What are the best practices for antibiotic use in feline upper respiratory tract disease?

The following article is the first in a three-part series summarizing information fromthe new guidelines on the use of antimicrobials in dogs and cats with respiratory tract disease. These recommendations were developed by the Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases.

(Shutterstock)Overview

Feline upper respiratory tract disease (URTD) can present with clinical signs that include serous or mucopurulent nasal discharge, sneezing, epistaxis and conjunctivitis. The most common infectious causes of acute URTD in cats are feline herpesvirus 1 (FHV-1) or feline calicivirus (FCV), which can often be complicated by secondary bacterial infections caused by a variety of organisms. It is these secondary bacterial pathogens that are often the focus of treatment in cats with URTD.

A thorough patient history should be obtained with particular attention paid to vaccination status; exposure to other cats; recent shelter, veterinary clinic or kennel exposure; recent environmental stressors; and contact with foreign bodies (such as house plants or grasses). Thoracic auscultation is performed to determine the presence of concurrent lower airway disease, and screening for feline leukemia and feline immunodeficiency viruses is recommended, given their detrimental impact on feline immunity. The diagnosis and treatment of URTD in cats can be further simplified by categorizing the disease into acute or chronic form.

Acute disease

The clinical signs are considered acute if they have been present for 10 or fewer days. While nasal cytology and bacterial cultures are often performed, they are not recommended by the guideline authors because the results are difficult to interpret due to the presence of commensal organisms or false negative results. The use of polymerase chain reaction (PCR) assays for Mycoplasma species, Chlamydia species, FHV-1 and FCV can also prove problematic because the diseases can be isolated from both healthy and diseased cats. Furthermore, recent vaccination can confound interpretation.

In cats with acute URTD, the working group recommends no antimicrobial treatment be initiated during a 10-day observation period, unless the patient is exhibiting fever, lethargy or anorexia along with mucopurulent nasal discharge. If antimicrobial therapy is indicated, the working group recommends empirical administration of doxycycline (5 mg/kg orally every 12 hours, or 10 mg/kg orally every 24 hours) for seven to 10 days. Doxycycline is recommended because of its broad spectrum of activity against common feline nasal pathogens and because it is well-tolerated by cats. To counteract the potential for esophageal stricture, tablets and capsules should be given coated with a lubricating substance, followed by water; administered in a pill treat, along with at least 2 ml of a liquid; or followed by a small amount of food.

If Chlamydophila felis or Mycoplasma species are not highly suspected, amoxicillin can be an alternate choice (22 mg/kg orally every 12 hours). The guideline authors thought that there is not enough evidence to support the use of cefovecin in this setting. For cats with acute disease that does not respond to antimicrobial therapy within 10 days or cats with recurrent infections, a more extensive diagnostic workup is recommended. Administration of an alternate antibiotic with a different antibacterial spectrum should be considered only if owners decline further workup and a bacterial cause is still suspected.

Chronic disease

Cats with URTD that has been present for more than 10 days are considered to have chronic disease. For these patients, the guideline authors recommend a more extensive workup and referral to a specialist for advanced imaging or rhinoscopy and biopsy to look for possible nonbacterial issues (e.g. parasites, foreign bodies or fungal disease). Antimicrobial selection and use in these patients should be guided by bacterial culture and antimicrobial sensitivity testing of nasal tissue samples. The empiric use of fluoroquinolones and third-generation cephalosporins should be avoided because of the emergence of bacterial resistance. The guideline authors caution, however, that nasal cultures can be difficult to interpret since many types of bacteria can be cultured from the nose of a healthy cat as well as an ill cat.

Use of azithromycin should be reserved for patients in which chlamydiosis is not considered likely and when other drugs (e.g. doxycycline and amoxicillin) are not viable options.

Although the optimal duration of therapy is unknown, the work group recommends continuing treatment for a minimum of seven days and for at least one week past clinical resolution or disease plateau. For cats with chronic, recurrent signs of upper respiratory tract disease, the guideline authors recommend use of the previously effective antimicrobial, but avoid repeated regular empirical treatment. If treatment is ineffective after 48 hours of therapy, a switch to an antimicrobial in a different drug class should be considered. If therapy is still ineffective, bacterial culture and antimicrobial sensitivity testing is recommended.

Table: First-line antimicrobial options

Type of infection

First-line drug options

Feline acute bacterial upper respiratory

infection (URI)

Doxycycline: 5 mg/kg PO every 12 hours, or 10 mg/kg PO every 24 hours

or

Amoxicillin: 22 mg/kg PO every 12 hours

Feline chronic bacterial URI

Doxycycline: 5 mg/kg PO every 12 hours, or 10 mg/kg PO every 24 hours

or

Amoxicillin: 22 mg/kg PO every 12 hours

***Choice should be based on culture and antimicrobial susceptibility testing if available

Lappin MR, Blondeau J, Boothe D, 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;31:279-294.

Link to article: http://onlinelibrary.wiley.com/doi/10.1111/jvim.14627/full