Introduction

Classification

Taxonomy

• Orthomyxoviridae, Type A (based on core proteins), Subtype H3N8 (based on surface glycoproteins); strains identified by geographic origin, host, year of isolation, and serial number. Subtype H3N2 emerged in US in 2014 from Korea. Believed to have originated in birds. First appeared in Asia around 2005-6.
  Print off the owner factsheet on Canine influenza to give to your client.

Etymology

• Greek: orthos (straight) and myxa (mucus).

Active Forms

Clinical Effects

Epidemiology

Habitat

• Obligate parasite of dogs; survives for hours to days outside of the dog.

Lifecycle

• Replicates in respiratory tract epithelia; shed in aerosol droplets.

Transmission

• Spread dog-to-dog via aerosol, direct transmission, and indirect spread via fomites.

Pathological effects

• Because these are relatively new viruses in dogs, most dogs are immunologically naive and susceptible to infection. Approximately 20% of dogs will not develop clinical signs following infection; most will experience mild disease. Most severe disease is seen in young or those with secondary bacterial infections.

• Infection and replication in respiratory epithelia leads to the destruction of these cells. Resultant inflammatory response contributes to tissue damage. Secondary infection with bacteria may occur, and may contribute to more severe disease.
• Incubation period of 2-5 days; virus is shed from the respiratory tract for approximately one week following appearance of clinical signs.

Other Host Effects

• Most affected dogs present with fever and moist cough that may persist for two weeks or longer. It is nonresponsive to antibiotics. Some dogs will exhibit a purulent nasal discharge that is usually due to secondary bacterial infection. A small percentage of dogs may experience more severe disease with evidence of pneumonia, including high fever, labored breathing, and evidence of lung consolidation on radiographs. Persistent cough is indicative of damaged respiratory epithelium and not of continual virus shedding.

Control

Control via animal

• Vaccines are currently available in the US for both H3N8 and H3N2 subtypes. A bivalent vaccine (VANGUARD® CIV H3N2/H3N8) is now available for protection against both strains.
  Infected dogs should be strictly isolated.

Control via chemotherapies

• Supportive care, including maintenance of hydration.
• Antibiotics Therapeutics: antimicrobial drug if secondary bacterial infection is suspected; cases with pneumonia should use broad-spectrum antibiotics.
• Influenza antivirals for use in humans are not approved for use in dogs; according to the AVMA, veterinarians who use approved drugs in a manner that is not in accord with approved label directions (eg use of an antiviral drug only approved for use in humans) must follow the federal extralabel drug use regulations of the Animal Medicinal Drug Use Clarification Act (AMDUCA).

Control via environment

• Routine recommendations for hygiene should be applied for canine influenza virus; routine disinfection will inactivate the virus. Hand washing after handling dogs, disinfection of equipment and supplies such as bowls, and avoiding aerosolization during cleaning are recommended.

Vaccination

• Inactivated canine influenza vaccines are available for H3N8 and H3N2 in the United States and a bivalent vaccine for protection against both strains is now available. The vaccines have been shown to reduce the incidence and severity of lung lesions, as well as the duration of viral shedding and other clinical signs such as coughing.
• The vaccine is administered by subcutaneous injection, by two doses given 3 weeks apart.
• The vaccine can be given to dogs from 8 weeks of age upwards, and then as part of the annual vaccination regimen.

Diagnosis

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Chen Y, Trovão N S, Wang G et al (2018) Emergence and Evolution of Novel Reassortant Influenza A Viruses in Canines in Southern China. MBio 9 (3) PubMed.
• Zhu H, Hughes J, Murcia P R (2015) Origins and evolutionary dynamics of H3N2 canine influenza virus. J Virol 89 (10), 5406-5418 PubMed.
• Deshpande M S, Jirjis F F, Tubbs A L et al (2009) Evaluation of the efficacy of a canine influenza virus (H3N8) in dogs following experimental challenge. Vet Ther 10 (3), 103-112 PubMed.
• Deshpande M S, Abdelmagid O, Tubbs A et al (2009) Experimental reproduction of canine influenza virus H3N8 infection in young puppies. Vet Ther 10 (1-2), 29-39 PubMed.
• Crawford P C, Dubovi E J, Castleman W L et al (2005) Transmission of Equine Influenza Virus to Dogs. Science 310 (5747), 482-485 PubMed.

Other sources of information

• Andrewes Viruses of Vertebrates (JS Porterfield, editor). 5th edition, 1989. London: Balliere Tindall.
• VANGUARD® CIV H3N2/H3N8: www.zoetisus.com/products/dogs/vanguard-civ-h3n2-h3n8/
• VANGUARD® CIV H3N2: www.zoetisus.com/products/dogs/canineinfluenzavaccineh3n2/index.aspx
• VANGUARD® CIV H3N8: www.zoetisus.com/products/dogs/vanguard-civ.aspx
• AVMA: www.avma.org/KB/Resources/Reference/Pages/H3N2v-Influenza.aspx; www.avma.org/KB/Resources/FAQs/Pages/Control-of-Canine-Influenza-in-Dogs.aspx?utm_source=smartbrief&utm_medium=email&utm_campaign=smartbrief-article
• UF College of Veterinary Medicine: hospitals.vetmed.ufl.edu/canine-influenza/
• Cornell University College of Veterinary Medicine: www.diaglab.vet.cornell.edu