Heartworm

Question 1

Heartworm scientific name

Answer 1

Dirofilaria immitis

Question 2

What stage of the lifecycle occurs in the mosquito?

Answer 2

The mosquito bites a dog and ingests microfilaria which mature from L1-L2 to L3 and migrate to the mosquitoes salivary gland and get injected into the dog

Question 3

What stage of the lifecycle occurs in the dogs skin/muscles?

Answer 3

L4-L5

L5 migrates into the systemic vascular system

Question 4

What is the prepatent period?

Answer 4

~6-7months

Question 5

What is the lifespan of an adult heartworm?

Answer 5

5-7yrs

Question 6

what clinical signs may you see with Caval syndrome?

Answer 6

anorexia, lethargy, RSCHF, haemolytic aenaemia, hemoglobinuria, hemoglobinaemia, hepatic + renal dysfunction, resp. signs

Question 7

What does a +ve AG test but negative mff test mean?

Answer 7

occult infection/immature adults, single sex infection or elimination of mff by recent tx (macrocyclic lactones)

Question 8

what pulmonary signs may be present w/ HW dz?

Answer 8

inc. bronchovesicular sounds, crackles, tachypnoea and a cough
exercise intolerance

Question 9

what abnormalities may you notice on cardiac auscultation of a dog with HW dz?

Answer 9

RS systolic heart murmur (tricuspid regurg)
Split S2 heart sound (dt pulmonary hypertension)
RSCHF (hepatomegaly, ascites + jugular venous distention/pulsation)

Question 10

What is an echo useful for in a dog with HW dz?

Answer 10

relatively insensitive in dx HW themselves but can evaluate heart size and function, and dx pulmonary hypertension

Question 11

What lung changes may you see on radiographs of a dog w/ HW dz?

Answer 11

pulmonary arterial enlargement/tortuosity/truncation, pulmonary interstitial changes

Question 12

What changes to the heart may you seen on rads of a dog with HW dz?

Answer 12

main pulmonary enlargement

RV enlargement

Question 13

What medications do you for 1 month prior to using an adulticidal?

Answer 13

1. Doxycycline 10mg/kg PO q12h to tx. Wolbachia spp
2. HW prophylaxis (moxidectin/ivermectin/milbemycin)
3. If Clinical - Prednisolone 0.5mg/kg PO q12h

Question 14

How do you administer Melarsomine?

Answer 14

2.5mg/kg IM kills males

1 month later 2 injections 24hrs apart kills females

Question 15

What additional precautions should be considered after treating a dog for heartworm dz w/ an adulticidal?

Answer 15

1. Exercise restriction for 4-6wks to reduce risk of PTE

2. Tapering prednisolone course after each injection

Question 16

When do you rpt antigen testing to verify successful treatment of HW dz?

Answer 16

6 months later

Question 17

What are 3 methods to test for microfilaria?

Answer 17

1. Filtration method: Knott’s or Wylie’s Test
2. Blood film
3. “Drop” method

Question 18

What is the aim of a pre-treatment assessment?

Answer 18

Stage severity of the disease and determine the level of risk with treatment

Question 19

How do you stage HWD?

Answer 19

Mild
Moderate
Severe
Caval Syndrome

Question 20

What stage is a HW AG+ dog w/ exercise intolerance, a cough and abnormal lung sounds?

Answer 20

Moderate

Question 21

Does a dog with Mild HWD have symptoms?

Answer 21

no - asymptomatic

Question 22

What stage if a HW AG +ve dog w/ ascites, exercise intolerance, hepatomegaly and dyspnoea?

Answer 22

Severe

Question 23

What are the 4 aspects of treatment of HWD?

Answer 23

1. Absolute rest
2. Adulticidal therapy
3. Adjunct therapy
4. Symptomatic: anti-inflam + reduce pulmonic hypertension

Question 24

List 4 monthly macrocyclic lactones

Answer 24

• Ivermectin
• Selamectin
• Moxidectin
• Milbemycin