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Home / Equine Research Bank / Infect Immun / Persistently infected horses are reservoirs for intrastadial...
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
  • Research Support
  • N.I.H.
  • Extramural
  • Research Support
  • 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

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