COVID-19 for people or animals at this time.

Veterinarians are familiar with other coronaviruses. Similar but different coronavirus species  cause several common diseases in domestic animals. Many dogs, for example, are vaccinated for another species of coronavirus (Canine Coronavirus) as puppies. However, this vaccine does not cross protect for COVID-19.

Can veterinarians test for COVID-19 in pets?

Yes. The Veterinary Diagnostic Laboratory at the College of Veterinary Medicine has recently purchased the needed equipment to test for the new COVID-19 in pets. They expect the test to be available to veterinarians starting March 15. Please contact the diagnostic laboratory with any further questions at 217-333-1620.

Why is the college offering a COVID-19 test for pets if they cannot get it?

Although current information suggests that our pets cannot become infected with COVID-19 and spread it to other animals and people, researchers at the college will begin offering this testing in the future in order to monitor the outbreak. We still have a lot to learn about this new virus, and it will be important to evaluate if our current understanding changes.

What animal did COVID-19 originate from?

Current research suggests that horseshoe bats are the reservoir species and the virus originated from that species as well. Previous human coronavirus outbreaks, SARS and MERS, originated in bats but passed through other species, such as the palm civet and camels.

If I am diagnosed with Covid-19, how do I protect my pet?

Since your pet is at minimal risk of COVID-19 infection there are no specific steps needed to protect them from infection. However, pets can have the virus ON THEM if they are in an environment with a large quantity of the virus and could serve to be a source of the virus for other people, including family members.  Therefore, to protect other people and yourself, the CDC recommends that you restrict contact with pets if you are sick with COVID-19, just as you would restrict your contact with other people. Avoid snuggling, being kissed or licked, and sharing food. If you must interact with your pet, wash your hands before and after, and wear a face mask.

Should my pet wear a face mask in public?

No. Face masks may not protect your pet from disease transmission and may cause other breathing difficulties.

Should I wear a face mask?

Wearing a surgical mask will not prevent anyone (human or animal) from being exposed to the virus. A mask should be used to prevent someone that is potentially infectious from spreading the virus to others via droplets through coughing, sneezing, or talking.

How do I protect my pet and myself from COVID-19?

Since your pet is at minimal risk of COVID-19 infection there are no specific steps needed to protect them from infection.

To protect yourself the CDC recommends the following steps:

  1. Wash your hands often with soap and water for at least 20 seconds!
  2. Avoid touching your eyes, nose, and mouth.
  3. Avoid close contact with sick people.
  4. Stay home when you are sick.
  5. Cover your cough or sneeze with a tissue, and then throw it away.
  6. Clean and disinfect frequently touched objects and surfaces.
  7. Voluntary home isolation: If you are ill with symptoms of respiratory disease, such as fever, cough, shortness of breath, sore throat, runny or stuffy nose, body aches, headache, chills or fatigue, stay home. The CDC recommends that you remain at home until at least 24 hours after you are free of fever (100 degrees F) or signs of fever without the use of fever-reducing medications.
  8. Veterinary practices should designate their clinic as a temporary NO HANDSHAKE ZONE. Ask colleagues and clients to refrain from shaking hands.

What other precautions do you recommend?

Visitation to nursing homes and long-term care facilities by service animals and their handlers should be discouraged at this time.

Abstract

Canine coronavirus (CCoV) is usually responsible for mild, self-limiting infections restricted to the enteric tract. We report an outbreak of fatal disease in puppies caused by a pathogenic variant of CCoV that was isolated from organs with severe lesions.

Keywords: Coronavirus, dog, mortality, dispatch

Coronaviruses are large, enveloped, positive-stranded RNA viruses (). Three different coronaviruses have been identified in dogs (,). Canine coronavirus (CCoV) type I and type II are included in group 1 coronaviruses, and their evolution is related to that of feline coronavirus (FCoV) type I and type II. FCoV type II originated by heterologous recombination between CCoV type II and FCoV type I, while CCoV type I is genetically more similar to FCoV type I than to CCoV type II (). In addition, 2 FCoV biotypes that differ in pathogenicity have been observed in cats.

The onset of acute fatal disease (feline infectious peritonitis) is caused by pantropic variants (able to disseminate throughout the organism) of enteric FCoVs with deletions or recombinations in the 3c and 7b genes at the 3´ end of the FCoV genome (). Similarly, changes in tissue tropisms in porcine and murine coronaviruses (,) and adaptation of the recently recognized severe acute respiratory syndrome–associated coronavirus () to humans have been related to mutations or deletions. A third canine coronavirus, CRCoV, detected in the respiratory tract, has <96.0% amino acid (aa) conservation in the spike (S) protein with bovine coronavirus within group 2 coronaviruses, which provides strong evidence for a recent host-species shift ().

Coronavirus infection in dogs is usually restricted to the enteric tract. The infection is self-limiting and in general produces only mild or asymptomatic forms of enteritis (). We report the identification of a pantropic, highly pathogenic variant of CCoV type II.

The Study

In May 2005, a severe outbreak of fatal systemic disease occurred in a pet shop in Bari, Italy. Clinical symptoms were initially observed in 3 miniature pinschers (45 days of age) and 1 cocker spaniel (53 days of age) and consisted of fever (39.5°C–40°C), lethargy, inappetence, vomiting, hemorrhagic diarrhea, and neurologic signs (ataxia, seizures) with death after 2 days. The same symptoms were observed 3–4 days later in 2 other miniature pinschers (45 days of age) and 1 Pekinese (56 days of age). Necropsy of the dogs showed hemorrhagic enteritis, abundant serosanguineous fluid in the abdominal cavity, and severe lesions in the parenchymatous organs. The lungs had multiple, patchy, red areas of consolidation. Livers were yellow-brown and congested, with hemorrhages on their surfaces, and spleens were enlarged with subcapsular hemorrhages. Variable gross changes in other organs included multifocal hemorrhagic renal cortical infarcts and petechial hemorrhages on lymph node surfaces.

Virologic and bacteriologic investigations on the parenchymatous organs did not detect common canine pathogens, notably canine parvovirus type 2, canine distemper virus, canine adenovirus type 1 and type 2. CCoV type I and type II were identified in the intestinal contents of all puppies by genotype-specific real-time reverse transcription–polymerase chain reaction (RT-PCR) assays (). CCoV type II RNA was also detected in lungs (median 1.08 × 106 RNA copies/μL of template), spleen (median 4.46 × 106 RNA copies/μL of template), liver (median 9.02 × 104 RNA copies/μL of template), kidney (median 7.54 × 104 RNA copies/μL of template), and brain (median 5.23 × 103 RNA copies/μL of template). Virus-induced cytopathic effect was observed in A-72 cells, and CCoV type II strain (CB/05) was isolated from all tissues examined except brain tissue. Immunohistochemical analysis with a CCoV-specific monoclonal antibody detected CCoV antigen in the organs with gross lesions that were examined (lungs, kidneys, liver, spleen, gut, and lymph nodes) (Figure 1).

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Immunohistochemical detection of canine coronavirus antigen (arrows) in canine lung tissue by a specific monoclonal antibody (magnification ×400).

The sequence of the 3´ end of the genome (8.8 kb) of the pantropic CCoV strain was determined by RT-PCR amplification and sequencing of overlapping fragments. The S, envelope, and membrane proteins and nucleoprotein showed a high degree of amino acid identity with the cognate open reading frame (ORF) of CCoV type II. The S protein of strain CB/05 had the highest identity to FCoV type II strain 79-1683 (Figure 2). Comparison with strain CB/05 was possible only with CCoV type II strains Insavc-1 () and BGF () and CCoV type I strains Elmo/02 and 23/03 (,) because of a lack of data on the 3´ end of the CCoV genome in the genes encoding for nonstructural proteins (NSPs) 3a, 3b, 3c, 7a, and 7b. NSPs 3a, 7a, and 7b were not altered. NSP 3b (22 aa) was 49 aa shorter than expected because of a 38-nucleotide deletion and a frame shift mutation in the downstream sequence that introduced an early stop codon. NSP 3c (244 aa) was 6 aa shorter and 79 aa longer than the cognate proteins of the enteropathogen strain BGF and the attenuated strain Insavc-1a, respectively.

An external file that holds a picture, illustration, etc.Object name is 05-0839-F2.jpg

Neighbor-joining tree of the spike protein of canine coronavirus (CCoV) and feline coronavirus (FCoV). The following reference strains were used for phylogenetic analysis: CCoV type I strains Elmo/02 (GenBank accession no. AY307020) and 23/03 (AY307021); CCoV type II strains Insavc-1 (D13096) and K378 (X77047); FCoV type I strains KU-2 (D32044), Black (AB088223) and UCD-1 (AB088222); FCoV type II strains 79-1146 (X06170) and 79-1683 (X80799); and bovine coronavirus (BCoV) strain ENT (NC_003045). The tree is rooted on BCoV-ENT and drawn to scale. A statistical support was provided by bootstrapping >100 replicates. The scale bar represents 20 substitutions per 100 sequence positions.feline coronavirus (FCoV). The following reference strains were used for phylogenetic analysis: CCoV type I strains Elmo/02 (GenBank accession no. AY307020) and 23/03 (AY307021); CCoV type II strains Insavc-1 (D13096) and K378 (X77047); FCoV type I strains KU-2 (D32044), Black (AB088223) and UCD-1 (AB088222); FCoV type II strains 79-1146 (X06170) and 79-1683 (X80799); and bovine coronavirus (BCoV) strain ENT (NC_003045). The tree is rooted on BCoV-ENT and drawn to scale. A statistical support was provided by bootstrapping >100 replicates. The scale bar represents 20 substitutions per 100 sequence positions.

To confirm the pathogenic potential of strain CB/05, we experimentally infected two 6-month-old dogs (authorization no. 67/2002-C released by Ministry of Health of Italy). Two milliliters of cryolysate of a lung-derived first-passage virus in A-72 cells were administered intranasally to the dogs. The cell cryolysate tested negative for other common canine pathogens and had a 50% tissue culture infectious dose of 105.50/50 μL on A-72 cells and 1.18 × 107 RNA copies/μL of template by real-time RT-PCR. The virus was reisolated from the experimentally infected dogs. Severe clinical symptoms characterized by pyrexia (temperature 39.8°C–40.1°C), anorexia, depression, vomiting, diarrhea, and leukopenia were observed that persisted 8–10 days. Despite the severe symptoms, the dogs slowly recovered from their illness.

Conclusions

Point mutations or deletions in the S protein and NSPs have been associated with changes in tropism and virulence of coronaviruses (,). CCoV strain CB/05 showed intact structural and nonstructural proteins, with an S protein closely related to that of other type II CCoVs. The only striking change was the truncated form of NSP 3b. Whether the deletion in the ORF of NSP 3b is involved in pathobiologic changes should be assessed with reverse genetic systems.

The present study describes for the first time the occurrence of fatal infections in dogs by coronaviruses. Experimental infection of dogs with the virus isolate resulted in a severe systemic disease that mimicked the clinical symptoms observed in the outbreak. However, the different ages at infection (6 months vs. <2 months) likely resulted in the disease being nonfatal. Accordingly, the appearance of pathogenic CCoV variants should always be regarded as a potential threat to domestic dogs and considered when unexplainable fatal disease outbreaks occur in puppies.

Epidemiologic studies are required to determine whether the pantropic CCoV strain is a new coronavirus variant emerging in canine populations or a widespread infectious agent of dogs that usually goes undetected. Vaccination trials could also help determine whether the CCoV vaccines currently available are effective against the highly virulent CCoV strain.

The 2002–2003 SARS epidemic has demonstrated that the study of animal coronaviruses is paramount to understanding the ecology and evolution of human coronaviruses. The coronaviruses of carnivores provide a paradigmatic model of how coronaviruses cross the species barriers, adapt to new host species, and change their pathogenicity.

Acknowledgments

This work was supported by grants from the Ministry of Health of Italy (Ricerca corrente 2003: Studio del coronavirus del cane come modello animale per le ricombinazioni genetiche dei coronavirus).

Biography

Dr Buonavoglia is professor of veterinary medicine at the University of Bari. His research interests include the study of viral pathogens of dogs, with particular emphasis on canine coronavirus.

Footnotes

Suggested citation for this article: Buonavoglia C, Decaro N, Martella V, Elia G, Campolo M, Desario C, et al. Canine coronavirus highly pathogenic for dogs. Emerg Infect Dis [serial on the Internet]. 2006 Mar [date cited]. http://dx.doi.org/10.3201/eid1203.050839

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