Canine infectious respiratory disease: Challenges and considerations in animal shelters (Proceedings)

It is common to use the terms "kennel cough" or"infectious tracheobronchitis" when talking about canine infectious respiratory disease complex (CIRDC), this is in many cases not approproiate. The disease complex is not limited to the trachea,and often presents with signs other than coughing. In many shelters CIRDC will present with sneezing, nasal and ocular discharge, and sometimes lower respiratory and/or systemic disease.

Viral pathogens associated with upper respiratory disease in dogs include

      Parainfluenza

      Adenovirus

      Canine respiratory coronavirus

      Canine herpesvirus

      Canine distemper

      Canine influenza

Bacterial pathogens implicated in CIRDC include:

      Bordetella bronchiseptica

      Mycoplasma spp.

      Streptococcus zooepidemicus (may cause severe systemic disease)

In addition to these pathogens it is likely that secondary bacterial invaders of many species play a significant role in causing more severe disease in some dogs, and we know that we are still unraveling the complicated etiology of CIRDC, as evidenced by the fact that several of the pathogens listed above have only been recognized in recent years.

There's a reason CIRDC is often referred to as "kennel cough" – several of the pathogens listed above are insufficient in themselves to cause disease without the additional stress, high contact rate, and other factors associated with kenneling.

Virtually all pathogens listed above can present with very similar overall clinical presentations. Although Bordetella-induced kennel cough is classically thought of as causing only relatively mild disease, shelters or boarding kennels with crowding, stress and a high load of secondary pathogens provide a synergistic effect and more severe disease is often the result. The cause of CIRDC can therefore not be diagnosed based on clinical signs in a single dog. The pattern of affected animals and clinical signs in a population can however provide some clue as to the likely pathogens. For example, if some animals show distinctive clinical signs, such as neurological signs characteristic of distemper, it is possible that other dogs showing milder disease are also infected with the same pathogen.

Diagnostic testing will often not affect your treatment plan and can be cost prohibitive. You may consider doing diagnostics such as culture and sensitivity or respiratory PCR panels if:

     • signs persist longer than expected

     • Unusually severe clinical signs

     • More frequent disease in population

Acutely affected animals should be sampled.

The ideal sample depends on the localization of clinical signs: if signs are predominantly upper respiratory, deep nasal swabs should be obtained. If lower respiratory disease is suspected, tracheal wash is the preferred specimen.

Samples should be submitted for bacterial culture and sensitivity for Bordetella, Mycoplasma, Streptococcus and others such as E.coli; Klebsiella, Pasteurella, enterobacter etc.

PCR is the most practical option for viral detection; panels are available which include most common viral pathogens. Keep in mind that false negatives may be caused by problems with sample handling or timing. For instance, canine influenza is shed only very early in the course of disease, and may be missed by the time clinical signs are recognized. False positives can occur following vaccination; this has been documented as long as three weeks after vaccination for canine distemper.

Prevention

Reduction of Crowding and Stress

Crowding and the attendant stress is undoubtedly the single greatest risk factor for severe respiratory (and other) disease outbreaks in shelter populations. Housing dogs in each side of a double-sided cage intended for a single dog; housing multiple unrelated dogs per cage (particularly if not done in "all in/all out" fashion"); failure to isolate symptomatic animals; and delays in moving animals through the facility are frequent precursors of serious outbreaks in crowded shelters. An underappreciated strategy for CIRDC prevention is to simply reduce the amount of time dogs spend in the shelter environment. One study showed that each day in a shelter increased the risk if CIRDC by 3%. Management practices that increase length of stay for shelter dogs should be carefully assessed to ensure the benefit of these practices outweighs the risk of disease they may create. Common points for possible delay in some shelters may include:

      Routine quarantine of apparently healthy animals

      Delays while dogs await behavior assessment or surgery

      Holding dogs away from public-viewing areas of the shelter even after they are available for adoption, due to lack of staff to move animals or lack of space in public viewing areas

Vaccination

Unfortunately CIRDC is not a vaccine preventable condition. There is no vaccine available for some of the contributory or primary pathogens, while other vaccines only provide partial protection at best. In spite of these deficits, vaccination definitely plays a role in controlling CIRDC. However, in some cases disease can be virtually entirely prevented (e.g. canine distemper), and in others frequency and severity can be mitigated. In one study, intranasal vaccination for Bordetella and parainfluenza of even a fraction of dogs on intake to a shelter resulted in a significant reduction in the risk of .

For protection against canine distemper, all dogs should receive a modified live (MLV) or recombinant subcutaneous vaccine immediately upon intake to a shelter (if not sooner). Puppies should be vaccinated starting at 4 – 8 weeks of age, and revaccinated every 2-4 weeks until 16-18 weeks of age.

In general, intranasal vaccination against Bordetella is recommended due to the demonstrated rapid onset of immunity (3-5 days) and the potential benefits of local IgA derived protection in the upper airway. Additionally, this vaccine can be used in puppies as young as 2-3 weeks of age, and may provide local immunity even in the face of maternal antibody.

Environmental decontamination/removal of infected animals

Most CIRDC pathogens survive in the environment no more than a few hours (canine distemper) to a few weeks (Bordetella) and are inactivated by virtually all routinely used disinfectants. Adenovirus is an exception; like other un-enveloped viruses, it is reliably inactivated by only a handful of disinfectants, including household bleach (5% sodium hypochlorite) diluted at 1:32, or by potassium peroxymonosulfate (Virkon® or Trifectant.)

Remember that mildly infected dogs may play a substantial role in maintaining CIRDC in a given population, especially for the less environmentally durable pathogens such as canine distemper. A common – and dangerous - misunderstanding is that a mildly infected dog is shedding only a mild pathogen. In fact, the severity of clinical signs is dictated as much by the dog's immune system as by the inherent virulence of the pathogen. Prompt removal of all symptomatic animals, no matter how mild the signs, has been critical in resolving many outbreaks. Because airborne transmission of CIRDC is a possibility, ideally isolation areas should have separate air flow. However, if this cannot be achieved, don't despair. Facilities have managed to maintain effective isolation by providing at least 20 feet of physical distance between sick and healthy dogs and paying careful attention to fomite control.

Treatment

Although there is no specific treatment for viral infections, secondary bacterial infection may play a significant role and thus antibiotics are often indicated. Antibiotics commonly used for treatment of Bordetella bronchiseptica kennel cough, such as Doxycycline, Clavamox, or Baytril, are generally not as effective for treatment of secondary infections associated with canine flu. Cephalosporins may be a good choice for treatment of the secondary infections associated with the milder form of disease. Remember that Bordetella is resistant to Cephalexin. Ideally, a transtracheal wash and culture and sensitivity testing should be performed to choose an antibiotic for treatment of severely ill dogs with lower respiratory tract disease. If an empirical treatment choice must be made, good choices should include a combination of broad spectrum antibiotics such as a fluoroquinolone + penicillin.

Cough suppressants do not tend to be helpful and should be avoided in dogs with a productive cough.

Oseltamivir (Tamiflu®) is a drug developed for treatment of influenza in humans. This drug should not be used for treatment of canine influenza or any other disease in shelter animals.

Outbreak management

As with any outbreak, management requires breaking the cycle of transmission between exposed, infected and new incoming dogs. The following steps can help manage an outbreak:

     • Create a clean, separate intake area for un-exposed dogs

          o At least a separate ward, ideally with separate ventilation

          o May consolidate all exposed dogs to a single ward in order to create clean ward for new intakes

          o For shelters with a single ward for all dogs, options to avoid depopulation or ongoing disease spread include either diverting new intakes to another facility or sending exposed dogs off site for quarantine.