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Guidelines for antimicrobial use of respiratory tract disease part one

Lappin MR, Blondeau J, Boothe D, Breitschwerdt EB, Guardabassi L, et al. Antimicrobial use Guidelines for Treatment of Respiratory Tract Disease in Dogs and Cats: Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases. J Vet Intern Med. 2017 Mar;31(2):279-294.

Rational and appropriate antibiotic use has increasingly become a major concern in veterinary (and human) medicine. Infections of the respiratory tract are a common concern in all species, and cats are no exception. The use of antimicrobials in the treatment of upper and lower respiratory infections has become increasingly controversial, as more conditions are found to be viral or self-limiting. This manuscript serves as a guideline from a panel of experts outlining diagnostic, therapeutic, and monitoring options for respiratory infections in cats and dogs. This summary will focus on the feline portion of the manuscript. This first portion will address upper respiratory infections, and the second lower respiratory tract infections.

While guidelines such as these do not provide new information to the veterinary community, they attempt to collect, quantify and qualify the evidence available to allow veterinarians to make rational treatment decisions.

The authors first define acute upper respiratory infections as lasting less than 10 days, and chronic greater than 10 days. Most cats with upper respiratory signs are infected with feline herpesvirus 1 (FHV-1) or calicivirus, with secondary bacterial infections, though some bacteria may cause primary disease. Bacteria of concern include Staphylococcus spp., Streptococcus spp., Pasteurella multocida, Escherichia coliChlamydia felis, Bordetella bronchiseptica, Streptococcus equi subspp. zooepidemicus, and Mycoplasma spp, as well as assorted anaerobes.

For cats with acute upper respiratory disease the authors recommend a full physical exam with detailed history and retrovirus testing. Culture and cytology were not recommended for acute disease. If disease is serous, the infection is likely viral and therapy is not recommended. Mucopurulent discharge does not ensure bacterial infection, however.

Treatment of acute bacterial URTI is only recommended if there is a combination of mucopurulent discharge with fever, lethargy, or anorexia. Without these signs, a 10 day observation period is recommended. If treatment is initiated, the recommended therapy is a 7 to 10 day course of doxycycline. Doxyxcyline is generally well tolerated with minimal resistance and is effective against bordetella, chlamydia, and mycoplasma spp, as well as many commensals. The authors also provide a detailed list of antimicrobial options including their general spectra of activity and pros and cons of their use.  If doxycycline is not tolerated or not available, amoxicillin is a reasonable first choice if mycoplasma and chlamydia are not suspected.

The use of cefovecin was not recommended by the working group due to insufficient data. Fluoroquinolones and third generation cephalosporins should only be used based on culture results. Data has not suggested that azithromycin is more effective than amoxicillin for most infections, and is less effective against chlamydia; as such it is not recommended as a first line option.

If clinical signs of infection persist for >10 days (especially if empirical therapy is not successful), further workup is warranted. Workup should include ruling out atypical infections (fungal, cuterebra, etc) and non infectious causes (neoplasia, allergy, foreign body, polyps, trauma, etc). Workup may include imaging (including advanced imaging such as CT), rhinoscopy, exploration for polyps or stenosis, and nasal lavage or brushings with cytology, PCR, and culture.

For chronic URTI without any underlying cause, antibiotics should be chosen on the basis of culture and sensitivity results. Therapy should be continued for at least 7 days, and if well tolerated, for 1 week past resolution or plateau of clinical signs. If signs recur, an additional 7-10 days of therapy is warranted. The authors recommend restarting therapy with the previously effective drug, with change to a new class or more active drug if no improvement is seen in 48h.

Intranasal drops were not recommended, with the exception of 0.9% saline as a mucolytic.

While there are always grey areas and special cases that will not be covered by a set of guidelines, this consensus statement provides an excellent starting point and series of evidence based recommendations to manage upper respiratory tract infections in cats. Following these guidelines will help veterinarians to provide consistent care backed by evidence, allowing better quality management of sick cats while minimizing risks of antimicrobial resistance.

A following post will continue the summary of this manuscript by discussing diseases of the lower respiratory tract. (MRK)

See also:
Morley PS, Apley MD, Besser TE, et al. Antimicrobial drug use in veterinary medicine. ACVIM consensus statement. JVet Intern Med. 2005;19:617–629.