As most of you know by now, H3N2 influenza was identified this month in 7 dogs in Essex County, Ontario (2 initial cases plus 5 in-contact dogs). These dogs were imported from Asia, via the USA. Visit Dr. Scott Weese’s excellent Worms and Germs blog for more information about these cases and canine influenza virus (CIV) in general. Dr. Weese was kind enough to answer a multitude of shelter-related questions for this blog. (Please note: Any errors are mine! LJ)
Source: Veterinary Team Brief
The short version of this blog
Should we panic? No.
Should we vaccinate shelter dogs for CIV? No.
What is the best test for CIV? The PCR test, using nasal swabs, in very early cases.
What’s the most important thing to do right now? Minimize risks and be prepared in the event of outbreaks. Devevelop, or review and revise, transport/importation, disease surveillance and outbreak prevention/management protocols. Ensure that your shelter is ready for the day influenza comes in the door. That’s more likely a “when” than an “if”.
The long version of this blog
Should we panic?
No. Thanks to prompt action, these cases were rapidly diagnosed and appropriate action taken. The outcome will become clearer over the next few weeks but at present it looks like the episode has been contained and there appears to be negligible risk to the community.
What’s the main significance of these cases?
This is (or should be) an important opportunity for shelters and rescues to review their animal importation and disease/outbreak management policies and protocols.
The two canine strains are H3N8 and H3N2. In the USA, H3N8 was first identified in 2004, and H3N2 in 2015. This map shows how the viruses have spread across the USA; and this one shows the prevalence of the viruses. So far, H3N8 has not been identified in Canada, and the two recent H3N2 cases are the first to be diagnosed here.
for transmission and spread into the broader canine community.
Is canine influenza zoonotic?
No (with the caveat that in biology, as in US Presidential politics, it’s unwise to use the words “never” or “impossible”). The dog would have to be simultaneously infected with a canine virus and a human virus, they would need to recombine and only then could the virus could jump to people – so the likelihood is exceptionally small. No cases of canine influenza have been reported in people to date.
Minimizing the risk of importing canine influenza
- Before bringing dogs in, ensure that your shelter has the knowledge and resources to manage imported infectious diseases. We might be worried about H3N2 now, but there are multiple potential risks. The Report of the Canadian National Canine Importation Working Group (even if you only have time to read the Executive Summary and list of diseases of concern) is a great resource for developing broad-based preventive and containment strategies.
- Identify and minimize known risks in advance of importation. USA map add Cornell link (below). Canine influenza is endemic in Thailand, South Korea and China, and can essentially be considered endemic in the USA. Ohio, Kentucky and Chicago are “hot spots” right now.
Canine influenza is clinically indistinguishable from other canine respiratory infections. Clinically it can range from mild to severe disease, with severe disease more likely to occur in juvenile, naïve and stressed animals, and in conjunction with co-infections.
Incubation and shedding
The incubation period is typically only 2-4 days. Dogs can shed large amounts of virus for a day or two before showing clinical signs. For H3N8, shedding after illness is a week or less, but H3N2 typically has a shedding period of 2 weeks, in some cases up to 3 weeks. This makes it higher risk
What should shelters do if we identify a case?
Animal influenza is reportable in Canada, so the local public health unit must be informed. Expert advice on dealing with new cases can be obtained from shelter medicine and infectious disease specialists. It might also be helpful to contact diagnostic laboratories or vaccine manufacturers, who might be willing to help with testing and vaccination costs.
What precautions should Canadian shelters take with imported dogs?
The first step is risk analysis. The more you can find out about the source of the dogs, the better. For example, the US is considered endemic for canine influenza but the risk is very different in different geographic areas. Obviously, the higher the known risk, the more precautions are needed. Avoiding high-risk imports is the ideal solution, but this isn’t always possible.
The highest value period for quarantine is the first 7 days, so this should be considered the minimum for all imported dogs. If there is known infection or high risk of H3N2, dogs should be quarantined for 3 weeks (this is recommended even if they show no clinical signs, because of subclinical infection or illness before transport). A 7 day quarantine period should be adequate for H3N8. Quarantine should include keeping the dogs in a closed group (cohort) and using gloves and gowns when handling, as well as being very careful to avoid fomite transmission via leashes, toys or food bowls.
Should dogs be available for adoption while in quarantine?
Open selection is advised for healthy dogs – in other words, adopters should be able to view the dogs, or information about them, and preselect them for adoption. As to whether healthy dogs should be released to their new homes within the quarantine period, that would depend on the risk assessment. Reducing length of stay is always preferred where possible, but that has to be balanced against the risk of introducing a new disease into a community, something no shelter wants to be remembered for!
The quarantine period should end when the last symptomatic animal in the group reaches the end of its potential shedding period. , so this is a minimum recommended period. The duration of quarantine should be risk-based.
How long does the virus persist in the environment?
Influenza only persists for a few days in the environment and is killed by routine disinfectants.
What screening tests and active surveillance are recommended?
Tests are expensive, so to get the most bang for your buck, use the highest value tests in the animals most likely to provide a useful result. Active surveillance is recommended for animals from a high-risk source. Testing several animals is more useful than testing only one, but there is no need to test every animal. If one animal tests positive, the whole cohort should be quarantined in any case, and all symptomatic dogs in the cohort would be presumed to have influenza, so testing every dog is not cost-effective.
The dogs that should be tested are the most acute cases – dogs that are just starting with clinical signs, such as reduced appetite and fever. Testing healthy dogs in case they are shedding isn’t cost-effective.
Dr. Weese recommends the PCR test for canine influenza. This is offered by IDEXX, Antech and AHL. Respiratory virus panels are preferable, because coinfections are common and have implications for severity and management. The PCR test will remain positive longer for H3N2 because of the long shedding period, whereas it can become negative quite quickly after H3N8 infection. For this reason, only the most acute cases should be sampled. Nasal swabs are recommended over pharyngeal swabs.
Serology requires acute and convalescent samples, making it a very slow diagnostic method. There is no clinical reason to use serology over the PCR and it is most useful for epidemiological purposes. Serum samples can be frozen in case serology might be needed retrospectively.
Can samples be pooled to save money?
Maybe, but this could reduce sensitivity. It’s better to sample dogs individually and select cases most likely to give a diagnostic result.
If a shelter or practice provides services for dogs from other shelters or rescues, what precautions should they take to avoid influenza?
If the dogs are from a high-risk area, it would be prudent to wait 21 days from their date of importation, or from the last day of clinical signs in the group, before bringing them in to a facility.
Should we vaccinate shelter animals against CIV?
Only killed, injectable CIV vaccines are available at present (a MLV intranasal vaccine may be on the way). A minimum of 2 initial vaccines are required. A booster must be given 2-4 weeks after the initial vaccine, and partial protection has been demonstrated 2 weeks later. Compare this 4-6 week wait with onset of protection within a few hours to days after MLV vaccines for distemper or parvo, and it’s immediately clear that the benefit of CIV vaccines in shelters is limited. The other drawback is the partial immunity produced by influenza vaccines – duration and severity are reduced but full protection does not occur.
Should we vaccinate selected shelter animals?
Shelters might consider vaccinating long-stay animals if the risk of CIV becomes higher, but right now the cost:benefit analysis would come down on the side of not vaccinating. Scarce resources are better utilized for risk assessment, quarantine and testing.
Should vaccines be offered at public vaccine clinics to create herd immunity?
Maybe. However, we should consider where our resources can make the most impact for our local community, and right now CIV vaccination might not be the highest priority.
Are CIV vaccines available in Canada and which ones should be used?
If vaccinating, use a bivalent H3N2/H3N8 vaccine. The Nobivac (Merck) vaccine is available in Canada (call to order if it shows up as not being in stock). The Zoetis bivalent vaccine was not available here at the time of writing. The vaccine is given to dogs 7 weeks and older, with a booster after 2-4 weeks.
What is a good CIV resource for owners?
Shorter: AVMA information page
Longer: AKC information sheet
1. Worms and Germs blog
6. VetGirl Webinars: Updates in Canine Influenza Virus: Management, Diagnosis, Treatment, Prevention and Vaccination (2017) and NEW, FREE webinar, Canine Infectious Respiratory Disease Complex: 2018 Update on Canine Influenza and Bordetella