Heartworm Life Cycle
heartworm life cycle begins in the mosquito. Only worms that
mature inside a mosquito can grow inside a dog. The mosquito then
passes larvae into dogs that can grow up to 12 to 14 inches and live
for years inside the dog."
The heartworm life cycle starts inside the mosquito. When a
mosquito bites an infected dog, they absorb microfilariea (young
worms) into the mosquito. The microfilarieae start to develop
inside the mosquito. Development continues for 10 days to 14
days. These macrofilariea continue to grow until they become
what is known as larvae. Larvae is another word for an
The larvae get passed to a dog when the mosquito bites the dog.
During the bite the larvae transfer from the mosquito into
the dog and enter through the bite made by the mosquito.
Over a 6 to 7 month period, the heartworms will grow up to 12 inches
and move through the blood into the heart arteries and lung.
If male and female heartworms are present, they will produce
more macrofilariae. The macrofilariea cannot develop into an
adult heartworm without first maturing inside a mosquito.
Picture Heartworm Life
Heartworm Life Span
A heartworm can live inside a dog for 5 to 7 years. Given
this long lifespan, a dog can be bitten by more than 1 mosquito over
several different incidents and be passed heartworms each time.
Unfortunately, blood tests, the best way to determine if a
dog has heartworm, cannot detect the presence of worms if they have
been inside the dog less than 6 to 7 months.
Canine Heartworm Symptoms
The initial signs for heartworm in dogs include coughing, weight loss,
decreased appetite and a reluctance to exercise.
Symptoms may not appear for months or years.
Many of the symptoms will develop over time and are not easy
to distinguish from other diseases since the canine heartworm symptoms
are general (e.g.; appetite loss is associated with many diseases).
In severe cases dogs can develop liver disease and heart failure.
As the worms grow they can block blood flow that carries
needed oxygen in the body. As the body and lungs become
oxygen deprived, the heart beats harder, possibly resulting in heart
Severe cases of canine heartworm result in a condition called caval
syndrome. Associated symptoms include difficulty breathing, pale gums,
darkened urine and a dog that is very reluctant to move.
Canine Heartworm Treatment
Treatment for heartworm involves an adulticide given by injection into
the dog followed by several weeks of rest (4 to 6 weeks).
After treatment a preventative is used to avoid future
problems. Treatment is highly effective. In severe
cases surgery is used to physically remove the worms.
Canine Heartworm Prevention
Veterinarians where mosquitoes live will recommend that dogs take a
heartworm preventative. Most have the added benefit of also
helping dogs either avoid other worms (Heartgard Plus, Interceptor).
Both are given orally via a flavored chewable 1x a month.
Other products such as Sentinel help to avoid fleas.
Revolution heartworm protection also protects against fleas.
There is also 1x every 6 month injection that is
available called ProHeart 6, however it only protects against
A good source for discount heartworm medicine is
References for Heartworm Life Cycle:
American Heartworm Society