Effect of diethylcarbamazine citrate on Brugia malayi infections in cats following daily, weekly, or monthly administration

Cats with patent infections of Brugia malayi were treated by intraperitoneal injection of diethylcarbamazine citrate (DEC) for 6 consecutive days, weekly for 6 consecutive weeks or monthly for 3 months. Each cat received a total of 100 mg DEC per kg. At necropsy 7 months after infection, no living worms were recovered from any of eight cats treated weekly and only one of nine cats treated daily had a single living Brugia. Five of nine cats treated monthly and six of eight untreated controls had one or more living worms. Cats treated weekly showed a larger decline in microfilariae than those of the other treated groups. The mean microfilariae level of untreated controls increased 2-fold. At necropsy, gross appearance of regional lymphatics in daily and weekly treated cats resembled those of uninfected controls more closely than those in cats treated monthly or untreated. Differences in degree of histological changes between groups of infected cats were not apparent. Weekly administration of DEC appeared to be the most effective regimen; monthly treatment was less effective.