Heartworm disease is a devastating, but preventable, parasitic disease that can affect dogs and cats of all ages. Many owners of senior pets assume their aging companion no longer requires regular preventive care, or that they have built up an immunity to diseases and parasites. However, your senior pet’s immune system weakens as they age, leaving them more susceptible to common infections. All pets should receive year-round protection, especially your senior pet, who is part of the most vulnerable population. 

What is heartworm disease in senior pets?

Heartworm disease is caused by a parasitic worm, Dirofilaria immitis, that has an affinity for the heart and lungs. Mosquitoes pick up larval worms when they ingest blood from an infected canine host and can transmit the worms to other animals they bite. Once inside a suitable host, the larval worms undergo a six- to seven-month maturation period and migrate to the heart and lung blood vessels. Adult worms reproduce and create thousands of microscopic larval worms (i.e., microfilariae) that circulate in the infected pet’s bloodstream. Over months to years, an untreated dog will accumulate a large worm burden that can obstruct blood flow, cause inflammation, and lead to heart failure. 

Can my senior cat develop heartworm disease?

Dogs are the heartworm’s preferred host, but cats can develop a different disease form called heartworm-associated respiratory disease (HARD). While heartworms cannot reproduce inside a cat, only a few worms can incite significant inflammation that leads to respiratory problems, since cats are particularly sensitive to the worms’ presence.

What are heartworm disease signs in senior pets?

Senior dogs who develop a heartworm infection may not show signs for a year or longer, since the worms have such a long life cycle. However, once the worm population builds and blood flow is interrupted, you may observe the following signs in your dog:

* Tiring more quickly than normal

* Decreased appetite

* Coughing

* Vomiting

* Difficulty breathing

Cats can develop signs soon after infection, because the larval worms can trigger a significant inflammatory reaction. Respiratory signs in cats may include:

* Coughing

* Wheezing

* Difficulty breathing

* Open-mouth breathing

* Sudden collapse

Some cats are asymptomatic, and sudden death is unfortunately possible. Abnormal signs and behaviors of any type in your senior pet warrant immediate veterinary care, since many medical conditions can develop and progress quickly.

How is heartworm disease diagnosed in senior pets?

An annual heartworm test is part of your senior pet’s routine wellness and preventive care. A negative test confirms that your pet is heartworm-free and can continue year-round prevention. If your pet’s blood test is positive, further diagnostic testing, such as additional blood work and X-rays, will be needed to determine the infection severity. 

Every pet, including those who receive year-round prevention, should receive an annual heartworm test to ensure they are heartworm-free. Your pet can develop an infection after missing only one preventive dose, vomiting a dose, or spitting the preventive out behind the couch. Heartworm infection is devastating for pets, so be safe rather than sorry. 

How is heartworm disease treated in senior pets?

Heartworm disease treatment, which is lengthy, costly, and difficult for pets to endure, is especially hard on senior dogs. Treatment involves injecting an arsenic compound deep into a dog’s lumbar muscles. The treatment period typically lasts several months and requires severe exercise restrictions to prevent dying worms from lodging in lung vessels and causing a deadly pulmonary embolism. Additional medications are prescribed to minimize inflammation and kill the bacteria the worms carry. 

Unfortunately, no medication has been approved that can eliminate heartworm disease in cats. Instead, treatment focuses on minimizing inflammation and managing signs until the worms die on their own, which may take several years. Senior cats can develop more severe disease, so prevention is particularly critical.

How can I protect my senior pet from heartworm disease?

Fortunately, protecting your senior companion from heartworm disease is easy. Many preventive types, from monthly chewables to topical treatments, to annual injections, are available. Speak with your family veterinarian to decide which option best fits your senior pet’s lifestyle and needs. 

Several conditions can affect your senior pet’s quality of life. If your senior pet’s health has declined, our telehospice service can walk you through a quality-of-life assessment to help you determine whether veterinary hospice care is appropriate, or the time has come for in-home euthanasia.