Identification And Analysis Of Hard Tick (Ixodidae) Species And Their Important Tick-borne Pathogens From Cattle And Sheep In Some Areas Of Shaanxi Province

Ixodes are a kind of obligate parasitic bloodsucking arthropod,which often parasitize on the body surface of livestock and wild animals.They feed on the blood of the host,resulting in anemia,malnutrition and other clinical symptoms.Plus,ticks carry and spread a variety of pathogens including parasites,viruses and bacteria,which does harm to the health of humans and animals,and poses a great threat to the development of animal husbandry as well.Shaanxi Province is rich in forest and vegetation resources and has a wide variety of tick species.With the continuous development of animal husbandry and tourism industry,the distribution area of ticks has gradually expanded,leading to the increasing threat of tick-borne diseases.Therefore,the understanding of tick species and tick-borne pathogens in different regions of Shaanxi Province will lay a foundation for the specific prevention and control measures of ticks and tick-borne pathogens.Morphological observation combined with molecular biology methods were used to identify the species of ticks collected from cattle and sheep in some areas of Shaanxi Province(Yan ’an city,Yulin city and Ankang city).Normal PCR and Nestler PCR were used to detect the pathogens such as Rickettsiales,Babesia,Theileria,Anaplasma ovis,Anaplasma phagocytophilum,A.bovis,Brucella in ticks(adult ticks,eggs and larval ticks)and sheep blood.The following results are obtained:1.Morphological observation together with molecular biology methods were applied,and a total of four ticks species are identified from 569 tick samples collected from parts of Shaanxi Province.They are Dermacentor nuttali and Dermacentor silvarum in Northern Shaanxi(Yan ’an city and Yulin city),Rhipicephalus microplus and Ixodes acutitarsus in Southern Shaanxi(Ankang city).2.Under the scanning electron microscope,the morphology of Dermacentor nuttali,Dermacentor silvarum,Rhipicephalus microplus and Ixodes acutitarsus are observed and described.The micro morphological structures of tooth shape,peritreme,claw and coat of four kinds of Ixodes are supplemented on the basis of previous studies.3.PCR was used to detect tick-borne pathogens in 580 tick samples and 47 sheep blood samples from parts of Shaanxi Province,and a total of 8 pathogens are detected in tick samples,namely,Rickettsia Raoultii,R.sibirica,R.japonica,A.phagocytophilum,A.ovis,A.bovis,T.sinensis,T.orientalis.Among them,the carrying rate of Rickettsia,A.phagocytophilum,A.ovis,A.bovis and Theileria in ticks is 41.1%,8.1%,65.2%,0.2% and 13.5%,respectively.However,Babesia and Brucella are not detected in the four ticks species.Two pathogens are detected in sheep blood samples,R.raoultii and A.ovis,with positive detection rate of 4.3% and 12.8%,respectively,and these two pathogens are consistent with those in some ticks collected in Yan ’an city.It is speculated that ticks may have the ability to carry and transmit R.raoultii and A.ovis.However,no positive samples of A.phagocytophilum,A.bovis and Theileria are detected in sheep blood collected this time.In conclusion,tick species such as Dermacentor nuttali,Dermacentor silvarum,Rhipicephalus microplus and Ixodes acutitarsus distribute in some areas of Shaanxi Province(Yan ’an city,Yulin city and Ankang city),and they carry at least eight different pathogens including Rickettsia Raoultii,R.sibirica,R.japonica,A.phagocytophilum,A.ovis,A.bovis,T.sinensis,T.orientalis.Among them,R.raoultii and A.ovis can bear and transmit pathogens to the host.The results of this study are helpful to comprehend the distribution of tick species in some areas of Shaanxi Province and the risk of tick-borne pathogens transmission,which provide basic information and reference for the rational prevention and control and further researches on tick-borne pathogens.