In a dog diagnosed and verified as heartworm positive, either by:
• Positive antigen (Ag) test verified with microfilaria (MF) test, OR if no MF are detected,
• Confirm with a second Ag test with a new sample on a different type of testing platform
1. Administer appropriate heartworm preventive (monthly [topical or oral] or injectable)
– If MF are detected, pre-treat with antihistamine and glucocorticosteroids, if not already on prednisone, to reduce risk of anaphylaxis
– Observe for at least 8 hours for signs of reaction
2. Administer doxycycline 10 mg/kg BID for 28 consecutive days
• Reduces pathology associated with dead heartworms
• Disrupts heartworm transmission
3. Begin activity restriction—the more pronounced the signs, the more rigid the activity restriction
4. Administer an EPA- or FDA-approved ectoparasiticide product designed for use in dogs that has demonstrated mosquito-killing activity

If the dog is symptomatic in addition to the items above:
• Stabilize with appropriate therapy and nursing care
• Prednisone prescribed at a tapering dose of 0.5 mg/kg BID 1st week, 0.5 mg/kg SID 2nd week, 0.5 mg/kg every other day (EOD) for the 3rd and 4th weeks

Communicate with the client to ensure:
1. Completion of the full course of doxycycline
2. Administration of heartworm preventive (unless injectable heartworm preventive was administered on day 0)
3. Administration of an EPA- or FDA-approved ectoparasiticide product designed for use in dogs that has demonstrated mosquito-killing activity

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A one-month wait period after administration of doxycycline but before administration of melarsomine is currently recommended

1. Administer heartworm preventive (unless injectable heartworm preventive was administered on day 0)
2. Administer 1st (of 3) melarsomine injections, 2.5 mg/kg intramuscularly (IM)
a. Monitor for post-injection anaphylaxis
b. Prescribe appropriate pain control
3. Prescribe a tapering dose of prednisone of 0.5 mg/kg BID 1st week, 0.5 mg/kg SID 2nd week, 0.5 mg/kg EOD for the 3rd and 4th weeks
4. Start rigid activity restriction (or maintain if started on day 0): cage restriction, on-leash when taken outside to eliminate
5. Administer an EPA- or FDA-approved ectoparasiticide product designed for use in dogs that has demonstrated mosquito-killing activity

1. Administer heartworm preventive (unless injectable heartworm preventive was administered on day 0)
2. Administer 2nd (of 3) melarsomine injection, 2.5 mg/kg intramuscularly (IM)
a. Monitor for post-injection anaphylaxis
b. Prescribe appropriate pain control
3. Prescribe a tapering dose of prednisone of 0.5 mg/kg BID 1st week, 0.5 mg/kg SID 2nd week, 0.5 mg/kg every other day (EOD) for the 3rd and 4th weeks
4. Administer an EPA- or FDA-approved ectoparasiticide product designed for use in dogs that has demonstrated mosquito-killing activity

1. Administer 3rd (of 3) melarsomine injection into the opposite epaxial muscle from the injection site on day 90, 2.5 mg/kg intramuscularly (IM)
a. Monitor for post-injection anaphylaxis
b. Prescribe appropriate pain control
2. Continue rigid activity restriction for the next 6–8 weeks: cage restriction, on-leash when taken outside to eliminate

1. Quantitatively test (e.g., Modified Knott Test) for presence of MF regardless of patient’s MF-status on day 0
• If positive, treat with a microfilaricide and retest every 4 weeks until no MF detected. If MF persist, additional testing for resistance should be considered
2. Continue a year-round heartworm and mosquito prevention program as described under Prevention
3. Gradual return to normal activity over the next 4 weeks

Resume annual HW-screening protocol (9 months after last melarsomine injection)
• Antigen test
• Microfilaria test
If still Ag-positive, re-treat with 28 days of doxycycline followed by 2 injections (2.5 mg/kg IM each) of melarsomine 24 hours apart
• Monitor for post-injection anaphylaxis
• Prescribe appropriate pain control • Prescribe a tapering dose of prednisone of 0.5 mg/kg BID 1st week, 0.5 mg/kg SID 2nd week, 0.5 mg/kg for the 3rd and 4th weeks
• Institute and maintain strict activity restriction for 6–8 weeks: cage restriction, on-leash when using yard

Additional Notes

* This At-Home Treatment Plan is only meant to serve as a guide. Please consult your veterinarian for important information about the treatment and prevention of Heartworm Disease.