Heartworm disease FAQ

How do Heartworms damage pets?

Infected mosquitoes inject tiny immature worms called microfilariae into our pets. The microfilariae swim through the blood vessels and create turbulence that damages blood cells and vessel walls. The damage causes clotting, scarring, and narrowing of blood vessels. The blood pressure goes up. As the pressure goes up, the heart pumps harder to get the blood through the vessels. This causes the heart to fail. The more worms damaging the blood vessels, the faster the damage occurs. Heartworm s can live from 3-5 years. That’s a lot of damage.

The pet’s symptoms are caused because Heartworm s prefer to live in the heart and main pulmonary artery in the lungs. If the pulmonary artery or smaller arteries weaken, Heartworm s enter the air passages and can be coughed up. Sometimes a pet that’s coughing up worms will look like it’s vomiting, but the worms are coming from the lungs. Pets with advanced Heartworm disease have signs of heart failure including frequent coughing, tiring easily, abdominal swelling, decreased appetite, weight loss, fainting, and blood clotting problems.

What‘s the scientific name for Heartworms?

Dirofilaria immitis.

What time of year do I need to give Heartworm disease prevention medication?

The American Heartworm Society recommends that most pets remain on Heartworm protection year round because when the medication isn’t given consistently some pets are developing Heartworm disease. The Society feels it is easier for most pet owners to remember to give a medication every single month than to give it a few months of the year. Discuss what would be best for your pet with your veterinarian.

Can one dog give another dog Heartworms?

Heartworm infections do not go directly from one dog to another. However, if a dog has Heartworm infection, and a mosquito bites that dog, the mosquito can pick up the Heartworm microfilariae, which it can transmit to other pets.

Why do I need a prescription before starting Heartworm disease prevention medication?

Federal law requires a prescription for Heartworm disease prevention medication because giving this medication to pets that already have Heartworm infections can cause serious illness or death. For your pet’s safety, the veterinarian needs to assess Heartworm status before prescribing medication.

Do some breeds, especially collies, have a problem with Heartworm disease prevention medication?

I missed two months of Heartworm disease prevention medication. Now what?

It is usually best to resume the medication and have the dog tested in 7 months. Wait 7 months to test for Heartworm s because it takes that long for the worms to mature and produce the antigens that these tests measure. The likelihood that your pet was infected during the medication lapse depends on the time of year and the mosquito concentration. The American Heartworm Society recommends continuing monthly medication through the off-season in cooler climates if Heartworm disease prevention medication was missed for longer than 10 weeks during a period of mosquito activity.

Why do dogs need blood tests before starting Heartworm disease prevention medication?

Before starting Heartworm prevention, veterinarians test to make sure the pet doesn’t already have a Heartworm infection. Giving Heartworm disease prevention medications to pets that already have infections can cause severe illness, or death.

Pets less than 7 months old can begin Heartworm prevention without testing but the vet may recommend testing 4-7 months after starting the medication. This is because it takes 6-7 months after being infected for microfilariae to mature to the point they produce a positive test.

I live in Nebraska. How long should my dog be on Heartworm disease prevention medication?

Your veterinarian will advise you, but in the cold-wintered Midwest , Heartworm disease prevention medication is generally used June through November. If you travel to warm states in the winter with your pet, year-round medication may be best.

After a mosquito bites a pet and injects Heartworms, how long does it take before the blood test is positive?

It takes 7 months for the Heartworm microfilariae to mature so that an infection is detected and the test is positive.

If Heartworm prevention medications are combined with medicines that kill intestinal worms, could the combination be so strong that it harms my pet?

Heartworm prevention medications have been tested and confirmed safe by the FDA. To make a product that prevents Heartworm disease and kills intestinal parasites (such as hookworms, roundworms, or whipworms), two different medications are combined. The two medications are safe to use together. Your pet is not being exposed to an abnormally high concentration of either medication in order to prevent Heartworm disease and intestinal parasite disease.

Can my pet be allergic to chewable Heartworm disease prevention medication?

Yes. Pets can be allergic to medications for 2 reasons. First, they may be allergic to the medication itself, just like humans can be to penicillin. Second, they can be allergic to flavoring agents, such as beef, pork, corn, wheat, milk products, soy, brewers yeast, etc. For example, Interceptor has soy, pork, and milk (lactose). If a pet has allergies to these, consider switching to an unflavored product, or to a topical such as Revolution.

Do some pets hide their Heartworm disease prevention pills under the sofa?

Yes. Some pets, even those belong to veterinarians, spit out their medications under the sofa. When giving an oral medication, use something moist and tasty to get the pet’s saliva flowing. For example, offer a bit of cheese, liver sausage, or hamburger. Try following these steps:

• Offer a treat.
• Offer the medication wrapped in treat. Let the pet see you have another larger treat waiting.
• Offer the largest treat.
• Provide water.
• Examine the mouth to make sure it’s empty.

Do some pets pass chewable Heartworm disease prevention medications right through the digestive tract and out the other end without digesting it?

Yes. Some dogs pass entire Heartworm tablets. This is more likely to happen if a pet is “pilled” rather than encouraged to chew the medication. “Pilling” is opening the pet’s mouth and placing the medication into the back of the throat where it is swallowed. Pilling is useful if the medication tastes bad and we want the pet to accept it; but even then, the medication should be wrapped in something delicious—cream cheese, hotdog, honey…

If giving a chewable medication, don’t encourage the pet to swallow it. Encourage the pet to chew it. If your pet isn’t chewing the medication, there are 3 options:

• switch to a non-chewable form;
• have the pharmacy compound a chewable medication for you that the pet will chew; or
• switch to a topical Heartworm disease prevention product, such as Revolution.

Can I switch my pets from one Heartworm disease prevention medication to another?

Yes, pets can switch from one Heartworm med to another

• with their veterinarian’s advice, and
• following a negative Heartworm test.

Why would I want to switch my pet’s medication? Let’s say a pet is on an ivermectin preventative (Heartgard, Heartgard Plus, Iverhart Plus) and has trouble with whipworms; this pet may be better off with Interceptor, which kills whipworms. Or, a pet may be on Interceptor and have trouble with hookworms or roundworms. Although Interceptor has some activity against hookworms and roundworms, if the pet has been on it and has these worms, it may be better off with an ivermectin preventative, such as Heartgard Plus, or Iverhart Plus.

If my dog has Heartworms, should it get a Heartworm disease prevention medication?

Perhaps. See your veterinarian who will assess your pet’s heart and lungs and decide on therapy. Your veterinarian may advise a treatment that kills adult Heartworm s so that your pet’s heart and lungs can return to normal. Or, your veterinarian may advise using a Heartworm disease prevention medication continuously for 2 years to kill microfilariae and allow the adult worms to die gradually.

It can be especially dangerous to give a pet with a large number of Heartworm s Interceptor because it immediately kills Heartworm s. It’s the pet’s reaction to a large number of dying Heartworm s that can be fatal. Heartgard provides a slower, safer kill of adult worms, but is not FDA-approved for use in Heartworm -positive dogs. Revolution is approved for use in Heartworm -positive dogs. Your veterinarian will decide which is the best treatment.

Compare different Heartworm medications here.

The articles here were answered by a variety of pharmacists and veterinarians   Date Category Topic 02/20/08  Other  SIGNS AND SYMPTOMS OF HEARTWORMS 02/19/08  Heartworm Medicine  HEART WORM PREVENTION 02/12/08  Other  HARD TO EXPLAIN... 02/11/08  Cough  COUGHING AND WORMS 02/11/08  Allergy  HEART GARD AND TRI-HEART 02/10/08  Flea & Tick  MIXING OF MEDS 02/10/08  Vaccines  MEDICATIONS 02/07/08  Cough  COUGH WITH WHITE MUCIS 02/03/08  Heartworm Medicine  COLLIE HEARTWORM MEDICATION 02/01/08  Other  NEW PUPPY 01/27/08  Heartworm Medicine  HEARTWORM MEDICINE 01/21/08  Heartworm Medicine  ONLINE PURCHASE 01/21/08  Digestive Care  REGURGITATION 01/20/08  Flea & Tick  GREAT DANES 01/19/08  Other  WEIGTH LOSS/ALLERY/ANXITY 1 2 3 4 5 »»

 

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