research article seroprevalence and risk factors of...

Research ArticleSeroprevalence and Risk Factors of Chlamydia abortusInfection in Tibetan Sheep in Gansu Province Northwest China

Si-Yuan Qin12 Ming-Yang Yin2 Wei Cong12 Dong-Hui Zhou2 Xiao-Xuan Zhang12

Quan Zhao1 Xing-Quan Zhu2 Ji-Zhang Zhou2 and Ai-Dong Qian1

1 College of Animal Science and Technology Jilin Agricultural University Changchun Jilin Province 130118 China2 State Key Laboratory of Veterinary Etiological Biology Lanzhou Veterinary Research InstituteChinese Academy of Agricultural Sciences Lanzhou Gansu Province 730046 China

Correspondence should be addressed to Ji-Zhang Zhou zhoujizhangcaascn and Ai-Dong Qian qianaidong0115163com

Received 27 June 2014 Revised 6 August 2014 Accepted 12 August 2014 Published 23 October 2014

Academic Editor Peirong Jiao

Copyright copy 2014 Si-Yuan Qin et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Chlamydia abortus an important pathogen in a variety of animals is associated with abortion in sheep In the present study 1732blood samples collected from Tibetan sheep between June 2013 and April 2014 were examined by the indirect hemagglutination(IHA) test aiming to evaluate the seroprevalence and risk factors of C abortus infection in Tibetan sheep 323 of 1732 (1865)samples were seropositive for C abortus antibodies at the cut-off of 1 16 A multivariate logistic regression analysis was used toevaluate the risk factors associated with seroprevalence which could provide foundation to prevent and controlC abortus infectioninTibetan sheepGender of Tibetan sheepwas left out of the finalmodel because it is not significant in the logistic regression analysis(119875 gt 005) Region season and age were considered as major risk factors associated with C abortus infection in Tibetan sheepOur study revealed a widespread and high prevalence of C abortus infection in Tibetan sheep in Gansu province northwest Chinawith higher exposure risk in different seasons and ages and distinct geographical distribution

1 Introduction

Chlamydia an obligate intracellular gram-negative bac-terium is known to cause a variety of diseases in animals andhumans [1 2] Chlamydiaceae have a single genus Chlamydiathat includes nine species among them C abortus and Cpecorum can cause diseases in sheep [1ndash3] In particularC abortus is recognized as a major cause of abortion andlamb loss throughout the world especially in the intensivelymanaged farms [4ndash6] C abortus usually causes ulcerationof endometrial epithelium resulting in placental infectionif infection was acquired during the early stages of thatpregnancy More typically infection acquired during lategestation will result in abortion in the following gestation andthe symptoms caused by C abortus also include epididymi-tis pneumonia arthritis and conjunctivitis [7ndash9] Recentreports described the presence of C abortusDNA in the eyes

of ewes [10 11] C abortus not only causes economic loss inthe sheep industry but also induces abortions in humans dueto contact with aborting sheep or goats [12ndash14]

Chlamydial infection of sheep has been reportedthroughout the world [10 15ndash18] including China Howeveron account of Tibetan sheep breeding only in northwestChina no more reports were available on epidemiology ofC abortus infection in Tibetan sheep in China except thatseveral reports about C abortus infection in Tibetan sheepin Qinghai were published in local journals [19 20] and onlyone article concerning C abortus infection in Tibetan sheepin Tibet was documented in the international literature [21]

Tibetan sheep is one of the three main original sheepbreeds living in the Qinghai-Tibetan Plateau passing throughparts of regions of Gansu province northwest China wherethe solar radiation is strong and the temperature and oxygencontent are low [19] Tibetan sheep are recognized as a major

Hindawi Publishing Corporatione Scientific World JournalVolume 2014 Article ID 193464 6 pageshttpdxdoiorg1011552014193464

2 The Scientific World Journal

source of income for local Tibetans due to its high qualitypelage and nutritive and delicious meat However it is yetto know whether Tibetan sheep are infected with C abortusin Gansu Province northwestern China The objective ofthe present study was to evaluate the seroprevalence andrisk factors of C abortus infection in Tibetan sheep inTianzhu Tibetan Autonomous County and Gannan TibetanAutonomous Prefecture Gansu province northwest China

2 Materials and Methods

21 The Study Site The serum samples used in the presentstudy were collected from Tibetan sheep in Tianzhu TibetanAutonomous County and Gannan Tibetan Autonomous Pre-fecture including Maqu County and Luqu County in GansuProvince northwest China The Tibetan sheep in Gansuwere mainly bred in Tianzhu and Gannan in which mostof the Tibetans also live The sampling site is between theeastern longitudes of 102∘071015840-103∘461015840 and northern latitudesof 36∘311015840ndash37∘551015840 in Tianzhu Tibetan Autonomous Countyand the average annual temperatures are from minus8 to 4∘CGannan Tibetan Autonomous Prefecture is located betweenlongitudes 100∘451015840 to 104∘451015840 east and latitudes 33∘061015840 to35∘341015840 north in which the average annual temperatures arefrom 1 to 13∘C

22 Serum Samples Blood samples were collected from 1732Tibetan sheep in 3 counties in Gansu province from June2013 to April 2014 The samples were collected randomlyfrom 8 Tibetan sheep herds including 4 random herds inTianzhu Tibetan Autonomous County and 4 random herdsof the farms in Gannan Tibetan Autonomous PrefectureSerum samples were separated from blood samples in localveterinary stations and then were taken to the laboratory andstored at minus20∘C until further testedThe detailed informationof animals was obtained from local herdsmen by questioning

23 Serological Examination A commercially available Indi-rect Hemagglutination Assay (IHA) kit (Lanzhou VeterinaryResearch Institute Chinese Academy of Agricultural Sci-ences Lanzhou China) was purchased to test antibodies toCabortus and it was carried out according to themanufacturerrsquosinstructions as described previously [20ndash22] The IHA kitwas employed following the standard method describedby China CADC and the sensitivity and specificity of theexperiment are 100 and 95 respectively The Ministryof Agriculture of China (NYT 562-2002) has validated thesensitivity and specificity values for the testing kit usedin this study In brief serum samples were added to 96-well V-bottomed polystyrene plates which were diluted 4-fold serially beginning with 1 4 to 1 1024 Then the Cabortus antigen was added and the plates were shakengently for 2min and incubated at 37∘C for 2 h Each testwas performed with positive negative and blank controlsand serum samples which had positive reaction at dilutionsof 1 16 or higher dilutions were considered positive for Cabortus antibodies Positive results between 1 4 and 1 16were considered ldquosuspectrdquo and were retested

24 Statistical Analysis Differences in the seroprevalence ofC abortus among Tibetan sheep of different geographicalorigins genders seasons and age groups were analyzedwith Chi-square tests using the SPSS software (SPSS IncIBM Corporation Version 19 USA) The differences wereconsidered statistically significant if 119875 lt 005 and the 95confidence intervals (CI) are also calculated

3 Results

In the present study 323 (1865) out of 1732 serum samplesfrom Tibetan sheep in Gansu province were seropositive forC abortus infection by IHA at a 1 16 cut-off (Table 1) Asshown in Table 1 the seroprevalence of C abortus infectionin Tianzhu County (119899 = 962) Maqu County (119899 = 588)and Luqu County (119899 = 182) was 1632 2262 and1813 respectively The numbers of seropositive animalsand seroprevalence of individual herd were described inTable 2 All of the sampled 8 Tibetan sheep herds wereserologically positive Male sheep had a higher prevalence(2151) compared to females (1739) The positive sampleswere distributed among four seasons (Spring 119899 = 480Summer 119899 = 398 Autumn 119899 = 479 Winter 119899 = 375) inwhich the prevalences of C abortus infection were 18542211 2046 and 1280 (119875 lt 005 Table 1) respectivelyThe ages of the examined Tibetan sheep varied from 0 yearsto 3 years or greater and seroprevalence in different agegroups ranged from 746 to 2441 (Table 1) The highestseroprevalence was found in Tibetan sheep older than 3 years(2441) and the lowest in 0 years to 3 years (746) Table 3summarizes the antibodies titers in different ages regionsgenders and seasons with IHA titers of 1 16 in 188 samples(5820) 1 32 in 72 samples (2229) 1 64 in 34 samples(1053) 1 128 in 14 samples (433) 1 256 in 12 samples(372) 1 512 in 2 samples (062) and 1 1024 in 1 sample(031)

According to forward stepwise logistic regression genderof Tibetan sheep was not significant in the logistic regressionanalysis (119875 gt 005) and left out of the final modelMultivariable analysis of such 4 factors showed that Cabortus seropositivity was associated with regions seasonsand ages Tibetan sheep in Luqu County was more than 14-fold increase (OR= 140 95CI= 107ndash184119875 = 0014) at riskofC abortus infection compared to Tibetan sheep in TianzhuCounty and no regional differences were found in LuquCounty compared to Tianzhu County (119875 gt 005) Ages ofTibetan sheep which were 1 lt years le 2 years old (1582) hada 25-fold increase higher risk of being seropositive comparedto that of Tibetan sheep which were 0 lt years le 1 years old(746) (OR = 248 95 CI = 151ndash407 119875 lt 0001) whileTibetan sheep of 2 lt years le 3 and gt3 years old had a 3-foldincrease (OR = 140 95 CI = 172ndash519 119875 lt 0001) and 40times (OR = 402 95 CI = 258ndash626 119875 lt 0001) higherrisk compared to Tibetan sheep of 0 lt years le 1 age groupseparately (Table 4) In terms of seasons the risk ofC abortusinfection in summer was more than 20-fold increase (OR =197 95 CI = 133ndash291 119875 = 0001) compared to C abortusinfection in winter (Table 4)

The Scientific World Journal 3

Table 1 Seroprevalence of Chlamydia abortus infection in Tibetan sheep associated with different factors in Gansu province northwestChina by indirect hemagglutination assay (IHA)

Factor Category Tested numbers Positive numbers Prevalence ()

RegionTianzhu County 962 157 1632Maqu County 588 133 2262Luqu County 182 33 1813

Sex Male 530 114 2151Female 1202 209 1739

Season

Spring 480 89 1854Summer 398 88 2211Autumn 479 98 2046Winter 375 48 1280

Age (yr)

0 lt yr le 1 335 25 7461 lt yr le 2 392 62 15822 lt yr le 3 194 38 1959yr gt 3 811 198 2441

Total 1732 323 1865

Table 2 Seroprevalence of Chlamydia abortus infection in Tibetan sheep in eight herds in two regions in Gansu China

Region Herd numbers Examined numbers Positive numbers Prevalence ()

Tianzhu

Herd (1) 242 43 1777Herd (2) 216 38 1760Herd (3) 255 31 1216Herd (4) 249 45 1807Total 962 157 1632

Gannan


Table 3 Seroprevalence of Chlamydia abortus infection in Tibetan sheep in Gansu China determined by indirect haemagglutination (IHA)test

Biometric data Category Antibody titers Positive numbers Tested numbers Prevalence ()1 16 1 32 1 64 1 128 1 256 1 512 1 1024

Age (years)

le1 16 4 0 3 2 0 0 25 335 7461 lt yr le 2 39 12 7 2 2 0 0 62 392 15822 lt yr le 3 19 10 4 2 3 0 0 38 194 1959yr gt 3 114 46 23 7 5 2 1 198 811 2441

RegionTianzhu County 83 30 21 12 10 0 1 157 962 1632Maqu County 85 35 8 2 1 2 0 133 588 2262Luqu County 20 7 5 0 1 0 0 33 182 1813

Sex Male 76 24 9 2 2 1 0 114 530 2151Female 112 48 25 12 10 1 1 209 1202 1739

Season

Winter 28 10 4 3 2 0 1 48 375 1280Spring 48 20 11 4 6 0 0 89 480 1854Autumn 62 22 8 5 1 0 0 98 479 2046Summer 50 20 11 2 3 2 0 88 398 2211Total 188 72 34 14 12 2 1 323 1732 1865


Table 4 Odds ratios for ages seasons and geographical origin of Tibetan sheep are taken as risk factors forChlamydia abortus seroprevalencein Tibetan sheep

Factor Category Tested numbers Positive numbers Prevalence () OR (95 CI) 119875 value

RegionTianzhu County 962 157 1632 ReferenceMaqu County 588 133 2262 091 (056ndash148) 0694Luqu County 182 33 1813 140 (107ndash184) 0014

Season

Winter 375 48 1280 ReferenceSpring 480 89 1854 167 (108ndash257) 0022Autumn 479 98 2046 178 (121ndash262) 0003Summer 398 88 2211 197 (133ndash291) 0001

Age (yr)

0 lt yr le 1 335 25 746 Reference1 lt yr le 2 392 62 1582 248 (151ndash407) lt00012 lt yr le 3 194 38 1959 299 (172ndash519) lt0001yr gt 3 811 198 2441 402 (258ndash626) lt0001

4 Discussions

Members of the family Chlamydiaceae can result in a broadrange of diseases in both humans and animals includingsheep which could cause health problems and heavy eco-nomic losses [23] In particular lamb loss in sheep wascaused by C abortus in North America Africa and partsof Europe including UK in which costs to the farmingindustry due to C abortus in sheep were estimated to bepound 20000000 per annum [1] Tibetan sheep surveyed inthe present study were free-ranging on the grassland inTianzhu Tibetan Autonomous County and Gannan TibetanAutonomous Prefecture and the meat production of whichwas not only transported to other Cities of Gansu provinceincluding Lanzhou as the provincial capital but also trans-ported to adjacent provinces including Qinghai SichuanShanxi and Ningxia However there was little informationavailable about the prevalence of C abortus in Tibetan sheepin Gansu province northwest China

In the present study the overallC abortus seroprevalencein Tibetan sheep in Gansu province was 1865 which ishigher than the 1269 seroprevalence among Tibetan sheepin Tianjun County [19] and 801 in Yushu County ofQinghai province China by IHA [24] It is lower than thevalues of 209 in Tibetan sheep in Tibet [21] and 263in sheep in Gansu China [25] The different prevalenceobserved was probably due to differences in animal-welfaresanitation climates and husbandry practices In view ofherds surveyed although seropositive samples were foundin all examined herds seroprevalence in each herd variedobviouslyMany seropositive animals in one tested herd couldhave an effect on high level of seroprevalence in evaluatedregion and the high seroprevalence may not be connectedwith individual region but with high level of infection atthe herd level which may be the main season for highseroprevalence in Gannan

Chlamydia infection in humans and animals was causedby direct contacts with infected animals The transmissionof Chlamydia occurs mainly through inhalation or ingestionof these infectious dust contaminated materials [26] Mostof the time Tibetan sheep are free-ranging on the grassland

and sheds of sheep are simple and crude which increasethe opportunity to be infected with C abortus The farmsof Tibetan sheep herds were located in mountainous areasbelonging to Qinghai-Tibet Plateau in which a lot of yakslived around with Tibetan sheep Yaks infected with C abor-tus have been reported in Qinghai [22] and Gansu provinces(unpublished) which indicated a high risk as a source ofC abortus infection for Tibetan sheep This may be one ofthe possible reasons for the high C abortus seroprevalence(1865) in Tibetan sheep in Gansu northwestern China

In the present study the C abortus seroprevalence inmale and female sheep was 2151 and 1739 respectivelyHowever there was no significant difference in C abortusseroprevalence between genders (119875 gt 005) which isconsistent with the studies of Huang et al [21] in which theyreported negative association between sex and C abortusprevalence in Tibetan sheep in Tibet implying that gendermay not be a crucial factor for C abortus infection in Tibetansheep

This study revealed that the geographical origin ofTibetan sheep is one of the risk factors associated with Cabortus seroprevalence Tibetan sheep in Gannan TibetanAutonomous Prefecture (2156) had a higher risk of beingCabortus seropositive compared to Tibetan sheep in TianzhuTibetan Autonomous County (1632) The geographic dif-ferences in prevalence may be related with differences inliving environment and husbandry practices According tolocal herdersrsquo introduction wild animals including wild yakssika deer and Tibetan antelope were found in field and farmsof Gannan Tibetan Autonomous Prefecture and all of thesespecies are susceptible to C abortus In Gannan people havelow awareness of disease prevention and control and it isdifficult for veterinarians to reach the places to implementimmunization programs Therefore living environment andhusbandry practices were two main risk factors associatedwith C abortus

Season is a significant risk factor forC abortus prevalencedue to different climates in different seasons includingdiverse temperature precipitation and humidity In additionthe seasonal seroprevalence datamay be related to persistenceof antibody following abortion Abortion occurred in spring


resulting in generating many antibodies for resistance to Cabortus and the rubbish of abortion may be contacted byother healthy sheep which led to high seroprevalence insummer As time went on the antibody level reached thelowest in winter

Age of Tibetan sheep (years) as a continuous variablewas analyzed in the logistic regression model and the resultsshowed that the prevalences were different significantly withages demonstrating that age is a predisposing factor for Cabortus prevalence As the growth of the age the seropreva-lence of C abortus infection went up all the time indicatingthat there may be a cumulative likelihood for exposure to Cabortus infection with age in these surveyed regions

IHA is regarded as a simple safe and useful methodfor examination of C abortus antibodies which has beenemployed in previous serological surveys [21 22] The sen-sitivity and specificity values of the testing IHA kit have beenvalidated by the Ministry of Agriculture of China whichdemonstrates that the IHA is not only more efficient thanthe CFT but also more inexpensive than the ELISA [27]Due to these advantages it may be the most appropriatecommercially available kit for detecting C abortus infectionin Tibetan sheep

5 Conclusions

Results of the present study revealed a high C abortusseroprevalence in Tibetan sheep in Gansu province whichcan cause significant economic losses to the local ovineindustry and pose a potential threat to Tibetans in theseareas This study also showed that region season and agearemain risk factors forC abortus seroprevalenceThereforeit is necessary to implement integrated control and efficientmanagement measures to prevent and control C abortusinfection in Tibetan sheep in Gansu province

Ethical Approval

This study was approved by the Animal Ethics Committee ofLanzhou Veterinary Research Institute Chinese Academy ofAgricultural Sciences (Approval No LVRIAEC2013-010)TheTibetan sheep from which the serum samples were collectedwere handled in accordance with good animal practicesrequired by the Animal Ethics Procedures and Guidelines ofthe Peoplersquos Republic of China

Conflict of Interests

The authors declare that they have no conflict of interests

Authorsrsquo Contribution

Si-Yuan Qin and Ming-Yang Yin contributed equally to thispaper

Acknowledgments

Project support was provided in part by the NationalNatural Science Foundation of China (Grant no 31272566)

the Science Fund for Creative Research Groups of GansuProvince (Grant no 1210RJIA006) and the Program forOutstanding Scientists in Agricultural Research to Xing-Quan Zhu

References

[1] D Longbottom and L J Coulter ldquoAnimal chlamydioses andzoonotic implicationsrdquo Journal of Comparative Pathology vol128 no 4 pp 217ndash244 2003

[2] G Rohde E Straube A Essig P Reinhold and K SachseldquoChlamydial zoonosesrdquoDeutsches Arzteblatt vol 107 no 10 pp174ndash180 2010

[3] R S Stephens G Myers M Eppinger and P M BavoilldquoDivergence without difference phylogenetics and taxonomy ofChlamydia resolvedrdquo FEMS Immunology and Medical Microbi-ology vol 55 no 2 pp 115ndash119 2009

[4] D Longbottom M Livingstone S Maley et al ldquoIntranasalInfection with Chlamydia abortus Induces Dose-DependentLatency and Abortion in Sheeprdquo PLoS ONE vol 8 no 2 ArticleID e57950 2013

[5] J C Nietfeld ldquoChlamydial infections in small ruminantsrdquoVeterinary Clinics of North America-food Animal Practice vol17 no 2 pp 301ndash314 2001

[6] G Entrican and N M Wheelhouse ldquoImmunity in the femalesheep reproductive tractrdquo Veterinary Research vol 37 no 3 pp295ndash309 2006

[7] A Rekiki K Sidi-Boumedine A Souriau J Jemli S Ham-mami andA Rodolakis ldquoIsolation and characterisation of localstrains of Chlamydophila abortus (Chlamydia psittaci serotype1) from TunisiardquoVeterinary Research vol 33 no 2 pp 215ndash2222002

[8] A S Amin ldquoApplication of touchdown enzyme time release(TETR)-PCR for diagnosis ofChlamydophila abortus infectionrdquoResearch in Veterinary Science vol 74 no 3 pp 213ndash217 2003

[9] G Zhong ldquoKilling me softly chlamydial use of proteolysis forevading host defensesrdquo Trends in Microbiology vol 17 no 10pp 467ndash474 2009

[10] A Polkinghorne N Borel A Becker et al ldquoMolecular evidencefor chlamydial infections in the eyes of sheeprdquo VeterinaryMicrobiology vol 135 no 1-2 pp 142ndash146 2009

[11] A Gerber RThoma E Vretou et al ldquoOvine enzootic abortion(OEA) a comparison of antibody responses in vaccinated andnaturally-infected swiss sheep over a two year periodrdquo BMCVeterinary Research vol 3 article 24 2007

[12] I D Aitken Chlamydial Abortion Diseases of Sheep BlackwellScience Oxford UK 3rd edition 2000

[13] A Pospischil R Thoma M Hilbe P Grest D Zimmermannand J O Gebbers ldquoAbortion in humans by Chlamydophilaabortus (Chlamydia psittaci serovar 1)rdquo Schweizer Archiv furTierheilkunde vol 144 no 9 pp 463ndash466 2002

[14] A Rodolakis J Salinas and J Papp ldquoRecent advances on ovinechlamydial abortionrdquo Veterinary Research vol 29 no 3-4 pp275ndash288 1998

[15] H Lenzko U Moog K Henning et al ldquoHigh frequency ofchlamydial co-infections in clinically healthy sheep flocksrdquoBMC Veterinary Research vol 7 article 29 2011

[16] M Giangaspero B Bonfini R Orusa G Savini T Osawa andR Harasawa ldquo Epidemiological survey for Toxoplasma gondiiChlamydia psittaci var ovis Mycobacterium paratuberculosis


Coxiella burnetii Brucella spp leptospirosis and Orf virusamong sheep from northern districts of Japanrdquo The Journal ofVeterinary Medical Science vol 75 no 5 pp 679ndash684 2013

[17] N Borel M G Doherr E Vretou E Psarrou R Thoma andA Pospischil ldquoSeroprevalences for ovine enzootic abortion inSwitzerlandrdquoPreventiveVeterinaryMedicine vol 65 no 3-4 pp205ndash216 2004

[18] J Bagdonas S Petkevicius P Russo M Pepin and A Sal-omskas ldquoPrevalence and epidemiological features of ovineenzootic abortion in Lithuaniardquo Polish Journal of VeterinarySciences vol 10 no 4 pp 239ndash244 2007

[19] W C Li ldquoDetection of antibodies against Toxoplasma gondiiChlamydia abortus and Bacterium burgeri in Tibetan sheeprdquoChinese Journal of Veterinary Medicine vol 48 no 2 pp 58ndash59 2012 (Chinese)

[20] X Q Zhang andW C Li ldquoSerological investigation of Chlamy-dia abortus in local Tibetan sheep inQinghai provincerdquoChineseJournal of Veterinary Medicine vol 47 no 10 p 45 2011(Chinese)

[21] S Y Huang S MWuM J Xu et al ldquoFirst record ofChlamydiaabortus seroprevalence in Tibetan sheep in Tibet Chinardquo SmallRuminant Research vol 112 no 1ndash3 pp 243ndash245 2013

[22] Q Chen X Gong F Zheng X Cao Z Li and J ZhouldquoSeroprevalence of Chlamydophila abortus infection in yaks(Bos grunniens) in Qinghai Chinardquo Tropical Animal Health andProduction vol 46 no 3 pp 503ndash507 2014

[23] K Sachse E Vretou M Livingstone N Borel A Pospischiland D Longbottom ldquoRecent developments in the laboratorydiagnosis of chlamydial infectionsrdquo Veterinary Microbiologyvol 135 no 1-2 pp 2ndash21 2009

[24] Q L Qi Y L Chao and H La ldquoReport of Chlamydiaabortus detection in Tibetan sheep in Yushu County QinghairdquoShandong Journal of Animal Science and Veterinary Medicinevol 34 no 9 p 64 2013 (Chinese)

[25] C Y Wang and Y M Wei ldquoSerological investigation ofChlamydia in sheep in alpine pastoral areardquo Journal of AnimalScience and Veterinary Medicine vol 28 no 3 pp 80ndash81 2009(Chinese)

[26] A Rodolakis and K Yousef Mohamad ldquoZoonotic potential ofChlamydophilardquo Veterinary Microbiology vol 140 no 3-4 pp382ndash391 2010

[27] T T Jiang Y S Yang Q Y Meng Y L Fang and S L HanldquoStudy on detecting Chlamydia in swine by indirect hemagglu-tination assayrdquoHubei Journal of Animal and Veterinary Sciencesvol 3 no 4 pp 15ndash21 1983 (Chinese)

Submit your manuscripts athttpwwwhindawicom

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


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Oxidative Medicine and Cellular Longevity


PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

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Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom


source of income for local Tibetans due to its high qualitypelage and nutritive and delicious meat However it is yetto know whether Tibetan sheep are infected with C abortusin Gansu Province northwestern China The objective ofthe present study was to evaluate the seroprevalence andrisk factors of C abortus infection in Tibetan sheep inTianzhu Tibetan Autonomous County and Gannan TibetanAutonomous Prefecture Gansu province northwest China

2 Materials and Methods

21 The Study Site The serum samples used in the presentstudy were collected from Tibetan sheep in Tianzhu TibetanAutonomous County and Gannan Tibetan Autonomous Pre-fecture including Maqu County and Luqu County in GansuProvince northwest China The Tibetan sheep in Gansuwere mainly bred in Tianzhu and Gannan in which mostof the Tibetans also live The sampling site is between theeastern longitudes of 102∘071015840-103∘461015840 and northern latitudesof 36∘311015840ndash37∘551015840 in Tianzhu Tibetan Autonomous Countyand the average annual temperatures are from minus8 to 4∘CGannan Tibetan Autonomous Prefecture is located betweenlongitudes 100∘451015840 to 104∘451015840 east and latitudes 33∘061015840 to35∘341015840 north in which the average annual temperatures arefrom 1 to 13∘C

22 Serum Samples Blood samples were collected from 1732Tibetan sheep in 3 counties in Gansu province from June2013 to April 2014 The samples were collected randomlyfrom 8 Tibetan sheep herds including 4 random herds inTianzhu Tibetan Autonomous County and 4 random herdsof the farms in Gannan Tibetan Autonomous PrefectureSerum samples were separated from blood samples in localveterinary stations and then were taken to the laboratory andstored at minus20∘C until further testedThe detailed informationof animals was obtained from local herdsmen by questioning

23 Serological Examination A commercially available Indi-rect Hemagglutination Assay (IHA) kit (Lanzhou VeterinaryResearch Institute Chinese Academy of Agricultural Sci-ences Lanzhou China) was purchased to test antibodies toCabortus and it was carried out according to themanufacturerrsquosinstructions as described previously [20ndash22] The IHA kitwas employed following the standard method describedby China CADC and the sensitivity and specificity of theexperiment are 100 and 95 respectively The Ministryof Agriculture of China (NYT 562-2002) has validated thesensitivity and specificity values for the testing kit usedin this study In brief serum samples were added to 96-well V-bottomed polystyrene plates which were diluted 4-fold serially beginning with 1 4 to 1 1024 Then the Cabortus antigen was added and the plates were shakengently for 2min and incubated at 37∘C for 2 h Each testwas performed with positive negative and blank controlsand serum samples which had positive reaction at dilutionsof 1 16 or higher dilutions were considered positive for Cabortus antibodies Positive results between 1 4 and 1 16were considered ldquosuspectrdquo and were retested

24 Statistical Analysis Differences in the seroprevalence ofC abortus among Tibetan sheep of different geographicalorigins genders seasons and age groups were analyzedwith Chi-square tests using the SPSS software (SPSS IncIBM Corporation Version 19 USA) The differences wereconsidered statistically significant if 119875 lt 005 and the 95confidence intervals (CI) are also calculated

3 Results

In the present study 323 (1865) out of 1732 serum samplesfrom Tibetan sheep in Gansu province were seropositive forC abortus infection by IHA at a 1 16 cut-off (Table 1) Asshown in Table 1 the seroprevalence of C abortus infectionin Tianzhu County (119899 = 962) Maqu County (119899 = 588)and Luqu County (119899 = 182) was 1632 2262 and1813 respectively The numbers of seropositive animalsand seroprevalence of individual herd were described inTable 2 All of the sampled 8 Tibetan sheep herds wereserologically positive Male sheep had a higher prevalence(2151) compared to females (1739) The positive sampleswere distributed among four seasons (Spring 119899 = 480Summer 119899 = 398 Autumn 119899 = 479 Winter 119899 = 375) inwhich the prevalences of C abortus infection were 18542211 2046 and 1280 (119875 lt 005 Table 1) respectivelyThe ages of the examined Tibetan sheep varied from 0 yearsto 3 years or greater and seroprevalence in different agegroups ranged from 746 to 2441 (Table 1) The highestseroprevalence was found in Tibetan sheep older than 3 years(2441) and the lowest in 0 years to 3 years (746) Table 3summarizes the antibodies titers in different ages regionsgenders and seasons with IHA titers of 1 16 in 188 samples(5820) 1 32 in 72 samples (2229) 1 64 in 34 samples(1053) 1 128 in 14 samples (433) 1 256 in 12 samples(372) 1 512 in 2 samples (062) and 1 1024 in 1 sample(031)

According to forward stepwise logistic regression genderof Tibetan sheep was not significant in the logistic regressionanalysis (119875 gt 005) and left out of the final modelMultivariable analysis of such 4 factors showed that Cabortus seropositivity was associated with regions seasonsand ages Tibetan sheep in Luqu County was more than 14-fold increase (OR= 140 95CI= 107ndash184119875 = 0014) at riskofC abortus infection compared to Tibetan sheep in TianzhuCounty and no regional differences were found in LuquCounty compared to Tianzhu County (119875 gt 005) Ages ofTibetan sheep which were 1 lt years le 2 years old (1582) hada 25-fold increase higher risk of being seropositive comparedto that of Tibetan sheep which were 0 lt years le 1 years old(746) (OR = 248 95 CI = 151ndash407 119875 lt 0001) whileTibetan sheep of 2 lt years le 3 and gt3 years old had a 3-foldincrease (OR = 140 95 CI = 172ndash519 119875 lt 0001) and 40times (OR = 402 95 CI = 258ndash626 119875 lt 0001) higherrisk compared to Tibetan sheep of 0 lt years le 1 age groupseparately (Table 4) In terms of seasons the risk ofC abortusinfection in summer was more than 20-fold increase (OR =197 95 CI = 133ndash291 119875 = 0001) compared to C abortusinfection in winter (Table 4)





Sex Male 530 114 2151Female 1202 209 1739

Season


Age (yr)


Total 1732 323 1865



Tianzhu


Gannan




Age (years)



Sex Male 76 24 9 2 2 1 0 114 530 2151Female 112 48 25 12 10 1 1 209 1202 1739

Season






Season


Age (yr)


4 Discussions












5 Conclusions


Ethical Approval






Acknowledgments



References



































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of




















Sex Male 530 114 2151Female 1202 209 1739

Season


Age (yr)


Total 1732 323 1865



Tianzhu


Gannan




Age (years)



Sex Male 76 24 9 2 2 1 0 114 530 2151Female 112 48 25 12 10 1 1 209 1202 1739

Season






Season


Age (yr)


4 Discussions












5 Conclusions


Ethical Approval






Acknowledgments



References



































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of




















Season


Age (yr)


4 Discussions












5 Conclusions


Ethical Approval






Acknowledgments



References



































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of




















5 Conclusions


Ethical Approval






Acknowledgments



References



































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of


































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















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