Further variation of the adulticide protocol for the treatment of canine heartworm infection: can it be even shorter and cost less?

Table 1 Toronto Humane Society (THS) heartworm treatment protocol compared with 2020 American Heartworm Society (AHS) treatment guidelines. Modifications are shown in italics type. Day 0, day of diagnosis

	AHS guidelines, Nelson et al. [1]	Current THS protocol
Diagnosis	Day 0	Day 0
Macrocyclic lactone	Day 1, then monthly	Day 1, then monthly
Doxycycline	10 mg/kg PO BID, days 1–28	10 mg/kg PO SID, days 1–28
Prednisone	Prior to melarsomine if symptomatic At time of M1 (day 61); M2 (day 90) 0.5 mg/kg PO BID first week, 0.5 mg/kg SID second week, 0.5 mg/kg every other day for the third and fourth weeks	Prior to melarsomine if deemed necessary; dose and duration at clinician discretion At time of M1 and M2—as per AHS guidelines
Melarsomine	First injection day 61, second and third injections days 90 and 91	First injection day 14, second and third injections days 44 and 45
Test for microfilariae	Day 120 and 9 months after last melarsomine	Day 75 and 6 months after last melarsomine^a
Antigen test	9 months after last melarsomine	6 months after last melarsomine^a
Protocol complete	12 months from diagnosis	7.5 months from diagnosis

^aTesting 6 months after melarsomine was performed for dogs still in shelter care, or recommended to adopters if adopted earlier

ISSN: 1756-3305