CHICAGO––An outbreak of an Asian strain of canine influenza, H3N2, not before seen in the U.S., has hit more than 1,300 dogs in the Chicago area, spreading from Illinois into Wisconsin, Ohio, and Indiana.
But contrary to widespread rumor, there is no hard data yet, nor even strong circumstantial evidence, to link the H3N2 outbreak to rescues of dogs from Asian meat markets.
Rescue agencies in recent months are known to have transported fewer than 100 dogs to the U.S. from the regions of Asia where the H3N2 canine influenza virus occurs. None of those dogs are known to have reached the U.S. Midwest.
Did sniffer dog sneeze?
While the possibility of the H3N2 virus moving with a rescue dog cannot be totally excluded, there are many other ways in which it might have come to the U.S.
The simplest scenario might be that an infected sniffer dog might have sneezed while inspecting outbound cargo at an Asian airport. The H3N2 virus––or almost any flu virus––could remain alive and infectious for far longer than the 13:35 duration of a flight from Seoul to Chicago.
Upon arrival in Chicago, a U.S. sniffer dog inspecting incoming cargo might have inhaled the virus. Since most dogs do not suffer severe symptoms from canine influenzas, and since the viruses usually have an incubation period of up to a week, the infected U.S. dog might have spread the virus to any number of others before any U.S. dogs fell seriously ill.
The H3N2 virus was detected in the U.S., CBS News reported on April 5, “after several dogs at PetSmart boarding facilities got sick. The company temporarily closed three Chicago-area locations to be disinfected.”
WBBM 780 reporter Lisa Fielding added that groomers and “doggy day care” companies throughout the Chicago area were “limiting operations” to avoid infecting more dogs. PetSmart spokesperson Andy Izquierdo told Fielding that PetSmart was “reminding dog owners about the symptoms,” Fielding paraphrased, “which include a persistent cough, runny nose and fever.”
Separate from PetSmart boarding, grooming, and daycare facilities, the Luv-A-Pet adoption boutiques located in 1,404 PetSmart stores helped animal charities to rehome more than 470,000 dogs and cats in 2014. That connection was apparently enough to start the rumor mill humming.
The hum rose in pitch when the Chicago Anti-Cruelty Society, as a precaution, canceled a “Bark in the Park” fundraiser which was to have been held on May 3, 2015, and announced that it would instead hold an online event.
The hum increased to a shriek after Audie Cornish of National Public Radio on April 15, 2015 interviewed Edward Dubovi of the Cornell University Department of Population Medicine & Diagnostics and Cornell School of Veterinary Medicine.
“The outbreak really went into full force around the Easter holiday,” explained Dubovi, “when a number of people probably put their dogs into kennels, and so you had maybe a higher collection of dogs in smaller environments. And so this thing had an opportunity to expand very rapidly.
“We’ve had a virus in the dog population in the United States since 2004,” Dubovi continued, referring to an outbreak of canine influenza that began among racing greyhounds.
But that outbreak turned out to be a mutated form of the H3N8 equine influenza virus, identified in racehorses for more than 40 years. Occurring in racehorses in 13 nations during 2004, H3N8 somehow jumped into greyhounds at tracks in 11 U.S. states––several of which were dual-purpose tracks, used for both horse and greyhound racing, or had been used for both horse and greyhound racing at some time in the past.
“As we did some subsequent testing and the outbreak got a bit bigger,” Dubovi went on, “it became evident that this was not the normal canine influenza virus that we have been seeing in the U.S. And the preliminary evidence so far is that this virus is probably one that came out of Asia.
“And as it turns out, our requirements for movement of companion animals into the United States are fairly lax. And we certainly have situations now,” Dubovi speculated, “where animal rescue groups are rescuing dogs in China and Korea from their meat markets, and we know for a fact that, in fact, some of those dogs have found their way into the Chicago area.”
Asked by ANIMALS 24-7 for particulars of that allegation, Dubovi offered none, but referred ANIMALS 24-7 to Maddie’s Fund assistant professor of shelter medicine Cynda Crawford, of the University of Florida at Gainesville. Crawford, the lead researcher in identifying the H3N8 canine influenza virus in 2004, had recently been in Chicago investigating the H3N2 outbreak, Dubovi said.
“I generally keep to the business of disease diagnostics and test reporting,” Dubovi told ANIMALS 24-7. “I have probably reviewed most of the papers out of China and Korea about H3N2 and have been concerned about the appearance of this virus in the U.S., as it appears to be more pathogenic than our H3N8,” Dubovi added.
Crawford had more questions than answers.
Crawford was aware, ANIMALS 24-7 learned, that Humane Society International and the Change for Animals Foundation in January 2015 flew 23 dogs who had been rescued from a dog meat farm from Seoul, South Korea to Washington D.C..
Two months later, in March 2015, HSI and the Change for Animals Foundation flew another 57 dogs from a South Korean dog meat farm to San Francisco.
But the first 23 South Korean dogs were rehomed by the Animal Welfare League of Alexandria, the Fairfax County Animal Shelter, the Animal Welfare League of Arlington, the City of Manassas Animal Control & Adoption Shelter, Loudoun County Animal Services, and the Washington Animal Rescue League––all about 700 miles from Chicago.
The second 57 South Korean dogs were rehomed by the San Francisco SPCA, the East Bay SPCA, the Marin Humane Society, and the Sacramento SPCA––all more than 2,000 miles from Chicago.
“I am afraid I don’t have any more information than what can be found on the Internet,” Crawford told ANIMALS 24-7. “I certainly support the laudable work of HSI, the Change for Animals Foundation, the Asia Canine Protection Alliance, and other international animal welfare groups to stop the dog meat farming and trade. There is no evidence that I know of for inadvertent introduction of the Asian H3N2 virus via their efforts.
“The importation of South Korean dogs to shelters in north Virginia in early January would be within the time frame of the start of the Chicago cases in late January/early February,” Crawford acknowledged. “However, I do not know if any of these Korean dogs or any dogs that had contact with them made it to Chicago. I am curious if the dogs had respiratory signs on arrival to stateside shelters, or shortly thereafter, and were considered to have ‘kennel cough’” associated with the stress of long distance travel. It would also be interesting to know if any of the resident dogs in the receiving shelters developed ‘kennel cough’ after the arrival of the Korean dogs.”
But several layers of biosecurity requirements for importing dogs into the U.S.––if observed––would appear to preclude any of the dogs rescued by Humane Society International and the Change for Animals Foundation being infected with H3N2.
The Centers for Disease Control & Prevention requires dogs “be vaccinated against rabies and be healthy upon arrival,” summarizes https://help.cbp.gov/app/answers/detail/a_id/461/~/quarantine-requirements-for-imported-dogs,-including-puppies.
“Dogs that have never been vaccinated against rabies must be vaccinated at least 30 days before entering the United States,” the site adds. “Puppies must not be vaccinated against rabies before three months of age, so the youngest that a puppy can be imported into the United States is four months of age. The rabies vaccination requirement applies to all dogs including service animals. The only exception is for dogs arriving from areas designated as being rabies-free who have lived there for at least the last six months or since birth.”
The CDC requirement implies that imported dogs must have been under health observation and in secure custody, if not actual quarantine, for more than four times longer than the normal incubation period for canine influenza.
Stronger USDA-APHIS requirement
The USDA Animal & Plant Health Inspection Service on August 18, 2014 introduced an even stricter rule governing the import of dogs “from any part of the world into the continental United States or Hawaii for purposes of resale, research, or veterinary treatment, unless the dogs are in good health, have received all necessary vaccinations, and are at least six months of age,” according to the regulatory language.
Specifically, USDA-APHIS requires vaccinations for rabies and distemper, hepatitis, leptospirosis, parvovirus, and parainfluenza virus.
Moreover, the USDA-APHIS rule was introduced with text specifically rejecting exemptions for “imports for rescue purposes.”
“Because the canine flu viruses are a quick-hit virus with short shedding periods,” explained Crawford, “it would seem difficult to import an infected dog who was still in the contagious period. That said,” Crawford cautioned, “the biggest flu outbreak in Australia occurred in horses in 2007. Australia was an equine influenza-free country and this status was maintained by strict quarantine of imported horses for three weeks. In 2007, equine influenza virus was brought into the country via an infected horse, possibly due to a breach in quarantine, and the virus spread like wildfire to hundreds of horses with many deaths. Like the canine virus, the equine flu virus also is a quick-hit, short shedding period (7 days) virus.”
“Many potential routes”
“The H3N2 virus,” Crawford elaborated, “is typically shed for seven days, possibly 10 days in some cases. The incubation period is typically 2-3 days, meaning the virus is already in day 2-3 of its short 7-10 day shedding cycle by the time dogs start coughing. A subset of dogs have subclinical infection – they shed virus for a few days but do not display clinical signs. The flu viruses do not persist in the environment for more than 12-24 hours, depending on ambient conditions,” meaning that H3N2 might survive outside of a host animal for the duration of a direct flight from Southeast Asia, but would probably not survive for longer unless flown in a frozen form.
“Flu viruses can be viable after freeze/thawing,” Crawford noted.
But while the temperatures in aircraft holds often dropped below freezing in earlier generations of high-flying jets, the Boeing and Airbus jets usually used on transoceanic flights today typically maintain hold temperatures of close to 40 degrees Fahrenheit.
“Obviously, there are many potential routes by which this virus could breach our borders,” Crawford said. “We may never know how the H3N2 virus was introduced into the U.S. –– the most important thing right now is finding out how to stop the spread.”
“There are likely more questions than answers,” agreed Program for Monitoring Emerging Diseases infectious disease moderator Tam Garland of Texas A&M University, at http://www.promedmail.org.
“For example, did the strain originate in birds? How did it adapt to dogs? Did it pass through an intermediate host such as humans or pigs prior to adapting to dogs? Does it present a risk to humans? The risk to humans is likely small,” Garland anticipated, “or we would have had affected human caretakers of these affected dogs coming down with this strain of the flu.”
Responded Crawford to the question of avian origin, which might suggest a link to the illegal but extensive commerce between the U.S. and Southeast Asia in gamecocks, “The H3N2 canine virus evolved from avian H3N2 viruses in Korea, but several mutations have occurred over the years associated with adaptation to the dog as the new host. I think these mutations have distanced the dog virus from the bird virus. There are several published papers on the phylogenetics of the dog H3N2 virus compared to avian and human H3N2 viruses.”
“Keep dogs separated”
Concerning the potential risk to humans, Dubovi told Audie Cornish of NPR, “Right now we have no evidence that the virus is moving from the dogs into the human population,” but that does not mean such a cross-species infection could not happen.
“If you had a sick dog in your house,” Dubovi said, “you could transmit the virus to another animal in the house through what we call fomites –– just saliva, or if a dog sneezes on you, and you move to another animal. “
Dubovi warned that “The Asian variety of the flu also can infect cats. There is a vaccine against the U.S. variety,” Dubovi said, but cautioned, “We are unable at this point in time to indicate whether or not it will afford any protection against the virus we think is coming from Asia.
“The best thing to do right now until this calms down,” Dubovi advised, “is to keep dogs separated as much as possible. The fewer contacts your dog has with another dog, the lesser the chance of it picking this particular virus up, or any other virus for that matter.”