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Parasite load and genotype are associated with clinical outcome of piroplasm-infected equines in Israel

BACKGROUND: Equine piroplasmosis is a highly endemic protozoan disease of horses worldwide, caused by Theileria equi and Babesia caballi. While most horses in endemic areas are subclinically infected, the mechanisms leading to clinical outcome are vastly unknown. Moreover, since clinical signs of di...

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Autores principales: Tirosh-Levy, Sharon, Steinman, Amir, Levy, Hadas, Katz, Yotam, Shtilman, Margarita, Gottlieb, Yuval
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7240905/
https://www.ncbi.nlm.nih.gov/pubmed/32434550
http://dx.doi.org/10.1186/s13071-020-04133-y
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author Tirosh-Levy, Sharon
Steinman, Amir
Levy, Hadas
Katz, Yotam
Shtilman, Margarita
Gottlieb, Yuval
author_facet Tirosh-Levy, Sharon
Steinman, Amir
Levy, Hadas
Katz, Yotam
Shtilman, Margarita
Gottlieb, Yuval
author_sort Tirosh-Levy, Sharon
collection PubMed
description BACKGROUND: Equine piroplasmosis is a highly endemic protozoan disease of horses worldwide, caused by Theileria equi and Babesia caballi. While most horses in endemic areas are subclinically infected, the mechanisms leading to clinical outcome are vastly unknown. Moreover, since clinical signs of disease are not specific, and the prevalence in endemic areas is high, it is difficult to determine if equine piroplasmosis is the cause of disease. To identify possible mechanisms leading to the clinical outcome in an endemic area, we compared parasite loads and genotypes in clinically and subclinically infected horses. METHODS: Blood was collected from horses with clinical signs consistent with equine piroplasmosis, and from apparently healthy horses in Israel. Packed cell volume and total solids were measured. Quantitative and diagnostic polymerase chain reaction were used to identify, quantify and classify equine piroplasmosis infection. Phylogenetic analyses were used to determine the genotype of both parasites. RESULTS: For both parasites, clinical cases were associated with low mean packed cell volume and high mean parasite load (P < 0.001), enabling the determination of a cut-off value to distinguish between clinically and subclinically infected horses. Samples of Theileria equi from subclinical horses were classified into three different 18S rRNA genotypes, D (n = 23), A (n = 12) and C (n = 5), while samples from all clinical cases (n = 6) were classified as genotype A. The sequences of T. equi equi merozoite antigens 1 (ema-1, n = 9) and 2 (ema-2, n = 11) genes were fairly conserved and did not differ between clinical and subclinical cases. Babesia caballi rhoptry associated protein-1 (rap-1) was classified into sub-genotypes A1 (n = 14) and A2 (n = 5) with no association to clinical outcome. Classification of the 18S rRNA gene (sub-genotypes B1 and B2) agreed with the rap-1 classification. CONCLUSIONS: The results of this study suggest that quantification of parasite loads of infected horses may be used to distinguish between infections resulting in disease and subclinical cases. Although number of clinical cases is limited, we identified T. equi 18S rRNA genotype A to be associated with clinical disease. This finding emphasizes the importance of in-depth genetic characterization of T. equi genotypes to identify possible markers for virulence. [Image: see text]
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spelling pubmed-72409052020-05-29 Parasite load and genotype are associated with clinical outcome of piroplasm-infected equines in Israel Tirosh-Levy, Sharon Steinman, Amir Levy, Hadas Katz, Yotam Shtilman, Margarita Gottlieb, Yuval Parasit Vectors Short Report BACKGROUND: Equine piroplasmosis is a highly endemic protozoan disease of horses worldwide, caused by Theileria equi and Babesia caballi. While most horses in endemic areas are subclinically infected, the mechanisms leading to clinical outcome are vastly unknown. Moreover, since clinical signs of disease are not specific, and the prevalence in endemic areas is high, it is difficult to determine if equine piroplasmosis is the cause of disease. To identify possible mechanisms leading to the clinical outcome in an endemic area, we compared parasite loads and genotypes in clinically and subclinically infected horses. METHODS: Blood was collected from horses with clinical signs consistent with equine piroplasmosis, and from apparently healthy horses in Israel. Packed cell volume and total solids were measured. Quantitative and diagnostic polymerase chain reaction were used to identify, quantify and classify equine piroplasmosis infection. Phylogenetic analyses were used to determine the genotype of both parasites. RESULTS: For both parasites, clinical cases were associated with low mean packed cell volume and high mean parasite load (P < 0.001), enabling the determination of a cut-off value to distinguish between clinically and subclinically infected horses. Samples of Theileria equi from subclinical horses were classified into three different 18S rRNA genotypes, D (n = 23), A (n = 12) and C (n = 5), while samples from all clinical cases (n = 6) were classified as genotype A. The sequences of T. equi equi merozoite antigens 1 (ema-1, n = 9) and 2 (ema-2, n = 11) genes were fairly conserved and did not differ between clinical and subclinical cases. Babesia caballi rhoptry associated protein-1 (rap-1) was classified into sub-genotypes A1 (n = 14) and A2 (n = 5) with no association to clinical outcome. Classification of the 18S rRNA gene (sub-genotypes B1 and B2) agreed with the rap-1 classification. CONCLUSIONS: The results of this study suggest that quantification of parasite loads of infected horses may be used to distinguish between infections resulting in disease and subclinical cases. Although number of clinical cases is limited, we identified T. equi 18S rRNA genotype A to be associated with clinical disease. This finding emphasizes the importance of in-depth genetic characterization of T. equi genotypes to identify possible markers for virulence. [Image: see text] BioMed Central 2020-05-20 /pmc/articles/PMC7240905/ /pubmed/32434550 http://dx.doi.org/10.1186/s13071-020-04133-y Text en © The Author(s) 2020 Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
spellingShingle Short Report
Tirosh-Levy, Sharon
Steinman, Amir
Levy, Hadas
Katz, Yotam
Shtilman, Margarita
Gottlieb, Yuval
Parasite load and genotype are associated with clinical outcome of piroplasm-infected equines in Israel
title Parasite load and genotype are associated with clinical outcome of piroplasm-infected equines in Israel
title_full Parasite load and genotype are associated with clinical outcome of piroplasm-infected equines in Israel
title_fullStr Parasite load and genotype are associated with clinical outcome of piroplasm-infected equines in Israel
title_full_unstemmed Parasite load and genotype are associated with clinical outcome of piroplasm-infected equines in Israel
title_short Parasite load and genotype are associated with clinical outcome of piroplasm-infected equines in Israel
title_sort parasite load and genotype are associated with clinical outcome of piroplasm-infected equines in israel
topic Short Report
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7240905/
https://www.ncbi.nlm.nih.gov/pubmed/32434550
http://dx.doi.org/10.1186/s13071-020-04133-y
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