Issue cover
Research Article | 10 Jul 2026

Molecular detection, genetic characterization, and phylogenetic relationships of Theileria orientalis in cattle and associated ticks from Wasit Province, Iraq

Abbas H. K. Sray1 ORCID , Ghassan J. K. Al-Abedi2 ORCID , Thuraya Khaled Abdulwahed3 ORCID , Israa M. Essa4 ORCID , Zeid Alsadoon5 ORCID , and Hasanain A. J. Gharban6 ORCID Show more
VETERINARY WORLD | Article No. 11 | pg no. 2850-2863 | Vol. 19, Issue 7 | DOI: 10.14202/vetworld.2026.2850-2863
Cited by 0
View PDF

Cite this Article

  • APA
  • MLA
  • Chicago
  • Vancouver
  • Harvard

                            
                        


                    


                


            


            


            
        

              


                  

                      
ABSTRACT

                      
Background and Aim: Theileria orientalis is an emerging tick-borne hemoprotozoan that has become a major cause of bovine theileriosis, leading to anemia, reduced productivity, and substantial economic losses in cattle. Despite increasing reports from neighboring countries, molecular epidemiological information and phylogenetic evidence for T. orientalis in Iraq remain scarce. This study aimed to determine the molecular prevalence of T. orientalis in cattle and their naturally infesting ticks in Wasit Province, Iraq; identify host-associated risk factors; and characterize the genetic diversity and phylogenetic relationships of local isolates relative to global reference strains. 
Materials and Methods: A cross-sectional study was conducted on 170 naturally tick-infested cattle from Wasit Province, Iraq, during July-August 2025. Whole blood and corresponding tick samples were collected from each animal. Genomic DNA was extracted and screened for T. orientalis using conventional polymerase chain reaction targeting the 18S rRNA gene. Positive amplicons were sequenced by Sanger sequencing, followed by sequence alignment, GenBank submission, and phylogenetic analysis using MEGA 11. Associations between infection and animal-related risk factors were evaluated using Chi-square analysis, odds ratio, relative risk, and 95% confidence intervals. 
Results: Molecular analysis detected T. orientalis DNA in 21/170 (12.35%) cattle and 16/170 (9.41%) tick samples. Infection prevalence differed significantly according to age and sex. Cattle aged >3-6 years exhibited the highest infection risk, whereas male cattle showed significantly greater positivity and relative risk than females. Sequence analysis demonstrated high genetic conservation among Iraqi isolates. Phylogenetic reconstruction revealed that all cattle isolates clustered closely with a Turkish T. orientalis isolate (HQ197736.1), whereas tick isolates showed close genetic relationships with Turkish isolates (HQ197736.1 and OR211412.1) and a Chinese isolate (PQ207062.1), suggesting regional genetic connectivity and possible transboundary circulation of T. orientalis lineages. 
Conclusion: This study provides the first molecular detection and comprehensive phylogenetic characterization of T. orientalis simultaneously in cattle and associated tick vectors from Wasit Province, Iraq. The findings establish the first molecular evidence linking genetically related cattle and tick isolates in the country and provide an important baseline for understanding the epidemiology of oriental theileriosis. Expanded nationwide molecular surveillance, genotype-specific characterization using additional genetic markers, and integrated tick management programs are warranted to improve disease monitoring and reduce the impact of T. orientalis infection on the Iraqi cattle industry. 
                      
Keywords: 18S rRNA, cattle, genetic characterization, Iraq, molecular epidemiology, phylogenetic analysis, Theileria orientalis, tick-borne disease.