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Heartworm Disease: Management 1423

Heartworm Disease: Management
VetBooks.ir Positive heartworm test result in a dog

Repeat (or confirm with) antigen test,
especially if in area of low endemicity

Positive Negative

If overt clinical signs are Preadulticide staging: • False-positive initial result
present, initiate the following • Thoracic radiographs • No adulticide treatment; begin/
while proceeding with • CBC, serum biochemistry panel continue preventive
preadulticide staging: • Urinalysis • Repeat antigen test immediately
• Supportive care as needed • Microfilaria test with heat-treated sample and/or
• Prednisone 0.5 mg/kg PO • Echocardiography if: in 3 months
q 12h × 1 week, then 0.5 Radiographic cardiac changes, and/or
mg/kg PO q 24h × 1 week, Physical evidence of caval syndrome, and/or
then 0.5 mg/kg PO q 48h × Evidence of concurrent heart disease
2 weeks Begin exercise restriction
• Doxycycline 10 mg/kg PO • Echocardiographic confirmation of
q 12h × 4 weeks caval syndrome if not already done
• Surgical heartworm removal
Transjugular approach
Is there evidence of caval syndrome (p. 418)? (forceps, brushes; ultrasound- and/
• Physical (abdominal enlargement, cachexia) Yes or fluoroscopy-guided)
• Diagnostic test results (right-sided cardiomegaly, heartworms seen Transatrial approach (highly
in right atrium/right ventricle echocardiographically, ascites, pleural invasive, not preferred)
effusion, hemoglobinuria) • Guarded prognosis
No
Begin treatment for Wolbachia if not already underway:
doxycycline 10 mg/kg PO q 12h × 28 days, and administer dose
of monthly preventive 1 month later, administer second dose of
monthly preventive 1 month later (2 months postdiagnosis),
administer third dose of monthly preventive and begin adulticide After complete recovery
treatment: (usually several weeks)
• Melarsomine 2.5 mg/kg deep IM once, then
• Treatment with prophylactic drugs alone to • Strict exercise restriction 30 days, then
achieve an adulticide effect is variable/ • Melarsomine 2.5 mg/kg IM twice 24 hours apart, then
unpredictable in efficacy, and can require • Strict exercise restriction 30 days
more than 1 year of treatment for effect
• Not recommended as a substitute for
melarsomine Yes Continue monthly preventive if using microfilaricidal
preventive (e.g., milbemycin); otherwise, treat with
Initially microfilaremic?
microfilaricide (e.g., imidacloprid-moxidectin
[Advantage-Multi]) in addition to monthly preventive
No
• Treatment is finished
• Continue with monthly preventive/
prophylaxis and repeat antigen test Repeat microfilaria test 2 to 4 weeks post-microfilaricide
3 months post-adulticide
Negative Positive
Positive Negative Clinical Algorithms
antigen test antigen test
Confirm with second opinion (e.g., rule out
Acanthocheilonema)
Continue monthly prophylaxis and
annual antigen testing
True positive: repeat microfilaricide treatment

Continue with monthly preventive/prophylaxis and repeat antigen test 3 months post-adulticide

Negative Positive

CBC, Complete blood count; IM, intramuscular.
Additional information available on the American Heartworm Society website: www.heartwormsociety.org.
AUTHOR & EDITOR: Etienne Côté, DVM, DACVIM
www.ExpertConsult.com