Archived Articles : Heartworm
Heartworm in Ferrets.
Recent post mortems in the Perth Metropolitan area have confirmed the cause of death was heartworm. Heartworm disease is caused by a parasite that lives within the ferret’s heart and pulmonary vessels. The parasite is transmitted by the bite of a mosquito which transmits the small larvae under the skin. The larvae migrate through the soft tissue of the ferret into the blood vessel and into the heart. Once in the heart the larvae develop into adult worms. The migration takes around 3-5 months after the ferret has been infected by the bite of the mosquito.
In the heart the adult heartworm, thin (1-2mm) but some 20-30cm in length, causes inflammation of the endothelial lining of the heart and blood vessels damaging the valves. Over time (months to years) the damage progresses and congestive heart failure develops.
Clinical signs in ferrets can include lethargy, coughing, difficulty breathing, wheezing and often fluid in the abdomen (ascites). Many ferrets simply have sudden death from the occlusion of major vessels in the heart. This can occur in ferrets as young as 3 years of age. Specific diagnosis of infection in ferrets can be done with blood tests for microfilaria (heartworm) antigen. Most heartworm antigen tests are suitable for ferrets. Dirogen antigen test is said to be marginally better than most.
Treatment of infected ferrets is very difficult and involves the use of arsenic based compounds like thiacetarsemide.
Recent research indicates that persistant dosing with ivermectin-like drugs over a 12 month or longer period can lead to the gradual death of the adult parasite in the heart.
Revolution, a new avermectin has been used very successfully by myself to prevent heartworm infection in ferrets. The recommended dose need only be applied once a month.
The Revolution is applied directly to the back of the ferret’s neck and besides preventing heartworm, the drug also controls fleas, sarcoptic mange and ear mites, all common problems of ferrets.
Other methods of heartworm control can be achieved by feeding the ferret a quarter of a Heartgard Chewable once a month.
Like most diseases, prevention is much better than trying to treat the disease.
Dr Don Nickels
Cottesloe Animal Hospital.
First Published in Issue 95 of Ferreting Around (July / August 2000)