NAVLE Prep

What does the heartworm antigen test detect?

adult female worms

Describe common radiographic findings in a patient with HWD

enlarged pulmonary artery (>1.6 times width of ninth rib), blunted/tortuous pulmonary arteries, patchy perivascular pulmonary infiltrates, +/- pleural effusion, chylothorax (feline)

What causes the pulmonary hypertension, rCHF, and thrombosis often seen in HWD?

lobar arterial enlargement, tortuosity, and obstruction

Why might you get a false negative on a heartworm antigen test?

low worm burdens (< 5 worms), single-sex (male) infection

Microfilaria concentration tests have very ___ sensitivity and ____ specificity

low; high

What are heartworm larvae called?

micofiliariae

Cough in cats is more common in which stage of HWD? a. mild infestation b. moderate infestation c. severe infestation

mild infestation (commonly occurs early in disease prior to established adult infection)

What is the vector that transmits HWD?

mosquitoes

List common physical examination findings of a dog with a mild to moderate infestation of heartworm

no abnormalities

Describe the historical findings that you would likely find in a dog with a mild heartworm infestation.

often asymptomatic or occasional cough

List some risk factors for HWD in cats

outdoor lifestyle, lack of prophylaxis

List the effects on the respiratory system seen in heartworm disease?

pulmonary hypertension, thromboembolism, allergic pneumonitis, eosinophilic granulomatosis (uncommon)

Heartworm disease is caused by an infestation of what parasite?

Dirofilaria immitis

List the effects on the hemic/lymphatic/immune system seen in heartworm disease?

venous inflow to the heart can become obstructed by worms causing traumatic hemolytic anemia and cardiogenic shock (caval syndrome)

What clinical signs predominate in cats for chronic HWD?

vomiting and respiratory signs

The severity of signs in HWD is directly related to...

worm number, duration of infestation, host response, and host activity level

What is caval syndrome?

worms in caudal vena cava collapse and death almost complete blockage of all blood flow

True or False: In heartworm-associated respiratory disease (HARD), clinical signs and pulmonary pathology will not occur if adult infection is never established

False; clinical signs and pulmonary pathology that occur 2-4 months post-infection even when adult infection is never established

List common physical examination findings of a cat with heartworm disease

Usually normal, increased bronchovesicular sounds, arrhythmia

Describe the heartworm life cycle

A mosquito bites an infected dog, taking in heartworm microfilariae as it feeds. The microfilariae develop into infective stage larvae within the mosquito. The mosquito transmits the infective stage larvae to a healthy dog. The larvae migrate through the tissues, eventually reaching the heart. Heartworms can grow up to 12 inches in length.

Which tests are most sensitive for detecting heartworm in feline patients

Antibody test (ELISA or immunochromatographic tests)

What geographic areas of the U.S. is HWD is most common in?

Atlantic/Gulf coasts and Ohio/Mississippi river basins

Why must exercise be avoided after administering adulticides in a patient with heartworm?

Pulmonary damage can be exacerbated after death of adult worms with exercise

List the geographic areas that HWD is considered endemic to?

North, Central, South America, southern Europe, and Australia

True or False: HWD is diagnosed in all 50 states of the U.S.

True

True or False: Incidence/prevalence of HWD is virtually 100% in unprotected dogs living in highly endemic regions

True

List common CBC/CHEM/UA findings with canine HWD

anemia (extent depends on severity of infestation), +/- eosinophilia and basophilia, inflammatory leukogram and thrombocytosis associated with thromboembolism, +/- hyperglobulinemia, hemoglobinuria (caval syndrome), proteinuria (chronic infestation), hemog

Describe the historical findings that you would likely find in a dog with a severe heartworm infestation.

cachexia, exercise intolerance, syncope, and/or abdominal distension (rCHF)

Describe the historical findings that you would likely find in a dog with caval syndrome?

cardiogenic shock, pigmenturia, abdominal distension (rCHF)

List some historical findings of HWD in cats

cough (early infection), dyspnea, vomiting, acute respiratory failure and death from PTE

Describe the historical findings that you would likely find in a dog with a moderate heartworm infestation.

coughing and exercise intolerance associated with moderate pulmonary damage

Why can periarterial edema occur in HWD?

endothelial damage leads to myointimal proliferation and inflammation

List some risk factors for HWD in dogs

residence in endemic areas, outside habitat, lack of prophylaxis, environmental temperatures >57 F

List the effects on the cardiovascular system seen in heartworm disease?

severe pulmonary hypertension causing right ventricular hypertrophy and, in some dogs, rCHF (ascites)

List common physical examination findings of a dog with more severe infestations of heartworm

severe pulmonary hypertension or pulmonary thromboembolism, labored breathing and/or crackles, tachycardia, weight loss, exercise intolerance, syncope, coughing, pale or light pink mm, dyspnea, ascites, jugular vein distension/pulsation, hepatomegaly (rCHF), hemoptysis (occasionally)

HWD is most common in _________ and _________ zones

tropical; subtropical

List common CBC/CHEM/UA findings with feline HWD

varies with stage of dz, mild non-regenerative anemia, +/- eosinophilia, concurrent basophilia should increase suspicion, hyperglobulinemia