Heartworm Disease and Your Pet
Summer may be over, but mosquitoes are hearty pests, and protecting your pet from heartworm disease is a year-round responsibility. Heartworm disease is most prevalent in hot, humid areas, such as the Southeastern U.S., but has been diagnosed in every state—including Alaska—throughout the year. According to the Companion Animal Parasite Council, more than 1,700 New Jersey pets were diagnosed with heartworm disease in 2019, with 174 cases diagnosed in Monmouth County pets.
The heartworm life cycle in pets
Heartworm disease is caused by the parasitic worm, Dirofilaria immitis. A mosquito bites a heartworm-infected dog and picks up microscopic larval worms along with its blood meal. Once the larvae mature inside the mosquito, they can be transmitted to any animal a mosquito bites, although dogs are their preferred host. Inside a dog’s body, the larvae migrate to the large blood vessels near the heart and lungs, where they mature over six months, begin reproducing, and can accumulate to a large population over months to years. Once mature worms begin reproducing, larval worms circulate through the bloodstream, and can be picked up by mosquitoes to infect other pets.
If a cat is bitten by an infected mosquito, the larval worms can mature to adulthood, but cannot reproduce.
Heartworm disease in pets
As heartworms multiply, they accumulate in the lung vessels. They may also enter the heart, if an infection reaches advanced stages. Heartworms in a pet’s blood vessels and heart can cause several problems, including:
- Inflammation — The presence of foreign parasites in the blood vessels and heart triggers significant inflammation that leads to vessel scarring and rigidity.
- Stress — Extra volume places strain on the heart, which must work harder to pump blood through the body.
- Obstruction — Worms taking up space in blood vessels interfere with normal blood flow, leading to inadequate oxygen delivery to tissues. In severe cases, whole worms or pieces of dead worms can completely obstruct a vessel, leading to a pulmonary embolism.
Heartworm signs in pets
Heartworm disease clinical signs are caused by the inflammation, stress, and blood flow obstruction related to worm presence, and include:
The severity of a pet’s clinical signs is related to the lung damage caused by the worms. If heartworm disease is not treated, worms will eventually accumulate to a burden that interferes enough with heart function to cause death.
Although cats may experience similar clinical signs, caused by inflammation triggered by the few worms they harbor, affected cats may suffer silently, collapse, or suddenly die.
- Decreased appetite
- Exercise intolerance
- Difficulty breathing
- Abdominal distension
Heartworm disease diagnosis in pets
We use a simple blood test to screen for heartworm disease during your pet’s annual wellness exam. If your pet tests positive, further diagnostic tests, such as comprehensive blood work, radiographs (i.e., X-rays), and ultrasound, may be performed to assess your pet’s overall health, and stage their heartworm disease.
Heartworm disease treatment in pets
Heartworm disease treatment involves a course of several medications that may include:
Treatment is essential to prevent heartworm infection from advancing and causing death but can also be risky. Pieces of dead worms can lodge in blood vessels, causing a pulmonary embolism that blocks blood flow to lung tissue, and often sudden death. Dogs with a large worm build-up are at highest risk for pulmonary embolism. Your dog’s activity must be extremely restricted throughout treatment, to reduce the risk of this deadly complication.
No approved treatment is available to kill adult heartworms in cats. Treatment for heartworm-positive cats focuses on managing inflammation to reduce the risk of lung damage and death.
- Adulticide — Several injections are administered over two to three months to kill adult heartworms.
- Larvicide — Medications are administered to also kill heartworm larvae before they can mature to adults.
- Antibiotics — Antibiotics will be administered to kill bacteria that heartworms carry that help them develop and may help trigger inflammation in infected pets.
- Anti-inflammatories — Non-steroidal anti-inflammatory drugs (NSAIDs) or steroids are often used to control inflammation throughout treatment.
Heartworm prevention in pets
Heartworm disease can have deadly consequences for your pet but, fortunately, is easily preventable. We can recommend and prescribe several medications, including oral, spot-on, and injectable forms, that prevent heartworm larvae from developing into the adults that can cause dangerous disease. It is imperative that every pet be treated year-round to prevent infection. Ask one of our team members about heartworm disease preventives for your pet.
Don’t assume the end of summer means pausing your pet’s heartworm protection until warm weather returns. If your pet is due for their annual heartworm test or a preventive refill, give us a call to schedule this life-saving appointment.