Upper airway troubles (Proceedings)

Key Points

• The most common causes of chronic nasal discharge include neoplasia, aspergillosis or cryptococcosis, nasal foreign body, rhinitis secondary to dental disease, and idiopathic or inflammatory rhinitis.

• In the chronic phase of feline rhinitis/sinusitis syndrome, the underlying etiology is unknown, although chronic viral or bacterial infections are often implicated. Many of the clinical signs are likely related to an irreversible destructive process within the nasal cavity that promotes secondary bacterial invasion and deep-seated infection and inflammation.

• With idiopathic inflammatory rhinitis of dogs, or lymphoplasmacytic rhinitis, the underlying cause is also not often apparent. Specific diseases must be ruled out before attempting palliative care.

Viral Disease

Viral 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.

Canine Distemper

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

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.

Aspergillosis (Aspergillus fumigatus)

Dogs and cats with nasal or pulmonary disease can be serologically screened for antibodies against Aspergillus fumigates. Results must be interpreted with those from cytology, radiology, histopathology, and culture. Circulating antibodies are detected in serum by agar gel immunodiffusion (AGID), counterimmunoelectrophoresis (CIEP), and ELISA. The presence of serum antibodies can indicate exposure or infection. Some infected dogs will be falsely negative. Due to long titer duration in some treated dogs (> 12 months), serologic response to therapy is not helpful.

Nasal turbinate destruction seen radiographically suggests either aspergillosis or nasal neoplasia. Cytologic analysis and culture of canine nasal exudate alone are not diagnostic of infection because fungal elements may be sparse or nondetectable in affected dogs while being found in noninfected dogs and dogs with nasal tumors. Nasal lavage rarely demonstrates the organism. Nasal biopsy is indicated and can be performed by a coring procedure or surgical biopsy. Techniques will be covered in the oncology section of this course. Definitive diagnosis should be based on serologic and culture evidence of infection or serologic and radiographic evidence of infection. In the rare case of disseminated disease, cytologic evaluation of aspirates of affected tissue may be useful. If the organism cannot be demonstrated by biopsies obtained through the nares, positive serologic tests may support exploratory surgery.

Cryptococosis (Cryptococcus neoformans)

Cryptococcus neoformans is a saprophytic yeast found worldwide and affects cats of all ages. Infection induces the formation of a granulomatous mass that results in a mucopurulent to hemorrhagic nasal discharge. Local destruction creates large granulomas visible as swelling around the cats nose. The diagnosis of cryptococcosis is confirmed by identifying the organism in Wright's stained aspirates or impression smears made from affected tissues. The organism has a 1 to 7 (m center surrounded by a nonstaining 1 to 30 μm capsule. Latex cryptococcal antigen testing (LCAT) is a sensitive method to detect the capsular polysaccharide antigen in serum and cerebrospinal fluid. Cryptococcal antigen titers increase with severity of disease ad can be used to monitor the response to therapy.

Allergic diseases

Eosinophilic, lymphocytic, and plasmacytic rhinitis occurs in dogs and cats. The primary etiologies are hypersensitivity reactions and nasal parasitism. Often, dogs with allergic rhinitis are hypersensitive to multiple antigens on intradermal skin testing. Animals with histopathologic evidence of eosinophilic, lymphocytic, or plasmacytic rhinitis should be treated for nasal parasitism prior to the administration of corticosteroids.

Parasitic infections

Pneumonyssus caninum and Eucoleus boehmi are the 2 most common nasal parasites infecting dogs in the United States. Pneumonyssus caninum infection is documented by direct visualization of the mite on the nasal mucosa. Eucoleus boehmi infection is documented by demonstration of ova in feces or histopathologic demonstration of the organism on nasal biopsy. Eucoleus boehmi is a capillarid; ova look like Trichuris vulpis.