Veterinary Respiratory Diseases

• SAM VTHT 2301: Respiratory Diseases

Structures of Respiratory System

• Upper Respiratory Tract: Includes nostrils, nasal passages, pharynx, larynx, and trachea
• Lower Respiratory Tract: Includes bronchi, bronchioles, alveolar ducts, and alveoli

Respiratory Disease Symptoms

• Nasal discharge can be serous, mucoid, mucopurulent, or hemorrhagic, and can be unilateral or bilateral
• Nasal congestion leads to open-mouth breathing
• Anorexia can occur, especially in cats that cannot smell food
• Other symptoms include sneezing, coughing (productive or non-productive), dyspnea, and orthopnea

Respiratory Diseases

• Common respiratory diseases include Rhinitis/sinusitis, Epistaxis, Laryngeal paralysis, Collapsing trachea, Pneumonia, Pleural Effusions, Pneumothorax, Diaphragmatic hernia, Infectious Canine Tracheobronchitis, K-9 Influenza, Feline Upper Respiratory Infections, Systemic Fungal diseases, and Pulmonary Neoplasia

Rhinitis/Sinusitis

• Signs: Nasal discharge that is serous, mucoid, or mucopurulent
• Symptoms: Sneezing, coughing, and gagging
• Most commonly caused by a tooth root abscess
• Swelling ventral to medial canthus of eye due to the carnassial tooth (maxillary 4th premolar)
• Diagnosis: Clinical signs, radiographs, and C/S if bacterial infection is suspected
• Treatment: Appropriate antibiotics and removal of the affected tooth, if sinusitis is caused by a tooth root abscess

Epistaxis

• Characterized by bleeding from the nose
• Can be caused by systemic disease, infection, or clotting problems
• Can also be associated with trauma, foreign objects, or neoplasms
• Diagnosis: Rhinoscopy, C/S, cytology, imaging (radiographs, CT, MRI)

Laryngeal Paralysis

• Caused by damage to nerves and muscles controlling larynx
• Common in dogs and rare in cats
• Typically acquired in middle-aged to older, large and giant breed dogs, with less common hereditary or congenital causes
• This condition leads to dry cough, voice changes, and noisy breathing that progresses to marked dyspnea with stress, exertion, stridor, and collapse; progression of clinical signs is generally slow
• Diagnosis: Clinical signs and laryngoscopy under light anesthesia
• Treatment: Tranquilizers and corticosteroids temporarily in mild cases, surgery to enlarge the glottic opening

Collapsing Trachea

• Affects middle-aged to older toy and miniature breed dogs, and is rare in cats
• Occurs in obese dogs with concurrent CV disease or chronic bronchitis
• Tracheal rings cannot keep their "C" shape, collapsing during inspiration
• Characterized by progressive disease, nonproductive, honking, chronic cough, inspiratory or expiratory dyspnea
• Diagnosis: Bronchoscopy or U/S to view collapse, R/O other
• Treatment: Weight loss, exercise restriction, use harness, reduce excitement and stress, antitussives, antibiotics, bronchodilators, and corticosteroids; surgery to reinforce tracheal rings

Pneumonia

• Distribution may be focal, lobar, or diffuse
• Caused by bacteria, viruses, fungi, toxins, or aspiration
• Most develop in the cranioventral portions of the lungs.
• Symptoms include lethargy, anorexia, deep cough, progressive dyspnea, cyanosis, and fever
• Diagnosis: Physical exam (auscultation), CBC (leukocytosis), radiographs, BAL (C/cytology)
• Treatmen: Support, oxygen, antibiotics, nebulization, coupage, and bronchodilators

Pleural Effusions

• Congestive heart failure causes transudate
• Pyothorax (empyema) leads to accumulation of pus in the pleural cavity, caused by bacteria, fungi, or Mycoplasma species
• Medical treatment: Thoracic drain, lavage and aspiration, appropriate antimicrobial treatment
• Chylothorax causes accumulation of chyle in the pleural cavity; relatively rare, seen most often in cats
• Tx: Surgical intervention like thoracic duct ligation (TDL)
• Dx: Clinical signs, radiography, thoracocentesis to remove fluid, cytology, +/- C/S
• Transudate is low in protein and cellularity
• Exudate is high in protein and cellularity (neutrophils)
• Chylous fluid is milky white with fat and lymphocytes

Diaphragmatic Hernia

• Trauma from being hit by a car is a common cause, as is congenital defects of the diaphragm
• Acute cases lead to dyspnea that varies with severity, and chronic cases cause weight loss as a common symptom
• Physical Exam: Decreased lung sounds on auscultation with GI sounds in the thorax
• Diagnosis: Radiographs, with contrast studies if needed
• Treatmen: Surgical repair of the hernia

Infectious Canine Tracheobronchitis

• Usually mild, self-limiting disease - “kennel cough”
• Primary pathogen can be viral or bacterial
• Canine parainfluenza virus, canine adenovirus 2 (CAV-2), or canine distemper virus
• Bordetella bronchiseptica
• Especially in dogs <6 mo old
• Cats can be infected too
• Other bacteria (usually G- bacteria such as Pseudomonas sp, E. coli, and Klebsiella pneumoniae) may cause secondary infections after viral injury to respiratory tract.
• Highly contagious isolate dog, supportive care, central cough suppressants (hydrocodone, butorphanol) and antibiotics based on C/S, bronchodilators
• Characteristic cough suddenly develops 5–10 days after exposure to other susceptible or affected dogs.
• Prevention: Vaccination 2-3 weeks prior to boarding

Canine Influenza

• Caused by canine influenza virus – Orthomyxovirus H3N2 & H3N8
• 1st identified in Greyhounds in Florida 2004 Transmitted via aerosols (barking, sneezing, coughing)
• Remained in environment up to 48 hr.
• Clinical signs like Kennel cough: Rhinitis, coughing, sneezing, lethargy, anorexia, tracheitis, bronchitis, pneumonia, fever (104°-105°F) Morbidity up to 80%, mortality 10%
• Diagnosed by clinical signs, PCR
• Treatment: Supportive care, fluids if dehydrated, cough suppressants, antibiotics for secondary infections, NSAIDs for fever to reduce inflammation
• Prevention: Non-core vaccine for dogs who attend events with other dogs

Feline Respiratory Disease Complex

• Causes include Feline viral rhinotracheitis (FVR), feline calicivirus (FCV), Chlamydophila felis, or Mycoplasma felis, or combinations with the most acute feline URI caused by FVR virus
• Transmission occurs via aerosol droplets and fomites, plus convalescent cats may harbor the virus for months
• Dx by clinical signs
• Tx: Symptomatic and supportive care, antibiotics for secondary infections
• Preventative measures include vaccination

Feline Viral Rhinotracheitis (FVR)

• Caused by Feline herpesvirus type 1
• Fever, frequent sneezing, conjunctivitis, rhinitis, and salivation, (ulcerative stomatitis and ulcerative keratitis develops in some cats)
• Signs may persist for 5-10 days in milder cases and as long as 6 wks. in severe cases.
• It usually has low mortality and good prognosis.

Feline Calicivirus (FCV)

• Many serologically related strains of feline caliciviruses
• Some of the strains include oral ulcers, others severe lung disease
• Cause limping syndrome, due to painful joints, self-limiting
• Differentiating FVR from FCV infection is clinically challenging
• Results in lesion of oral mucosa and tongue
• Lymphocytic-plasmacytic gingivitis and stomatitis are common

Chlamydophila Felis

• Obligate intracellular bacteria that form inclusions within cytoplasm of epithelial cells
• With Infectious form of organism called elementary body Conjunctivitis, associated with sneezing and nasal discharge
• Found Generally in cats less than 1 yr old, with those 2-6 months old appearing to be at highest risk of infection
• Transmission via direct contact
• Treated with Doxycycline up to 6 wks, and all cats must be treated.
• There exists a rare zoonotic risk for immunocompromised people.

Systemic Fungal Diseases

• Blastomycosis is the result of Blastomyces dermatitidis: characterized by Pulmonary, disseminated, and local cutaneous forms
• Incubation 5-12 weeks
• More common in dogs than cats
• Coccidiomycosis is the the result of Coccidioides immitis and is referred to as "Valley fever”
• Histoplasmosis is the result of Histoplasma capsulatum and spread via bird or bat droppings
• Cryptococcosis is the result of Cryptococcus neoformans, a Mucoid capsule, which can be identified via India ink stain
• Commonly infects the nasal cavity and skin in cats, and dogs CNS
• Aspergillosis can affect German Shepherd Dogs, and immunocompromised animals and result in sinus and nasal infections

Fungal Pneumonia

• Blastomyces dermatiditis, Coccidioides immitis, Histoplasma capsulatum, Cryptococcus neoformans, Pneumocystis jiroveci, Aspergillus spp, Candida spp
• Typically from inhalation of spores .
• Soil organisms: Most commonly chronic disease causing Pyogranulomatous inflammation
• Symptoms include Productive cough, mucoid to mucopurulent nasal discharge, dyspnea including emaciation, weakness, generalized lymphadenopathy,
• Blastomycosis causes multiple cutaneous and SQ nodules with draining tracts, emaciation and diarrhea in dogs
• Coccidiomycosis and can resultin osteomyelitis in dogs, with skin lesions in cats
• Uveitis or granulomatous chorioretinitis
• Diagnosed with Thoracic radiographs, cytology with characteristic fungal organisms, culture, serology
• Treated with Itraconazole, fluconazole, amphotericin B, and terbinafine

Pulmonary Neoplasia

• Primary lung tumors are uncommon, with most being adenocarcinoma
• Metastatic lung tumors are common in Mammary or thyroid tumors
• Nonproductive cough, exercise intolerance, wt. loss, dysphagia, anorexia
• Dx includes Radiographs or biopsy with histopathology
• Rx includes Surgical excision (lobectomy), or treatment of primary tumor for metastatic lesions
• Px: Guarded