Effects Of Ivermectin On The Development And Reproduction Of Haemaphysalis Longicornis

Haemaphysalis longicornis is blood-sucking ectoparasites which is widely distributed in the world and can attack a great diversity of host animals. It can carry a variety of pathogens and spread diseases. Hence, studies on ticks are of great significance for economics, medicine and epidemiology.Ivermectin is fermentation product of the fungus Streptomyces vermitilis, which is a new kind of antiparasitic agent with broad spectrum, high efficiency and low toxicity. Ivermectin is used to treat parasites especially on roundworms and arthropods.The efficacy of ivermectin on infestation of larval, nymphal and adult H. longicornis was evaluated after dose subcutaneous injection in rabbits. 24 hours after injection, the rabbits were artificial infested with larvae, nymphs and adults, and the bite-rate, feeding period, engorged weight, preoviposition period, oviposition and mortality were recorded. Results showed that different doses subcutaneous injection of ivermectin were not significantly reduced in the bite-rate and preoviposition period(p>0.05). It was significantly reduced in the engorged weight, oviposition, hatchability and mortality of larvae and nymphs(p<0.05).Observation on morphology of ovaries of the experimental and control group was conducted by the stereomicroscope. The average size of ovaries in experimental group was smaller than that of the control group. The follicles of experimental group ticks were dysontogenesis.On the day 7th, 14 th and 21 th after injection with 0.4 mg/kg ivermectin, rabbits were infested with 50 unfed adults. The engorged weight, oviposition period and hatchability of ticks were recorded. Results indicated that, no significant difference was observed in these biological parameters( p>0.05), which suggested that a single dose of ivermectin cannot last for a long time.This paper argues that ivermectin has no significant effect on bite-rate of ticks, but it has significantly effect on engorged weight, oviposition, hatchability and mortality of larvae and nymphs. It can inhibit the development and reproduction of ticks by significantly reducing the engorged weight and oviposition.