Presenting Problem: Dyspnea in Ferrets

Recognizing the dyspneic ferret

Ferrets (Mustela putorius furo) with respiratory disease exhibit clinical signs that are similar to those seen in dogs and cats, including non-specific signs of illness (Fig 1), such as reduced appetite, lethargy, and weight loss, sneezing, oculonasal discharges, as well as tachypnea, and labored breathing or dyspnea. When compared to other species like the dog, cough is relatively rare in the dyspneic ferret.

prone ferret

Figure 1. Ferrets with respiratory difficulty often exhibit non-specific signs of illness such as anorexia and lethargy.

Key points of urgent care

Initial management of the dyspneic ferret should focus on stabilization, including supplemental oxygen. Oxygen can be delivered via face mask, with the diaphragm removed, or by placing the ferret in an oxygen cage. Pulse oximetry is an easy and non-invasive technique, however this equipment is not intended for use in ferrets and the accuracy of results is questionable. Nevertheless, changes or trends in oxygen saturation may provide valuable clinical information.

Although it is desirable to establish intravenous access as soon as possible in a dyspneic patient, this is not always possible or practical in the ferret. Use your own clinical judgment to determine if your patient will tolerate the necessary restraint.

 

Case management

Signalment and history

  • How old is the ferret?

Some infections, such as distemper virus and feline infectious peritonitis (FIP)-like disease, are more commonly reported in young animals (Perpiñán et al 2008, Garner et al 2008)

  • Is the vaccination status of the ferret current?

Ferrets are extremely susceptible to canine distemper virus.

  • Obtain a detailed clinical history. Have the owner describe the onset and progression of clinical signs.

Some conditions, such as bacterial pneumonia, may be associated with acute episodes of labored breathing (Martínez et al 2011).

Physical examination

Ferrets that present severely dyspneic with open-mouth breathing and/or cyanosis should first be stabilized and provided with supplemental oxygen (see Key Points above). Carefully observe the patient’s breathing pattern and carefully auscultate the lung fields and heart. Perform a complete physical examination to look for clues to the underlying cause of respiratory difficulty. For instance, the ferret with canine distemper will display not only respiratory signs, but also dermatologic and gastrointestinal problems (Fox and Marini 2014, Perpiñán et al 2008) (Box 1).

Box 1. Clinical signs of canine distemper infection in the ferret
Respiratory signs

 

Mucopurulent oculonasal discharge
Sneezing
Coughing
Dyspnea
Dermatologic signs

 

Facial, chin, and perineal dermatitis
Pruritus
Crusting dermatitis of lips, eyes, nose, footpads, and perineum
Gastrointestinal signs Diarrhea
Neurologic signs Muscle tremors, seizure activity, and coma are possible but rare

Clinical signs of feline infectious peritonitis (FIP)-like disease can include dyspnea, but more commonly ferrets suffer from diarrhea and central nervous system deficits (Garner et al 2008).

 

Differential diagnoses

A variety of etiologies can be associated with respiratory difficulty in ferrets, ranging from degenerative disease and infection to neoplasia or trauma. Among the many potential causes of respiratory signs in the ferret, the most important differentials include:

Influenza is a common, but fortunately relatively harmless, cause of respiratory signs in pet ferrets. Ferrets are susceptible to influenza type A and B. Although it is theoretically possible for ferrets to transmit influenza virus to people, transmission occurs primarily via aerosol droplets from ferret to ferret or from human to ferret (Barron and Rosenthal 2012, Maher and DeStefano 2004). As in their human counterparts, influenza infection commonly begins as rhinitis that progresses to tracheobronchitis. Clinical signs in afflicted ferrets include the rapid onset of sneezing, nasal discharge, lethargy, and fever. Infection can extend to interstitial pneumonitis but this is rare except in the very young or the immunocompromised patient. The course of clinically illness typically lasts 3 to 5 days in uncomplicated cases (Maher and DeStefano 2004).

Traumatic or structural injury, like hemothorax or diaphragmatic hernia, is another potential cause of respiratory distress in the pet ferret. Lymphoma, associated with pleural effusion and possibly a mediastinal mass, is also a possible cause for dyspnea in the ferret. A viral disease of growing importance is a systemic pyogranulomatous inflammation resembling FIP. Partial DNA sequencing indicates this virus is related to ferret enteric coronavirus (Garner et al 2008, Martina et al 2003). Ferrets are also susceptible to pneumonia and pleuritis caused by bacterial infection or fungal agents such as  Blastomyces dermatitids, Coccidiodes immitis, Cryptococcus spp., and Histoplasma capsulatum (Darrow et al 2014, Fox and Marini 2014, Martínez et al 2012, Eshar et al 2010). The fungal agent Pneumocystis carinii has also caused pneumonia in immunosuppressed ferrets (Stokes et al 1987).

 

Diagnostics

Anemia and hypergammaglobulinemia have been reported with distemper virus and FIP-like infection (Perpiñán et al 2008, Garner et al 2008). Thrombocytopenia has also been described in FIP-like infection (Garner et al 2008).

Look for cardiomegaly, consolidation or parenchymal masses, pleural effusion, or increased soft tissue density within the mediastinum.

  • Perform thoracic ultrasound to more thoroughly evaluate the heart, mediastinum, and pleural space.
  • Use fine needle aspiration to collect samples for cytologic evaluation of pleural effusion or intrathoracic mass lesions.

Therapy

Treatment will vary with the underlying cause of dyspnea, but may include nebulization with saline, antimicrobials, and/or mucolytics; thoracocentesis of pleural effusion to allow lung re-expansion, and/or anti-inflammatory agents. For many conditions, drug regimens and drug dosages are extrapolated from what is used in cats. For instance, furosemide (1-4 mg/kg PO, SC, IM, IV q8-12h), nitroglycerin (1/16-1/8 in per animal q12-24h), and an anxiolytic such as midazolam (0.25-0.3 mg/kg SC, IM) may prove therapeutic in congestive heart failure (Morrisey 2013).

 

Prognosis

Prognosis varies with the underlying cause of disease, ranging from good in uncomplicated cases of influenza to grave for ferrets with distemper virus infection. In a recent case report, most animals with distemper died or were euthanized because of respiratory complications (Perpiñán et al 2008).

 

References