Page 352 - Small Animal Internal Medicine, 6th Edition

324 PART II Respiratory System Disorders

and rehoming facilities have shown that the major variable and canine influenza. These vaccines do not prevent infec-
associated with development of cough in newly arrived dogs tion but aim to decrease clinical signs should infection occur.
VetBooks.ir is time in the facility. They may also reduce the duration of shedding of organ-
isms after infection. A study by Ellis et al. (2001) indicated
Organisms can be shed by infected dogs before the onset
of clinical signs. After the onset of signs, canine influenza
similar protection based on antibody titers, clinical signs,
virus (H3N2) was isolated from an infected dog after 26 that both intranasal and parenteral Bordetella vaccines afford
days, although most dogs were negative by PCR of nasal upper airway cultures, and histopathologic examination of
swabs after 20 days (Newbury et al., 2016). Therefore a tissues after exposure to organisms. The greatest benefit was
minimum isolation period of at least 21 days for dogs with achieved by administering both forms of vaccine sequen-
signs of CIRDC is prudent. Bordetella may persist in the tially at 2-week intervals (two doses of parenteral vaccine
airways of dogs for up to 3 months after infection, but it has and then a dose of intranasal vaccine), but such an aggres-
been assumed that shedding is minimal once clinical signs sive schedule is not routinely recommended. Also in experi-
have completely resolved. mental settings, protection against challenge after intranasal
To minimize exposure to CIRDC organisms, dogs are vaccination against B. bronchiseptica and PIV began by 72
kept isolated from puppies or dogs that have been recently hours (but not earlier) after vaccination and persisted for
boarded. Careful sanitation should be practiced in kenneling at least 13 months (Gore, 2005; Jacobs et al., 2005). Again
facilities. Caretakers should be instructed in the disinfection in an experimental setting, intranasal vaccination against B.
of cages, bowls, and runs, and everyone working with the bronchiseptica provided superior protection compared with
dogs must wash their hands after handling each animal. oral vaccination (Ellis et al., 2016). Intranasal Bordetella vac-
Dogs should not be allowed to have face-to-face contact. cines occasionally cause clinical signs, predominantly cough.
Adequate air exchange and humidity control are necessary The signs are generally self-limiting but are disturbing to
in rooms housing several dogs. Recommended goals are at most owners.
least 10 to 15 air exchanges per hour and less than 50% Canine influenza vaccines are killed products, and a
humidity. An isolation area is essential for the housing of booster vaccination is required 2 to 4 weeks after initial vac-
dogs with clinical signs of infectious tracheobronchitis. cination to achieve protection. Annual vaccination is recom-
Facilities experiencing chronic problems should be referred mended thereafter for dogs at risk.
to a shelter medicine specialist (www.sheltervet.org).
In the veterinary setting, reception staff should be trained CANINE CHRONIC BRONCHITIS
to recognize historic signs that could be associated with
CIRDC. Dogs with such signs should not be allowed into the Etiology
waiting room but rather taken directly (ideally through a Canine chronic bronchitis is a disease syndrome defined
different entrance away from any other dogs) into an exami- clinically as cough that occurs on most days of 2 or more
nation room. Protective clothing should be worn as some consecutive months in the past year in the absence of other
organisms can survive on clothing. Careful disinfection active disease. Histologic changes in the airways are those
practices should be followed. of long-term inflammation and include fibrosis, epithe-
Injectable and intranasal vaccines are available for three lial hyperplasia, glandular hypertrophy, and inflammatory
of the major pathogens involved in CIRDC (i.e., B. bronchi- infiltrates. Some of these changes are irreversible. Exces-
septica, PIV, and CAV2). An oral vaccine is available for B. sive mucus is present within the airways, and small airway
bronchiseptica. Injectable modified-live virus vaccines are obstruction occurs. In people, chronic bronchitis is strongly
available against CAV2 and PIV. Killed, injectable vaccines associated with smoking. It is presumed that canine chronic
are available for both identified strains of canine influenza bronchitis is a consequence of a long-standing inflammatory
virus (H3N8 and H3N2), including in combination as a biva- process initiated by infection, allergy, or inhaled irritants or
lent vaccine. toxins. A continuing cycle of inflammation likely occurs as
Modified-live CAV2 and PIV are conveniently included mucosal damage, mucus hypersecretion, and airway obstruc-
in most combination distemper vaccines and are considered tion impair normal mucociliary clearance, and inflammatory
core vaccines. Because maternal antibodies interfere with the mediators amplify the response to irritants and organisms.
response to vaccines, puppies must be vaccinated with the
combination distemper vaccines every 2 to 4 weeks, begin- Clinical Features
ning at 6 to 8 weeks of age and through 14 to 16 weeks Chronic bronchitis occurs most often in middle-aged or
of age. At least two vaccines must be given initially. For older, small-breed dogs. Breeds commonly affected include
most healthy dogs, a booster is recommended after 1 year, Terriers, Poodles, and Cocker Spaniels. Small-breed dogs
followed by subsequent vaccinations every 3 years (see are also predisposed to the development of tracheobron-
Chapter 93). chomalacia and mitral insufficiency with left atrial enlarge-
Dogs at high risk for disease, such as those in kennels ment. These causes for cough must be differentiated, and
where the disease is endemic, those that participate in group their contribution to the development of the current clini-
dog sports or activities, or those that are frequently boarded, cal features determined, for appropriate management to be
may benefit from annual vaccination against B. bronchiseptica implemented.