Dirofilaria immitis in Dogs

A parasitic nematode transmitted indirectly through mosquitoes, causing heartworm disease.

The time it takes for heartworm larvae to reach sexual maturity and start producing microfilariae in a dog (6-7 months).

The mosquito that carries and develops the heartworm larvae.

The first larval stage of Dirofilaria immitis, present in the host's blood.

The host in which the parasite reaches maturity, like dogs, and some wild animals.

Indirect transmission via the intermediate host (mosquito).

Singular form of microfilariae, tiny larval stage of Dirofilaria immitis in the blood.

Heartworm life cycle involves mosquitoes as intermediate hosts, with larvae migrating through the host's tissues and vascular system before reaching sexual maturity in the heart.

A parasitic infection caused by the Dirofilaria immitis worm, affecting cats. While cats are less susceptible than dogs, they can still develop heartworm disease.

Cats have a natural resistance to heartworm infection, meaning they typically develop fewer adult worms compared to dogs. A larger exposure to infective larvae is needed for cats to get infected.

When adult heartworms develop in places other than their usual location in the heart (such as body cavities, brain, or other arteries). This is more common in cats because of their lower worm burden.

Cats often have only male or female heartworms. This is because they typically have fewer worms compared to dogs.

Infection with Dirofilaria immitis in cats, often with no visible microfilariae, leading to potential severe respiratory issues and even death.

Requires both antigen and antibody testing, as microfilariae are often absent due to the cat's immune system.

No approved treatments, often relying on managing symptoms and allowing natural death of worms. Anti-worm medications are experimental and risky for cats.

Controversial whether testing is needed; safe to start monthly prevention as early as 8 weeks of age, using oral or topical medication.

Available medications include ivermectin, milbemycin oxime, selamectin, and moxidectin, administered orally or topically.

Heartworms complete their entire life cycle in a dog in 6-7 months, first residing in subcutaneous tissues for ~2 months, then maturing in the pulmonary arteries for ~4-5 months.

Heartworms cause arteritis, damage pulmonary blood vessels, increase fluid leakage, and cause thickening/narrowing of vessel walls, leading to enlarged, twisted arteries and right ventricle enlargement.

Heartworm disease causes decreased exercise tolerance, lethargy, non-productive cough, labored breathing, fainting, distended abdomen due to fluid buildup (ascites), and general ill health (cachexia).

Caval syndrome is a deadly condition where heartworms block the vena cava and right side of the heart, requiring surgical removal for treatment.

Heartworm is diagnosed using microfilaria tests (Modified Knott or Millipore filter) and antigen tests. These tests identify the presence of adult female heartworms.

Heartworms are transmitted by mosquitoes, requiring a hot and wet environment for mosquito breeding, and warm temperatures for larval development.

Adult heartworms live 5 to 7 years in dogs, causing significant pathology and clinical issues in the heart and lungs.

Heartworm infection can lead to right-sided heart failure, often characterized by a reverse 'D' shaped heart, fluid buildup in the abdomen (ascites), and enlarged liver (hepatomegaly).

Heartworm can cause a non-productive cough, pulmonary embolism (blocked blood vessels), pulmonary crackles (collapsed alveoli), and coughing up blood (hemoptysis).

Heartworms can physically obstruct blood vessels, heart chambers, and heart valves, leading to right-sided heart failure.

Dogs under six months old are typically antigen and microfilaria negative, and thus, no heartworm test is needed. Heartworm preventative can be started at 8 weeks of age; a heartworm test is performed six months later to confirm the dog's status was negative when preventative was started.

Dogs over six months old require an antigen test. A negative result (NAD antigen or NOO microfilariae) does not confirm the dog is completely heartworm-free; the infestation may be too recent for detection in the prepatent period.

Heartworm treatment involves a sequence of treatments: (1) microfilaricide (two doses), (2) doxycycline (30 days), (3) adulticide (three-dose protocol with melarsomine).

A medication to eliminate microfilariae in heartworm treatment. Administered two months apart, starting 60 days before the adulticide.

Used in heartworm treatment to reduce Wolbachia spp. numbers, decrease pulmonary pathology, and increase adulticide effectiveness.

Melarsomine is the adulticide used in a three-dose protocol to kill adult heartworms. Administered IM.

Before heartworm treatment, evaluate the dog with urinalysis, CBC, chemistry profile, and chest radiographs to determine the dog's ability to withstand the treatment.

Pulmonary thromboembolism, characterized by blood clots in the lungs, can occur 7-10 days (up to 30 days) after adulticide treatment, potentially leading to the dog’s death.

A substance recognized as foreign by the body, capable of triggering an immune response and binding to specific antibodies.

Labored breathing, difficulty breathing.

Temporary loss of consciousness due to insufficient blood flow to the brain.

Abnormal fluid buildup within the peritoneal cavity (space in your abdomen).

Loss of appetite or lack of desire to eat.

Severe state of general ill health, malnutrition, and wasting.

Coughing up blood, indicating bleeding in the respiratory tract.

A blood clot attached to the vessel wall, potentially blocking blood flow.