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Heartworm Disease


What is Heartworm Disease and how does an animal get infected?

Heartworm Disease is transmitted when a mosquito carrying microscopic heartworm larvae bite your pet’s skin, allowing the larvae to enter through the bite wound and into your pet’s blood. Over several months, the worms migrate to the vital blood vessels of the heart and lungs where they grow to be the size of spaghetti and cause considerable damage.

How can I tell if my pet has Heartworm Disease?

Unfortunately, there are no early signs of Heartworm infection. By the time that you notice any symptoms (coughing, difficulty breathing, loss of energy) your pet may already have severe damage to the heart and lungs and may lead to heart failure.

Fortunately, your pet can be tested for Heartworm Disease with a simple blood test. If the test is negative, your pet can be started on a once-a-month heartworm preventative medication. This medication will kill any heartworm larvae that may have entered your pet’s bloodstream within the past month, and prevent future infection.

If your pet tests positive for Heartworm Disease, the treatment takes several months during which time your pet is given a series of injections to kill the worms. Your pet’s activity will need to be restricted during treatment because the killing of the heartworms can cause severe side effects that are exacerbated by exercise. It is critical that your pet be kept quiet and inactive during the entire treatment period (8-12 weeks).

Is it true that we don’t have a problem with Heartworm Disease in San Diego County?

No! While we see less Heartworm Disease here in San Diego than in some areas of the country, we see positive cases on a regular basis right here in Lemon Grove. San Diego County has seen several hundred documented cases of Heartworm Disease in the past decade. There are a number of factors that contribute to your pets’ risk of becoming infected with Heartworm Disease including travel, lifestyle, exposure to water sources, and the amount of time spent outdoors. Since California is composed of many different microclimates, there are opportunities for traveling animals to become infected. Therefore, it is critical that owners who choose to travel, camp, and hike with their pet are aware of this increased risk. We even see Heartworm Disease in dogs that live strictly indoors. Mosquitoes are not confined to the outdoors!

Do cats get Heartworm Disease?

Yes, but much less so. Although dogs have often been the focus of heartworm prevention, cats are also susceptible. Clinical signs of feline Heartworm Disease mimic those of chronic respiratory Disease because the worms tend to mainly target the lungs of cats. Having your cat tested for Heartworm Disease and administering a monthly preventative is the best way to prevent infection.

Does San Diego Pet Hospital have a Heartworm policy?

Yes, we do. Based on the latest information available, we recommend that all dogs be tested for Heartworm Disease annually, and receive a monthly heartworm preventative all year around. The blood test can be run in-house, takes only ten minutes, and can be done while you wait.

Annual testing is important even in animals receiving a monthly preventative, because of the emergence of new strains of Heartworms that are resistant to the preventative medications. Also, some animals have been known to discard their pills behind the couch or outdoors when their owners aren’t looking!

Consistency is the key to keeping your pet heartworm free. So, if you miss more than two consecutive months of prevention, we recommend a retest of your pet’s blood to make sure that they have not been infected while unprotected.

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San Diego Pet Hospital


7368 Broadway Lemon Grove, CA 91945

Clinic Hours

Mon-Fri: 8 am -6 pm
Sat 8am-5 pm closed Sunday