Heartworm

Question 1

What parasite causes heartworm disease?

Answer 1

Dirofilaria immitis

Question 2

Heartworm life cycle

Answer 2

Mosquito with microfilaria in saliva

Microfilaria matures to L3 in the vessels (takes up to 14 days)

L4 within the tissues

L5 moves throughout the body until it has found the pulmonary arterioles (oxygen rich blood) –> mature to adult

Adults produce L1 (microfilaria) which circulate in the blood; picked up by mosquito in blood meal

Question 3

What are Wolbachia

Answer 3

Rickettsial intracellular, gram-negative bacteria

D. immitis + Wolbachia have a symbiotic relationship

Question 4

How to diagnose heartworm disease

Answer 4

Antigen:
Female reproductive tract
Infection if positive (means have L5s and adults in body)

Antibody:
Exposure

Microfilaria:
Knotts test

False negatives and false positives depend on prevalence in the area

Question 5

Classification and Staging of Heartworm Disease

Answer 5

Asymptomatic

Respiratory signs; cough/tachypnea with exercise

Cor Pulmonale; pulmonary vascular disease (pulmonary hypertension) can cause right sided heart failure

Right sided CHF; due to pulmonary hypertension

Caval syndrome

Question 6

What is Caval Syndrome?

Answer 6

Hepatic congestion, intravascular hemolysis with hemoglobinuria

After pulmonary arterioles are taken up and the pulmonary artery (right heart) is also taken up worms will back up into the vena cava

Death

Question 7

Comorbidities of Heartworm

Answer 7

Antibody-antigen complex formation (glomerulus- PLN)

Thrombocytopenia

Anemia

Question 8

What does Melarsomine target?

Answer 8

ONLY adults

Question 9

What do preventatives target?

Answer 9

L1, L3, and L4 microfilaria

Question 10

How do you kill Wolbochia?

Answer 10

Doxycycline

Question 11

How do you kill L5?

Answer 11

You cannot they are invincible; need them to become adults in which you will use Melarsomine (3-4 months to mature)

Question 12

Heartworm Disease

Treatment; Fast Kill Method

Answer 12

Adulticide therapy with Melarsomine

2 doses (1st dose followed by a 2nd dose 24 hours later)

3 doses (1st dose, 2nd dose 1 month later, 3rd dose 24 hours after 2nd dose)

Treat ASAP if pulmonary hypertension exisits

May have to do surgical removal of worms (especially if patient has Caval Syndrome)

Question 13

Feline Heartworm Disease

Diagnosis

Answer 13

Clinical signs similar to feline asthma (thoracic radiographs and echocardiogram may help diagnose)

Same as canine:
Antigen (adult female)
Antibody (exposure)
Microfilaria (Knotts test)

Question 14

Feline Heartworm Disease

Treatment

Answer 14

Adulticide therapy not recommended; this can kill the patient due to systemic immune response (anaphylaxis)

Rx: steroids or bronchodilators