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Veterinary world2026; 19(9); 4244-4258; doi: 10.14202/vetworld.2026.4244-4258

Serological and molecular detection and phylogenetic characterization of Taylorella equigenitalis in horses in Iraq.

Abstract: Contagious equine metritis caused by is an important venereal disease of equids that can impair reproductive performance and facilitate transmission through clinically inapparent carriers. Information on infection in Iraqi horses remains limited. This study aimed to determine the serological and molecular occurrence of in horses in Iraq, evaluate associations with clinical and epidemiological factors, and characterize PCR-positive isolates using sequencing and phylogenetic analysis. Unassigned: A total of 157 adult horses from Baghdad, Babylon, Nineveh, and Wasit provinces were examined from March to September 2025. Clinical information was recorded, and blood and genital swab samples were collected. Serum samples were examined using a qualitative enzyme-linked immunosorbent assay (ELISA), whereas DNA extracted from genital swabs was subjected to conventional polymerase chain reaction (PCR) targeting the gene. PCR-positive products were sequenced, submitted to GenBank, and analyzed phylogenetically. Associations between infection status and clinical and epidemiological variables were statistically evaluated. Unassigned: Of the 157 horses, 52 (33.12%) were ELISA-positive and 23 (14.65%) were PCR-positive for . Twenty-one (13.38%) horses were positive by both methods, 31 (19.74%) were ELISA-positive/PCR-negative, two (1.27%) were ELISA-negative/PCR-positive, and 103 (65.61%) were negative by both methods. In mares, seropositivity was significantly associated with reproductive disorders, with the highest proportion detected among those with abnormal vaginal discharge (68.42%), whereas PCR positivity was highest among mares with infertility (50%). Seropositivity was higher in horses aged >10 years (62.86%) and females (52.38%), whereas PCR positivity was highest among horses aged >5-6 years (38.1%) and females (25%). Sequencing of 23 PCR-positive isolates generated GenBank accession numbers PZ146151.1-PZ146173.1. The Iraqi isolates showed 97.18%-99.12% sequence identity with an Iranian isolate (DQ840456.1). Unassigned: The findings provide serological and molecular evidence of infection among horses in Iraq and demonstrate associations with reproductive and epidemiological characteristics. Combined serological and molecular surveillance, routine screening of breeding horses, and higher-resolution molecular studies are warranted to clarify transmission dynamics and strengthen prevention and control strategies.
Copyright: © Hussein, et al.
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Publication Date: 2026-09-24 PubMed ID: 42928766PubMed Central: PMC13695703DOI: 10.14202/vetworld.2026.4244-4258Google Scholar: Lookup
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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.

Overview

  • This study investigated the presence of Taylorella equigenitalis, the bacterium causing contagious equine metritis (CEM), in horses across Iraq using serological and molecular tests.
  • It also analyzed how infection relates to clinical symptoms and horse demographics, and characterized bacterial strains through DNA sequencing and phylogenetic analysis.

Background

  • Contagious equine metritis (CEM) is a venereal disease in horses caused by the bacterium Taylorella equigenitalis.
  • CEM impairs reproductive performance and can be transmitted by horses that show no symptoms (asymptomatic carriers).
  • Information on the prevalence of T. equigenitalis infection in horses in Iraq has been limited prior to this study.

Objectives of the Study

  • Determine the serological (antibody) and molecular (DNA) prevalence of T. equigenitalis in Iraqi horses.
  • Explore associations between infection and clinical symptoms, such as reproductive disorders, as well as epidemiological factors like age and sex.
  • Sequence and phylogenetically analyze PCR-positive samples to understand genetic relationships of the bacterial strains found in Iraq.

Methods

  • Study population: 157 adult horses from four Iraqi provinces – Baghdad, Babylon, Nineveh, and Wasit.
  • Timeframe: March to September 2025.
  • Samples collected included blood for serology and genital swabs for molecular detection.
  • Serology: Enzyme-linked immunosorbent assay (ELISA) to detect antibodies against T. equigenitalis.
  • Molecular testing: Conventional PCR targeting a specific gene of the bacterium from genital swabs.
  • Sequencing of PCR-positive samples and submission of sequences to GenBank.
  • Phylogenetic analysis performed to compare Iraqi isolates to those from other regions.
  • Statistical analysis to identify significant associations between infection and clinical/epidemiological variables.

Results

  • Seropositivity (ELISA-positive) was found in 52 out of 157 horses (33.12%).
  • PCR detected the presence of the bacterium in 23 horses (14.65%).
  • Overlap of results: 21 horses were positive by both ELISA and PCR.
  • Divergent results included 31 ELISA-positive but PCR-negative horses and 2 PCR-positive but ELISA-negative horses.
  • Clinical associations:
    • In mares, seropositivity correlated significantly with reproductive disorders, especially abnormal vaginal discharge (68.42%).
    • PCR positivity was highest among infertile mares (50%).
  • Epidemiological factors:
    • Seropositivity was higher in females (52.38%) and in horses older than 10 years (62.86%).
    • PCR positivity was highest in females (25%) and horses aged 5–6 years (38.1%).
  • Genetic analysis:
    • Sequenced PCR products received GenBank accession numbers PZ146151.1 to PZ146173.1.
    • Iraqi isolates shared 97.18% to 99.12% genetic identity with an Iranian T. equigenitalis isolate (GenBank DQ840456.1), indicating close relation.

Conclusions and Implications

  • This study provides the first serological and molecular evidence confirming T. equigenitalis infection among horses in Iraq.
  • The data highlight significant links between infection and clinical signs related to reproduction, particularly in female horses.
  • Findings underscore the importance of combined serological and molecular surveillance methods for accurate detection of CEM.
  • The observed genetic similarity with nearby regional isolates suggests possible regional transmission dynamics.
  • Recommendations include:
    • Routine screening of breeding horses to identify and manage infected animals.
    • Further high-resolution molecular studies to map transmission pathways.
    • Enhanced prevention and control strategies to reduce disease spread and reproductive losses.

Cite This Article

APA
Hussein ZS, Radhy AM, Mosa ST, Gharban HAJ. (2026). Serological and molecular detection and phylogenetic characterization of Taylorella equigenitalis in horses in Iraq. Vet World, 19(9), 4244-4258. https://doi.org/10.14202/vetworld.2026.4244-4258

Publication

Veterinary world
ISSN: 0972-8988
NlmUniqueID: 101504872
Country: New Zealand
Language: English
Volume: 19
Issue: 9
Pages: 4244-4258

Researcher Affiliations

Hussein, Zaid Salah
  • Zoonoses Research Unit, College of Veterinary Medicine, University of Baghdad, Baghdad, Iraq.
Radhy, Amanee Mohammed
  • Department of Internal and Preventive Veterinary Medicine, College of Veterinary Medicine, University of Baghdad, Baghdad, Iraq.
Mosa, Saba Thamer
  • Department of Internal and Preventive Veterinary Medicine, College of Veterinary Medicine, University of Baghdad, Baghdad, Iraq.
Gharban, Hasanain A J
  • Department of Internal and Preventive Veterinary Medicine, College of Veterinary Medicine, University of Wasit, Wasit, Iraq.

Conflict of Interest Statement

The authors declare that they have no competing interests.

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