Fischer Animal Hospital

Small Animal Veterinary Clinic
(636) 240 - 7646

 

FAQ: 

Heartworms

Image description

"What are heartworms?"

Heartworms are a deadly blood-borne parasite spread by mosquitoes.  They infect susceptible mammals including dogs, cats, wolves, foxes, ferrets, and (rarely) humans.  They are found in the arteries of the lungs and right side of the heart.

It is recommended by our veterinarians, and the American Heartworm Society, that preventative is given year round. Missouri weather is variable and most heartworm preventatives also help with intestinal parasites - which can be infective year round.

Image description

"What is the life cycle of heartworms?"

Image description

The following excerpt is from the American Heartworm Society: www.heartwormsociety.org:

How Heartworm Happens: The Life Cycle

First, adult female heartworms release their young, calledmicrofilariae, into an animal's bloodstream. Then, mosquitoes become infected with microfilariae while taking blood meal from the infected animal. During the next 10 to 14 days, the microfilariae mature to the infective larval stage within the mosquito. After that, the mosquito bites another dog, cat or other susceptible animal, and the infective larvae enter through the bite wound. It then takes a little over 6 months for the infective larvae to mature into adult worms. In dogs, the worms may live for up to 7 years. Microfilariae cannot mature into adult heartworms without first passing through a mosquito.


Source: http://www.heartwormsociety.org/pet-owner-resources/heartworm.html

"Why does my dog need to be tested for heartworms before starting preventative?"

Heartworm preventatives will kill off the microfilaria circulating through your pet's tissue and/or bloodstream.  When there are large amounts of microfilaria circulating, and many die off at one time, a systemic reaction may take place resulting in anaphylactic shock.  This is why heartworm preventatives are prescription products.  Yearly heartworm tests are required, even when preventative is given year round, because no product is 100% guaranteed.  Testing pets allows us to monitor for drug resistance and incidents of product failure.

"Help! I missed a dose of heartworm preventative!"

When you miss a dose you need to mark the calendar (when it was due) and start your monthly schedule over.  Call your veterinarian and ask them to send a reminder in 6 to 9 months to retest for heartworms.  It takes 6 months for the microfilaria to mature to an adult which will produce more microfilaria - this is what is detected in the blood test.   If you missed several doses in a row, call your veterinarian before giving preventative.