| Ticks are a specific blood-sucking parasite which can carry and transmit bacteria,viruses and other pathogens that are widely distributed around the world.Ticks are the second largest vector of infectious diseases after mosquitoes.Human beings are accidental hosts of ticks,while other hosts also include mammals,birds,reptiles and amphibians.The population dynamics and life cycle of ticks determine the epidemiological characteristics of tick-borne diseases.This helps us grasp the geographical distribution,population dynamics and life cycle of ticks.Thus,this in return provides scientific support for the development of public health,tourism and animal husbandry.In addition to that,it also provides scientific basis for the formulation of tick population control and prevention of tick-borne diseases.Part I Investigation on tick species and geographical distribution in Hebei ProvinceObjective: To grasp the species and geographical distribution of ticks in Hebei Province.Methods: 1.Tick distribution data in Hebei province were retrieved.2.Select the collection site.3.The collection site was collected by flagging vegetation method.4.The tick samples were identified by stereoscopy and scanning electron microscopy.5.Count the number and species of ticks collected.Results: 1 Tick species distribution data.1.1.Statistical Record of Chinese Economic Insects records 11 species of ticks distributed in Hebei Province.1.2.A total of 64 Chinese and English documents were retrieved,including 53 in English and 11 in CNKI.There are 11 documents about tick species distribution in Hebei province(excluding the same place to collect),including 6 in English and 5 in CNKI.There are 18 ticks in Hebei province.Among these 11 documents,3 were summary documents,which recorded 18 species of ticks in Hebei Province,and the other 8 were experimental documents,which recorded 5 species of ticks in Hebei Province.2.Morphological identification Stereoscopy and scanning electron microscopy were used to identify ticks.Three species of ticks were collected,namely,Haemaphysalis longicornis,Dermacentor silvarum and Ixodes.persulcatus.3.Sample classification statistics A total of 2035 ticks were collected,belonging to 3 genera and 1 family.They are H.longicornis,D.silvarum and I.persulcatus,respectively.Among them,1620 H.longicornis(79.6%)were collected,352 D.silvarum(17.2%)and 63 I.persulcatus(3%)were collected.H.longicornis is the dominant tick species in Hebei Province.4.Geographical Distribution of Samples.H.longicornis distributes throughout Hebei Province;D.silvarum mainly distributes in plateau,mountain,hill and basin of northern and northwestern Hebei Province;I.persulcatus mainly distributes in plateau area of northern Hebei Province.Conclusion: Five species of ticks can be identified in Hebei Province: H.longicornis,D.silvarum,I.persulcatus,and H.japonica and D.nuttalli.were collected in the document.H.longicornis is the dominant tick species,which was distributed throughout Hebei Province.The remaining ticks were not collected,but it did not indicate that they had disappeared in Hebei Province.Through this study,it is imperative to establish a normalized tick distribution monitoring system in Hebei Province.Part II Population dynamics of Haemaphysalis longicornisObjective: As the dominant tick in Hebei Province,H.longicornis grasps the dynamic changes of tick population,and provides scientific basis for controlling tick population and preventing tick-borne diseases in Beijing,Tianjin and Hebei.Methods: 1.Selection of acquisition location and time.2.Ticks were collected by flagging vegetation method at the experimental site.3.Collection of temperature and humidity data at experimental sites.4.Microsoft Office was used for statistical analysis of tick numbers and temperature and humidity data.Results: 1.Climate data Monthly means temperature and humidity data from February to November 2016 and February to November 2017.2.Population dynamics of H.longicornis.Adult ticks of H.longicornis appeared and began to move in the 2nd week of March every year.The highest population appeared in the 1st week of June,the second peak appeared in the 4th week of June and then disappeared from vegetation in the 3rd week of August.Nymphs of H.longicornis begins to move at the 4th week of March every year.The first peak population activity appeared in the third week of April,and the second peak of population activity appeared in the third week of May.After that,the number gradually decreased and disappeared from the vegetation in the 3rd week of September.The larvae of H.longicornis began to move in the 2nd week of May,then disappeared on the vegetation.The number of larvae began to increase in the 4th week of July,peaked in the 1st week of September and disappeared on the vegetation in the 1st week of November.Conclusion: H.longicornis has its peak activity at different developmental stages of the year: adult tick activity in May and June in summer,nymph activity in April and May at the turn of spring and summer and larvae activity in August and September in autumn.The early warning of tick population activity should be adapted to local conditions,with the average temperature of different regions as early warning indicators.Part III Life cycle of Haemaphysalis longicornis under Laboratory ConditionsObjective: New experimental conditions were established to shorten the life cycle of H.longicornis and observe the morphology at different developmental stages.Methods: 1.The non-bloodsucking H.longicornis at different developmental stages was weighed.2.H.longicornis was inoculated into rabbit ears at different developmental stages.3.Ticks should be weighed when they are full of blood and shed off.4.After weighing,the ticks were cultured in an artificial climate box.5.The development time,morphological changes,number and regularity of oviposition of ticks before and after blood saturation were observed and recorded.6.Ticks at different developmental stages were observed by stereoscopy and scanning electron microscopy.Results:1.It was found that under laboratory conditions,young ticks of H.longicornis,if full of blood,and adult female ticks would leave the host and molt or lay eggs,which is a three-host type.Its complete life cycle consists of four phases: eggs,larvae,nymphs and adult ticks.It takes 103 to 144 days to complete a life cycle,with an average of 117.3 days.2.Female ticks are very active at the initial stage of full blood shedding.At the same time,they will have 2-3 days of pre-oviposition.After oviposition,the activity of female ticks gradually decreases and dies after oviposition.At the beginning of spawning,the amount of spawning is small but increases.On the fourth day,the peak of ovipositing was about 400 grains,and then decreased gradually.The spawning stopped around 22 days.3.The correlation coefficient r = 0.459 between body weight and oviposition of female ticks of H.longicornis.REI is 12.63 and RFI is 8.05.4.The body weight of H.longicornis changed significantly before and after bloodsucking.The weight gain of ticks at different developmental stages was 23 times that of larvae,11.8 times that of nymphs,126.9 times that of female adult ticks and 1.41 times that of male adult ticks.5.Scanning electron microscopy of the back and ventral surfaces of female,male,nymph and juvenile ticks of H.longicornis.Conclusion: H.longicornis will change its host at different stages of development when it is full of blood and falls off.It is a three-host tick.The morphology and volume of H.longicornis at different developmental stages were significantly different.It takes 103-144 days(average 117.3 days)to complete the whole generation of H.longicornis under laboratory conditions of(24±1)?and(90±1%)humidity.It can reproduce 2-3 generations a year.There is a positive correlation between the number of eggs laid by female ticks and their body weight.The larger the body weight,the more the number of eggs laid.The trend of the number of eggs laid by female ticks is unimodal,with the largest number on the fourth day,and then gradually decreases. |
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