Dogs are ideal hosts for heartworms (Dirofilaria immitis), parasitic worms transmitted by mosquitoes that live in the heart and blood vessels and cause serious damage or death. Dogs living in mosquito-prone areas are most at risk, but no dog is immune to infection. Because heartworm infection in dogs is potentially fatal, preventative care is essential.

 Lifecycle of Heartworms:

The life cycle of a heartworm begins inside an already-infected animal, where an adult female and male heartworm produce babies, called microfilariae, that are passed into the animal’s bloodstream. Mosquitoes are then able to pick up the microfilariae when they bite into the infected animal. The microfilariae grow inside the mosquito into infective larvae within a couple of weeks. When the infected mosquito bites another dog, the larvae are then transferred to the animal, where they migrate to the heart and lungs and begin to grow. Female heartworms reach a size of 12 inches about one year following infection.

 Unfortunately, a single mosquito bite is sufficient to infect an otherwise healthy dog with heartworms.

Diagnosing Heartworms:

Symptoms of heartworm infection in dogs vary, with some dogs exhibiting no symptoms and others becoming severely ill. The most common symptoms include coughing, breathing difficulties, vomiting, weight loss, fatigue after exercise, and general listlessness. Symptoms are generally more severe in advanced infections.

Your veterinarian will examine your dog for signs of heartworm before prescribing treatment or beginning preventative medication. Blood work and an ultrasound may be necessary to confirm or rule out infection. Blood tests can detect heartworms in dogs about six months after infection occurs.

Preventing Heartworm Infections:

Fortunately, heartworms are easily preventable with affordable medication designed to kill the heartworm microfilariae. Most preventative regimes involve a once-monthly dose of medication administered during mosquito season. For maximum protection, the American Heartworm Society now recommends treatment year-round.

Treating Your Dog for Heartworms:

Once infection occurs, prompt treatment is essential to prevent congestive heart failure and other potentially fatal complications. Typically, treatment involves a series of injections with adulticides, which are petmeds designed to kill adult heartworms. These injections are given into your dog’s muscles either in the hospital or on an outpatient basis. Following treatment, your dog may need several weeks of exercise restriction to complete his recovery.

While treatment for heartworms carries some risk, untreated infections may quickly lead to severe illness. All dogs should undergo preventative care for heartworm infections and any dog that exhibits symptoms of infection requires prompt veterinarian attention to prevent complications and death.