Parasites are gross and uncomfortable, but more than that, your
pet’s parasites can cause them physical harm. Heartworm
infections, which are spread by mosquitoes, can morph over
several months into heartworm disease. If untreated, this
disease can have an extremely severe impact on a dog’s health
and may potentially be fatal. As you think about how you can
handle and prevent this disease, keep these five facts in mind:
1. Prevention is good for your dog…and all dogs
There’s a lot of conversation about the importance of
prevention when it comes to tackling the problem of heartworms.
The monthly dosage of a heartworm preventative
works by attacking the larval heartworms that dogs get after
mosquito bites. This stops the infection in its tracks for your
dog. But this also means that mosquitoes that bite your dog
cannot get the larva and pass them on to other dogs. Using the
preventative treatment has a ripple effect: Not only will you
help your dog, but you’ll lessen the spread of the disease, and
help prevent other nearby dogs from being exposed to the
2. Prevention tops treatment
This probably won’t be a surprise, but as with most things in
life, prevention is easier than treatment. Where treatment is
expensive, uncomfortable, and lengthy, preventative treatments
are generally just a monthly chewable tablet. Giving a dog the
preventative drug is easy. The hardest part is probably
remembering the monthly task and making the initial appointment
at the vet to get a prescription. Also, it helps to have some
understanding of what you can expect from heartworm medication for dogs.
3. Can I catch it from my dog?
No. Heartworms spread through mosquito bites. And, if you have
two dogs, and one has heartworm disease, the second dog will
not catch it from the first. This is true even if both dogs are
bit by the same mosquito bite in short succession since the
heartworm larvae need an incubation period within the mosquito
before it can be transmitted to another dog. Note that while
humans can get heartworms, it’s very, very rare.
4. From Arizona to Alaska
Since mosquito bites are so vital to the spread of heartworm
infections, the disease is most likely to spread in hot, humid
states, which are comfortable environments for mosquitoes. That
said, heartworms have been detected in states as dry as Arizona
and as chilly as Alaska. Bottom line: All dogs should be given
preventive treatment, regardless of where they live. This will
also help if you take your dog on a road trip, and wind up in a
state where mosquitoes are more likely to thrive.
5. Growing and growing and growing
It’s the female heartworms that get long, and those female
heartworms get quite long, growing up to a foot in length. The
picture that snaking around in your dog’s heart and lungs, and
you get a sense of why heartworm have such a negative impact on
a dog’s health. The male heartworms are shorter, reaching about
four to six inches.
Don't Let Heartworm Get Your Pet's Heart
Heartworms, or Dirofilaria immitis, are worm-like
parasites that can reach up to a foot in length. While many
warm-blooded mammals, including ferrets and cats, can get
heartworms, dogs are the main target of heartworms. Heartworms
are transmitted by mosquitoes, who leave a larval form of them
behind after bites. Adult heartworms travel to the pet's lungs.
If untreated, these heartworms cause extreme health issues,
which may lead to death.
When a mosquito bites a dog with a heartworm, it ingests the
microfilaria, or baby heartworms, along with the dog’s blood.
These microfilariae mature over the course of about a week
within the mosquito, transforming into a larval form of the
heartworm. After the larval form is achieved, the mosquito
passes it along to other dogs that it bites.
Without the intermediary step of the mosquito, heartworm
disease would not spread. Because of the parasite’s reliance on
mosquitoes, the disease spreads particularly rapidly during the
summertime, when temperatures are warmer.
The best way to handle heartworms is to give your dog a monthly
preventative treatment like Tri-Heart Plus. The American
Heartworm Society recommends that preventatives be given
year-round. This treatment helps stop your dog from getting
heartworm disease, but it also helps stop other dogs from
The preventative treatments do not prevent mosquitoes from
biting and transmitting the heartworms; rather, the medications
destroy the microfilariae within the dog's bloodstream.
In addition to year-round preventatives, dogs should be given
an annual heartworm test, which serves to double-check that the
preventatives are working and that no doses have been missed.
The heartworm test actually checks to see if your dog got
heartworm disease the previous year. The tests cannot detect
heartworms until they have reached maturity and given birth to
During a heartworm test, vets will take a sample of the dog’s
blood and look for either sign of microfilaria or for antigens
that the heartworms give off. A heartworm test is also
generally required before starting your dog on a preventative
or switching preventative medications.
In the early stages of heartworm disease, there are virtually
no symptoms. Heartworm disease has four stages, and as it
progresses, the symptoms become more noticeable and disruptive.
Some signs of the disease are a cough, a reluctance to
exercise, and lethargy. As the disease progresses, dogs may
start to bleed from their lungs.
During treatment of heartworm disease, vets will need to
destroy the microfilaria, as well as the adult heartworms. Two
different courses of treatment are necessary for the different
stages of heartworms. For the young heartworm, ivermectin-based
preventatives can be given. Adult heartworms will require
treatment with an adulticide, to kill them off. Since killing
off the adult heartworm is a traumatic experience for a dog, a
month-long rest period is required after the first treatment,
which is an injection of medication into the dog, usually given
in a hospital. During the rest period, it is very important for
dogs to abstain from all activity. Although trying and
expensive, treatment is generally successful.
How to Prevent Heartworm in
Heartworm Tests Explained
This information is for informational purposes only and
is not meant as a substitute for the professional advice of, or
diagnosis, or treatment by, your veterinarian with respect to
your pet. It has, however, been verified by a licensed
veterinarian for accuracy.