Heartworm Medications

THESE MEDICATIONS ARE EXTREMELY IMPORTANT IN HAWAII…please be sure to afford your pet the opportunity to live heartworm free by asking your Doctor or any staff member about how easily this debilitating disease can be prevented.


Heartworm is a parasiticroundworm (Dirofilaria immitis) that is spread from host to host through the bites of mosquitoes. The heartworm is a type of filaria, a small thread-like worm. The parasite is commonly called "heartworm" because the adult reproductive stage of its life cycle resides primarily in the right ventricle of its host where it can live for many years. Heartworm infection may result in serious disease for the host; infected dogs that are untreated may die and treatment also has risks. The best defense against heartworm disease is the use of prophylactic treatment given monthly during the life span of your pet.


Heartworms can only be transmitted from animal to animal by mosquitoes. When a mosquito bites an infected animal, young heartworms called microfilariae enter into that mosquito's system. Within two weeks, the microfilariae develop into infective larvae inside the mosquito; these infective larvae can be transmitted to another animal when this mosquito takes its next blood meal. The infective larvae mature into adult heartworms in approximately six months. During the first three months, the larvae migrate through the animal's body, eventually reaching the blood vessels of the lungs. During the last three months, the immature worms continue to develop and grow to adults, with females growing to lengths of up to 14 inches. If adult worms (5-7 months post-infection) of both sexes are present, they will mate and produce new microfilariae. This life cycle continues when a mosquito bites the infected animal and becomes infected by the microfilariae. After development of the microfilariae to infective larvae within the mosquito (10 to 14 days later) the infective heartworm larvae are capable of infecting another animal. Adult heartworms can survive for 5 to 7 years in dogs.


Yes! Heartworm disease is very serious. Heartworms interfere with the normal flow of blood from the right side of the heart to the vessels serving the lungs. The worms damage the blood vessels, and reduce the heart's pumping ability, resulting in severe lung and heart disease. If left untreated, canine heartworm disease can result in congestive failure of the heart and other organs, considerably reduce your dog’s quality of life, and ultimately lead to death.


Geographically, heartworms are a potential threat in every state as well as in many other countries around the world. All dogs, regardless of age, sex, or living environment (colder areas as well), are susceptible to heartworm infection.


At first an infected dog may show few signs of infection, but as the heartworms grow and mature, they cause increasing damage. Your pet may become listless, tire easily after exercise, develop an occasional or persistent cough, and become anemic. In advanced cases, dogs often suffer congestive heart failure. Complications may also develop in the liver and kidneys.


Heartworm infection is almost 100% preventable in dogs. There are several FDA-approved heartworm preventives available in a variety of formulations. Your veterinarian can recommend the best method of prevention based upon your pet's risk factors and lifestyle. Of course, you have to remember to give your pet the preventive in order for it to work! The preventives do not kill adult heartworms, and will not eliminate heartworm infection. Therefore, a blood test for existing heartworm infection is recommended before beginning a prevention program to assess the pet's current heartworm status. Heartworm tests should be performed annually to ensure that your pet doesn't subsequently become infected with the disease and to ensure the appropriate amount of medication is being prescribed and administered. There have been reports of pets developing heartworm infection despite year-round treatment with a heartworm preventive, so having your pet tested regularly is the best way to keep them protected!