• Blog >
  • April is Heartworm Disease Awareness Month
RSS Feed

April is Heartworm Disease Awareness Month

April is Heartworm Disease Awareness Month

April is National Heartworm Disease Awareness Month. With warmer, wet weather, mosquitoes will soon be out in full force.  Mosquitos are not just a nuisance; they also carry heartworm disease which can be deadly for dogs and cats.

Heartworms are blood parasites that start out as small, microscopic microfilaria in the bloodstream. A mosquito bites an infected dog, cat or wild animal--fox and coyotes can be carriers and act as reservoirs for the disease--ingesting microfilaria. Microfilariae mature inside the mosquito’s gut in about two weeks. The mature larvae are then injected into a new host when the mosquito bites another animal to feed. These larvae grow into adult worms up to a foot long that live within the heart and large blood vessels in the heart and lungs. It takes about seven months for the larvae to grow into adult worms and they can live inside the heart for many years causing serious damage.

Heartworm disease is found in all 50 states, and, while more prevalent in the south, dogs and cats are at risk everywhere, including in Pennsylvania. The good news is, this deadly disease can be easily prevented with a variety of safe oral, topical or injectable medications. And, while mosquitos are seasonal in York county, it is recommended to use preventatives year-round for optimum protection. Many preventatives also protect against intestinal worms like roundworms and hooksworms and some protect against fleas and other parasites.

Periodic testing every one to two years (or if a pet has lapsed on preventative) is also required for dogs using heartworm preventatives. Puppies under six months of age can start preventatives without being tested as there would not have been enough time for worms to mature. Tests for cats are not very accurate, but screening blood tests are available.  Luckily, humans are not affected by heartworm disease.

In the early stages there may be no symptoms. As worms mature and damage the heart and lungs, dogs may develop a cough, exercise intolerance and weight loss. Over time, congestive heart failure may develop. Cats may have coughing or asthma-like attacks, vomiting or sudden collapse/sudden death as a result of heartworm infection.

Monthly preventatives must be given at the same time every month to remain effective. All preventatives work by eliminating larvae. But larvae quickly mature in as little as 51 days into a stage that is not killed by preventatives. So, giving a monthly preventative even two weeks late could lead to heartworm infection. An injectable product called Proheart 12 (dogs only) provides a continuous full year of heartworm protection with a single injection under the skin.

Heartworm disease is easy to prevent, but difficult to treat once the pet is infected. There is no approved treatment for cats who often develop severe lung disease. Cats are not the normal host for heartworms, so even one or two adult worms do significant damage to the cat’s heart and lungs. Dogs can be treated, but the treatment is harsh, lengthy and costly. Dogs must start antibiotic and steroid treatment then undergo a series of deep intramuscular injections with an arsenic-like compound to kill the worms. While this treatment is often successful, it does have risks including pain, allergic reaction and even death, especially in dogs with more advanced disease.

If your pet is on heartworm preventative, please continue to give it as directed to continue protecting your pet. If your pet is not on preventative or has missed doses, please talk to our staff for guidance on restarting preventative or about what options are available for your pets to protect against heartworm disease. Keep pets safe and healthy this spring and summer!

This blog brought to you by the Patton Veterinary Hospital serving Red Lion, York and the surrounding communities.


Find us on the map

Office Hours

Our Regular Schedule


8:00 am-8:00 pm


8:00 am-8:00 pm


8:00 am-8:00 pm


8:00 am-8:00 pm


8:00 am-8:00 pm


8:00 am-2:00 pm




Read What Our Clients Say

    Very nice pet hospital. We were extremely pleased. Impressed by the education they give you as well. Our dog had her teeth cleaned and the nurse spent 10 minutes going over post-op procedures. Also we needed to come back in one week to have sutures looked at and they don't charge you an office visit for that like Leader Heights Animal Hospital would do


    I am extremely happy with the care that my puppy Cody received when he had his recent hip surgery. I highly recommend Patton Veterinary Hospital.

    Allison & Troy W.

    I would absolutely recommend Patton to anyone who has pets. Fabulous service every time by all the staff. Thank you


    The entire staff is courteous, friendly, and helpful. They all seem to have a true love for all pets. They follow-up promptly and we have never had a problem with any of the doctors (Dr. Doug is our primary) or any of the other staff.

    Charles & Sally