Ron Hines DVM PhD 4/2406

Canine Coronavirus ties with Canine Parvovirus as the leading causes of severe diarrhea in puppies. Clinically, the two infections can be indistinguishable. In retrospect, Canine Coronavirus rarely kills the puppy while Canine Parvovirus often does.

Canine Coronavirus is widespread in the dog population worldwide. It is primarily a disease of puppies. The virus was first recognized in 1971 in Germany. Some scientists speculate that Canine Coronavirus mutated from another coronavirus that causes transmissible gastroenteritis in swine. Because slight (antigenic) differences have been found between coronavirus strains isolated from puppies with diarrhea; puppies and dogs immune to a particular strain of Coronavirus may not be immune other serotypes (strains) of Coronavirus.

Most adult dogs have antibody to this disease which indicates that they were, at one time, exposed to the virus. These “silent” subclinical infections seem to be the norm with coronavirus. That is, the vast majority of dogs do not become ill when they contract Coronavirus or the disease produced is too mild to notice. Although we often vaccinate for Coronavirus, we do so out of habit referring back to a time when we did not realize how benign Coronavirus diarrhea actually was.

Canine Coronavirus is an RNA-type virus and a member of the Group I Coronaviruses. When they are viewed under an electron microscope the virus particles have a halo-like crown of projections or “Corona”.
The virus is encased in a fatty protective coating which makes it rather easy to kill with detergent and solvents that dissolve fats. This is in contrast to Parvovirus, which is very difficult to inactivate. Coronavirus is spread from dog to dog through infected feces.

Symptoms Of Coronavirus
The main sign of Coronavirus in puppies is watery diarrhea. It differs from the diarrhea produced by eating trash objects in not containing much mucous. It differs from the diarrhea produced by Parvovirus in that it rarely contains digested blood. It also differs from Parvovirus in that it does not typically cause vomiting. Coronavirus diarrhea is often less effusive than Parvovirus diarrhea. However, there is enough overlap of symptoms so that Canine Coronavirus can not be differentiated from Canine Parvovirus by clinical signs alone. Coronavirus diarrhea typically lasts 2-4 days and mortality is quite low. There are recorded cases of puppies being infected with Canine Coronavirus and Canine Parvovirus simultaneously. Such cases are usually fatal.

Dynamics Of The Disease
Within 2-3 days of ingesting the virus, Coronavirus can be found in the upper two-thirds of the small intestine. In very rare cases the virus may also invade the spleen, liver and brain and lungs. During this same period diarrhea begins. Diarrhea usually lasts 2-7 days. The diarrhea is due to malabsorption of nutrients and a deficiency in digestive enzymes.
Most infected dogs shed Coronavirus in their stools for 6-9 days. But shedding can be prolonged in some pups. Most puppies recover after a few days of diarrhea and inappetence. However, puppies less than three months of age may die of Coronavirus if they are weakened by intestinal parasites, are the runts of the litter or come from overbred, poorly maintained mothers. Infection is rarely accompanied by fever and in contrast to Parvovirus, white blood cells do not decrease. Vomiting is also uncommon.
When I palpate the tummies of these puppies they are often bloated. I can usually feel gas-filled tender loops of intestine and enlarged mesenteric lymph nodes.

Treatment
There is no specific treatment that combats the Canine Coronavirus. We are faced with attempting to correct the dehydration that accompanies all severe diarrheas. Often, the puppies are not too sick to drink Gatorade or Pedialyte provided frequently in small amounts. If this is not sufficient the puppies need intravenous or subcutaneous fluids to correct dehydration (lactated ringer’s solution @ 10-20millileters per pound).
We also give medicines that relax intestinal spasms such as metoclopramide (Reglan, 0.1-0.25mg/lb three times a day) and trimethobenzamide (Tigan, 1.5mg/lb three times a day). Chilled puppies need additional sources of heat such as a heating pad or heat lamp. Many of these puppies have internal parasites that complicate the disease. If I detect protozoa in fecal samples I place the pups on metronidazole (Flagyl, 7.5mg/pound twice a day). If I detect hookworms I worm the pups with pyrantel pamoate (Strongid, Nemex, 2.5mg/pound). I fast the puppies for two days and then give them frequent small amounts of a bland intestinal diet such as Canine i/d or EN.

Prevention
Avoiding dog to dog contact or contact with objects that are contaminated with the virus prevents infection. Crowding, dirty facilities, grouping large numbers of dogs, and all types of stress make outbreaks of this disease more likely. Enteric Coronavirus are moderately stabile in heat acids and disinfectants but not nearly so much as Parvovirus.

Several inactivated vaccines are available to protect puppies against canine Coronavirus. The use of these vaccines in adult animals is not required. The use of inactivated Coronavirus vaccines is controversial among the scientific community. Their effectiveness has yet to be fully determined. Experiments show that the vaccines provide limited protection against diarrhea but do not prevent infection. We still do not know if they work under field conditions. Serum antibodies against coronavirus which these vaccines stimulate do not protect against infection. It appears that antibodies called IgAs or mucosal antibodies operating in the intestine itself are required to prevent infection. In 1983 a live virus Coronavirus vaccine was marketed in the United States. It was quickly withdrawn because it caused neurological disease, pancreatitis, meningitis and death. A second attempt was made to introduce a modified live virus vaccine in 1994 but this also was quickly recalled.

The disease is a big problem in large puppy “mills” where sanitation and husbandry is less than ideal. The disease often breaks out in pet stores soon after the puppies arrive from these breeders. These outbreaks can be prevented by quarantining newly-arrived puppies and sanitizing the facility with a 1:20 dilution of ordinary household bleach. The multivalent vaccines that I give puppies at 12, 14 and 18 weeks of age contain attenuated (weakened) Canine Coronavirus. Immunity derived from these vaccines lasts at least a year but we do not know how much longer.

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