All Pets Veterinary Clinic
HEARTWORMS & HEARTWORM PREVENTATIVES
Heartworms are a parasite of the circulatory system. Dogs and cats can obtain
heartworms from mosquitoes. Immature heartworms are picked up from infected
dogs and cats when a mosquito takes a bloodmeal. The mosquito can then transmit
immature heartworms to another animal. The immature heartworm larva develop into
large adult worms that live within the major blood vessels of the heart and lungs.
The adult worms can then cause slowly progressive, fatal disease. Heartworms
have been demonstrated in almost all 50 states and Illinois is no exception. Because
of the potentially devestating effects of untreated heartworm disease, we recommend
--Start heartworm preventative for puppies at age 7-8 weeks
Rationale: Even puppies can get heartworms. Starting preventative
early not only helps protect your pet from heartworms but aids in
protection against many common intestinal parasites.
--Year round heartworm preventative
Rationale: Our winters are not consistently cold enough to
guarantee against mosquito activity. Warmer falls and early
springs can lead to mosquitoes and mosquitoes are the casue of
--Year round heartworm preventative for all outdoor cats
Rationale: Heartworms can and do infect cats. Infections can be
more severe (sudden death is one of the most common signs) in
cats and there are no approved treatments available. Thus,
prevention of heartworm disease is critical for cats.
--Consideration of year round heartworm preventative for indoor cats
Rationale: Mosquitoes can and do come inside. Given the difficulties
in diagnosis and treatment of feline heartworm disease, prevention
is the best option.
--Annual heartworm testing
Rationale: While heartworm preventatives are very effective there is
always a chance for product failure. Since heartworm disease can
be a slow, silent process in the early stages, it is possible to have
disease without knowing. Early detection allows for treatment to
begin earlier and will likely result in fewer complications. Early
detection can only be accomplished by screening at regular intervals.
If there have been gaps/delays in heartworm protection annual retesting
is recommended. In 2005, the American Heartworm Society removed their
recommendation for every other year testing of animals that are on preventative
year round. They now recommend once a year testing for all dogs regardless
of frequency of heartworm preventative administration.
These recommendations are consistent with the recommendations made
by the Amercian Heartworm Society.
There are several different medications available for heartworms. The most
common are Heartgard, Interceptor, Sentinel, and Revolution. Each
of these medications protects against heartworms. In addition, many will kill
other intestinal (roundworms, hookworms, whipworms) or external parasites (fleas
and ticks). The following chart describes which preventatives cover for
what parasites. For additional information on these medications, please don't
hesitate to contact us.
Background & Buttons by AAA Backgrounds
Karen Blakeley, DVM, MPH
Last update: 28 June 2014