Abstract:

Objective: In this paper, we studied the population dynamics of the dominant hard tick (Haemaphysalis longicornis) in the forest environment in the western mountainous areas of Beijing, and investigated the influence of the weather factors on questing activity of H. longicornis, in order to protect tourists and forest workers from their bites. Method: Three experimental sites in the western mountainous scenic area of Beijing were selected, and the tick population in the sites was sampled every two weeks from 2017 to 2018, and the dragging method was used to investigate tick population for 3 hours in each site. During investigation, 9 weather factor data, such as temperature, relative humidity, dew-point temperature and solar radiation, were collected by hygrothermograph and automatic weather station. The principal component analysis, T-test and Pearson correlation coefficient were used to analyze the difference in the number of ticks between different sites and the effects of weather factors on questing activity of H. longicornis. Result: The results showed that:1) The annual population dynamics of the H. longicornis presented a bimodal pattern with the peaks occurred in May and September, respectively, and the number of peaks in May was 13.9 times of that in September. 2) There was a difference in the number of ticks among different sites. The average number of ticks collected in Tangjiachang, where animal husbandry was the main activity, was significantly greater than that collected in Donggou (t=-3.38, P < 0.01) with a small amount of agricultural activity, and also significantly greater than that collected in Beigou (t=-3.00, P < 0.01) with fewer human activity. However there was no difference in the number of ticks between Donggou and Beigou (t=-0.77, P>0.05). 3) The solar radiation, saturation difference and evaporation were positively correlated with questing activity of H. longicornis, while relative humidity, leaf-litter layer relative humidity and the dew-point temperature were negatively correlated to questing activity of H. longicorni. 4) Principal component analysis method was used to reduce the dimension of 9 weather factors, and 2 principal components were extracted, and their cumulative contribution rate was 78.32%. The first principal component was defined as the temperature factor, with the maximum contribution of sampling temperature, saturation difference, solar radiation and evaporation, reaching 42.39%; the second principal component was defined as the humidity factor, which contributed the most to the relative humidity, the leaf-litter layer relative humidity and the dew-point temperature, with 35.93%. Conclusion: The adult ticks of H. longicornis have two peak periods in spring and autumn, especially in spring when ticks are more active in warm and dry weather and its population is higher than that in autumn. The coupling of the two attributes makes spring a high incidence of invasion and bites of H. longicornis in northern China. In the livestock area, due to the large number of hosts, the population of H. longicornis significantly increases and therefore, the supervision of tick-borne diseases should be strengthened in the above-mentioned region and weather conditions, especially in spring.

Key words: Haemaphysalis longicornis, temporal-spatial dynamics, weather factors, influence