Introduction

• Dirofilariasis or heart worm disease is an uncommon disease.
• Ferrets are considered aberrant hosts.
• Dogs are primary reservoir.
• Cause: Dirofilaria immitis.
• Signs: similar to those seen in the dog (exercise intolerance, dyspnea, lethargy, ascites, coughing, anorexia, weakness, anemia and cyanosis).
• Diagnosis: history, auscultation, radiography/angiography, echocardiography, heartworm antigen testing, microfilariae testing, complete blood count, serum chemistries.
• Treatment: adulticide therapy, symptomatic treatment, transvenous heartworm extraction, microfilaricide therapy, 
• Prognosis: fair to guarded if asymptomatic infection; poor if symptomatic.

Pathogenesis

Etiology

• Caused by an infection with Dirofilaria immitis.
• Most commonly found in the right ventricle, cranial vena cava, main pulmonary artery.
• Cause villous endarteritis.
• May develop severe heart disease with only a single worm, although burdens of up to 21 worms have been reported. Fatal right sided heart failure has occurred with 2 adult worms causing mechanical obstruction of blood flow.
• The susceptibility and life cycle of D. immitis have been studied extensively in ferrets and were found to be similar to those in dogs.
• Because of the ferret’s small size, the clinical presentation more closely resembles that of infected cats.

Predisposing factors

General

• Ferrets housed outdoors in endemic areas are at risk.
• Endemic areas include Atlantic and Gulf coasts of the United States, tropical and semi-tropical areas, some Mediterranean countries and Australasia.
• Transmission in unlikely in regions or seasons where the ambient temperatures are not on average higher than 18°C/65°F during a 30-day period.

Pathophysiology

• D. immitis is a filarial parasite that is transmitted by mosquitoes, which serve as a vector and intermediate host for the parasite.
• Microfilaria are ingested by mosquitoes (usually from female mosquitoes feeding on microfilaria-positive dogs). 
• Mosquito deposits infective third stage larvae into the skin, which then migrate subcutaneously to the thorax and vascular system.
• Microfilaria can be found within the small pulmonary arteries of as many as 50-60% of infected animals.

Epidemiology

• Uncommon disease of ferrets.

Diagnosis

Treatment

Prevention

Outcomes