Heartworm disease

Question 1

What is the life cycle of dirofilaria?

Answer 1

• mosquito ingests microfilariae
• L3 stage transmitted to animal
• develops to L4 stage and migrates to lungs to mature
• adult females produce microfilariae

Question 2

When is a patent infection of dirofilaria noticeable?

Answer 2

6-9 months post-infection in dogs

Question 3

What are the clinical signs of heartworm infection?

Answer 3

• cough
• exercise intolerance
• dyspnea
• abdominal distension
• syncope
• weight loss

Question 4

What is found on physical exam of heartworm infection?

Answer 4

• right-sided murmur
• split S2
• arrhythmia
• pulmonary crackles
• ascites

Question 5

How do you diagnose heartworm?

Answer 5

• antigen test that detects antigen released by female dirofilaria (can have false negatives)
• microfilariae test that distinguishes dirofilaria from A. reconditum (can be - in Ag+ dog)
• thoracic radiographs

Question 6

What is seen on thoracic radiographs of heartworm?

Answer 6

• main pulmonary artery enlargement
• RV enlargement
• enlarged and tortuous pulmonary arteries
• interstitial to alveolar pattern
• right-sided CHF

Question 7

What is involved in adulticide therapy for heartworm?

Answer 7

• melarsomine
• 2 injection protocol (2 IM injections, 24h apart)
• 3 injection protocol (1 IM injection, wait a month, 2 IM injections 24h apart)

Question 8

What is involved in the adjunctive therapy for Wolbachia in heartworm infections?

Answer 8

• intracellular bacteria found in D. immitis

- use doxycycline, which decreases the inflammatory response associated with worm death

Question 9

What other adjunctive therapy for heartworm is there?

Answer 9

• steroids to decrease inflammation associated with pulmonary thromboembolism
• preventatives against younger larvae

Question 10

What are macrocyclic lactones?

Answer 10

• preventative therapy administered 2-3 months prior to adulticide therapy (eliminates larvae <2mo)
• decreases circulating microfilariae

Question 11

What is caval syndrome?

Answer 11

migration of worms from arteries to vena cava and right atrium

Question 12

What is essential to a good recovery from heartworm?

Answer 12

exercise restriction

Question 13

What are some complications that can arise from heartworm infections?

Answer 13

glomerulonephritis

• right-sided heart changes and CHF
• caval syndrome
• sudden death

Question 14

What are the clinical signs of caval syndrome?

Answer 14

• severe lethargy
• dyspnea
• pale MM
• weakness
• hemoglobinuria
• right-sided systolic murmur

Question 15

When should you re-test for heartworm?

Answer 15

antigen test 6 months after treatment

Question 16

What is important to know about feline heartworm disease?

Answer 16

• worm maturity not necessary to cause pathology
• lower worm burden
• male-only infection

Question 17

What are the two stages of development of feline heart heartworm?

Answer 17

1. arrival to pulmonary vasculature

2. death of adult worms

Question 18

What is heartworm associated respiratory disease (HARD)?

Answer 18

• inflammatory disease that correlates with arrival of worms to lungs
• results in asthma-like signs, so test all gouging cats for heartworm

Question 19

How do you diagnose feline heartworm disease?

Answer 19

• antibody test (doesn’t indicate active infection)
• antigen test (false negatives)
• thoracic radiographs
• microfilaremia

Question 20

How do you treat feline heartworm disease?

Answer 20

• prevent the infection, although melarsomine is CONTRAINDICATED
• treat symptoms