Coronavirus: Deadlier than you may have thought
THIS COMMON VIRUS CAUSES MORE THAN JUST DIARRHEA. A NEW STUDY SHOWS INFECTION CAN BE FATAL—EVEN WITHOUT PARVOVIRUS.

Dear Doctor Fort Dodge Animal Health March/ April 2006

Dogs get diarrhea. Often the illness doesn't require treatment and is more an inconvenience than a health threat. Owners might get a little nervous about their pets' loose bowels, but managing food intake and keeping dogs hydrated usually helps them recover quickly. However, one virus that causes diarrhea can be much more serious—even fatal. If dogs can be protected from this virus, shouldn't they be? John Ellis, DVM, PhD, thinks so.
A preventable illness
"The idea that you wait until an animal gets sick and then treat it doesn't make sense to me," says Dr. Ellis, a board-certified veterinary pathologist and microbiologist.
Dr. Ellis is talking about illnesses like coronavirus infection, a common cause of diarrhea in dogs. One study found coronavirus in 74 percent of diarrheic dogs and in 94 percent of kennel dogs.1 Another study found 73 percent of U.S. shelter dogs with diarrhea were also infected with coronavirus.2
However, the U.S. study also showed 60 percent of healthy shelter dogs had the virus. Many clinicians believe this statistic, coupled with the fact that coronavirus infection usually isn't fatal, proves vaccination isn't necessary. To Dr. Ellis, this reasoning isn't logical.
"There are a lot of diseases we vaccinate for that aren't fatal," he says. "As veterinary health professionals, we not only focus on stopping mortality but also reducing morbidity. If we can do that through vaccination, that's the approach to take."
More than diarrhea
Coronavirus is most often associated with diarrhea and vomiting and sometimes anorexia and depression. The main concern of many practitioners is that dogs can be concurrently infected with coronavirus and deadly parvovirus. Because the viruses infect different cells in the intestine, they deal a double blow. But it turns out coronavirus infection on its own may be a greater concern than many practitioners have thought. James Evermann, MS, PhD, recently headed a study that found coronavirus to be fatal even without the presence of parvovirus.3
"It's been the perception that corona-virus by itself didn't do anything to dogs," Dr. Evermann says. "But our report indicates puppies still died of coronavirus lesions when there was no evidence of parvovirus."
This means practitioners must consider vaccinating for coronavirus. All breeds and ages of dogs are susceptible to the virus, but those at especially high risk include dogs in kennels, shelters, boarding situations, and shows. Puppies from 4 to 12 weeks old are most susceptible to the virus and have the highest risk of serious illness or death.
A respected veterinary text recommends vaccinating "outdoor enthusiast" dogs for coronavirus but says vaccination is optional for "kennel/grouped housing" and "outdoor socialite" dogs.4 Dr. Evermann disagrees. "I would place all three of these groups in the recommended category," he says.
Vaccinate dams to protect puppies
Dr. Evermann believes vaccination is especially important for breeding bitches and any dog that might become pregnant. He recommends giving dams boosters with the coronavirus vaccine four to six weeks before breeding. The vaccine protects the dam, but the biggest benefit is it protects her newborn puppies, which carry the highest risk of dying from coronavirus.
"The dam must be satisfactorily immunized to confer protection to her puppies," Dr. Evermann says. "You vaccinate the mother to protect the offspring. It's not a novel concept. We've been doing it for years in pigs and cattle to protect against the coronavirus family." It's a good time for small animal practitioners to think about adopting a similar protocol, Dr. Evermann says. "We don't consider our pets as livestock but as members of the family," he says. "We have to reconsider our thinking to maximize protection." Dr. Ellis agrees whole-heartedly. "Improving passive immunity should be on the radar of veterinarians practicing companion animal medicine," he says.
Another important aspect of vaccinating adult dogs is decreasing coronavirus shedding. Clinically affected and healthy dogs can shed the virus in feces for 37 days or even longer.5 Therefore, household dogs can contract the virus from walking in the park or through the neighborhood.
The extremely contagious nature of coronavirus is a concern for Dr. Ellis, who believes puppies should also be vaccinated. "The coronavirus vaccine is apparently very safe, so it's appropriate for puppies as well," he says.
"I recommend coronavirus vaccine for most puppies because it's a good way to prime them for a lifetime of immunity, which will be boosted by natural exposure to the virus," he says. "The major problems with coronaviruses occur when animals are young, so that's the time to offer strong clinical protection."

An underdiagnosed infection
The first step in protecting the canine population from coronavirus is vaccination. The second step is improving diagnosis, Dr. Evermann says. "Diagnostic facilities need to look for coronavirus," he says. "They're calling some puppy deaths parvovirus infection based on appearances, but they don't investigate. Coronavirus infection is underdiagnosed."
To improve diagnosis, practitioners need to instruct clients to collect a diarrhea stool sample, label the bag with the date, and freeze the contents until they can bring the sample to the clinic. Practitioners may then send the samples to a laboratory for electron microscopy, which is particularly important if a dog has died.
By implementing a careful vaccination protocol and obtaining more accurate diagnoses, practitioners can help decrease the spread of coronavirus infection—and save dogs' lives.

References
1. Yesilbag K, Yilmaz Z, Torun S, et al. Canine coronavirus infection in Turkish dog population. J Vet Med B Infect DisVet Public Health 2004;51:353-355.
2. Sokolow SH, Rand C, Marks SL, et al. Epidemiologic evaluation of diarrhea in dogs in an animal shelter. Am J Vet Res 2005:66:1018-1024.
3. Evermann JF, Abbott JR, Han S. Canine coronavirus-associated puppy mortality without evidence of concurrent canine parvovirus infection. J VetDiagn Invest 2005:17:610-614.
4. Greene CE. Infectious diseases of the dog and cat. 3rd ed. Philadelphia, Pa:WB Saunders Co, 2005:1080.
5. Pratelli A, Martella V, Elia G, et al. Severe enteric disease in an animal shelter associated with dual infections by canine aden-ovirus type 1 and canine coronavirus. J Vet Med B Infect Dis Vet Public Health 2001 ;48:385-392.