Heartworm Flashcards
Heartworm scientific name
Dirofilaria immitis
What stage of the lifecycle occurs in the mosquito?
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
What stage of the lifecycle occurs in the dogs skin/muscles?
L4-L5
L5 migrates into the systemic vascular system
What is the prepatent period?
~6-7months
What is the lifespan of an adult heartworm?
5-7yrs
what clinical signs may you see with Caval syndrome?
anorexia, lethargy, RSCHF, haemolytic aenaemia, hemoglobinuria, hemoglobinaemia, hepatic + renal dysfunction, resp. signs
What does a +ve AG test but negative mff test mean?
occult infection/immature adults, single sex infection or elimination of mff by recent tx (macrocyclic lactones)
what pulmonary signs may be present w/ HW dz?
inc. bronchovesicular sounds, crackles, tachypnoea and a cough
exercise intolerance
what abnormalities may you notice on cardiac auscultation of a dog with HW dz?
RS systolic heart murmur (tricuspid regurg)
Split S2 heart sound (dt pulmonary hypertension)
RSCHF (hepatomegaly, ascites + jugular venous distention/pulsation)
What is an echo useful for in a dog with HW dz?
relatively insensitive in dx HW themselves but can evaluate heart size and function, and dx pulmonary hypertension
What lung changes may you see on radiographs of a dog w/ HW dz?
pulmonary arterial enlargement/tortuosity/truncation, pulmonary interstitial changes
What changes to the heart may you seen on rads of a dog with HW dz?
main pulmonary enlargement
RV enlargement
What medications do you for 1 month prior to using an adulticidal?
- Doxycycline 10mg/kg PO q12h to tx. Wolbachia spp
- HW prophylaxis (moxidectin/ivermectin/milbemycin)
- If Clinical - Prednisolone 0.5mg/kg PO q12h
How do you administer Melarsomine?
2.5mg/kg IM kills males
1 month later 2 injections 24hrs apart kills females
What additional precautions should be considered after treating a dog for heartworm dz w/ an adulticidal?
- Exercise restriction for 4-6wks to reduce risk of PTE
2. Tapering prednisolone course after each injection
When do you rpt antigen testing to verify successful treatment of HW dz?
6 months later
What are 3 methods to test for microfilaria?
- Filtration method: Knott’s or Wylie’s Test
- Blood film
- “Drop” method
What is the aim of a pre-treatment assessment?
Stage severity of the disease and determine the level of risk with treatment
How do you stage HWD?
Mild
Moderate
Severe
Caval Syndrome
What stage is a HW AG+ dog w/ exercise intolerance, a cough and abnormal lung sounds?
Moderate
Does a dog with Mild HWD have symptoms?
no - asymptomatic
What stage if a HW AG +ve dog w/ ascites, exercise intolerance, hepatomegaly and dyspnoea?
Severe
What are the 4 aspects of treatment of HWD?
- Absolute rest
- Adulticidal therapy
- Adjunct therapy
- Symptomatic: anti-inflam + reduce pulmonic hypertension
List 4 monthly macrocyclic lactones
- Ivermectin
- Selamectin
- Moxidectin
- Milbemycin
