What is feline heartworm disease?
Heartworm disease is caused by a roundworm called Dirofilaria
immitis. Heartworms are most commonly found in dogs although
they can infect a wide variety of mammals including ferrets, sea lions, bears, foxes, wolves, coyotes, and cats. Adult heartworms live in the heart and major arteries of the lungs, where they interfere with the function of the heart and lungs.
How Are Heart Worms Transmitted?
Heartworms can only be transmitted from one animal to
another by mosquitoes. Adult worms living in the heart and
arteries of the lungs produce microfilariae (small immature
heartworms) which are found circulating in the blood of the
infected animal, usually a dog.
If a mosquito feeds on an infected dog with microfilariae in
the blood, the mosquito will ingest some of these immature
heartworms along with the blood meal. Inside the mosquito,
the immature heartworms develop to a stage called the
infective larval stage. When the mosquito feeds on another
dog or a cat, some of these infective larvae will escape
from the mosquito during the blood meal. The larvae pass
through the animal's skin through the bite wound left by
the mosquito. Once the infective larvae have entered an
animal, they will begin migrating through the tissues.
They eventually make their way to the heart and lungs
where they will mature and begin producing microfilariae.
How Does My Cat Get Heartworms?
Although dogs are the most commonly infected mammals,
cats can also get heartworms. Current research suggests
infected dogs are the source of most infections for other
animals. If your cat lives in an area where heartworm
infection is seen in dogs, your cat could be bitten by a
mosquito that was infected by a dog.
are the Signs of
Heartworm Disease in Cats?
In cats, heartworms live for one to two years and it
is uncommon for cats to have more than two or three
adult heartworms. Small numbers of heartworms,
however, may cause serious disease in cats.
Clinical signs of heartworm disease in cats vary considerably.
Some cats do not show any significant clinical signs of
may appear normal. Other cats develop chronic (long-lasting)
,disease. Vomiting or respiratory signs (coughing and difficulty
in breathing) are commonly seen in chronic cases of heartworm
disease in cats. Vomiting tends to be sporadic and
may or may not be related to eating. Coughing may be intermittent
or occur in severe, sudden attacks that may take
place days apart. in some cases, cats may have severe, acute
disease with signs of respiratory collapse and, in some cases,
sudden death. In acute cases, death may be so rapid that
there is insufficient time to make a diagnosis or offer treatment.
Cats that die from heartworms can appear clinically normal
one hour before death.
Many other diseases can cause similar clinical signs so it
is almost impossible to diagnose feline heartworm disease
based on clinical signs alone.
How do I Know if My Cat Has Heartworm
If your cat lives in an area where heartworm is seen in dogs
or if your cat is showing signs suggestive of heartworm disease,
you should take your cat to your veterinarian. Because the
clinical signs of heartworm infection in cats are also seen
with other diseases, your veterinarian will probably need to
perform diagnostic tests in addition to conducting a thorough
physical examination. Many diagnostic tests, such as radiography (X-rays),
ultrasound of the heart and lungs, and blood
tests, including a new test developed specifically for diagnosis
of heartworm infection in cats, are helpful in diagnosing the
disease. Ask your veterinarian at the time of your pets next annual exam.
My Cat is an Indoor Cat, Can it Be Infected With Heartworms?
Cats that remain indoors are at much lower risk of getting
infected than are cats that go outdoors because of the
reduced exposure to mosquitoes. Despite this, heartworm
infections have been reported in strictly indoor cats; These
infections are thought to be caused by infected mosquitos that
gained access to the house.
Should I Get My Cat Tested for Heartworm Infection?
If you lives or travels to an area where heartworm is seen in dogs,
or if your cat has signs suggestive of feline heartworm
disease, you should consult your veterinarian to discuss
having your cat tested.
What Can Be Done if My Cat Has Heartworms?
Unfortunately, treatment to remove heartworms from
infected cats can be difficult and hazardous to your cat's
health. Various medications can, however, be used to
help minimize the clinical signs (coughing, vomiting,
difficulty in breathing) your cat may be exhibiting.
See your veterinarian for advise on management of
feline heartworm disease.
Berkshire Veterinary Hospital
730 1/2 Crane Avenue
Pittsfield, MA 01201