November 01, 2004

 

 Multidisciplinary task force tackles Chicago distemper outbreak - November 1, 2004

Posted on October 15, 2004
 
 

Questions raised about vaccinations

A task force of veterinarians, a virologist, and animal control officials is searching for the cause of a canine distemper outbreak in the Chicago area, and advising the city's municipal shelter on disease control and eradication measures.

Cases of canine distemper were first confirmed by laboratory tests in April; since then, more than 100 dogs have tested positive for the disease at the Chicago Department of Animal Care and Control shelter. Some of the dogs may have been infected at the shelter, whereas many others came in with the disease, according to Nikki Proutsos, the director of the Chicago department of Animal Care and Control. Additionally, area veterinarians have reported more than 20 confirmed cases outside the shelter to the Chicago VMA.

Some of the dogs that developed signs of distemper at the shelter had been vaccinated, said Dr. Dan Parmer, the director of Cook County Animal Control and a task force member. Proutos said it was hard to say whether enough time had passed between vaccinations at the shelter and exposure to the virus. And members of the task force are questioning whether too few animals have been vaccinated against distemper in the area, or whether the vaccines being used are not as effective as had been presumed.

"We don't know if routine vaccinations are protecting animals from the virus," said Dr. Sheldon Rubin, a private practitioner and task force member.

Dr. Marek Dygas, the supervising veterinarian, discovered the outbreak after he ordered a distemper test, in addition to a postmortem rabies test, for a dog that was returned to the shelter by adopters after it began showing neurologic signs, Proutsos said. Proutsos credited Dr. Dygas for his vigilance, and she said his professional experience in countries where canine distemper cases are more common helped him to detect the disease. The dog, which had been adopted in April, was returned after developing neurologic signs; it had appeared healthy while at the shelter.

Proutsos said it's difficult to rule out previous distemper cases at the shelter because the shelter did not test for distemper in the previous year. But the shelter has not seen this type of outbreak before.

"If we haven't changed what we've been doing in the last (several) years, there has to be something going on," she said.

A call to action
Canine distemper has become rare in dogs in the United States since modified-live virus vaccines became available in the 1960s. In fact, according to Dr. Rubin, many younger veterinarians may have never seen a case. The disease, however, has remained a substantial problem in some wildlife species—particularly raccoons. Infected wildlife can serve as a reservoir for the disease, passing it to dogs or, in some cases, zoo animals.

The outbreak in Chicago is unusual, said Dr. Julie Dinnage, the president of the Association of Shelter Veterinarians. Shelters in the northern United States rarely see cases of the disease, though it's more common in the South. Outbreaks in shelters are not common even when infected animals are detected, because distemper virus does not spread as easily as other viruses.

"We do have cases in some parts of the country, but it's not something that's devastating like parvovirus," she said.

Dr. Dinnage said it would take more research to determine the cause of the Chicago outbreak.

Members of the task force said they've contacted shelters across the country to find out whether they've experienced similar problems, and shelters in Georgia, Texas, and Washington state have seen the disease recently.

The officials from the Chicago VMA who are serving on the task force are attempting to gather information about the scope of the Chicago outbreak, said Patricia Montgomery, the executive director of the association. The VMA sent out mass e-mails and faxes to veterinarians, warning them of the outbreak and asking them to report the disease, which is not classified as a reportable disease by federal and state agencies. The Illinois State VMA also has sent information to members about the outbreak.

Containment a priority
The most immediate goal of the task force has been to advise the shelter on steps to stop the spread of the virus. That task has been complicated by the fact that the shelter handles more than 26,000 animals each year, including some of the highest risk populations—the city's strays and feral animals, and nuisance wildlife. Also, the disease can spread through droplets of body fluids.

On the basis of the task force's recommendations, the shelter officials have taken several steps, including the following: 

  • Instituting a 30-day moratorium on dog adoptions starting in August
  • Transferring or referring healthy or owner-relinquished animals to other shelters
  • Designating an animal control truck to exclusively transport nuisance wildlife
  • Stopping the housing and euthanatizing of nuisance wildlife inside the facility
  • Requiring shelter staff members to put on disposable garments and sanitize their shoes before moving among the areas where animals are housed

Veterinary staff are also immediately examining and vaccinating each dog that enters the facility. Additionally, a new quarantine protocol has been implemented. The facility is arranged into several rooms or pavilions, each with separate outdoor air exchange systems. The shelter staff has instituted a system by which a pavilion is power washed and sanitized, and then new dogs are brought in.

After the 45-kennel pavilion is full, the dogs inside are quarantined and observed for three weeks. If none of the dogs develops signs of distemper, all the dogs become eligible for adoption or transfer to other facilities. Unfortunately, if any dog develops signs of the disease, all animals in the pavilion must be euthanatized, Dr. Rubin said.

Task force members agreed the best way to control the disease is at the veterinarian-client-patient level, where veterinarians can ensure that dogs are vaccinated, advise clients to prevent their dogs from being exposed, and watch for signs of disease. Once the disease reaches a shelter that handles thousands of animals, it is much more difficult to control, Proutsos said.

Searching for clues
Veterinarians and a virologist from the Conservation Medicine Center of Chicago at Loyola University's Stritch School of Medicine—a collaborative effort between Loyola, the University of Illinois College of Veterinary Medicine, and the Brookfield Zoo—are also on the task force. They've been studying canine distemper in area raccoons for more than eight years. Now, they are working to identify the strain of the virus causing the outbreak in dogs, and trace its source.

The center's studies have revealed that canine distemper virus causes outbreaks in the local raccoon population roughly every three years. Various strains of canine distemper virus recently cycled through the raccoons. Research on these strains was published in the Virology Journal, an online journal, on Sept. 2, and is available to the public, free, at www.virologyj.com/content/1/1/2.

On the basis of preliminary information about the genetic sequence of the virus causing the current outbreak, John Lednicky, PhD, a virologist from Loyola University Medical Center who also works with the center, said it appears to be a variant of the virus that cycled through raccoons in 2001. He said it's too early, however, to determine whether the disease was transmitted from raccoons to dogs or vice versa.

Dr. Lednicky said he hopes to partner with other researchers to conduct challenge tests on dogs to answer the task force's questions about the role of vaccines in the outbreak. He plans to provide Ronald Schultz, PhD, of the University of Wisconsin with canine distemper virus isolated during the current outbreak. Dr. Schultz, an expert on distemper vaccinations and disease in the United States, has offered to conduct challenge tests on dogs to see whether current vaccines are effective.

"It will give us an idea whether people haven't been vaccinating, or whether the virus has drifted significantly and the vaccines are less protective," Dr. Lednicky said.

Ultimately, task force members hope their multidisciplinary approach will help end the current outbreak and provide information that will prevent future outbreaks.

Dr. Thomas Meehan, the head of the Department of Veterinary Sciences at the Brookfield Zoo and a member of the center, said the approach has become more common since the emergence of West Nile virus, which highlighted the importance of coordination and communication between disciplines.

"The diseases don't notice the difference between human medicine, veterinary medicine, and ecosystem health," he said.