Glenway Animal Hospital

6272 Glenway Ave
Cincinnati, OH 45211






Heartworm Prevention Awareness

 Heartworm disease is a dangerous condition that can affect many animals including:  dogs, cats, ferrets, cattle and horses.  Heartworm disease is very dangerous and potentially fatal.  The good news is that it is preventable.  Although prevention medication is available, heartworm still occur in our area due to lack of knowledge and compliance by pet owners.  As the map below indicates,an average of 1-5 cases of heartworm are diagnosed per clinic in our area each year.

Heartworm map - Glenway Animal Hospital - Cincinnati,Ohio   

Heartworms are a parasite, which are carried from host to host by mosquitos.  The mosquito picks up the microfilarie, a baby heartworm, from the infected host.  The heartworm continues to develop within the mosquito and the L3 larvae is deposited on the new host's skin when the mosquito lands for its next meal.  Multiple heartworms then begin to grow under the host animals skin until they reach the adult stage and migrate to the right side of the heart and the pulmonary arteries.  The adult heartworms then settle and begin to mate.  The female heartworms give birth to live microfilariae, which are then carried throughout the bloodstream to be picked up by the next mosquito and transferred to a new host.  Microfilariae can live for approximately 2 weeks, but the adult heartworms can live, grow and reproduce for 5-7 years. 

heartworm life cycle - Glenway Animal Hospital - Cincinnati,Ohio


Heartworm - Glenway Animal Hospital - Cincinnati,Ohio

Image of a deceased dogs heart.  Dog had heartworm disease.


Dogs symptoms range in severity depending on the number of heartworms present.  If a dog only has a few heartworms, there may not be any clinical symptoms, but as the heartworms progress to heart disease clinical symptoms began to emerge, such as:

fatigue with exercise, difficulty breathing, cough, pot-bellied appearance, lethargy, arrythmia

The heartwoms cause inflammation in the arteries as the body's immune system attacks them.  The abundance of heartworms block the arteries causing the heart to work harder to pump the blood through the clogged arteries.  Fluid accumulates in the lungs and chest cavity.  The heart muscle thickens due to the additional strain and an arrythmia may develop.

Heartworms can be diagnosed with a simple blood test and chest x-ray.  Heartworms are difficult to treat because killing them can be dangerous to the dog.  If too many heartworms or microfilariae are extinguished at once, the dog may have an embolism.  This is also the reason it is important to do a blood test before starting and continuing heartworm prevention medication.

Cats are not natural hosts for heartworm, but they are susceptible.  Even one adult heartworm can be deadly for a cat, because feline blood vessels are so small.  While canine heartworm disease is mostly cause by the obstruction of blood flow due to the worms, feline heartworm disease is caused by the inflammatory reaction due to the cat's immune system reacting to the migrating adult larvae.  Cats with heartworms develop symptoms mimicking lung disease.  These symptoms include:


Because of the symptoms and difficulty in a reliable feline heartworm test, heartworm in cats is often misdiagnosed as asthma.