Give The Gift Of A Parasite-Free Holiday This Season!


When budgeting for all the holiday spending this year, one of the temptations may be to not pick up a refill of your pet’s heartworm preventative this winter. You may be thinking to yourself, “Does my pet really need heartworm preventative in the winter in Maryland?”

The answer to that is a resounding yes!

It is important to protect pets from heartworm disease all year. Heartworms are parasites that live in the heart and major blood vessels. They are transmitted to your pet by mosquitoes, and one bite from one mosquito is all that it takes for a pet to get heartworm disease. Dogs are the primary host of heartworms, but several other species including cats, ferrets and other mammals have been shown to get heartworm disease as well. Unfortunately, heartworms are present in all 50 states, so pets in all states must be protected.

While mosquitoes are less common in the colder months, they are occasionally still present. Mosquitoes are known to be able to adapt to colder environments and can remain alive long into the winter by finding warmer microhabitats, including inside of your house. This means that it is almost impossible to know the first day mosquitos will be present, or when the last mosquito will die. If heartworm preventatives are started too late, or if they are ended too soon, your pet could be at risk from growing these worms inside their bloodstream.

Pets with heartworms may not show signs of disease right away. However, the longer the heartworms are present, the worse the signs become. Signs may range from a mild cough to lethargy, exercise intolerance, and more. The worst cases can have pets develop severe disease such as heart failure and blood clots, which are life-threatening. These severe infections are difficult and expensive to treat, and many pets are not able to survive. This is why it is so important to prevent disease before it happens.

There are several types of heartworm preventatives available for pets, including oral preventatives such as Heartgard or Simparica Trio (which also covers fleas and ticks), topical preventatives such as Advantage Multi or Revolution, or injectable preventatives such as Proheart 12, an injectable product that protects your pet from heartworms for a full year. Preventatives have been proven to be safe, affordable and successful in protecting your pet against heartworm disease. However, if a pet has been off of preventatives, acquired heartworm disease and then preventatives are restarted, your pet is at risk of having the worms die so quickly that they can cause their host (your pet) to go into shock and pass away. This is why we should never stop preventatives, even in the cooler months.

Many preventatives also help to treat intestinal parasites, including roundworms, whipworms and hookworms. These parasites can be picked up by pets any time of the year, and can spread to humans, causing disease in the entire family.

Because of the year-round risk of heartworm disease, as well as the benefits of intestinal parasite protection, it is important to keep your pets on heartworm preventatives year-round. Talk to your veterinarian about which option best fits your pet’s lifestyle, medical history and budget.

If you have any questions about parasite prevention, contact VCA Calvert Veterinary Center at 410-360-7297 or online at


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