Microfilaricidal Efficacy of Ivermectin on Zoonostic Brugia malayi in Naturally Infected Cats

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Sirichai Phantana
Nopporn Sarataphan
Gaysorn Chansiri
Kosum Chansiri



This study focused on the determination of the periodicity of microfilaria in naturally Brugia malayi infected adult cats and the evaluation of the efficacy of ivermectin as a microfilaricidal drug. Periodicity was achieved by collection of blood from 5 infected cats at 2-hour intervals over a period of 24 hours. The results showed that the parasites of all investigated cats were nocturnally subperiodic B. malayi, with the highest peak at approximately 24.00 hour. Five groups of cats were investigated for the efficacy of ivermectin. Groups 1 and 2 were given orally using two different single doses of ivermectin at 50 and 100 μg/kg body weight, respectively. Groups 3, 4 and 5 were subcutaneously injected using doses of 200, 400 and 1,000 μg/kg body weight, respectively. The results indicated that the microfilarial density of all ivermectin-treated cats had significantly dropped after 30 days of treatment (p < 0.01). In addition, similar results were observed when the same ivermectin dosages were given at day 30 after the first dose (p < 0.05). This study showed that the repeated doses of ivermectin given at 30-day interval were able to reduce the microfilaria of B. malayi in the blood circulation. This study also indicated that the oral and subcutaneous application of ivermectin was effective for rapid clearance of microfilaria in the blood circulation.

Keywords : Brugia malayi, ivermectin

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