Heartworm

Heartworms in Dogs: Causes, Symptoms & Prevention

Heartworms (Dirofilaria immitis) are parasites that primarily affect dogs, but can also infect cats and wild animals. They are transmitted by mosquitoes, which deposit the microscopic worm larvae into a dog’s body while feeding on blood. From there, the larvae travel through the bloodstream to the heart and pulmonary arteries—a process that takes several months. Untreated infections can lead to severe health problems and may even be fatal.

How does infection occur?

Mosquitoes ingest the larvae when they bite an already infected animal. During their next bite, they transmit the larvae to another dog. The risk is especially high in warm regions or during mosquito season.

Symptoms of a Heartworm Infection

An infection often goes unnoticed for a long time. Early signs are usually nonspecific but can worsen significantly over time:

• Mild, chronic cough

• Fatigue and reduced stamina

• Weight loss despite normal appetite

• Breathing difficulties

• Abdominal fluid buildup (due to heart failure)

The earlier the infection is detected, the better it can be treated.

Diagnosis and Treatment

A veterinarian can detect heartworms through a blood test. Additional examinations such as X-rays or ultrasound are often recommended to determine the extent of the infestation.

In our animal welfare work, we unfortunately encounter dogs that test positive for heartworms on a regular basis.

What does this mean for adoption?

A dog with heartworms can still be adopted! What matters is that the treatment is continued—we are happy to advise you on this and support you throughout the therapy.

When adopting, the spot-on treatments are provided. Many of these dogs have very little chance otherwise, even though they have so much love to give.

Several heartworm-positive dogs are currently in our care and urgently depend on their treatment.

For this, we need:

• Spot-on products (e.g., Advocate, Stronghold, Milbemax, Nexgard Spectra, etc.)

Prevention – the most important protection

The best measure against heartworms is consistent prevention. There are various products (tablets, spot-ons) that can be given monthly or biannually. Prevention is essential, especially for dogs living in or traveling to high-risk areas (e.g., Southern and Eastern Europe).