Investigation On The Infection With Anaplasma Phagocytophilum In Ticks From Forest Area In Northeast Of China

Tick is a serious harmful arthropod which is widely distributed in China. It cantransmit a variety of pathogens. Tick can harm human and animals by biting directly,and can cause amphixenosis by changing host. So tick-borne disease is a major threatto the health of residents and visitors in forest area of China. Human granulocyticanaplasmosis (HGA) is a new acute febrile tick-borne disease caused by Anaplasmaphagocytophilum. HGA spreads mainly through tick bites. Many provinces and cities inChina have the outbreaks. Forest area in northeast is an old natural foci of HGA. Furthermore, the accidental infection of many susceptible people in non-disease area hasincreased because of the development of forest tourism and the sideline occupation.This study selected forest areas from Mudanjiang City, Heilongjiang Province innortheast for the survey area. This study combined the field-site investigation andlaboratory analysis to do the follow-up investigation in the natural foci of HGA. GltAfragment was amplified by Polymerase chain reaction method to analyze the infectionsituation of AP in ticks of northeastern forest area, and to confirm the positive fragmentsby amplifying and sequencing16S rRNA fragment. As a whole, a total of2293tickswere tested, including1161in2010and1132in2011, with the positive rates ofA.phagocytophilum were4.91%and4.24%respectively. There is no significantdifference between the two years by chi-square test. The positive rates of Ixodespersulcatus, Haemaphysalis longicornis and Dermacentor silvarum were4.86%,3.41%and0. There is no significant difference among them by chi-square test. Combined theresults of test and the ecological environment analysis showed that temperature andrainwater influence to the tick distribution. At the same time, the soil type and the typeof niche are the risk factors possibly which can affect the infection of AP in ticks. Phylogenetic analysis showed that the kinship distance of AP is different among regionssignificantly.At the same time, the potential vector Ixodes persulcatus which is distributed inforest area of northern China and aggressive to human and animals was elected in thestudy, to research the pattern of AP’s transmission through propagation test. Usesfluorescence quota PCR the method detect the AP infection in ticks. And the resultsshowed that there are transphasic transmission and transovarial transmission of AP inticks. But the efficiency of transovarial transmission is low.Integrated the natural environment of northeast and the molecular biology testresults analyze the dominant vector and the transmission patterm of AP, and to clarifythe risk factors of AP infection. The results of this study showed that there is infectionof AP in ticks in forest area of northeast, and Ixodes persulcatus and Haemaphysalislongicornis are the intermediate host of AP. This study confirmed the existence oftransphasic transmission and transovarial transmission in Ixodes persulcatus for the firsttime. The results of this study provide a scientific basis for predicting the occurrence ofticks accurately and measures for prevention and control of ticks reasonably.