Contact Us: (618) 344-7949 | Get Directions | After Hour Emergencies: 618-344-7949

Heartworm disease is caused by an infection of parasitic worms (Dirofilaria immitis) that are transmitted by mosquitoes.  When infected mosquitoes feed on cats and dogs, they inject the heartworm larvae, which then migrate to and live in the right side of the heart and in the blood vessels that supply the lungs with blood. These worms cause inflammation in the blood vessels and lungs, and can lead to heart failure if left untreated  In cats, heartworm disease usually causes an asthma-like condition, but can also cause sudden death.

Unfortunately, heartworm infestations are very common in the Metro-East!  At Horseshoe Lake Animal Hospital, we diagnose over one new case per week.  Some people believe that indoor dogs can’t get heartworms.  This is wrong!  We see many “house dogs” with heartworms. Studies on cats in Illinois showed that half of infected cats lived exclusively indoors.  While heartworm disease in dogs can be treated, the treatment can be expensive and is not without the potential for complications.

 The good news is heartworms can be easily prevented.  There are a number of effective and affordable options for preventing heartworms in dogs and cats.  Most of these preventatives also provide protection against fleas and intestinal parasites.  Any dog over six months of age must be tested for heartworms before starting on heartworm prevention and then re-tested annually.  Heartworm testing is not required before starting cats on preventative.  Our veterinarians would be happy to help you decide which preventative would be the best choice for your pet.  It is important to keep your pet on heartworm prevention all year round.  Unlike many flea preventatives, heartworm preventative is prescription only and cannot be bought over-the-counter. If you think you’re giving your dog preventative and you purchased it anywhere but from a veterinarian – it isn’t heartworm preventative!  

Contact Us

Horseshoe Lake Animal Hospital


5230 Horseshoe Lake Rd. Collinsville, IL 62234

New Business Hours

Mon-Fri: 8 AM - 6 PM Sat: 8 AM - 3 PM Sun: Closed