The Wright Animal Clinic

12050 Southshore Pointe Drive
Midlothian, VA 23112


Straight Facts about Heartworm Disease in Dogs and Cats

Heartworm disease in dogs:
·              Heartworms are transmitted by mosquitoes.
·              A mosquito bites a dog infected with heartworms, microfilaria (early microscopic stage of heartworm) enter the mosquito as it takes its blood meal.
·              The microfilariae develop into the next larval stage, (still microscopic) within the mosquito.
·              The mosquito takes its next blood meal from another dog and transmits the larval heartworms to that dog.
·              These larvae move through the tissues and bloodstream of the dog, growing and developing as they journey to the heart.
·              After 3 months, later stage larvae are in the dogs lungs damaging tissue and blood vessels. Within 6 months, without the intervention of a monthly preventative, adult heartworms are living in the pulmonary artery of the dog.
·              Mature heartworms can be up to 16 inches in length.
·              A severely infected dog can have as many as 250 heartworms in its body, most in the right side of the heart.
·              Adult heartworms, left untreated, can live up to 5-7 years in the dog if the dog survives the infection.
·              Possible signs of Heartworm disease:
o         SUDDEN DEATH
o         Difficulty breathing, coughing
o         Lethargy
o         Reduced ability to exercise (tires easily)
o         Weight loss
o         Loss of consciousness

·              Without a preventive the larvae develop and make their way to the heart.
·              Monthly preventive intervenes by killing the larvae in the tissue and in the bloodstream that the dog has acquired over the preceding 30 days.
·              Heartworm disease is completely preventable!! In Virginia, year-round protection is needed. Did you know it takes just a few consecutive days of 60-70 degree temperatures for mosquito eggs to hatch and for adults to emerge from hibernation?
·              All dogs should be tested once per year to ensure the preventive has been given as recommended, that the dog has truly eaten the entire chew or tab and to ensure the preventative is working as it should. Dogs that have missed any doses should be retested in accordance with the veterinarian's recommendations.
·              Some of the preventives available : Iverhart, Interceptor, Sentinel, Revolution, Heartgard
·              The treatment for heartworm disease is very harsh for the patient and more costly than the total cost of monthly heartworm prevention given over the lifetime of most pets. 
·              First the severity of the disease must be evaluated: This is determined through chest x-rays, ECG, full bloodwork panel, urinalysis and physical exam.
·              If the patient is deemed healthy enough for treatment, an adulticide (kills adult heartworms) that is arsenic based is injected into the deep muscles of the back. Depending on the severity of the disease one or more injections may be required. An oral microfilariacide (kills the larval heartworms) is also administered. Then the patient must be on restricted exercise and cage rest for weeks to months throughout and following treatment.
·              It is important to note that while every effort is made to determine that the pet is healthy enough to make it through treatment, serious complications or death may occur while the patient is being treated.
Cats and Heartworm Disease
·              Cats get heartworm disease in the same manner as dogs? through a mosquito bite.
·              Once in the blood stream and tissues the microfilariae begin to migrate toward the heart.
·              Adult heartworms can live up to 2-3 years in the cat.
·              Most of the irreversible damage caused by heartworms in cats occurs in the lungs. It takes just 3 months without the intervention of a monthly heartworm preventative for the larvae to reach the cat's lungs.
·              Symptoms:
o         Wheezing
o         Coughing
o         Difficulty breathing
o         Sudden death
·              Many cats that survive heartworm infection live with severe asthma, requiring daily medications and monitoring for the rest of their lives.
·              Heartworm disease is completely preventable!! In Virginia, year-round protection is needed. Did you know it takes just a few consecutive days of 60 degree days for mosquito eggs to hatch?
·              There is no cure for feline heartworm infection or the associated respiratory disease it can cause, therefore monthly prevention is our only tool.
·              There is no clear-cut one-step test available to determine whether a cat has heartworms, so yearly testing is not currently required before starting a prevention medication.
·              Heartworm preventives available for cats: Revolution (topical), Heartgard (chew), Interceptor (tablet)
·              Symptoms of the associated respiratory disease may be managed with medication and will require management for life. The heartworms will eventually die and if the cat is placed on a preventive no subsequent disease will occur, but the damage caused in the lungs is irreversible, and the natural death of the worms may cause the cat's death due to complications.