Page 351 - Small Animal Internal Medicine, 6th Edition

CHAPTER 21 Disorders of the Trachea and Bronchi 323

disease and for obtaining antibiotic sensitivity information preparations; however, it has questionable efficacy in dogs.
to guide antibiotic selection. Cold remedies with additional ingredients such as antihista-
VetBooks.ir provides information that will redirect treatment of an indi- mines and decongestants should be avoided. Pediatric liquid
Testing for specific pathogens by serology or PCR rarely
preparations are palatable for most dogs, and the alcohol
vidual dog but may be helpful in managing outbreaks. Con-
Narcotic cough suppressants are more likely to be effective.
sultation with the diagnostic laboratory is recommended for contained in them may have a mild tranquilizing effect.
optimizing results. The timing and recommended site of Butorphanol is available as a veterinary labeled product
specimen collection varies with the infection of greatest (Torbutrol, Zoetis, Parsippany, NJ). Hydrocodone bitartrate
concern. Serology for canine influenza viruses is the most is a potent alternative for dogs with refractory cough.
sensitive method to detect infection but will be falsely nega- In theory, antibiotics are not indicated for most dogs with
tive before seroconversion. Influenza viruses are most readily CIRDC for two reasons: (1) The disease is usually self-
identified by PCR from nasal swabs. The H3N8 strain is only limiting and tends to resolve spontaneously, regardless of any
shed early in the course of disease, whereas the H3N2 strain specific treatment that is implemented, and (2) no antibiotic
has been identified for as long as 26 days (Newbury et al., protocol has been proven to eliminate Bordetella or Myco-
2016). Testing by PCR for other CIRDC organisms is gener- plasma organisms from the airways. The Antimicrobial
ally performed on pharyngeal swabs, although testing of Guidelines Working Group of the International Society for
bronchial brushings or airway washings would minimize Companion Animal Infectious Disease (ISCAID) recom-
false positive results from the carrier state. Positive PCR mends that antimicrobial treatment be considered within the
results can be obtained for up to 28 days in dogs that have first 10 days of signs ONLY if fever, lethargy, or inappetence
been vaccinated with intranasal B. bronchiseptica, canine is present together with mucopurulent discharges (Lappin
parainfluenza virus (PIV), and canine adenovirus 2 (CAV2) et al., 2017). In practice, however, antibiotics are often pre-
(Ruch-Galle et al., 2016). A negative PCR result for any of scribed, and their use is justified because of the potential
the CIRDC organisms does not rule out the possibility of presence of these organisms. Doxycycline (5 mg/kg q12h or
their involvement. 10 mg/kg q24h, followed by a bolus of water) is effective
against Mycoplasma spp. and many Bordetella isolates.
Treatment Although the ability of doxycycline to reach therapeutic con-
Uncomplicated CIRDC is a self-limiting disease. Rest for at centration within the airways has been questioned because
least 7 days, specifically avoiding exercise and excitement, is it is highly protein bound in the dog, the presence of inflam-
indicated to minimize the continual irritation of the airways matory cells may increase locally available concentrations of
caused by excessive coughing. Cough suppressants are valu- the drug and account for its anecdotal success. Amoxicillin
able for the same reason but should not be given if the cough with clavulanate (11 mg/kg orally q8h) is effective, in vitro,
is overtly productive or if exudate is suspected to be accu- against many Bordetella isolates. Fluoroquinolones provide
mulating in the lungs on the basis of auscultation or thoracic the advantage of reaching high concentrations in the airway
radiograph findings. Because CIRDC is a tracheobronchitis, secretions, but their use is ideally reserved for more serious
dogs with CIRDC will have exudate and excess mucus in infections. Bacterial susceptibility data from tracheal wash
their airways whether apparent externally or not. Therefore fluid can be used to guide the selection of an appropriate
cough suppressants should be used judiciously to treat fre- antibiotic. Antibiotics are administered for 5 days beyond
quent or severe cough, to allow for restful sleep, and to the time the clinical signs resolve, or for at least 10 days.
prevent exhaustion. Glucocorticoids should not be used. No field studies have
A variety of cough suppressants can be used in dogs (Table demonstrated any benefit of steroid therapy, either alone or
21.1). Dextromethorphan is available in over-the-counter in combination with antibiotics.
If clinical signs have not resolved within 2 weeks, further
diagnostic evaluation is considered. As with colds and flu in
TABLE 21.1 people, signs may be prolonged in some instances but careful
monitoring is in order. See Chapter 22 for the management
Common Cough Suppressants for Use in Dogs* of bacterial pneumonia.

AGENT DOSAGE Prognosis
The prognosis for recovery from uncomplicated CIRDC is
Dextromethorphan † 1-2 mg/kg PO q6-8h excellent.
Butorphanol 0.5 mg/kg PO q6-12h
Hydrocodone bitartrate 0.25-0.5 mg/kg PO q6-12h Prevention
CIRDC can be prevented by minimizing an animal’s expo-
PO, By mouth. sure to organisms and by providing vaccination programs.
*Centrally acting cough suppressants are rarely, if ever, indicated
for use in cats and can result in adverse reactions. The preceding Excellent nutrition, routine deworming, and avoidance of
dosages are for dogs only. stress improve the dog’s ability to respond appropriately to
† Efficacy is questionable in dogs. infection without showing serious signs. Studies in shelters