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Heartworm and your pet


Heartworms live in the heart and main blood vessels of the lungs, and grow up to 30 cm long. Both dogs and cats may be infected, though the incidence of infection in dogs is much higher than in cats. Heartworm disease is a serious threat to the well-being of the infected animal, with severe and often irreparable damage occurring before clinical signs may be noticed.

Mosquitos are the main vectors for the spread of infection - a mosquito bites an infected animal and ingests the immature heartworms (microfilariae) with blood. The microfilariae mature in the mosquito over a 2-3 week period and are transferred to another animal when the mosquito feeds again. The worms migrate from the site of the mosquito bite to the vessels of the heart and lungs, where they develop into sexually mature worms by 7 months after infection.

 

Clinical signs of heartworm infection in dogs are related to blockage and weakening of the blood vessels. In dogs, clinical signs include persistent coughing, laboured breathing, general lethargy and tiring easily after exercise, a distended abdomen, collapse and sometimes death. In cats, clinical signs include coughing, difficulty breathing, vomiting, and sudden death.

Treatment for the condition is both expensive and traumatic for the animal - prevention is very definitely better than cure.

 

Heartworm Testing and Prevention

Heartworm infection can cause serious and life-threatening illness, and treatment can have serious complications. Therefore we recommend that all dogs should receive heartworm preventatives from 12 weeks of age to protect against these parasites.

If your dog is older than six months of age and has not already started on heartworm prevention, a blood test will be necessary before starting these preventatives - this blood test can be completed in a standard consultation. The test involves clipping a small amount of hair from your dog's foreleg, and taking a very small amount of blood from the cephalic vein.  The result of the test is known in about 5 minutes.

The blood test result:

If the test is negative we would then start your dog on heartworm prevention, and plan to retest in about 6 months time.  This is necessary as it takes 6 months from the mosquito bite to develop a positive test, retesting ensures no recent infections are missed. 

If the test is positive a plan for the treatment for your pet will be formulated.

 

Preventative medication:

There are a number of options available for heartworm prevention, ranging from daily tablets, to monthly tablets, chewables and 'spot-on' preparations, to an annual heartworm prevention injection.

 

We've found that most people prefer the convenience of the monthly preparations or annual injection. These also have the advantage of being slightly more flexible - there is no concern if you are a couple of days late in dosing your pet with monthly medication or having the yearly injection administered, whereas a missed daily tablet may lead to heartworm infection.

Monthly heartworm prevention medication also comes in combination forms - tablets for heartworm prevention and control for most of the gastrointestinal worms. We can give you more information about these products if you are interested.

An important point to note: "Allwormer" medications, while successfully controlling gastrointestinal worms, does not offer any protection against heartworm.