26. coughing

coughing

• what is it triggered by

• what is the mechanism

• what is an acute vs chronic cough

• what do we have to rule out when we see cough

• Cough reflex triggered by stimulating cough receptors in the larynx, trachea or bronchi

• Draw air into the lungs to augment force of expulsion

  • Different from expiratory reflex where there is NO draw in of air

• Acute cough = <3wk duration

  • Greater than = chronic

• Describe the animal’s cough, history, environment

• RULE OUT CARDIAC DISEASE

canine infectious respiratory disease (CIRD, tracheobronchitis)

• how is it classified

• is acute

• 2 categories of etiology

• Any contagious, acute-onset respiratory infection of dogs, typically involving upper respiratory tract

• Acute and highly contagious

• Etiology

  • Bacterial and/or viral

  • Synergistic infections

 

Viral	Bacterial
Canine parainfluenza virus (CPIV)  #1 most common Canine adenovirus 2 (CAV-2) Canine herpesvirus 1 (CHV-1) Canine distemper virus (CDV) Canine respiratory coronavirus (CRCoV) Canine influenza virus (CIV) Canine pneumovirus (CnPnV)	Bordetella bronchiseptica Mycoplasma cynos Streptococcus equi subsp. Zooepidemicus

bordetella bronchiseptica

• is it a commensal

• what morbidity and mortality

• often seen with what virus

• incubation period

• transmission route

• hallmark clinical signs

• 2 major mechanisms that help it infect

• how does this present in cats

• Can be a normal inhabitant of resp tract

• Gram negative aerobic bacillus

• More commonly a ‘2ndary’ pathogen, but can

• cause severe primary infections

  • High morbidity, low mortality

• Often seen with CPIV

• Incubation 2-10 days, may be shed for months

• Variable presentation: mild upper-respiratory signs, to severe

• bronchopneumonia

• Transmission via inhalation/airborne route, highly contagious

• CS: Dry paroxysmal cough, nasal discharge;

  • In severe cases: depression, pneumonia and death

Mechanisms

• Unknown stimuli can lead to bacteria attaching to and

• colonizing respiratory epithelium

• Initiates ciliostasis

• Express exo/endotoxins to promote cellular injury & bacterial survival (lipopolysaccharide, adenylate cyclase haemolysin, dermonecrotic toxin, tracheal toxin)

• Adhere to respiratory cilia via adhesins(fimbriae, filamentous hemagglutinin, pertactin)

Cats

• Can be a primary pathogen in cats!

• Incidence: Overcrowding, stress, age

• More upper respiratory signs in adults

• Sneezing, nasal discharge

• May progress to dyspnea, cyanosis, death especially in kittens

• Can transmit dog → cat

mycoplasma

• pathogenic species

• commensal species

• what does this lack

• where does it colonize

• how is it transmitted

• how long does it persist

• Many Mycoplasma spp are commensal

  • Likely a pathogenic role of M. cynos and a commensal role of M. canis and M. edwardii in lower respiratory tract in dogs

• Lack a cell-wall, fastidious

• Colonizes ciliated & non-ciliated epithelium

  • Genital, GI, resp

• M cynos can persist in lungs for 3 wks following infection and be transmitted via aerosols

Streptococcus equi subsp zooepidemicus

• how do dogs get it

• what is hallmark CS in dogs

• β-hemolytic, Lancefield C streptococcus

• Contact with horses has been identified in some, but not all infected dogs

• Acute, severe bronchopneumonia in dogs

  • Initially mild signs, progresses rapidly over 24-48 hours

  • Severe, fibrinosuppurative, necrotizing, hemorrhagic bronchopneumonia

• Disease course may be similar to strep. exotoxin-induced toxic shock syndrome in people

• Overexuberant immune response from pyrogenic exotoxins = superantigens?

  • TNF-a, IL6,8 → necrosis and hemorrhage in lungs

• Lungs from infected dogs had much higher mRNA levels of proinflammatory cytokines than controls

viral etiologies of coughing (6)

• canine parainfluenza

• canine adenovirus 2

• canine coronavirus

• canine influenza H3N8

• canine influenza H3N2

• canine distemper

canine parainfluenza

• what are 2 key features of this virus

• shedding period

• what is hallmark CS

• Paramyxoviridae, enveloped RNA virus (disinfectant works)

• Most common viral isolate of CIRD

  • Very contagious; sheds 8-10 days

• Pure viral - mild signs; high pitched ‘honking’ cough from vocal fold swelling (dry, stridor)

• Does not survive well in environment

canine adenovirus 2

• incubation period

• where do we isolate it from

• generally CS

• can it survive in environment

• Adenoviridae, non-enveloped double-stranded DNA virus

• Incubation: 1 week

• Frequently isolated in upper respiratory disease

• Mild signs; usually with other agents

• Very contagious, survives in environment for months

canine coronavirus

• is it attached to CIRD

• is it similar to the enteric form

• species specific?

• Enveloped RNA virus; Coronaviridae

• No evidence it is a primary CIRD pathogen (usually secondary)

  • First detected in UK in 2003

  • Now identified in US and worldwide

• Different than the enteric virus (enteric is more common)

• Species specific

  • Signs typically mild; strains can mutate

canine influenza H3N8

• what are general signs

• what percentage are asymptomatic vs fatal

• incubation period

• viral shedding period

• 2 methods of dx

• First identified in Greyhounds in 2004 -horse origins

• Now recognized in many states and many dogs – community acquired (breeding)

• CS: upper respiratory disease – cough, nasal discharge

• Up to 20% are asymptomatic; 1-5% may have fatal hemorrhagic pneumonia

• Incubation is 2 – 4 days

• Virus shedding 7 – 10 days

• CS: Cough, nasal discharge, bronchopneumonia (< 20%)

• Dx

  • Paired serology

  • virus detection by PCR (nasal swabs); should be done early in disease

canine influenza H3N2

• what animal did it OG effect

• where was it discovered

• Identified first in 2007 in South Korea

  • Mutated avian influenza virus that has now adapted to the dog

• Identified in USA in 2015

how to treat and prevent canine influenza

• how long in environment

• prevention

• what is tx

• what should we not use

• Tx: very contagious

  • Supportive care

  • Virus persists in env. 2 days

• Prevention: vaccine available

• Oseltamivir (tamiflu) not been investigated, not recommended

canine distemper

• what family

• is it enveloped

• what is infection and disease rate relative to reach other

• what percent are subclinical and clear it

• when is incidence highest

• what age has it more severe

• Morbillivirus, family Paramyxoviridae

  • Single negative stranded RNA, enveloped

• Infection rate > disease rate

• Approximately 25 - 75% of susceptible dogs are subclinically infected and clear

• Temporal infection: high incidence in winter

• Puppies are more severe dz than older dogs

canine distemper transmission

• 2 methods of spread

• what is the main way

• how long is it excreted post infection

• what 3 factors that determine infection

• Spread by aerosol: contact between animal is main method of spread

• Excreted up to 60 - 90 days post infection

• Don’t forget about racoons

• Direct

• Indirect (hygiene)

• Factors:

  • Infectious dose

  • Strain virulence

  • Host defenses

canine distemper CS

• what 4 organ systems does it affect

• what 2 diseases is it often confused for

• what is the 2 hallmark signs

• what do you see on histopath

• what CS = poor prognosis

• Respiratory tract is not the primary target of CDV

• Varies with virulence of strain, age of host, immunocompetence, body systems affected

  • Neuro, GI, upper resp, conjunctivitis (eye)

• Vx against CDV was associated with lower risk of CIRDC and severe respiratory signs.

• Many can be subclinical

• Confused with kennel cough and sometimes parvovirus if GI signs predominate

• Syncytial cells predominant + interstitial inclusion bodies

• Severe systemic infection

  • Most common in puppies

  • Initial fever, depression, anorexia

  • Conjunctivitis, cough

  • Vomiting/diarrhea/dehydration

  • Sudden death

  • Pneumonia

• Neuro

  • chewing gum seizures, myoclonus

  • Poor prognosis

canine distemper dx

• what do you see on fundic exam

• what do see on histopath

• what are 2 testing methods we use in combo to dx

• what globulin do we want to see to dx

• CS

• Ophthalmologic exam

  • Gold medallion lesion

• CBC, biochem

• Intranuclear inclusion bodies

• Radiology? - not pathognomonic

• Serology - IgG & IgM

  • IgG - more vx

  • IgM - acute and will rise and fall

• + PCR - urine

  • Positive for unknown amount of time post vx

• Virus isolation - difficult, more for research

canine distemper tx

• main thing you should do to prevent spread

• how do we prevent disease

• how do we treat symptoms of canine distemper

• what vx should we use and not use

• ISOLATION

• Supportive

• Tx secondary infections

• Nutritional support

• Seizures - anticonvulsants

• Maternal immunity - colostrum

• Modified live vx or recombinant

• Attenuated live → encephalitis if immunocompromised and <6 wks age

• CDV involvement in CIRDC rare due to vx

uncomplicated infectious tracheobronchitis (CIRDC) clinical findings

• incubation period

• hallmark CS

• duration of dz

• tx

• Usually a mild self-limiting disease

• All ages susceptible

• Incubation: 3 - 10 days

• Dry, harsh, non-productive cough +/- discharge

• Duration: 7 - 10 days (or longer)

• No other clinical findings

• Tx: supportive care

complicated infectious tracheobronchitis (CIRDC) clinical findings

• what age group affected

• hallmark CS

• what do you seen on rads

• duration

• is it severe?

• tx

• Young puppies, immunocompromised

• Productive cough → pneumonia

• Fever, depression, anorexia

• Naso-ocular discharge

• Thoracic rads: signs of infection

• Lasts 1 - 3 weeks, may be fatal

• Tx: antibiotics if bacterial

dx of infectious tracheobronchitis (CIRDC)

• what does bloodwork look like

• when do we do C&S

• what samples do we submit

• when do we consider PCR and serology

• History of exposure?

• May have normal blood work and radiographs

• Culture and sensitivity (TTW, ETW)

  • usually done in complicated cases

• Nasal swab bacterial culture is not representative of 1º etiology

  • Submit all samples: conjunctiva, thorat, nose

• PCR panels: interpret and use with caution, serology +/-

  • Consider if rapid progression, CS > 10 days or outbreak

tx of infectious tracheobronchitis (CIRDC)

• does everyone needs antibiotics

• what 2 drugs could potentially be helpful

• collar or harness

• how long does bordetella shed

• how long is bacterial CIRDC course

• Complicated or uncomplicated?

• Treat specific infection

  • Bordetella or Mycoplasma cynos?

• Not everyone needs antibiotics!!!

• Humidify air

• Cough suppressants +/-, Bronchodilators +/- (can be helpful)

• Rest/ no collars (harness)

• Isolation for at least 2 weeks

• Shedding of bordetella: at least a month and sometimes several months

• Bacterial CIRDC CS resolve quickly (1-2 wks)

Prevention of infectious tracheobronchitis (CIRDC)

• what vaccines are core

• what vaccines are non-core

• what to avoid in the environment

• Avoid contaminated areas

• Decrease stress and overcrowding

• Vx

  • No vx completely prevents disease

  • Maternal antibodies present

• Core vx

  • DA2PP

  • Rabies

• Non-core

  • Bordetella

  • Canine influenza (H3N8/H3N2)

3 Etiologies of upper respiratory coughs

• Parasitic

  • Filaroides osleri

  • Crenosoma vulpi

  • Capillaria aerophilia

  • (aka Eucoleus aerophilus)

  • Dx: baermann (not 100%)

  • Tx: prophylactically

• Foreign body

  • Rocks, toys, grass awn, teeth

• Irritant

  • Chemical (bleach)

  • mechanical

chronic bronchitis in canines

• what is hallmark resp sign

• what can we auscultate

• 7 etiologies

• Incurable with insidious onset

• Chronic and persistent cough

• No identifiable or persistent primary cause found

• Syndrome not necessarily a final dx

• PE: 

  • Normal BCS (usually)

  • Auscult wheezes, crackles, and increased airway

  • Persistent cough often with terminal retch (gag) often the primary complaint

• Etiologies

  • Defect in muco-ciliary function

  • Airway parasites

  • Infections (previous damage)

    • Kennel cough

  • Inhaled irritants

    • Smokers, air freshener

  • Allergy

  • Aerodigestive disorders

    • Inhale stomach acids from primary GI dz

5 differential dx for chronic bronchitis

• what must we rule out

• which one is regional

• Left atrial enlargement

  • MUST RULE OUT CARDIAC DISEASE

• Heartworm disease

• Collapsing trachea

• Neoplasia

• Fungal → SE

dx of chronic bronchitis

• it is a diagnosis of ____

• what dx is typically normal

• what is a more objective test

• what rad pattern do we see

• what might we see on washes

• what makes prognosis worse

Diagnosis

• Exclusion of all potential primary or secondary causes = frustrating & inconclusive

  • Rule out contributing dz

• Baseline bloodwork; typically normal, but pay attention to eosinophilia

• Fecal for lungworms (baermann), heartworm testing

• Arterial blood gas and pulse oxygenation

• 6 minute walk test < 400 m = sick

• Consider pet lifestyle and environment as potential triggers

Rads

• Prominent bronchial structures (donuts, tramlines)

• Interstitial infiltrate

• Bronchiectasis

  • Rubbery and blown out

  • Secondary

• Overall not super specific

TTW, ETW

• Inflammation - neutrophils and mucus

• Culture, +/- bacteria (lungs are not sterile)

Bronchoscopy

• Collapse of intrathoracic airway has worse prognosis

4 tx goals for chronic bronchitis

• Reduce inflammation

• Limit cough

• Improve exercise stamina

• Slow progression of disease and reduce airway remodeling 

6 tx for chronic bronchitis

• is this curable

• what is a first choice abx

• Reduce env. Contamination

  • Smoking, scented candles/cleaners

  • Avoid dog parks, groomers, public areas to reduce infectious disease contribution

• Reduce obesity and modify behaviors

  • Consider consult nutritionist

  • Harness instead of collar, curtail excessive barking (anxiety tx)

• Corticosteroids

  • Anti-inflammatory

  • ↑ receptor sensitivity to beta-agonists

  • ↓ sensitivity to allergens

  • Inhaled glucocorticoids can be effective

    • Fluticasone

    • Oral → wean oral start inhaled → wean both

    • Aerodog

• Bronchodilators

• Antitussives - judgement call

• Antibiotics

  • Suspect concurrent infection

  • Reserve for acute exacerbation, infectious encounters

  • Doxycycline and azithromycin = reasonable 1st line choice

• Various therapies necessary for control (lifelong) - not curable

• Signs may wax and wane and therapeutic adjustments will be necessary 

7 ways to treat a cough

1. cough suppressants

2. antitussive therapy

3. hydrocodone

4. maropitant (cerenia)

5. neuromodulators

6. mucokinetic drugs

7. antihistamines

indications and contraindications for cough suppressants

• Indications:prevent coughing

  • When nonproductive, exhausting, painful or potential for lung damage

• Contraindications:

  • Cough defense mechanism is very important

  • Productive cough?

    • The cough is needed to remove possible infectious fluids and secretions from lung

4 drugs that make up antitussive therapy

• Central acting - narcotics

  • Hydrocodone (#1), butorphanol, lomotil, atropine 

• Dextromethorphan - not really central

  •  NMDA receptor antagonist

• Maropitant +/-

  • Substance P inhibitor

• Bronchodilators 

hydrocodone

• often combined with what other drug

• 2 atropine effects

• Hydrocodone combined with atropine (homatropine)

• Atropine does exert significant effects (vagal suppress = bronchodilation)

• Atropine limits dosing, so discourages abuse

• Suspected action is based on binding to 𝜇-opioid receptor

maropitant

• what receptor does it act on

• what binds to that receptor

• what 3 effects does it have on bronchial epithelial cells

• is it suitable for chronic canine bronchitis

• NK1 receptor antagonist

• Substance P (SP) is a potent NK1 agonist, maropitant is a SP inhibitor

• SP from immune cells can induce bronchoconstriction, chemotaxis, and neutrophil adhesion to bronchial epithelial cells

• Perceived clinical improvement but not decrease airway inflammation (not suitable tx for CCB)

neuromodulators

• 2 examples

• for what type of cough

• Gabapentin, amitriptyline

• Chronic, idiopathic cough

  • Sensory neuropathy, laryngeal irritability

  • Optimal dose, length, true benefit not yet determined

mucokinetic drugs

• mechanism

• 2 examples

• Help eliminate resp secretions by changing viscosity

• Acetylcysteine

  • Destroys mucoprotein disulfide bonds, creates smaller, less viscous molecules

  • Antioxidant properties

  • Administered via nebulization – this can lead to bronchospasm in cats (avoid) - good for dog

• Guaifenesin

antihistamines

• indicators

• mechanism

• May be useful if cough is suspected to have allergic component

• Direct effects occur by blocking H1 receptors in the central and peripheral nervous systems

• Indirect effects include reduced mucus secretion and sedation

coughing in cats

• are cats specifically treated for cough

• what is often the underlying pathology

• what does it resemble

• Not as common as dogs

• Cats not tx specifically for coughing

• Often caused by chronic lower airway inflammatory dz (paroxysmal coughing, resembles coughing up hairballs)