小五台山地区长角血蜱若虫日间寻求节律

Diurnal questing activity of Haemaphysalis longicornis (Acari: Ixodidae) nymphs in Xiaowutai Mountain Area

目的旨在了解长角血蜱若虫日间寻求活动节律及其变化原因,为研究者规划合理采样时间,从而准确评估蜱传疾病风险提供理论依据。方法在河北省小五台山地区选取半封闭山路设置3处样带,于长角血蜱种群数量高峰期内,连续5 d从6∶00-19∶00,每隔1 h采用拖旗法对处于寻求状态若虫进行有放回抽样调查,同时记录气温,相对温度和露点温度。结果 不同样带间蜱采样数量差异显著(F=66.50,P <0.01),离居住地越近蜱数量越多;各样带间长角血蜱若虫均表现出相同寻求活动节律,受气温和露点温度影响,6∶00-8∶00若虫数量下降,8∶00-12∶00有一起伏,随后逐渐上升至16∶00趋于稳定并于19∶00达到最大,16∶00-19∶00为日间长角血蜱若虫采集数量最高时段,占总采集数量的48.4%。结论 宿主活动强度对蜱数量分布有较大影响;蜱寻求节律与空气中水汽含量有关,清晨水汽含量过大植被凝集露水,中午水汽含量过小,空气干燥,都可降低蜱寻求活动,导致不同时间下采样可造成蜱种群密度估计和蜱传疾病风险评估误差,16∶00-19∶00环境条件适宜,蜱寻求活动强烈,是最接近蜱种群密度的采样时间,建议在制定林间蜱种群密度调查方案时,应统一采样时间以便数据具有可比性。

We investigated the diurnal questing activity of Haemaphysalis longicornis (Acari: Ixodidae) nymphs. In the Xiaowutai mountain area of Hebei Province, we selected three quadrats during the peak period of the tick population (May). We used the dragging method to count the number of nymphs showing questing activity from 5 AM to 7 PM for five consecutive days. The temperature, relative temperature, and dew-point temperature were all recorded at the same time. The study shows that there was a significant difference in the frequency of sampling among the quadrats ( F=66.50, P <0.01);the closer to the place of residence, the greater was the number. The nymphs collected from all the quadrats exhibited the same rhythm of questing activity. The findings from this study further revealed that depending on the temperature and dew-point temperature, the number of nymphs decreased from 6 AM to 8 PM, there was a rise and fall between 8 AM and 12 PM, and the number gradually increased at 16 PM which was stable, and reached a maximum at 19 PM. For most of the days, the nymph collection was the maximum from 16 AM to 19 PM accounting for 48.4% of the total collection. The results showed that host activity intensity had a greater impact on the tick distribution. Furthermore, the diurnal questing activity of the nymphs was related to the water vapor content in the air. In the early morning, the water vapor content was too high and the vegetation contained dew condensation. However, at noon, the water vapor content was too less and the air was dry resulting in a reduction of the questing activity. This phenomenon led to a risk assessment error in the estimation of tick population density and tick-borne diseases across different sampling times. However, from 16 AM to 19 PM, the environmental conditions were favorable for the questing activity, and this sampling time could give the estimate of the true population density of the ticks. Therefore, while planning a tick population density survey, the sampling time should be uniform so that the data can be accurate and comparable.