Heartworm Disease II- CardioRush

No (requires injection on L3 phase, microfilaria are L1)

Can puppies get adult HWs from infection with microfilaria across the placenta?

Prepatent infection, live adult infection, persistent Ab following death of adult in previous infection

What 3 scenarios cause a positive antibody test for HWD in a cat?

6 months (minimum)

What age must a puppy be before using a HW antigen test?

Iatrogenic, immune mediated, unisex infection, prepatent infection

What are some causes of an occult HW infection?

Cough, dyspnea, exercise intolerance, syncope, collapse, abdominal distention, weight loss, lethargy, cachexia

What are some examples of possible clinical signs of HWD in a dog?

Direct smear, microhematocrit test

What are some other less sensitive tests than the modified Knotts that can be used to test for microfilaremia?

Cough, inspiratory crackles, dyspnea, cyanosis, hemopysis

What are some respiratory PE findings that can be consistent with HWD?

Weight loss, cachexia, fever, petechia, ecchymosis, hemorrhage, icterus, hemoglobinuira, NM or ocular findings

What are some systemic PE findings consistent with HWD?

Immature worms (prepatent infection), single sex infection, low worm burden

What are the 3 most common reasons for false negative antigen tests for HWD?

Hemoptysis, fever

What are the signs consistent with PTE in animals with HWD?

History, PE, serology, Knotts test, rads, echo, minimum database

What are the ways we diagnose and stage HWD?

Low worm burden, all males, prepatent infection, antigen bound to immune complexes

What can cause a false negative on the HW antigen test?

Hemolysis from caval syndrome

What causes icterus and hemoglobinuria associated with HWD?

Pulmonary hypertension

What causes loud or split S2 in animals with HWD?

DIC

What causes petechia, ecchymosis, and hemorrhage associated with HWD?

Pulmonary hypertension

What causes tricuspid regurgitation in animals with HWD?

Exposure, NOT active infection

What does a positive antibody test for HW in a cat indicate?

Pulmonary hypertension

What does it mean if the pulmonary artery is larger than the vein?

ELISA for protein released from adult female repro tract

What does the HW antigen test specifically target?

RV hypertrophy

What does the shape of the heart mean on this view?

Unisex infection

What is a common reason for occult HWD infection in cats?

Pneumonitis

What is circled?

Enlarged MPA

What is the arrow pointing to?

RV

What is the arrow pointing to?

CBC, Chem, urinalysis, UPC

What is the minimum database that should be collected in HWD?

Iatrogenic

What is the most common cause of occult HW infection?

Inadequate prevention

What is the most important aspect of history in animals with HWD?

Modified Knotts test (concentration test that utilizes full mL of blood)

What is the most sensitive test for microfilaria in the blood?

Pulmonary disease

What is the primary manifestation of HWD?

Antibody test

What is the primary screening test for HWD in cats?

Antigen test

What is the primary screening test for HWD in dogs?

Enlarged MPA

What is the red arrow pointing to?

Large PA

What is the red arrow pointing to?

High specificity, good sensitivity

What is the sensitivity and specificity of the HW antigen test in a dog?

Higher sensitivity, lower specificity

What is the sensitivity and specificity of the antibody test for HWD in cats compared to Ag test?

Occult infection

What is the term for active HW infection without circulating microfilaria (amicrofilaremia)?

Antigen bound to Ig will be freed, more likely to be caught by ELISA

What is the theory behind heat treating a serum sample before HW antigen testing?

90%

What percentage of cats that are HWD infected will test positive on an antibody test?

66%

What percentage of cats with HWD have an occult infection?

Negative Ag but HW highly suspected, confirms result

What samples can heat treatment be used in?

Start preventative, baseline echo, treat symptomatically as needed

What should you do for a cat that has a confirmed heartworm infection?

Antigen test

What should you do if a cat tests positive on an antibody test?

CBC, rads, echo, microfilaria test, start preventative

What should you do if a cat tests positive on the antibody test but negative on the antigen test?

Ag test, echo

What tests are needed to confirm HWD after a positive antibody test in cats?

6-7 months

What time after infection can an antigen test detect HWD?

Immediately after, decays to 0 by 12 weeks

When does the antigen level increase following adulticide or adult worm death?

Early as 2-3 months, usually by 5 months

When following infection can an antibody HW test be positive in an infected cat?

Use in monitoring effectiveness of slow kill treatment

Why did heat treating samples before HWD antigen tests become popular?

Low worm burdens make it much less sensitive

Why is antigen testing for HWD not used for a screening test in cats?

Occult infections prevalent

Why is finding microfilaria an insensitive method for diagnosing HWD?

7 months after peak exposure

Why should dogs be tested annually in the late spring for HWD?

False (not a confirmation)

True or false: Ab testing in cats is a confirmatory test for HWD

Eosinophilic pneumonitis

A heartworm positive dog presents with coughing and radiographs are taken. What is the most likely finding?

False (it is specifically for testing in cats)

True or false: HW antibody testing can be used in dogs

True

True or false: If a particular dog doesn't seem to make sense of having Dirofilaria but has microfilaria, then you should ask the lab to speciate the microfilaria

False (they are an essential component of pretreatment eval, tells how severely they are affected)

True or false: chest rads are ideal for establishing how affect an animal is in HWD, but not essential for treatment

False (always double check suspicious cases by looking for microfilaria)

True or false: dogs with suspicious clinical findings that aren't positive on an antigen test usually don't need to be checked for microfilaria

True

True or false: false positive antigen test is uncommon and is most likely a lab error

False (Don't need to test before 6 months, wouldn't give another adulticide treatment before then even if still positive)

True or false: it is best to retest for HW antigen every week during adulticide treatment

False (Also caused by Acanthocheilonema reconditum)

True or false: only Dirofilaria immitis causes microfilaremia

Yes

Can microfilaria be passed through the placenta?

False (it is semiquantitative, repeat if the test is a weak positive)

True or false: the HW antigen test is quantitative

True

True or false: the majority of dogs that are diagnosed with HWD are caught by screening and are asymptomatic

Macrolide preventative kills microfilaria

How can an occult infection be iatrogenic?

6 months

How long after worm or larval death with antibodies persist in a cat?

3 or more females

How many worms present usually cause the HW antigen test to be positive?

Confirmatory test after Ab screening

How should antigen tests be used in cats to detect HWD?

CBC, chem, rads, macrolides therapy, adulticide theraapy

If a dog tests positive on an antigen test, but a modified Knotts test is negative, what should you do?

Chem, tells most if healthy otherwise

If you have to chose just one test from the minimum database to do before moving forward with treatment, which should you chose and why?

No

Is it necessary to heat treat every sample of serum before testing for HWD using the antigen test?

Loud or split S2, murmur from tricuspid regurg, S3 gallop, RCHF signs

Though the majority of dogs have no abnormalities on PE, what are some possible PE findings that may occur with HWD specific to the heart?

True

True or false: ALL dogs that are positive by Ag test should also be tested for microfilaremia