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Infection and immunity2008; 76(8); 3525-3529; doi: 10.1128/IAI.00251-08

Persistently infected horses are reservoirs for intrastadial tick-borne transmission of the apicomplexan parasite Babesia equi.

Abstract: Tick-borne pathogens may be transmitted intrastadially and transstadially within a single vector generation as well as vertically between generations. Understanding the mode and relative efficiency of this transmission is required for infection control. In this study, we established that adult male Rhipicephalus microplus ticks efficiently acquire the protozoal pathogen Babesia equi during acute and persistent infections and transmit it intrastadially to naïve horses. Although the level of parasitemia during acquisition feeding affected the efficiency of the initial tick infection, infected ticks developed levels of > or =10(4) organisms/pair of salivary glands independent of the level of parasitemia during acquisition feeding and successfully transmitted them, indicating that replication within the tick compensated for any initial differences in infectious dose and exceeded the threshold for transmission. During the development of B. equi parasites in the salivary gland granular acini, the parasites expressed levels of paralogous surface proteins significantly different from those expressed by intraerythrocytic parasites from the mammalian host. In contrast to the successful intrastadial transmission, adult female R. microplus ticks that fed on horses with high parasitemia passed the parasite vertically into the eggs with low efficiency, and the subsequent generation (larvae, nymphs, and adults) failed to transmit B. equi parasites to naïve horses. The data demonstrated that intrastadial but not transovarial transmission is an efficient mode for B. equi transmission and that persistently infected horses are an important reservoir for transmission. Consequently, R. microplus male ticks and persistently infected horses should be targeted for disease control.
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Publication Date: 2008-05-19 PubMed ID: 18490466PubMed Central: PMC2493223DOI: 10.1128/IAI.00251-08Google Scholar: Lookup
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  • Journal Article
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  • N.I.H.
  • Extramural
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  • U.S. Gov't
  • Non-P.H.S.

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article investigates how the parasite Babesia equi, which infects horses, is transmitted via ticks, where one type of transmission (intrastadial) is found to be highly efficient, while another (transovarial) is not. The research also concludes that infected horses serve as an important reservoir for the parasite, hence control measures should be evolved to deal with the tick vector and these infected horses.

Research Objectives and Methodology

  • The primary goal of this research was to understand how the horse-infecting parasite Babesia equi is transmitted by ticks. The researchers were particularly concerned with the modes of transmission, their relative efficiency, and the role of infected horses in the parasite’s lifecycle.
  • For the study, they used adult male Rhipicephalus microplus ticks and studied how they acquired the parasite during acute and persistent infections and transmitted it intrastadially (within a single life stage) to naïve (uninfected) horses.

Findings on Parasite Acquisition and Transmission by Ticks

  • While the level of parasitemia (presence of parasites in the bloodstream) during the tick’s feeding influenced the initial tick infection’s efficiency, it was found that once infected, all ticks developed high parasite levels in their salivary glands. This showed that the ticks’ internal parasite replication compensated for any initial differences in the infectious dose and exceeded the threshold for successful transmission.
  • It was also found that the B. equi parasites within the tick’s salivary glands expressed different levels of surface proteins than those existing within the host horse’s red blood cells. This serves to highlight the potential adaptability of the parasite to different host environments.

Inefficiency of Transovarial Transmission

  • In contrast to successful intrastadial transmission, the researchers found that female R. microplus ticks that fed on horses with high levels of parasitemia only passed the parasite into eggs with low efficiency. Moreover, the subsequent generation (larvae, nymphs, and adults) of these ticks failed to transmit the parasites to uninfected horses.

Role of Persistently Infected Horses and Disease Control Recommendations

  • The research also underscored the importance of persistently infected horses as disease reservoirs, indicating that these horses play a crucial role in maintaining the lifecycle of B. equi.
  • Given these findings, the researchers recommend that disease control measures should be focused on both male R. microplus ticks and persistently infected horses, as these were found to be the most effective in transmitting the Babesia equi parasite.

Cite This Article

APA
Ueti MW, Palmer GH, Scoles GA, Kappmeyer LS, Knowles DP. (2008). Persistently infected horses are reservoirs for intrastadial tick-borne transmission of the apicomplexan parasite Babesia equi. Infect Immun, 76(8), 3525-3529. https://doi.org/10.1128/IAI.00251-08

Publication

Infection and immunity
ISSN: 1098-5522
NlmUniqueID: 0246127
Country: United States
Language: English
Volume: 76
Issue: 8
Pages: 3525-3529

Researcher Affiliations

Ueti, Massaro W
  • Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040, USA. massaro@vetmed.wsu.edu
Palmer, Guy H
    Scoles, Glen A
      Kappmeyer, Lowell S
        Knowles, Donald P

          MeSH Terms

          • Animals
          • Antigens, Protozoan / biosynthesis
          • Babesia / isolation & purification
          • Babesiosis / parasitology
          • Babesiosis / transmission
          • Babesiosis / veterinary
          • Disease Reservoirs / parasitology
          • Disease Transmission, Infectious
          • Female
          • Horse Diseases / parasitology
          • Horses
          • Infectious Disease Transmission, Vertical
          • Male
          • Membrane Proteins / biosynthesis
          • Protozoan Proteins / biosynthesis
          • Rhipicephalus / parasitology
          • Salivary Glands / parasitology
          • Tick-Borne Diseases / parasitology
          • Tick-Borne Diseases / transmission

          Grant Funding

          • T32 AI007025 / NIAID NIH HHS

          References

          This article includes 20 references
          1. Battsetseg B, Lucero S, Xuan X, Claveria F, Byambaa B, Battur B, Boldbaatar D, Batsukh Z, Khaliunaa T, Battsetseg G, Igarashi I, Nagasawa H, Fujisaki K. Detection of equine Babesia spp. gene fragments in Dermacentor nuttalli Olenev 1929 infesting mongolian horses, and their amplification in egg and larval progenies.. J Vet Med Sci 2002 Aug;64(8):727-30.
            pubmed: 12237521doi: 10.1292/jvms.64.727google scholar: lookup
          2. Battsetseg B, Lucero S, Xuan X, Claveria FG, Inoue N, Alhassan A, Kanno T, Igarashi I, Nagasawa H, Mikami T, Fujisaki K. Detection of natural infection of Boophilus microplus with Babesia equi and Babesia caballi in Brazilian horses using nested polymerase chain reaction.. Vet Parasitol 2002 Aug 22;107(4):351-7.
            pubmed: 12163246doi: 10.1016/s0304-4017(02)00131-0google scholar: lookup
          3. Dalgliesh RJ, Stewart NP. The use of tick transmission by Boophilus microplus to isolate pure strains of Babesia bovis, Babesia bigemina and Anaplasma marginale from cattle with mixed infections.. Vet Parasitol 1983 Nov;13(4):317-23.
            pubmed: 6686384doi: 10.1016/0304-4017(83)90047-xgoogle scholar: lookup
          4. Friedhoff KT. Transmission of Babesia. p. 23-52. In M. Ristic (ed.), Babesiosis of domestic animals and man. CRC Press, Boca Raton, FL.
          5. Futse JE, Ueti MW, Knowles DP Jr, Palmer GH. Transmission of Anaplasma marginale by Boophilus microplus: retention of vector competence in the absence of vector-pathogen interaction.. J Clin Microbiol 2003 Aug;41(8):3829-34.
            pmc: PMC179812pubmed: 12904396doi: 10.1128/jcm.41.8.3829-3834.2003google scholar: lookup
          6. Guimarães AM, Lima JD, Ribeiro MF, Camargos ER, Bozzi IA. Ultrastructure of sporogony in Babesia equi in salivary glands of adult female Boophilus microplus ticks.. Parasitol Res 1998;84(1):69-74.
            pubmed: 9491430doi: 10.1007/s004360050359google scholar: lookup
          7. Howell JM, Ueti MW, Palmer GH, Scoles GA, Knowles DP. Transovarial transmission efficiency of Babesia bovis tick stages acquired by Rhipicephalus (Boophilus) microplus during acute infection.. J Clin Microbiol 2007 Feb;45(2):426-31.
            pmc: PMC1829031pubmed: 17166964doi: 10.1128/jcm.01757-06google scholar: lookup
          8. Howell JM, Ueti MW, Palmer GH, Scoles GA, Knowles DP. Persistently infected calves as reservoirs for acquisition and transovarial transmission of Babesia bovis by Rhipicephalus (Boophilus) microplus.. J Clin Microbiol 2007 Oct;45(10):3155-9.
            pmc: PMC2045367pubmed: 17687016doi: 10.1128/jcm.00766-07google scholar: lookup
          9. Ikadai H, Sasaki M, Ishida H, Matsuu A, Igarashi I, Fujisaki K, Oyamada T. Molecular evidence of Babesia equi transmission in Haemaphysalis longicornis.. Am J Trop Med Hyg 2007 Apr;76(4):694-7.
            pubmed: 17426172
          10. Karakashian SJ, Rudzinska MA, Spielman A, Lewengrub S, Piesman J, Shoukrey N. Ultrastructural studies on sporogony of Babesia microti in salivary gland cells of the tick Ixodes dammini.. Cell Tissue Res 1983;231(2):275-87.
            pubmed: 6850804doi: 10.1007/bf00222180google scholar: lookup
          11. Knowles DP Jr, Kappmeyer LS, Stiller D, Hennager SG, Perryman LE. Antibody to a recombinant merozoite protein epitope identifies horses infected with Babesia equi.. J Clin Microbiol 1992 Dec;30(12):3122-6.
            pmc: PMC270599pubmed: 1280648doi: 10.1128/jcm.30.12.3122-3126.1992google scholar: lookup
          12. Knowles DP Jr, Perryman LE, Goff WL, Miller CD, Harrington RD, Gorham JR. A monoclonal antibody defines a geographically conserved surface protein epitope of Babesia equi merozoites.. Infect Immun 1991 Jul;59(7):2412-7.
            pmc: PMC258026pubmed: 1711016doi: 10.1128/iai.59.7.2412-2417.1991google scholar: lookup
          13. Labruna MB, Kerber CE, Ferreira F, Faccini JL, De Waal DT, Gennari SM. Risk factors to tick infestations and their occurrence on horses in the state of São Paulo, Brazil.. Vet Parasitol 2001 May 9;97(1):1-14.
            pubmed: 11337122doi: 10.1016/s0304-4017(01)00387-9google scholar: lookup
          14. Little SE, Hostetler J, Kocan KM. Movement of Rhipicephalus sanguineus adults between co-housed dogs during active feeding.. Vet Parasitol 2007 Nov 30;150(1-2):139-45.
            pubmed: 17904292doi: 10.1016/j.vetpar.2007.08.029google scholar: lookup
          15. Piesman J, Karakashian SJ, Lewengrub S, Rudzinska MA, Spielmank A. Development of Babesia microti sporozoites in adult Ixodes dammini.. Int J Parasitol 1986 Aug;16(4):381-5.
            pubmed: 3744675doi: 10.1016/0020-7519(86)90118-9google scholar: lookup
          16. Rudzinska MA, Lewengrub S, Spielman A, Piesman J. Invasion of Babesia microti into epithelial cells of the tick gut.. J Protozool 1983 May;30(2):338-46.
            pubmed: 6631777doi: 10.1111/j.1550-7408.1983.tb02927.xgoogle scholar: lookup
          17. Scoles GA, Ueti MW, Noh SM, Knowles DP, Palmer GH. Conservation of transmission phenotype of Anaplasma marginale (Rickettsiales: Anaplasmataceae) strains among Dermacentor and Rhipicephalus ticks (Acari: Ixodidae).. J Med Entomol 2007 May;44(3):484-91.
            pubmed: 17547235doi: 10.1603/0022-2585(2007)44[484:cotpoa]2.0.co;2google scholar: lookup
          18. Stiller D, Goff WL, Johnson LW, Knowles DP. Dermacentor variabilis and boophilus microplus (Acari: Ixodidae): experimental vectors of Babesia equi to equids.. J Med Entomol 2002 Jul;39(4):667-70.
            pubmed: 12144301doi: 10.1603/0022-2585-39.4.667google scholar: lookup
          19. Ueti MW, Palmer GH, Kappmeyer LS, Scoles GA, Knowles DP. Expression of equi merozoite antigen 2 during development of Babesia equi in the midgut and salivary gland of the vector tick Boophilus microplus.. J Clin Microbiol 2003 Dec;41(12):5803-9.
            pmc: PMC308990pubmed: 14662988doi: 10.1128/jcm.41.12.5803-5809.2003google scholar: lookup
          20. Ueti MW, Palmer GH, Kappmeyer LS, Statdfield M, Scoles GA, Knowles DP. Ability of the vector tick Boophilus microplus to acquire and transmit Babesia equi following feeding on chronically infected horses with low-level parasitemia.. J Clin Microbiol 2005 Aug;43(8):3755-9.
            pmc: PMC1233951pubmed: 16081906doi: 10.1128/jcm.43.8.3755-3759.2005google scholar: lookup

          Citations

          This article has been cited 39 times.
          1. Onzere CK, Herndon DR, Hassan A, Oyen K, Poh KC, Scoles GA, Fry LM. A U.S. Isolate of Theileria orientalis Ikeda Is Not Transstadially Transmitted to Cattle by Rhipicephalus microplus. Pathogens 2023 Apr 5;12(4).
            doi: 10.3390/pathogens12040559pubmed: 37111445google scholar: lookup
          2. Paulino PG, Peckle M, Mendonça LP, Massard CL, Antunes S, Couto J, Domingos A, Guedes Junior DDS, Cabezas-Cruz A, Santos HA. Differential Expression of Immune Genes in the Rhipicephalus microplus Gut in Response to Theileria equi Infection. Pathogens 2022 Dec 6;11(12).
            doi: 10.3390/pathogens11121478pubmed: 36558812google scholar: lookup
          3. Coultous R, Gotić J, McCann M, Sutton D, Beck R, Shiels B. Novel equi merozoite antigen (ema-1) gene heterogeneity in a geographically isolated Theileria equi population in Croatia. Parasit Vectors 2022 Oct 31;15(1):401.
            doi: 10.1186/s13071-022-05484-4pubmed: 36316753google scholar: lookup
          4. Peckle M, Santos H, Pires M, Silva C, Costa R, Vitari G, Camilo T, Meireles N, Paulino P, Massard C. Dynamics of Theileria equi Infection in Rhipicephalus (Boophilus) microplus during the Parasitic Phase in a Chronically Infected Horse. Pathogens 2022 Apr 29;11(5).
            doi: 10.3390/pathogens11050525pubmed: 35631046google scholar: lookup
          5. Coultous RM, Sutton DGM, Boden LA. A risk assessment of equine piroplasmosis entry, exposure and consequences in the UK. Equine Vet J 2023 Mar;55(2):282-294.
            doi: 10.1111/evj.13579pubmed: 35478189google scholar: lookup
          6. Salinas-Estrella E, Ueti MW, Lobanov VA, Castillo-Payró E, Lizcano-Mata A, Badilla C, Martínez-Ibáñez F, Mosqueda J. Serological and molecular detection of Babesia caballi and Theileria equi in Mexico: A prospective study. PLoS One 2022;17(3):e0264998.
            doi: 10.1371/journal.pone.0264998pubmed: 35259206google scholar: lookup
          7. Vimonish R, Dinkel KD, Fry LM, Johnson WC, Capelli-Peixoto J, Bastos RG, Scoles GA, Knowles DP, Madder M, Chaka G, Ueti MW. Isolation of infectious Theileria parva sporozoites secreted by infected Rhipicephalus appendiculatus ticks into an in vitro tick feeding system. Parasit Vectors 2021 Dec 24;14(1):616.
            doi: 10.1186/s13071-021-05120-7pubmed: 34952641google scholar: lookup
          8. Elsawy BSM, Nassar AM, Alzan HF, Bhoora RV, Ozubek S, Mahmoud MS, Kandil OM, Mahdy OA. Rapid Detection of Equine Piroplasms Using Multiplex PCR and First Genetic Characterization of Theileria haneyi in Egypt. Pathogens 2021 Oct 31;10(11).
            doi: 10.3390/pathogens10111414pubmed: 34832570google scholar: lookup
          9. Galon EM, Macalanda AM, Garcia MM, Ibasco CJ, Garvida A, Ji S, Zafar I, Hasegawa Y, Liu M, Ybañez RH, Umemiya-Shirafuji R, Ybañez A, Claveria F, Xuan X. Molecular Identification of Selected Tick-Borne Protozoan and Bacterial Pathogens in Thoroughbred Racehorses in Cavite, Philippines. Pathogens 2021 Oct 13;10(10).
            doi: 10.3390/pathogens10101318pubmed: 34684266google scholar: lookup
          10. Seo HJ, Truong AT, Kim KH, Lim JY, Min S, Kim HC, Yoo MS, Yoon SS, Klein TA, Cho YS. Molecular Detection and Phylogenetic Analysis of Tick-Borne Pathogens in Ticks Collected from Horses in the Republic of Korea. Pathogens 2021 Aug 24;10(9).
            doi: 10.3390/pathogens10091069pubmed: 34578102google scholar: lookup
          11. Onzere CK, Fry LM, Bishop RP, Silva MG, Bastos RG, Knowles DP, Suarez CE. Theileria equi claudin like apicomplexan microneme protein contains neutralization-sensitive epitopes and interacts with components of the equine erythrocyte membrane skeleton. Sci Rep 2021 Apr 29;11(1):9301.
            doi: 10.1038/s41598-021-88902-4pubmed: 33927329google scholar: lookup
          12. Idoko IS, Edeh RE, Adamu AM, Machunga-Mambula S, Okubanjo OO, Balogun EO, Adamu S, Johnson W, Kappmeyer L, Mousel M, Ueti MW. Molecular and Serological Detection of Piroplasms in Horses from Nigeria. Pathogens 2021 Apr 23;10(5).
            doi: 10.3390/pathogens10050508pubmed: 33922468google scholar: lookup
          13. Dirks E, de Heus P, Joachim A, Cavalleri JV, Schwendenwein I, Melchert M, Fuehrer HP. First Case of Autochthonous Equine Theileriosis in Austria. Pathogens 2021 Mar 4;10(3).
            doi: 10.3390/pathogens10030298pubmed: 33806575google scholar: lookup
          14. Paulino P, Vitari G, Rezende A, Couto J, Antunes S, Domingos A, Peckle M, Massard C, Araújo F, Santos H. Characterization of the Rhipicephalus (Boophilus) microplus Sialotranscriptome Profile in Response to Theileria equi Infection. Pathogens 2021 Feb 4;10(2).
            doi: 10.3390/pathogens10020167pubmed: 33557100google scholar: lookup
          15. Sears K, Knowles D, Dinkel K, Mshelia PW, Onzere C, Silva M, Fry L. Imidocarb Dipropionate Lacks Efficacy against Theileria haneyi and Fails to Consistently Clear Theileria equi in Horses Co-Infected with T. haneyi. Pathogens 2020 Dec 10;9(12).
            doi: 10.3390/pathogens9121035pubmed: 33321715google scholar: lookup
          16. Nasreldin N, Ewida RM, Hamdon H, Elnaker YF. Molecular diagnosis and biochemical studies of tick-borne diseases (anaplasmosis and babesiosis) in Aberdeen Angus Cattle in New Valley, Egypt. Vet World 2020 Sep;13(9):1884-1891.
            doi: 10.14202/vetworld.2020.1884-1891pubmed: 33132601google scholar: lookup
          17. Zhao S, Wang H, Zhang S, Xie S, Li H, Zhang X, Jia L. First report of genetic diversity and risk factor analysis of equine piroplasm infection in equids in Jilin, China. Parasit Vectors 2020 Sep 9;13(1):459.
            doi: 10.1186/s13071-020-04338-1pubmed: 32907616google scholar: lookup
          18. Mshelia PW, Kappmeyer L, Johnson WC, Kudi CA, Oluyinka OO, Balogun EO, Richard EE, Onoja E, Sears KP, Ueti MW. Molecular detection of Theileria species and Babesia caballi from horses in Nigeria. Parasitol Res 2020 Sep;119(9):2955-2963.
            doi: 10.1007/s00436-020-06797-ypubmed: 32647992google scholar: lookup
          19. Vimonish R, Johnson WC, Mousel MR, Brayton KA, Scoles GA, Noh SM, Ueti MW. Quantitative analysis of Anaplasma marginale acquisition and transmission by Dermacentor andersoni fed in vitro. Sci Rep 2020 Jan 16;10(1):470.
            doi: 10.1038/s41598-019-57390-ypubmed: 31949241google scholar: lookup
          20. Onyiche TE, Suganuma K, Igarashi I, Yokoyama N, Xuan X, Thekisoe O. A Review on Equine Piroplasmosis: Epidemiology, Vector Ecology, Risk Factors, Host Immunity, Diagnosis and Control. Int J Environ Res Public Health 2019 May 16;16(10).
            doi: 10.3390/ijerph16101736pubmed: 31100920google scholar: lookup
          21. Santodomingo A, Sierra-Orozco K, Cotes-Perdomo A, Castro LR. Molecular detection of Rickettsia spp., Anaplasma platys and Theileria equi in ticks collected from horses in Tayrona National Park, Colombia. Exp Appl Acarol 2019 Mar;77(3):411-423.
            doi: 10.1007/s10493-019-00354-8pubmed: 30923988google scholar: lookup
          22. Gondard M, Cabezas-Cruz A, Charles RA, Vayssier-Taussat M, Albina E, Moutailler S. Ticks and Tick-Borne Pathogens of the Caribbean: Current Understanding and Future Directions for More Comprehensive Surveillance. Front Cell Infect Microbiol 2017;7:490.
            doi: 10.3389/fcimb.2017.00490pubmed: 29238699google scholar: lookup
          23. Jaworski DC, Cheng C, Nair ADS, Ganta RR. Amblyomma americanum ticks infected with in vitro cultured wild-type and mutants of Ehrlichia chaffeensis are competent to produce infection in naïve deer and dogs. Ticks Tick Borne Dis 2017 Jan;8(1):60-64.
            doi: 10.1016/j.ttbdis.2016.09.017pubmed: 27729288google scholar: lookup
          24. Habibi G, Esmaeilnia K, Hablolvarid MH, Afshari A, Zamen M, Bozorgi S. Microscopic and Molecular Detection of Theileria (Babesia) Equi Infection in Equids of Kurdistan Province, Iran. Iran J Parasitol 2016 Jan-Mar;11(1):86-90.
            pubmed: 27095973
          25. Boyle WK, Wilder HK, Lawrence AM, Lopez JE. Transmission dynamics of Borrelia turicatae from the arthropod vector. PLoS Negl Trop Dis 2014 Apr;8(4):e2767.
            doi: 10.1371/journal.pntd.0002767pubmed: 24699275google scholar: lookup
          26. Scoles GA, Ueti MW. Amblyomma cajennense is an intrastadial biological vector of Theileria equi. Parasit Vectors 2013 Oct 23;6(1):306.
            doi: 10.1186/1756-3305-6-306pubmed: 24499587google scholar: lookup
          27. Wang M, Guo W, Igarashi I, Xuan X, Wang X, Xiang W, Jia H. Epidemiological investigation of equine piroplasmosis in China by enzyme-linked immunosorbent assays. J Vet Med Sci 2014 Apr;76(4):549-52.
            doi: 10.1292/jvms.13-0477pubmed: 24292247google scholar: lookup
          28. Ramsay JD, Ueti MW, Johnson WC, Scoles GA, Knowles DP, Mealey RH. Lymphocytes and macrophages are infected by Theileria equi, but T cells and B cells are not required to establish infection in vivo. PLoS One 2013;8(10):e76996.
            doi: 10.1371/journal.pone.0076996pubmed: 24116194google scholar: lookup
          29. Peckle M, Pires MS, Dos Santos TM, Roier EC, da Silva CB, Vilela JA, Santos HA, Massard CL. Molecular epidemiology of Theileria equi in horses and their association with possible tick vectors in the state of Rio de Janeiro, Brazil. Parasitol Res 2013 May;112(5):2017-25.
            doi: 10.1007/s00436-013-3360-0pubmed: 23474658google scholar: lookup
          30. Hall CM, Busch JD, Scoles GA, Palma-Cagle KA, Ueti MW, Kappmeyer LS, Wagner DM. Genetic characterization of Theileria equi infecting horses in North America: evidence for a limited source of U.S. introductions. Parasit Vectors 2013 Feb 11;6:35.
            doi: 10.1186/1756-3305-6-35pubmed: 23399005google scholar: lookup
          31. Kappmeyer LS, Thiagarajan M, Herndon DR, Ramsay JD, Caler E, Djikeng A, Gillespie JJ, Lau AO, Roalson EH, Silva JC, Silva MG, Suarez CE, Ueti MW, Nene VM, Mealey RH, Knowles DP, Brayton KA. Comparative genomic analysis and phylogenetic position of Theileria equi. BMC Genomics 2012 Nov 9;13:603.
            doi: 10.1186/1471-2164-13-603pubmed: 23137308google scholar: lookup
          32. Ueti MW, Mealey RH, Kappmeyer LS, White SN, Kumpula-McWhirter N, Pelzel AM, Grause JF, Bunn TO, Schwartz A, Traub-Dargatz JL, Hendrickson A, Espy B, Guthrie AJ, Fowler WK, Knowles DP. Re-emergence of the apicomplexan Theileria equi in the United States: elimination of persistent infection and transmission risk. PLoS One 2012;7(9):e44713.
            doi: 10.1371/journal.pone.0044713pubmed: 22970295google scholar: lookup
          33. Mealey RH, Kappmeyer LS, Ueti MW, Wagner B, Knowles DP. Protective effects of passively transferred merozoite-specific antibodies against Theileria equi in horses with severe combined immunodeficiency. Clin Vaccine Immunol 2012 Jan;19(1):100-4.
            doi: 10.1128/CVI.05301-11pubmed: 22038847google scholar: lookup
          34. Schwint ON, Ueti MW, Palmer GH, Kappmeyer LS, Hines MT, Cordes RT, Knowles DP, Scoles GA. Imidocarb dipropionate clears persistent Babesia caballi infection with elimination of transmission potential. Antimicrob Agents Chemother 2009 Oct;53(10):4327-32.
            doi: 10.1128/AAC.00404-09pubmed: 19620328google scholar: lookup
          35. Ueti MW, Knowles DP, Davitt CM, Scoles GA, Baszler TV, Palmer GH. Quantitative differences in salivary pathogen load during tick transmission underlie strain-specific variation in transmission efficiency of Anaplasma marginale. Infect Immun 2009 Jan;77(1):70-5.
            doi: 10.1128/IAI.01164-08pubmed: 18955472google scholar: lookup
          36. Gupta KK, Gupta N, Kumar S, Srivastava M, Kumar P. Equine piroplasmosis: an emerging tick-borne threat to equine health. Trop Anim Health Prod 2026 Jan 5;58(1):29.
            doi: 10.1007/s11250-025-04829-2pubmed: 41489672google scholar: lookup
          37. Ullah A, Geng M, Chen W, Zhu Q, Shi L, Zhang X, Akhtar MF, Wang C, Khan MZ. Effect of Parasitic Infections on Hematological Profile, Reproductive and Productive Performance in Equines. Animals (Basel) 2025 Nov 14;15(22).
            doi: 10.3390/ani15223294pubmed: 41302002google scholar: lookup
          38. Axt CW, Springer A, von Luckner J, Naucke TJ, Müller E, Strube C, Schäfer I. [Equine piroplasmosis: Case descriptions and overview of the epidemiological situation in Europe with focus on Germany]. Tierarztl Prax Ausg G Grosstiere Nutztiere 2025 Feb;53(1):49-58.
            doi: 10.1055/a-2457-5516pubmed: 39631762google scholar: lookup
          39. Li L, Li S, Ma H, Akhtar MF, Tan Y, Wang T, Liu W, Khan A, Khan MZ, Wang C. An Overview of Infectious and Non-Infectious Causes of Pregnancy Losses in Equine. Animals (Basel) 2024 Jul 2;14(13).
            doi: 10.3390/ani14131961pubmed: 38998073google scholar: lookup
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