If a dog has been showing upper respiratory signs for at least four days, serologic testing is the best way to diagnose canine influenza. These tests utilize hemagglutination inhibition to search for the presence of canine influenza virus antibodies. (Iowa State University, 2022) The most accurate method of testing for influenza virus requires paired acute serum samples (taken within seven days of the onset of clinical signs, at which time there should be little to no circulating antibody present) and convalescent serum samples (taken two to three weeks later, during the dog’s peak immune response). A diagnosis of canine influenza is made based on a four-fold increase in antibody titer from the acute to the convalescent sample. (American Veterinary Medical Association, 2015) If an acute sample is not available, convalescent samples can indicate exposure but will not indicate whether that exposure was recent or historic. The primary disadvantage of serology is that results can rarely be used to guide treatment due to the need to wait for a convalescent sample; the value of serology results lies primarily in disease surveillance. (Landolt, 2011) Still, the low cost and availability of serology makes it a valuable test that can be utilized in dogs that are slow to respond to treatment. Serologic testing is available for both the H3N8 and H3N2 strains of canine influenza virus through a number of university and commercial reference laboratories. Suspected influenza cases should always be tested for both strains to rule out canine influenza infection. (Richardson, 2015) Previously vaccinated dogs are likely to have a positive titer against one or both strains of canine influenza, which may complicate the utility of serologic testing to obtain an accurate diagnosis.
transport media, if available). These swabs can be processed through commercial laboratories or shipped via overnight delivery to participating university laboratories on ice. (Cornell University College of Veterinary Medicine, n.d.) The specificity of canine influenza PCR is relatively high, and false positives are rare; however, false negatives can occur if swabs are collected after the time of peak virus shedding. (American Veterinary Medical Association, 2015) This means that PCR testing is only recommended for dogs that are tested within the first four days of clinical signs of canine influenza. Virus isolation is another method that can be utilized in the diagnosis of canine influenza. However, like PCR, virus isolation is unlikely to be successful after the first three to four days of infection. Canine influenza viruses have been successfully isolated in embryonated eggs or cell cultures, depending on the viral strain. Like PCR, virus isolation can provide false negative results if samples are not collected within the early stages of clinical signs, as diagnosis is based on active viral shedding at the time of sample collection. Because canine influenza is often not suspected as a cause of upper respiratory illness until late in the course of disease, the utility of virus isolation is low in a clinical setting. (Iowa State University, 2022) Antigen-capture enzyme-linked immunosorbent assay (ELISA) tests do not seem to be useful in testing individual dogs for canine influenza, likely due to the small amounts of virus shed outside of the early clinical period. These tests have a lower reported sensitivity and specificity than PCR and virus isolation, making them unreliable in testing of individual dogs. Antigen-capture ELISA may, however, be useful during investigations of outbreaks involving large numbers of dogs, due to their ease of use. (Iowa State University, 2022)
TREATMENT: MEDICAL THERAPIES
Canine influenza treatment varies, depending on the severity of the case. Care is mostly supportive in nature, but Mild cases Mild cases of canine influenza should be treated like any other mild upper respiratory infection (i.e., kennel cough). This treatment primarily consists of supportive care. Antibiotics are typically not recommended for young, healthy dogs unless there is evidence of bacterial infection. Antibiotics will not aid in clinical resolution of viral signs, and indiscriminate antibiotic use may contribute to antibiotic resistance. (Su, 2014) The most common form of secondary bacterial infection seen with mild cases of canine influenza is purulent nasal discharge. Purulent nasal discharge in a dog with canine influenza is often caused by a secondary infection, often involving Staphylococcus spp. or Streptococcus spp . Dogs with influenza and purulent nasal discharge can often be treated successfully with cephalexin (35 mg/kg every 12 hours). There may be a slight benefit to cough suppressants in mild cases of canine influenza, but many practitioners have noted that the cough associated with influenza is poorly responsive to antitussives. In fact, this characteristic has been reported by some veterinarians to be helpful in the diagnosis of canine influenza infection. Therefore, if cough suppressants are prescribed, clients should be warned that they may not see immediate effects. Additionally, antitussives should be avoided in dogs with a productive cough as the medication will interfere with the clearance of secretions from the airways and may further increase the lung damage
severe cases will need a greater degree of supportive care than mild cases will need.
associated with the disease. (Moyer, 2011) (Crawford et al., 2010) Dogs that have other concurrent health issues, such as pregnancy, pre-existing lung disease (tracheal collapse, chronic bronchitis, etc.), or immunosuppression, may benefit from additional diagnostics or treatments even when only mild clinical signs of upper respiratory disease are noted. In these dogs, veterinarian should consider the use of antibiotics for any known or suspected secondary bacterial infections. (Dubovi, 2008) These antibiotics should be selected on the basis of culture and sensitivity testing, performed on a sample collected via transtracheal wash. In the absence of culture and sensitivity test results, a broad- spectrum antibiotic should be chosen. Many practitioners have found a combination of doxycycline (5 mg/kg every 12 hours) and clindamycin (5mg/kg to 11 mg/kg every 12 hours) to be beneficial in these cases. Also consider the use of fluids and nonsteroidal anti-inflammatory medications, if needed, to correct dehydration and reduce fever. (Dubovi, 2008) Ensure that affected dogs are eating and drinking normally at home and discuss appropriate quarantine procedures with their owners. With supportive care, canine influenza virus is self-limiting in most patients. Most mild cases of canine influenza will resolve within two to three weeks. (Dubovi, 2008)
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Book Code: VFL1526
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