TERRI JOHNSON, AAHA PRACTICE ACCREDITATION
Heartworms—can you imagine actually having worms in your heart?
Not a pleasant thought, but that’s exactly where they are.
The technical term for heartworm disease is dirofilariasis. Your veterinarian is checking for the presence of an
antigen that would be in your dog’s bloodstream as a result of this disease when
he/she does a yearly heartworm blood test.
disease is one of the major health problems affecting dogs in the United States,
and it is now being found in cats. The disease develops when a pet becomes
infected with parasites transmitted through the bite of an infected mosquito.
Dogs may be infected by a few or up to several hundred heartworms. Cats are
similarly infected, although usually by only a few worms.
Having heartworm disease can lead to other medical problems beyond
the heart, including lung, kidney and liver disease. The worms are found in the
right side of the heart and in the major vessels that bring blood to and from
the right chambers of the heart. The worms cause inflammation of the blood
vessels and block blood flow. This can lead to pulmonary thrombosis (clots in
the lungs) and heart failure. If left untreated, heartworm disease can result
in liver and/or kidney failure. And heartworm disease can result in death due
to one or a combination of these problems.
AAHA-accredited practices take a team approach to your pet’s
health, and providing important tests to determine and prevent diseases is just
one of the things they do to help your pet be healthy. It’s
easier, better for your pet and less expensive to prevent diseases than it is
to treat them.
Heartworm is a preventable disease for both dogs and cats but, prevention begins with you. With
the right tests and preventive medications, your AAHA-accredited health care
team can work with you to prevent many kinds of parasites. The practice staff members have
access to a full array of appropriate tests to help
prevent diseases and parasites from affecting your pet’s health.
Heartworm disease is evident in species other than dogs and cats. Ferrets
can also be infected. Pets that spend a lot of time outdoors are at a greater
risk for infection, especially in areas with a lot of mosquitoes. But even
indoor pets can become infected by heartworms because infected mosquitoes can get
inside your home. While heartworm disease primarily used to be a problem in the
south and humid regions of the United States, it’s now found throughout the
you travel with your pets, you may go into areas where there’s an increased
risk of infection. Preventive medications are really important because heartworms
breed in unprotected animals. Dogs that are not on heartworm preventive
medications and certain wildlife, such as coyotes, wolves and foxes, can be
carriers of heartworms.
best way for easy, safe prevention of heartworm infection is to administer a year-round
heartworm preventive prescribed by your veterinarian.
The American Heartworm Society and the Companion Animal Parasite Council recommend that all pets receive year-round heartworm protection so that pets are protected every month. It is critical that doses not be skipped or intervals between doses be extended because this results in an unprotected time during which animals may be exposed to heartworm larvae. Pets should also have annual heartworm testing by a veterinarian prior to prescribing a heartworm medication.
female heartworms can live in an infected dog or other hosts and release their
young, called microfilaria, into the bloodstream of that host. Mosquitoes are
infected by the microfilaria when they bite an infected animal. In 10 to 14
days, the microfilaria mature to the infective larval stage within the
mosquito. When the mosquito bites another dog, cat or susceptible animal, the
infective larvae exit the mosquito’s mouth and are deposited onto the surface
of the animal’s skin. The infective larvae can then enter the new host through
the fresh bite wound.
takes about 6 months for the infective larvae to mature into adult heartworms
in the new host. Mature, heartworms can live 5 to 7 years. Because they live so
long, each mosquito season has the potential of an increasing number of infestations
and increased infections in our pets.
Per guidelines from the American Heartworm Society, all dogs should
be tested for heartworms annually and before
starting a preventive program. Giving preventives to dogs that already have
adult heartworm infection can be harmful or even fatal because adult heartworms
produce millions of microscopic “baby” heartworms in the bloodstream.
a monthly heartworm preventive to a dog with circulating microfilaria could
cause the sudden death of the microfilaria, triggering a shock-type reaction.
Even if your dog does not have this type of reaction, heartworm preventives do
not kill the adult heartworms (although they may shorten the worms’ lives). This
means an infected dog will remain infected with adult heartworms.
both adult and baby heartworms must be eradicated to actually cure a dog. As
long as the dog remains infected, heartworm disease will progress and damage organs,
increasing the possibility of life-threatening problems. Giving heartworm
preventives to heartworm-positive dogs can mislead you into thinking that everything
is all right, while the heartworm disease is actually worsening.
Heartworm disease is more challenging to detect in cats than in
dogs. The preferred method for screening cats includes both an antigen and an
antibody test. Cats should be tested prior to starting a preventive program and
then annually thereafter. There is no approved treatment for heartworm
infection in cats, so prevention is very important.
detection and treatment are always best. With annual testing, you’ll know your
pet is heartworm-free.
Heartworm Life Cycle used with permission from the American Heartworm Society. For more information, please visit www.heartwormsociety.org.
Revised and updated Dec. 18, 2012.
This article originally appeared in PetsMatter July / August, published by the American Animal Hospital Association. Copyright © 2012 AAHA. Find out more.