NOT FOUND: dogsandheartworms.jpgCanine heartworm disease is a common condition in many regions of the world. It is caused by the filarial (threadlike) worm Dirofilaria immitis that lives in the pulmonary arteries (blood vessels leading from the heart to the lungs) in most infected dogs. The name “heartworm” is a bit misleading because only in very heavy infections do the worms actually reside in the heart itself. Nonetheless, the presence of these worms causes strain to the heart and an intense reaction in the blood vessels, resulting in problems for the dog. D. immitis is injected into the dog by infected mosquitoes. For this reason, heartworm disease is more common in tropical regions of the world, where the conditions of warmth and moisture are ideal for mosquitoes to live (this does include California and the Sacramento region). Some dogs do have a predisposition for heartworm disease; living outdoors and most importantly-not being on a preventative.

HOW DOES MY DOG GET HEARTWORMS?
Transmission occurs when a mosquito bites an infected dog and ingests heartworm larvae (baby heartworms), which live in the bloodstream. When the mosquito bites another dog or cat, some of the larvae are injected under the skin. The larvae grow for 3-4 months and eventually make their way into the heart where they develop into adults, and the process is ready to repeat itself. Impact on the pet is variable. Dogs can be without symptoms if the infection is light or has occurred recently. In some cases heartworm disease can cause severe debilitation and eventually may be fatal. Because heartworm disease is easily preventable, it has become a less common diagnosis in pets that receive regular veterinary care.

WHAT TO WATCH FOR:
Symptoms don’t usually develop until damage has already occurred to the heart. Dogs can have a wide range of symptoms, with some dogs being completely asymptomatic (no symptoms at all). Symptoms usually occur because of heart failure. These include: coughing, coughing up of blood, heavy breathing, unwillingness to exercise, signs of right sided congestive heart failure, which include fluid distention of the belly, pulsation of the jugular veins in the neck when the dog is sitting or standing and heavy breathing.

DIAGNOSIS
Two types of blood tests are used to establish the diagnosis:
Microfilaria screen. These are screening tests to detect the baby worms (microfilaria) circulating in the bloodstream (produced by the adult heartworms living in the pulmonary arteries). This test can either be a filter test, or a “Knott’s test (spinning down a sample of blood mixed with formalin and looking for the microfilaria with a microscope).
Heartworm serology. This test checks for proteins in the bloodstream of the dog that are produced by the heartworms. These tests are very sensitive and accurate.
Once diagnosed, to stage the heartworm disease the veterinarian may want to do further blood work, X-rays, ultrasound, or ECG (electrocardiogram). It is important to know how bad the infestation is as well as what complications the dog may have during treatment.

TREATMENT:
The adult heartworms must be killed. There are two main agents administered by veterinarians for adulticide treatment: (Immiticide): This drug is given by injection deep into the muscles of the back as either a two-day series (one injection per day, two consecutive days) or, in patients with more severe disease, as a split protocol (one injection, followed one month later by two consecutive injections one day apart for a total of three injections). Immiticide is currently the most commonly used type of treatment.
Killing of the baby worms (microfilaricide). This is done only in dogs with a positive filarial test. It is given one month after the adulticide treatment is completed. Interceptor is a monthly heartworm preventative, effective at killing the microfilaria. Once a dog has been treated there are very strict home care responsibilities such as keeping the dog from running and playing.

PREVENTATIVE CARE:
Prevention of heartworms disease is easy and should be undertaken in all dogs. Giving your pet a flavor tab once a month year round will keep them safe from heartworm disease.
Please come into VCA Highlands Animal Hospital and get to know our doctors and staff. We love helping you take care of your precious pets.
VCA Highlands Animal Hospital, 3451 Elkhorn Blvd. North Highlands, CA 95660, 916-332-2845