Molecular characterization of the Babesia caballi rap-1 gene and epidemiological survey in horses in Israel.
Abstract: Equine piroplasmosis imposes great concerns for the equine industry regarding international horse movement, and therefore requires reliable diagnostic tools. Recent studies from South Africa and Jordan, including a preliminary study in Israel, reported extremely low seroprevalence to Babesia caballi (B. caballi) (0-1%) using the acceptable rhoptry-associated protein-1 (RAP-1) cELISA. In accordance with the study from South Africa demonstrating a significant heterogeneity in the rap-1 gene sequence of South African B. caballi isolates, the objectives of this study were to phylogenetically characterize the rap-1 gene of the Israeli isolates and determine the prevalence of B. caballi in horses in Israel. Out of 273 horses tested using the RAP-1 cELISA, only one was sero-positive, while 9.3% were positive on PCR performed on the rap-1 gene. Phylogenetic analysis of the rap-1 gene grouped the Israeli isolates in a cluster together with the South African strains (99% nt identity), but in a separate cluster from the American/Caribbean strains (81-82% nt identity). These findings support the existence of heterogeneity in the RAP-1 amino-acid sequences of the Israeli and South African isolates as compared to that used in the cELISA commercial kit and raise doubts as to the ability of this assay to serve as a sole regulatory test for international horse movement. Risk factor analysis found management and age to significantly associate with prevalence of B. caballi, as higher prevalence was noted in horses held out on pasture and a negative association was recorded with age. In addition, B. caballi was not detected in horses in the steppe-arid and extreme-arid climatic regions as compared to the wetter regions. Findings of this study emphasize the need to combine several detection methods to ameliorate the control and spread of the disease.
Copyright © 2014 Elsevier B.V. All rights reserved.
Publication Date: 2014-02-10 PubMed ID: 24524984DOI: 10.1016/j.meegid.2014.01.033Google Scholar: Lookup
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- Journal Article
Summary
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This research focuses on understanding the rap-1 gene in Babesia caballi, a parasite causing equine piroplasmosis in horses. The researchers analyzed the genetic makeup of the parasite in Israel, finding differences compared to the versions commonly found elsewhere, and examined its prevalence amongst horses in various regions of the country.
Objectives and Methods
- The primary objectives of this study were to understand the genetic structure of the rap-1 gene in the Babesia caballi parasite isolated in Israel and to establish the prevalence of the disease in the country’s horse population.
- Scientists used a RAP-1 (rhoptry-associated protein-1) cELISA test, widely utilized for the diagnosis of Babesia caballi, on 273 horses to determine infection rates. The team also conducted a PCR test on the rap-1 gene of Babesia caballi from Israeli samples.
Results
- According to the RAP-1 cELISA test results, only one horse showed the presence of Babesia caballi. When a PCR test targeted specifically at the rap-1 gene was used, the rate rose to 9.3%.
- Through phylogenetic (genetic lineage) analysis, it was revealed that the rap-1 gene in the Israeli isolates of Babesia caballi closely resembles that of South African strains (99% similarity) but significantly differs from American/Caribbean strains (81-82% similarity).
- A risk factor analysis was also carried out, showing a higher prevalence of B. caballi in horses held outdoors and a declining trend with increasing age. In addition, the parasite was not present in horses residing in steppe-arid and extreme arid climatic regions compared to wetter regions.
Conclusions and Implications
- These results suggest that there may be different strains of B. caballi across various geographical areas, and the RAP-1 cELISA test widely used may not be reliably detecting all these strains.
- The findings question the diagnostic reliability of the RAP-1 cELISA test for Babesia caballi due to significant genetic differences in the rap-1 gene across different geographical strains. This impacts the regulatory diagnosis for international horse movements.
- This study reiterates the need for combined detection methods to effectively control the spread of equine piroplasmosis, given the apparent genetic diversity of the parasitic organism.
Cite This Article
APA
Rapoport A, Aharonson-Raz K, Berlin D, Tal S, Gottlieb Y, Klement E, Steinman A.
(2014).
Molecular characterization of the Babesia caballi rap-1 gene and epidemiological survey in horses in Israel.
Infect Genet Evol, 23, 115-120.
https://doi.org/10.1016/j.meegid.2014.01.033 Publication
Researcher Affiliations
- Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel.
- Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel.
- Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel.
- Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel.
- Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel.
- Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel.
- Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel. Electronic address: Steinman@agri.huji.ac.il.
MeSH Terms
- Amino Acid Sequence
- Animals
- Babesia / classification
- Babesia / genetics
- Babesiosis / blood
- Babesiosis / epidemiology
- Babesiosis / parasitology
- Genetic Heterogeneity
- Horse Diseases / blood
- Horse Diseases / epidemiology
- Horse Diseases / parasitology
- Horses
- Israel
- Molecular Sequence Data
- Phylogeny
- Phylogeography
- Protozoan Proteins / genetics
- Risk Factors
- Seroepidemiologic Studies
Citations
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