长角血蜱、嗜群血蜱经期传播莱姆病螺旋体Borrelia garinii的实验研究

Experiment infection and trans-stadial transmission of Lyme spirochetes in Haemaphysalis longicornis and H.concinna(Acari:lxodidae)

目的 探讨长角血蜱、嗜群血蜱经期传播莱病螺旋体的可能性。方法 通过皮下注射KM鼠建立实验感染动物模型 ,以此阳性感染鼠感染试蜱非感染种群 ,观察试蜱的感染能力以及以莱姆病螺旋体的保持能力。结果 通过剌叮阳性KM鼠 ,长角血蜱、嗜群血蜱幼蜱饱血后分别获得 6 1 3%、75 0 %的阳性感染 ,但所感染的螺旋体在感染后 2d即死亡消解 ,不能重新获得分离 ,PCR扩增阳性也只能持续到饱血后 8d ,幼蜱蜕化为若蜱后 ,所有检测结果均为阴性 ;这两种蜱的若蜱也都可通过吸血获得 70 0 %的检测阳性率 ,感染后长角血蜱、嗜群血蜱可分别在在饱血后 5、10d内保持螺旋体的活性 ,PCR检测阳性率可延迟至饱血后 15d。此后直至蜕化成为成蜱 ,所有血、蜱检测结果均呈阴性 ;长角血蜱、嗜群血蜱的不同种群在感染和保持螺旋体能力上表现一致。结论 长角血蜱、嗜群血蜱的幼蜱和若蜱虽可以感染莱姆病螺旋体但不能经期传播到下一发育阶段 ,不具备经期传播能力 ,作为莱姆病主要媒介的可能性不大。

Aim To study the possibility of H.longicornis and H.concinna to transmit Lyme spirochetes trans stadially Method With KM mouse model described previously,both larva and nymphs ticks of H.longicornisand H.concinna free from spirochetes were allowed to feed on it,and the possibility of the ticks to acquire and maintain the Lyme spirochets was tested.Results (1)The larval tick could acquire B.garinii by feeding on KM mouse.The gorged larva of H.longicornis and H.concinna were found harbored the agent and the positive rates were 61 3% and 75 0% respectively by PCR tests.While about 36 6% H.longicornis,50 0% H.concinna gorged larva were found harbored live spirochetes by cultivation.The spirochete infected could only be maintained alive in ticks within 2 days after replete and was detectable in H.longicornis,H.concinna within 4 days after replete.But all the gorged larvae were unable to maintain the sirochetes across the molting process.After molting,all the emerged nymphs and KM mice attacked by the nymphs were negative for B.gainii by both PCR and cultivation.(2)The nymphticks free from spirochete could also acquire B.garinii by sucking on KM mice.The agent in gored nymphs of 70 0% H.longicornis and 70 0% H.concinna were detectable by PCR.Spirochetes were also recovered from the gored nymphs.The positive rates were 36 7% and 70 0% respectively.The nymph ticks of H.longicornis could only keep active infection for 5 days,compared to H.concinna for 10 days after replete.B.garinii in H.longicornis and H.concinna gored nymphs were detectable for 15 days after replete.While,all the gorged nymphs were unable to maintain the spirochetes till the adult stage.After molting,neither the emerged adults nor KM mice attacked by the adult ticks were found infected.The same tick species collected from different sites had similar results.Conclusion H.longicornis and H.concinna were unable to transmit B.garinii(CHNM4) trans stadially.It seems to be impossible for H.longicornis and H.concinna to serve as the primary vector of the disease.