Heartworms are blood-borne parasites that are transmitted by mosquitoes. When a mosquito bites an animal, it deposits larvae into the host’s bloodstream. Over a period of 6-9 months, these microscopic worms grow up to a foot long and start producing their own larvae inside the dog’s heart. Mosquitoes can then bite the infected animal, serving as a reservoir for further spread of the disease.

Dogs are a primary host of heartworms, meaning that they provide an ideal environment for the heartworm to grow and multiply causing damage to the host dog’s lung and heart tissue. Other animals can less commonly become infected with heartworm. Cats do not provide an ideal host for heartworms but heartworms still cause severe damage in cats and even death. There are even a few case reports of humans getting this disease. It takes a minimum of approximately six months from the time a mosquito bites a dog or cat for the heartworm to develop into an adult worm*, this causes a delay in possible diagnosis of infection.

*Check out details on heartworms and their lifecycle at the Companion Animal Parasite Council’s (CAPC) website.

Even though we think of mosquitoes as outdoor pests, they do slip inside, and indoor only animals do go outside periodically, sometimes accidentally. Because of this reality, all cats and dogs are at risk of contracting heartworms. In this part of the country, we recommend year round prevention for all cats and dogs.

Symptoms

Many dogs and cats will show no symptoms of disease when initially infected with heartworms. Symptoms of advanced disease include exercise intolerance, coughing, labored breathing, and lethargy. The most common symptom of heartworm disease in cats is sudden death though some will present with asthma like symptoms.

Most heartworm preventative medications also contain an additional medication for intestinal parasite deworming as well (usually for roundworms and hookworms).

Dosing - It is important to monitor your pet’s weight. If your pet’s weight fluctuates you may need a different dosage of preventative, so be aware of your pet’s weight and the weight range protected by your chosen preventative. Large dogs sometimes need combined dosing to fully protect them.

Safety - All products are prescription and approved by the FDA and require a prescription. Collie-breeds with MDR1 mutation are significantly more sensitive to heartworm preventatives (and some other drugs as well) and can experience toxicity at a lower dose than other dogs. However, all FDA-approved heartworm prevention products use doses lower than those known to affect dogs with the MDR1 mutation and have been tested for safety in dogs with the MDR1 mutation. Therefore, these products are considered safe for most dogs if used at the manufacturer’s recommended dose.

Be sure that you are using a high quality protection and following appropriate instructions for your pet.

• For dogs we recommed:
  • Simparica Trio: Oral heartworm, intestinal parasite, flea, and tick treatment/prevention (monthly).
  • Heartgard Plus: Oral heartworm and intestinal parasite treatment/prevention (monthly). (Flea & tick prevention needed separately.)
• For cats we recommed:
  • Revolution Plus: topical heartworm, flea, tick, mite, and intestinal parasite medication- applied to skin once monthly..

Doagnosis

For Dogs: We recommend annual screening of a small blood sample. The test that we recommend for most dogs screens for the blood parasites heartworm, lyme, ehrlichia, and anaplasma. There are several individual and public health reasons that we recommend this testing annually:

• There is growing resistance to heartworm prevention products in the United States, so we need to ensure the product is working as intended.
• The treatment for heartworm disease is different from giving prevention, so we need to detect the disease early to treat it before it is too late.
• Heartworm disease typically has no symptoms until heart failure is present, making early detection crucial.
• Product guarantees are forfeited if annual screening is not performed. This may also affect treatment coverage by pet insurance.
• If your pet is positive and undiagnosed, he/she serves as a reservoir for infection to other dogs in your area via mosquitoes.
• Exposure to tick-borne illnesses (ehrlichia, anaplasma, Lyme disease) can occur even with tick prevention. We recommend treating these diseases if symptomatic.

Symptoms:

Many dogs and cats will show no symptoms of disease when initially infected with heartworms. Symptoms of advanced disease include exercise intolerance, coughing, labored breathing, and lethargy. The most common symptom of heartworm disease in cats is sudden death, though some will present with asthma-like symptoms.

Prevention:

Heartworm prevention stops larvae from developing into mature worms, thus preventing heartworm disease. Preventative medications have no effect on adolescent or adult worms. Missed doses of prevention increase the risk of having older worms in the body that will not respond to prevention.

Most heartworm preventative medications also contain an additional medication for intestinal parasite deworming as well (usually for roundworms and hookworms).

Dosing: It is important to monitor your pet’s weight. If your pet’s weight fluctuates, you may need a different dosage of preventative, so be aware of your pet’s weight and the weight range protected by your chosen preventative. Large dogs sometimes need combined dosing to fully protect them.

Safety: All products are FDA-approved and require a prescription. Collie-breeds with the MDR1 mutation are significantly more sensitive to heartworm preventatives (and some other drugs) and can experience toxicity at lower doses than other dogs. However, all FDA-approved heartworm prevention products use doses lower than those known to affect dogs with the MDR1 mutation and are tested for safety. These products are considered safe for most dogs if used at the manufacturer’s recommended dose.

Be sure that you are using high-quality protection and following appropriate instructions for your pet.

• For dogs we recommend:
  • Simparica Trio - oral heartworm and intestinal parasite/flea/tick treatment/preventative given once every month.
  • Heartgard Plus - oral heartworm and intestinal parasite treatment/preventative given once every month. (Don’t forget to give flea & tick prevention too!)
• For cats we recommend:
  • Revolution Plus - topical heartworm, flea, tick, mite, and intestinal parasite medication - applied to skin once monthly.

Diagnosis:

For Dogs: We recommend annual screening of a small blood sample. The test that we recommend for most dogs screens for the blood parasites heartworm, Lyme, ehrlichia, and anaplasma. There are several individual and public health reasons that we recommend this testing annually:

• There is growing resistance to heartworm prevention products in the United States, so we need to make sure the product is working as it should.
• The treatment for heartworm disease is different than prevention, so early detection is key as heartworm disease typically shows no symptoms until heart failure occurs.
• Product guarantees are forfeited without annual screening, which may also affect treatment coverage by pet insurance.
• If your pet is positive and undiagnosed, he/she serves as a reservoir for infection to other dogs in your area via mosquitoes.
• Exposure to tick-borne illness (ehrlichia, anaplasma, Lyme disease) can happen even with tick prevention, and treatment is recommended if symptoms occur.

For Cats: Heartworms develop differently in cats than in dogs, making detection more difficult. There is no treatment for cats with heartworm disease, so prevention is the only effective measure. Routine screening in asymptomatic cats is not common but can be performed if exposure is suspected.

Treatment:

For Dogs: The approved treatment for heartworm infection in dogs involves six months of exercise restriction, one month of oral medication, three deep, painful muscle injections with an arsenic-derived compound, three days of hospitalization, and can cost upwards of $1,000. The treatment carries a risk of life-threatening complications. Even with successful treatment, the damage to the heart and lungs caused by heartworms cannot be reversed, making it a lifelong condition.

For Cats: As mentioned, there is no approved treatment for heartworm disease in cats. Medications can be given to help control some symptoms, but the long-term prognosis is poor. Prevention remains the only solution.

If you have questions about your pet’s health and your pet is an existing patient of Local Mobile Vet, fill out the appointment request form, and we will reach out to get an appointment scheduled. You can also order your pet’s prevention at our online store right now.

If we have never seen your pet before, fill out the New Client Form, and we will reach out to help you determine if we are the right fit for you and your pet.