in the present study, all treated dogs were given a higher dosage of doxycycline (i.e. 10 mg/kg twice daily) for 30 days, and blood was collected from these dogs at 73 to 77 or 161 to 164 days after dosing was started. mosquitoes were allowed to feed on blood from the treated dogs or from matched control. L3 were collected from the mosquitoes 16 days later, and these L3 were injected SC into heartworm-naive beagle