for canine influenza virus. (Cornell University College of Veterinary Medicine, n.d.) Other samples tested during this time instead demonstrated evidence of parainfluenza, respiratory coronavirus, Bordetella , or other upper respiratory pathogens. This statistic underscores the Other influenza viruses in dogs In 2002, an equine influenza H3N8 outbreak was noted among a small population of foxhounds in the United Kingdom. Clinical signs of H3N8 infection included coughing, weakness, and lethargy, and a number of cases progressed to bronchointerestitial pneumonia. One dog died during this outbreak, and several were euthanized due to the severity of clinical signs noted. (Iowa State University, 2022) In 2009, human pandemic H1N1 influenza was isolated from two dogs in China and one dog in the United States. All three dogs demonstrated a severe cough; one dog only demonstrated mild depression and anorexia, while the other Canine influenza: General considerations Canine influenza virus is not a seasonal virus, like human influenza viruses tend to be. (Crawford et al., 2010) Therefore, sporadic outbreaks are typically noted year- round. Time of year cannot be used to predict the likelihood of a given case or outbreak of upper respiratory disease being caused by canine influenza virus. Canine influenza H3N8 and H3N2 do not pose a documented zoonotic disease risk to humans, including the owners of infected dogs.4 People with frequent exposure to high-risk dog populations do not demonstrate antibodies against canine influenza virus. (Krueger, 2014) All strains of canine influenza virus are readily transmitted between dogs. This transmission may occur via a variety of methods, including oronasal contact, respiratory droplets, and fomites (such as collars, leashes, food/water bowls, and kennel surfaces). (Crawford et al., 2010) (Krueger, 2014) Fecal shedding has not been observed with canine influenza virus, despite fecal shedding being a known mechanism by which birds can spread influenza viruses. (Moyer, 2011) Like other influenza A viruses, however, both canine influenza strains are thought to be spread by aerosols. (Moyer, 2011) Depending on environmental conditions, aerosol spread may occur over distances of up to 50 feet. Canine influenza aerosols may be produced naturally by coughing and barking dogs; however, cleaning techniques (such as spraying and hosing kennels) may also further contribute to the formation and dispersal of aerosols. (Moyer, 2011) Long-range aerosol transmission of canine influenza seems to occur more frequently in areas with poor ventilation. Outbreaks are most commonly reported when dogs are housed in close proximity to each other in an environment with closed circulation. (Landolt, 2011) The highest rates of canine influenza transmission are noted in dogs that reside in kennels or spend time in areas with transient dog populations (such as animal shelters and pet daycare facilities). Up to 40% of dogs spending time in these high- risk environments have been found to be seropositive for canine influenza. (Crawford et al., 2010) Dogs who come in contact with large groups of other dogs in other venues have demonstrated much lower rates of H3N8 exposure. A study of 399 blood samples collected from Iditarod sled dogs in 2010 demonstrated a canine influenza seroprevalence of 0%. (Pecoraro, 2012) Additionally, 100 blood samples collected from 2009 to
difficulties in diagnosis of this disease and its clinical similarities to other canine upper respiratory infections. Even during an outbreak, when veterinarians are presumably gaining experience with this disease, it can be clinically indistinguishable from other respiratory infections. two exhibited fever and lethargy consistent with pneumonia. All three dogs recovered with supportive care, though the two more severely affected dogs required hospitalization. (Iowa State University, 2022) There have been other isolated reports of dogs infected with avian influenza (H5N1 and H5N2) in Asia. Additionally, experimental infection with H9N2 avian influenza has led to respiratory signs and dogs that are seropositive to this virus have been noted in China. (Iowa State University, 2022) However, at this time, there is no indication that other strains of canine influenza are causing disease in the United States pet dog population. A 2024 review and meta-analysis examined 97 studies conducted worldwide on the global prevalence of canine influenza virus in dogs. (Leung, 2024) This study examined influenza prevalence in 27 different countries and found that the prevalence of canine influenza has been relatively stable, remaining under 10% for the last ten years. Additionally, this study noted that the most common influenza strains detected in dogs were H3N2 and H3N8, with other strains of canine influenza found solely in China.
TRANSMISSION
2010 demonstrated a canine influenza seroprevalance of only 1.9% among dogs participating in flyball tournaments. (Wiley, 2013) Without adequate cleaning measures, influenza particles may persist in the environment for up to 48 hours. (Wiley, 2013) Influenza viral particles may remain viable on hands and clothing for up to 24 hours, allowing influenza to be transferred to different locations. (Wiley, 2013) Fortunately, canine influenza is quickly killed by all common disinfectants used in kennels and veterinary hospitals, including quaternary ammonium compounds (e.g., benzalkonium chloride—Lysol ™ ), aldehydes, phenols, and bleach solutions. (Wiley, 2013) Therefore, routine disinfecting protocols should be adequate to limit the environmental persistence of canine influenza in a veterinary hospital. The incubation period of canine influenza is approximately one to four days. Viral shedding is at its highest during the incubation period and typically peaks at approximately four days post-exposure. (American Veterinary Medical Association, 2015) The asymptomatic shedding period associated with canine influenza infection complicates efforts to prevent transmission, because dogs are at their most contagious (shedding the largest number of viral particles) before they even begin showing clinical signs of illness. (Landolt, 2011) Viral shedding begins to decrease once signs of infection appear and has typically stopped by 7 to 10 days post- infection. (American Veterinary Medical Association, 2015) However, treatment with steroids has been demonstrated to prolong viral shedding to as long as two weeks. (Cornell University College of Veterinary Medicine, n.d.) Steroid treatment is not uncommon with canine influenza, so two weeks of viral shedding is not uncommon in infected dogs.
Page 37
Book Code: VFL1526
EliteLearning.com/Veterinarian
Powered by FlippingBook