PEER REVIEWED DIAGNOSTIC & THERAPEUTIC APPROACH Dogs Infected with Bordetella bronchiseptica & Canine Virus (H3N8) Laura A. Nafe, DVM, MS, Diplomate ACVIM (Small Animal Internal Medicine) University of Wisconsin–Madison

ordetella bronchiseptica and Virulence Factors. After B bronchiseptica colonizes virus (CIV) are common causes of infectious tra- the airways, it can evade the immune system by express- Bcheobronchitis and, occasionally, . ing various virulence factors that lead to:1,3 Combined, these and other pathogens cause the canine • Direct cellular injury of respiratory epithelium infectious respiratory disease complex (CIRDC), often • Impaired immune recognition referred to as kennel or infectious tracheobron- • Disrupted immune clearance. chitis. The multitude of bacterial and viral organisms Perhaps one of the most unique and important effects associated with CIRDC are listed in Table 1. of these virulence factors is the ability to paralyze the In general, morbidity for CIRDC is high with mortal- mucociliary apparatus—a key component of the respi- ity being low. Severe cases can result in life-threatening ratory tract’s local defense mechanisms—and create respiratory compromise due to pneumonia. acquired ciliary dysfunction.1,3,4 The mucociliary apparatus moves inhaled debris and DISEASE PROFILE opportunistic pathogens away from the lower respiratory Bordetella bronchiseptica tract, decreasing the risk of colonization by these organ- B bronchiseptica, a primary respiratory pathogen, is a isms and the potential for associated pneumonia. By gram-negative, aerobic coccobacillus that is often impli- paralyzing the cilia, B bronchiseptica not only improves cated as a complicating factor in dogs with concurrent its own virulence and chance for colonization, but also viral respiratory infections.1 predisposes the patient to opportunistic infections of the lower respiratory tract.1 Disease Spectrum. The spectrum of disease that Table 1. bacterial & Viral Pathogens results from infection with B bronchiseptica is wide, with associated with CirDC1,2 some dogs manifesting mild disease characterized by nasal discharge and intermittent cough and others devel- oping severe pneumonia that can be life threatening. • Bordetella bronchiseptica • Mycoplasmas (Mycoplasma cynos) Canine Influenza Virus • equi (subspecies zooepidemicus) CIV (H3N8) is most closely related to equine influenza CANINE VIRUSES virus, which suggests that a direct transmission from horses to dogs occurred.5 CIV was first detected in rac- • adenovirus 2 • Herpesvirus ing greyhounds in Florida, and since has become more • bocavirus • influenza virus prevalent among pet dogs, especially those in kennels, • Coronavirus • Parainfluenza virus shelters, and multidog households.6 (pantropic strain) • Pneumovirus Prevalence. The prevalence of serum antibodies • Distemper virus • reovirus against CIV in dogs with no clinical signs of respiratory • Hepacivirus • respiratory coronavirus disease has been shown to be 0.5% to 3%, depending on the risk of the population being evaluated (Figure 1).6

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are likely co-infected with other common viral and bacterial pathogens that encompass the CIRDC (Table 1). However, veterinarians should recognize that the prev- alence of CIV is much lower in client-owned dogs with respi- ratory signs, especially if they have not been recently exposed in a shelter or boarding kennel. Geographic Location. CIV is associated with geographic hot spots, and practitioners should become familiar with the partic- ular areas in which it has been identified. In a recent study, sero- Figure 1. Map of canine influenza cases, including all CIV positives between prevalence of CIV in dogs with 2007 and 2014 (207 positives). Individual pins may represent multiple cases. influenza-like illness was highest Courtesy IDEXX Laboratories in the northeast, west, and south- west United States, with the high- est representation being in New York, Colorado, and Florida.7 CONSIDERATIONS IN HOSPITAL Considering modes of transmission and environ- RISK FACTORS mental survival of the agent is important when dis- Both CIV and B bronchiseptica infections are highly con- cussing management of patients in hospital. Cli- tagious, and dogs of any age and breed may become infect- nicians should take precautions when handling ed. Those at most risk for exposure and infection include: these patients and make efforts to limit exposure • Dogs housed in boarding facilities, shelters, kennels, throughout the hospital. and pet shops8,9 • Hospitalize patients in isolation facilities • Puppies, especially those in the above housing situa- within the clinic to limit exposure to other dogs, tions, due to reduced immunity (both local and system- especially those that are immunocompromised. ic), which may result in severe infection and death.9 as much as possible, manage infected patients Factors that contribute to risk and severity of infection as outpatients. • Ensure that staff wear protective clothing, in puppies include: such as gloves and disposable gowns, when • Close contact with other dogs and puppies working with infectious patients. • Immature immune systems • Keep the veterinary team from handling • Immune dysfunction due to concurrent infections (viral, other patients of the same species during the bacterial, parasitic). same shift in which they have handled infectious Because puppies housed in shelters and pet shops are patients. often in closed ventilation spaces with other puppies from • Limit contact between critical patients that various environments, they are at highest risk. require oxygen therapy and close monitoring— who are not candidates for an isolation area— PREVENTION and other patients in the critical care unit. can help protect against infection and reduce • Implement precautions to limit fomite contami- severity of clinical disease. Turn to page 72 to read Dr. nation. an in-depth review of preventing CiV in the Richard Ford’s article, Kennel Cough Revisited, for a hospital setting is presented in the article Is Your discussion on current advances in vaccination for canine Practice Proactive or Reactive? (January/ respiratory disease. february 2012), available at tvpjournal.com (article library). TRANSMISSION Mode of Transmission Transmission of B bronchiseptica and CIV occurs via:1 Note that a positive antibody titer in a population of dogs • Oronasal contact with other dogs, caregivers, or fomites with no signs of respiratory disease likely indicates prior • Inhalation of aerosolized microdroplets of respiratory exposure to the virus, rather than active infection. secretions. In shelter dogs with signs of respiratory disease, seroprev- In high-density housing situations, direct contact among alence is as high as 50%, depending on length of time since dogs is most common. Less commonly, fomites serve as a intake to the shelter.7,8 Given the population, these patients source of transmission. tvpjournal.com July/August 2014 Today’s Veterinary Practice 31 | Bordetella bronchiseptica & Canine Influenza Virus (H3N8)

Figure 2. Radiographs from a 7-month-old basset hound puppy with Bordetella bronchiseptica pneumonia; note the diffuse heavy interstitial to alveolar lung pattern, which is most severe on the left side.

Shedding & Survival • Respiratory distress Most viruses begin shedding within 2 days post infection, • Signs of systemic illness (eg, lethargy, decreased appe- and may continue to shed for 6 to 10 days before viral tite). load decreases.5 B bronchiseptica can survive in the envi- In more severe cases, radiographs are necessary to evalu- ronment for extended periods of time,1 and can be shed ate if pneumonia is present. from dogs that appear healthy because it has the ability to Thoracic radiographs are not typically indicated in oth- elude the immune system for weeks to months. erwise healthy patients with acute onset of only cough- ing (no signs of respiratory distress, tachypnea, , or INITIAL DIAGNOSIS systemic illness). Although definitive diagnosis is pursued in some cases, a suspected clinical diagnosis can often be made based on: Laboratory Analysis • Clinical signs In complicated cases, a complete blood count and serum • Assessment of risk/exposure biochemical profile should be performed to assess sys- • Response to appropriate treatment. temic health, but these diagnostics are not generally nec- Clinical Presentation essary for diagnosis of B bronchiseptica or CIV. Clinical presentation varies among individual cases of B bronchiseptica and CIV infections, based on severity and concurrent bacterial and/or viral Table 2. B bronchiseptica & CIV Infections: pathogens involved. Clinical signs include: • Acute onset of a nonproductive cough (most Radiographic Appearance common clinical sign) TYPE OF INFECTION RADIOGRAPHIC APPEARANCE • Serous or mucopurulent nasal and/or ocu- Uncomplicated B • normal thoracic radiographs lar discharge bronchiseptica or CIV • Diffuse bronchial or • Sneezing (confined to upper bronchointerstitial lung pattern • Tachypnea, respiratory distress, systemic ill- respiratory tract) • narrow tracheal lumen, creating ness, and fever (more severe cases). a hypoplastic appearance due to tracheal mucosal edema Thoracic Radiographs Complicated B • Heavy interstitial, bronchial, or Thoracic radiographs may support a diagno- bronchiseptica or CIV alveolar lung pattern (Figure 2) sis of B bronchiseptica or CIV (Table 2) but, (lower respiratory tract • With B bronchiseptica, focal more important, help to rule out other causes involvement) alveolar pattern consistent with of acute cough. pneumonia Thoracic radiographs are recommended for • With CIV, diffuse or patchy any patient with: interstitial or alveolar lung pattern • Persistent (> 1–2 weeks) or worsening cough consistent with pneumonia

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DEFINITIVE DIAGNOSIS Bordetella bronchiseptica Definitive diagnosis of B bronchiseptica is based on isola- tion of the pathogen from aerobic culture of respiratory secretions. Sample Collection. For cytology and culture of bacte- ria, obtain airway samples via: • Transtracheal or endotracheal wash • Bronchoalveolar lavage (blind or bronchoscopy-guided). Patients with unresponsive focal pneumonia may require bronchoscopy-guided bronchoalveolar lavage fluid collec- tion to obtain a sample that accurately represents the caus- ative pathogen. Nasal, oral, oropharyngeal, and nasopharyngeal bacteri- al cultures are not recommended, as they yield growth of normal respiratory flora, making it difficult to determine the primary pathogen causing disease. In addition, deep Figure 3. Bronchoalveolar lavage fluid cytology oral swabs are not recommended in puppies with commu- demonstrating characteristic cytologic appearance nity-acquired pneumonia.10 of Bordetella bronchiseptica; note the adherence of Mycoplasma species cannot be seen on cytology and the coccobacilli to the ciliated respiratory epithelial are difficult to culture; consider submitting a mycoplasma cells (100×). Courtesy Tamara Hancock, DVM polymerase chain reaction (PCR) or mycoplasma culture, when indicated. Doxycycline Sample Preparation. Following collection of an air- Doxycycline (5 mg/kg PO Q 12 H or 10 mg/kg PO Q way sample, cytology should be performed as quickly as 24 H) is my treatment of choice for B bronchiseptica and possible (ideally within hours) to reduce disruption of the most infectious respiratory diseases. cells.11,12 Because many samples are fairly low in cellularity, Enamel Discoloration. Clinicians are often concerned a concentrated population of representative cells can be about using doxycycline in young patients due to its poten- evaluated by a cytospin or line smear preparation or man- tial to discolor enamel of developing teeth; however, it is ual smearing of pelleted cells. less likely to cause discoloration compared to other tetra- If the clinician is planning to send the sample to a clini- cycline . Limiting treatment to < 10 days further cal pathologist for evaluation, the sample should be stored reduces the risk.1 at 4°C and shipped overnight (ideally processed within 24 Doxycycline Resistance. Some isolates of B bronchi- hours after collection).12 septica are doxycycline-resistant, and patients may require Sample Evaluation. Evaluate the sample for the differen- treatment with a fluoroquinolone (enrofloxacin or mar- tial cell count and presence of bacteria or other infectious bofloxacin), azithromycin, or chloramphenicol; however, organisms. B bronchiseptica has a characteristic cytologic management of these patients should ideally be based on appearance, with the coccobacilli adhering to respiratory culture and susceptibility of airway samples. epithelial cells (Figure 3). Other Tetracyclines Canine Influenza Virus The current shortage of doxycycline has dramatically Definitive diagnosis of CIV is based on real-time PCR (RT- increased its cost; therefore, it is a less desirable option for PCR) identification of CIV from respiratory secretions. RT- owners with financial concerns. Most clinicians are using PCR (nasal or pharyngeal swabs) has replaced viral isola- other tetracycline drugs, such as minocycline, in place of tion via tissue culture or serology due to:13,14 doxycycline for treatment of tick-borne disease, but the • Difficulty in obtaining samples for culture antemortem pharmacokinetics of minocycline for various disease con- • Concerns about previous exposure clouding results of ditions in dogs is currently under investigation.15 serologic testing. Dosing for treatment of bordetellosis is currently Definitive diagnosis is a challenge in some patients unknown; recommended treatment of methicillin-resistant because viral shedding declines within approximately 7 to staphylococcal infections is 5 mg/kg PO Q 12 H or 10 mg/ 10 days post exposure, often prior to onset of clinical signs, kg PO Q 24 H. resulting in a false–negative RT-PCR.5 Other Antibiotics ANTIMICROBIAL THERAPY Other antibiotics to consider include: Antimicrobial therapy can be important in patients with • Azithromycin suspected B bronchiseptica infections or, if CIV or another • Fluoroquinolones viral respiratory pathogen is suspected, to treat secondary • Amoxicillin-clavulanate bacterial infections. • Cephalosporins.

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Managing Critically Ill Dogs 2. Improve Clearance of Respiratory Secretions When managing critically ill dogs with B bronchiseptica Critical patients often lose fluids through the and/or CIV, implement the following supportive therapy: respiratory tract, especially if they are febrile, leading to increased viscosity of secretions and reduced 1. Provide Increased Oxygen Concentrations ciliary clearance. Initiate IV fluids to replace fluids lost Severe cases of B bronchiseptica and CIV may and improve clearance of respiratory secretions. present in respiratory distress and require oxygen Nebulization with sterile saline (6–10 mL) results supplementation. in a liquid particulate suspension that improves Assess oxygenation via pulse oximetry and/ clearance of tracheal and bronchial secretions. or arterial blood gas analysis. Pulse oximetry is Nebulization followed by coupage may be performed noninvasive and available in most practices, but does for 15 to 20 minutes every 4 to 8 hours in hospitalized not always provide an accurate measurement. patients; owners may rent or purchase a handheld jet Provide oxygen supplementation to patients with nebulizer for use at home. an: 3. Treat Primary or Secondary Bacterial • SpO2 of < 92% to 94% or PaO2 < 80 mm Hg, especially if signs of respiratory difficulty are Pathogens present therapy is essentially the same for all • Increase in respiratory effort, even if the patient is patients (see ANTIMICROBIAL THERAPY); however, oxygenating appropriately. injectable antibiotics should be considered for Common methods of oxygen supplementation in critically ill patients, due to associated gastrointestinal hospital include oxygen cage, tent, nasal cannula(s), upset and poor bioavailability of oral antibiotics in and nasal prongs. Nasal cannula or prongs may work anorexic patients. Fluoroquinolones (enrofloxacin, best for highly contagious patients that must be iso- ciprofloxacin) may be preferred for injection because, lated, but require supervision to ensure the catheter compared to doxycycline, they provide more broad does not become dislodged (Figure 4). spectrum coverage for gram-negative organisms, are unlikely to result in phlebitis, and are less expensive.

Figure 4. Dog with nasal cannula in place.

Note that tetracyclines and fluoroquinolones readily cross the blood–bronchus barrier, but penicillins and cephalosporins do not and, therefore, may be associ- ated with treatment failure in some cases. Although fluoroquinolones are less desirable in young animals due to their effects on cartilage development, this risk may be of less concern in patients with life-threaten- ing infections.16

ADDITIONAL THERAPIES Glucocorticoids & Cough Suppressants Anti-inflammatory glucocorticoids and/or cough sup- pressants may be indicated for patients with infectious tvpjournal.com July/August 2014 Today’s Veterinary Practice 35 | Bordetella bronchiseptica & Canine Influenza Virus (H3N8)

tracheobronchitis or suspected tra- in cases of canine respiratory diseases key early event during colonization of canine tracheal tissue by Bordetella bronchiseptica. Microbiol 2004; cheitis secondary to frequent cough- that result in excessive tracheal and/ 150:2843-2855. ing. Ensure the patient has no evi- or bronchial secretions. 5. Crawford PC, Dubovi EJ, Castleman WL, et al. Transmission of equine influenza virus to dogs. dence of pneumonia and is otherwise However, I do not recommend ther- Science 2005; 310:482-485. systemically healthy before interven- apy with expectorants because: 6. Serra VF, Stanzani G, Smith G, et al. Point seroprevelence of canine influenza virus H3N8 in dogs ing with these therapies. • Nebulized N-acetylcysteine can be participating in a flyball tournament in Pennsylvania. Most patients with CIRDC do not irritating and result in broncho- JAVMA 2011; 238:726-730. 7. Anderson TC, Crawford PC, Dubovi EJ, et al. require these therapies, and I do not spasm, further worsening tracheo- Prevalence of and exposure factors for seropositivity recommend using oral/inhaled corti- and coughing. to H3N8 canine influenza virus in dogs with influenza- • like illness in the United States. JAVMA 2013; costeroids or cough suppressants in Guaifenesin, an expectorant often 242:209-216. patients with moderate to severe B paired with a cough suppressant, 8. Holt DE, Mover MR, Brown DC. Serologic prevalence bronchiseptica infection or CIV, espe- has no scientific or anecdotal (that of antibodies against canine influenza virus (H3N8) in dogs in a metropolitan animal shelter. JAVMA 2010; cially if pneumonia has developed. I have observed) evidence support- 237:71-73. Cough suppressants, in particular, are ing its use in patients with B bron- 9. Radhakrishnan A, Drobatz KJ, Culp WT, et al. Community-acquired infectious pneumonia in puppies: contraindicated in patients with bron- chiseptica or CIV. 65 cases (1993-2002). JAVMA 2007; 230:1493-1497. chopneumonia, as suppression of cough 10. Sumner CM, Rozanski EA, Sharp CR, et al. The use of deep oral swabs as a surrogate for transoral can prevent clearance of bacteria, wors- Antiviral Agents tracheal wash to obtain bacterial cultures in dogs with en disease, and/or delay recovery. The safety and efficacy of specific pneumonia. J Vet Emerg Crit Care 2011; 21:515-520. 11. Dehard S, Bernaerts F, Peeters D, et al. Comparison antiviral agents, such as neuroamini- of bronchoalveolar lavage cytospins and smears in Bronchodilators dase inhibitors (eg, oseltamivir phos- dogs and cats. JAAHA 2008; 44:285-294. 12. Nafe LA, DeClue AE, Reinero CR. Storage alters feline Methylxanthines (eg, theophylline, phate, zanaminir) has not been evalu- bronchoalveolar lavage fluid cytological analysis. J aminophylline) and beta-2 agonists ated in dogs.1 Therefore, these agents Feline Med Surg 2011; 13:94-100. 13. Anderson TC, Crawford PC, Katz JM, et al. Diagnostic are bronchodilators that prevent cannot be recommended for dogs performance of the canine influenza A virus subtype bronchospasm. There is evidence that with CIV or other respiratory viral H3N8 hemagglutination inhibition assay. J Vet Diagn methylxanthines improve ventilation diseases. Invest 2012; 24:499-508. 14. Pecoraro HL, Spindel ME, Bennett S, et al. Evaluation and diaphragmatic contractility in of virus isolation, one-step real-time reverse dogs, which may result in improved Intranasal Vaccines transcription polymerase chain reaction assay, and two rapid influenza diagnostic tests for detecting PaCO2 levels in severely affected pup- There are anecdotal reports promot- canine Influenza A virus H3N8 shedding in dogs. J Vet pies; however, there is no evidence of ing administration of the intranasal B Diagn Invest 2013; 25:402-406. 15. Maaland MG, Guardabassi L, Papich MG. Minocycline benefit in patients with uncomplicat- bronchiseptica vaccine in dogs with pharmacokinetics and pharmacodynamics in dogs: ed CIRDC.17 CIRDC. However, to date, there are Dosage recommendations for treatment of methicillin- resistant Staphylococcus pseudintermedius infections. If considering use of a bronchodi- no controlled studies that support its Vet Dermatol 2014; 25:182-190. lator in a patient with CIRDC, I pre- use as a “therapeutic” intervention in 16. Lim S, Hossain MA, Park J, et al. The effects of enrofloxacin on canine tendon cells and chondrocytes fer methlyxanthines due to their other dogs with B bronchiseptica infection proliferation in vitro. Vet Res Commun 2008; 32:243- potentially beneficial effects, includ- or CIV and, in critical patients with 253. 17. Jagers JV, Hawes HG, Easton PA. Aminophylline ing anti-inflammatory properties, this infection or virus, intranasal vac- increases ventilation and diaphragm contractility improved mucociliary clearance, and cine administration may worsen the in awake canines. Respir Physiol Neurobiol 2009; improved diaphragmatic contractili- course of disease because the immune 167:273-280. ty.17 Unlike cats and humans, dogs do system is already compromised, and not develop true smooth muscle bron- an immune response places additional choconstriction, and therefore, beta- stress on the system. n 2-agonists are not useful in the man- agement of canine respiratory disease. CIRDC = canine infectious respiratory disease complex; CIV = canine influenza Laura A. Nafe, In my opinion, bronchodilator ther- virus; PaCO = arterial partial pressure DVM, MS, Dip- apy, while extremely important in 2 of carbon dioxide; PaO2 = arterial partial lomate ACVIM management of feline lower airway pressure of oxygen; PCR = polymerase (Small Animal disease, has limited value in canine chain reaction; RT-PCR = real-time Internal Medi- respiratory disease and may have PCR; SpO2 = hemoglobin oxygenation cine), is a clinical undesirable adverse effects (cardiac, saturation measured by pulse oximetry instructor in small gastrointestinal). Therefore, I do not References animal internal medicine at Univer- recommend bronchodilators for treat- 1. Ford RB. Canine infectious tracheobronchitis. In sity of Wisconsin SVM–Madison. Greene CE (ed): Infectious Diseases of the Dog and She received her DVM from Uni- ment of infectious tracheobronchitis Cat, 4th ed. St. Louis: Saunders, 2012, pp. 55-65. or pneumonia caused by B bronchi- 2. Priestnall SL, Mitchell JA, Walker CA, et al. New and versity of Missouri then completed septica or CIV. emerging pathogens in canine infectious respiratory an internship in small animal medi- disease. Vet Pathol 2013 [Epub ahead of print]. cine and surgery at North Carolina 3. Mattoo S, Cherry JD. Molecular pathogenesis, Expectorants epidemiology, and clinical manifestation of respiratory State University, before completing infections due to Bordetella pertussis and other Aerosolized or oral expectorant or a residency in small animal internal Bordetella subspecies. Clin Microbiol Rev 2005; medicine at University of Missouri. mucolytic therapy is often instituted 18:326-382. 4. Anderton TI, Maskell DJ, Preston A. Ciliostasis is a

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