Upper airway troubles (Proceedings)
Viral DiseaseViral upper respiratory tract disease causes substantial morbidity in cats especially in shelter and cattery populations. Acute disease typically affects young kittens and is characterized by sneezing, fever, malaise, and bilateral nasal and ocular discharge (serous, mucoid, or purulent). In severe cases, dehydration, debilitation, and death can occur. A number of etiologic agents may be involved in the acute syndrome, and most infections are believed to involve feline herpesvirus type 1 (FHV-1), feline calicivirus (FCV), and/or Chlamydia. Historically, FHV-1 has been estimated to account for the majority of cases, although calicivirus may be more prevalent in some populations. There are no effective primary therapies for these agents. Most commonly, viral induction of inflammation results in local bacterial overgrowth and potentially, nasal chondritis and osteomyelitis. Treatment for secondary bacterial rhinitis is described under symptomatic therapy.
The primary viral disease in the dog causing sneezing and nasal discharge is canine distemper virus. Clinical signs of canine distemper vary depending on virulence of the virus, environmental conditions and host immune status. Many infections are subclinical (50-70%) and many others have mild clinical signs including listlessness, fever, and upper respiratory tract infections. The disease is often progressive in the immunosuppressed or immature dog. Starting with fever, a dry cough and a serous nasal discharge canine distemper can progress in a few days to a moist, productive cough with increased lower respiratory sounds. Vomiting and diarrhea can then develop which may be similar to other causes of viral enteritis. Animals that survive the early respiratory and gastrointestinal signs may develop neurologic disease 1 to 3 weeks later.
Diagnosis is based on clinical suspicion and is confirmed by immunocytologic examination of conjunctival, tonsilar or respiratory epithelial cells, skin biopsy, or polymerase chain reaction (PCR) testing of blood or cerebral spinal fluid. For immunocytologic staining, smears are made on clean slides, air-dried and fixed in acetone for 5 minutes. They can then be stained either directly or indirectly with fluorescein-conjugated canine distemper antibody and examine by fluorescent microscopy.
Therapy for distemper is supportive and nonspecific. Symptomatic care is described later in this section and in the section on bronchopneumonia. If the animal develops gastrointestinal signs, aggressive intravenous fluid replacement is indicated. Antibiotic coverage should be adjusted to prevent enteric bacterial from crossing the damaged intestinal mucosa and entering the bloodstream.
Brachycephalic Airway Syndrome
Brachycephalic dogs bred for short faces have a complex of anatomic features that can cause upper airway obstruction. Stenotic nares, elongated soft palate, everted laryngeal saccules, and a hypoplastic trachea are included in this complex (although surgeons just refer to the first three since they can fix those). All these dogs have increased upper airway resistance, but not all suffer clinical signs of disease. It can be difficult when presented with a dyspneic middle-aged animal to determine how much of the presenting complaint is due to the congenital malformation and how much is due to acquired pulmonary disease. Early surgical correction is recommended to avoid the development of secondary problems.
Nasopharyngeal polyps are a relatively common problem of young cats. The cats present with a variety of clinical signs including open mouth breathing, nasal discharge, dyspnea, and wheezing. Oral and pharyngeal examination under anesthesia are diagnostic. Surgical removal will resolve clinical signs and will be discussed in more detail in the surgery section of this course. Owners should be cautioned that recurrence is possible.
Miscellaneous Anatomic Diseases
Nasal foreign bodies, cleft palate, tooth root abscess and oronasal fistula are managed by treating the primary disease. Secondary bacterial infections are common and its management is discussed under symptomatic therapy. Tooth root abscesses are a common cause of chronic destructive rhinitis and nasal discharge. Tooth root abscesses are diagnoses by a combination of gross examination and periodontal probing, radiography looking for periapical abscesses and facial deformity in some advanced cases. Extraction and antibiotic therapy will be required for resolution.