Heartworms: What’s the Deal?

By:  Dr. Hilary Slaven

I saw two mosquitoes in my house last night as I was vegging out in front of the TV.

For the record, it is the middle of March in central Indiana.  What the heck.

“Yikes!”, I said.  And (naturally) I thought, “It’s heartworm transmission time.”mosquito03

(Yes, I am a veterinarian.)

All of us vets have seen and treated dogs that have had heartworm disease, watched animals suffer and folks have to spend a lot of money to treat it and I think that I can speak for all of us when we say:

We hate it.


Here’s how it works.

As soon as the days start to warm, the mosquitoes start feeding and laying eggs.  We know that female mosquitoes can over winter in homes, sheds, holes in trees, etc.  (See Purdue University’s Mosquito Information Page).

These mosquitoes take blood meals from mammals, including coyotes, dogs and cats.  They act as carriers for many diseases, including heartworms.

Mosquitoes carry the heartworm parasite from infected animals to uninfected animals.  They carry the super-small larvae form of the worm (sort of a ‘baby’ heartworm).  Infected animals could be dogs, cats, coyotes, or other wild animals.

(Here is a great three minute video on the life cycle of heartworms)

Heartworms live as an adult worm 4-12 inches long within blood vessels of mammals.  They lodge inside vessels of the lung and within the heart itself.


Adult worms feed off of nutrition from the blood and start reproducing within the animal.  The female worm produces a smaller larval stage of heartworm that moves throughout the vessels of the body.

Now imagine that a mosquito feeds on this infected animal.  When it takes a blood meal, it also takes in the heartworm larvae.  Then the mosquito moves to another dog, an uninfected furry friend, and takes another meal.  The tiny heartworm larvae then move from the infected mosquito into the bloodstream of the uninfected dog.  Now our furry friend is infected with the larval stage of heartworm.  In 6-8 months’ time, the heart will be full of these worms, causing inflammation and blockage of the vessels, death of lung tissue, and eventually death of the animal.

heartworm 2

Just take a look at this worm.  It’s one nasty bugger.

See what I mean?  I hate heartworms.

The good news is that dogs that take heartworm prevention medications stop the heartworm larvae in his tracks.  It kills the larvae before it develops into an adult worm.  Because adults develop 40-70 days after the dog is infected, that gives us a two month window in which to stop the larvae before they continue to grow into adults.  This is important because heartworm prevention products don’t kill adult worms.  Once they develop, a new protocol for treatment is necessary.

The complex life cycle of this worm makes it difficult to treat.  There is no drug available that kills both heartworm larvae and adult worms.  Only one drug kills adult heartworms; it is a parasiticide that has to be injected into the muscle.  It is expensive and it has to be given in a very specific protocol in the clinic, as it can have many potential side effects (including shock).

We treated 18 dogs for heartworm disease in 2014 in the Veedersburg clinic.  This does not include the many dogs out there aren’t tested and their heartworm status is unknown.

Veterinarians recommend a yearly blood test for heartworm disease (it’s a quick, 10 minute test that we run in the clinic) and year-round heartworm prevention.

Prevention comes in a couple of different forms:  a monthly chewable treat or an injection given every 6 months.

The chewable ‘treats’ come in a few different flavors and sizes.  Most of them also deworm for intestinal parasites and some kill fleas for 30 days, too.

Cats can get heartworm infections too!  They can be given a monthly preventive too, just like dogs — often we use a liquid that is applied monthly to the back of the neck.  (The one that we use kills ear mites and intestinal parasites too, it’s great.)  There is a chewable tablet for kitties too.

shih tzu runningOne thing to remember is that all heartworm prevention is prescription only.  However, most folks are surprised at how affordable the products are in the clinic.  Treatment for heartworms is always more expensive than prevention.

Come and see us, we can help find the product that works best for you and your furry friend.

Check out this website for more information about heartworms, it’s a wonderful resource:





Top Parasites in West Central Indiana 2015

By:  Dr. Hilary Slaven

March came in like a lion in west central Indiana.

cat dressed as lion

And not a cute itty bitty lion like this one. I mean snow. Lots of cold cold snow.



        But we are thinking spring here at West Central Veterinary Services!!

                       dog dressed as flower  Warmer temperatures mean… long walks and outdoor fetch with our furry friends.

 Warmer temperatures mean… flip flops and retrievers playing in Lake Hideaway.

 Warmer temperatures mean… tank tops and barn kittens.

 But warmer temperatures does NOT just mean just flowers and sunshine.

(Buzz kill!  I know!)

Warmer temperatures also means our outside pests come back —

Fleas, ticks, mosquitoes…

which are nasty creatures that are not just annoying, but spread disease, like heartworms and Lyme disease, which are highly prevalent here in Indiana and can be deadly.

And on top of that we see other bugs like…

Tapeworms, hookworms, roundworms, whipworms and heartworms …


Roundworms. This was the NICE picture.


Heartworms.  Watch the video about their life cycle.  It is eye-opening.


Hookworm up close and personal


We see these parasites daily in Fountain, Parke and Putnam counties.  Some real data has recently been published online (www.capcvet.org) to show both pet doctors and owners the prevalence of these parasites in our area.  Data maps were compiled based on 2014 numbers collected from local veterinarians.  It also shows state and national data and identifies key areas of the country that are at risk for disease.

The compilation was done by a group called the Companion Animal Parasite Council (CAPC), a national non-profit organization of parasite experts, which has collected data since 2002 in an effort to increase awareness for pet parasites and their disease.  The goal?  to ‘change the way veterinarians and pet owners approach parasite management’ and to encourage the best practices to keep pets parasite free and humans disease-free.

Let’s look at some of these numbers.

In the state of Indiana in 2014, 1 out of every 68 dogs tested positive for heartworm disease.  In Parke County, the prevalence was higher at 1 out of every 28 dogs.  Spread by mosquitoes, one blood meal can infect a dog.  After several months, worms start to

In Fountain County, 1 out of every 16 dogs tested positive for Lyme disease exposure.

In Indiana, 1 out of every 24 dogs tested positive for roundworms.

Check out the prevalence maps to see national, state and county data for parasites.  http://www.capcvet.org/parasite-prevalence-maps.  It really puts into perspective how much disease is out there.

It’s scary to think about all of the parasites out there that can kill your furry friend.  The other thing to think about is that several of these parasites can spread disease to humans, too.  For example, roundworms and hookworms can pass to us and get into our tissues and cause serious disease.  This is a serious thought, given that many of our pets are in the house with us.  The CDC has an excellent website called “Healthy Pets, Healthy People” that outlines diseases spread to people by our animals.  Please check it out.  A must for any informed pet owner.

The good news is that all of the parasites mentioned above are, in many cases, both highly detectable and preventable.  For example, Lyme disease is spread by deer ticks.  Keeping ticks off of our dogs with high-quality tick products and Lyme vaccination can protect our dogs.  Internal gut parasites like roundworms, hookworms, and whipworms can be detected with a microscope long before the worms themselves are shed in the stool.  Heartworms can be detected before a dog shows signs of disease, and can be killed before they grow into adult worms by giving a monthly prescription medication.

We have the tools for battle!  The key is regular visits to your veterinarian, early detection of disease with routine screenings of blood and stool, and giving monthly medications for prevention of disease.  Many wonderful products are available to us this year; monthly chewable pills that kill fleas and heartworms both, tick collars that last for 8 months (and don’t smell bad!), a heartworm prevention injection that lasts for 6 months, monthly heartworm chews that deworm for internal parasites too…we even have a flea and tick prevention chewable tablet that lasts for 3 months.

My advice?  Visit your veterinarian once or twice a year, get a good physical exam for your furry pal, along with a yearly heartworm test and stool sample to screen for disease.  Let them tailor a parasite prevention program for you and your family.

I don’t know about you, but I don’t want my indoor dog to carry any friends with him.  I don’t want him to get sick, and I don’t want my kids or myself to be exposed.

Parasites are everywhere, and we will continue to battle them in 2015.  Please call or make an appointment to ask your questions and to develop a personal plan for you and your pet to stay healthy and disease and parasite-free!