Serious disease outbreaks in cattle are usually associated with blood pathogens. This study aims to detect blood pathogens namely Trypanosoma evansi, Theileria, Anaplasma and Mycoplasma species, and studied their phylogenetic relationships, haemato-biochemical abnormalities and erythrocyte osmotic fragility (EOF) in Malaysian cattle. Methods : Molecular analysis was achieved by PCR amplification and sequencing of PCR amplicons of 18SrRNA gene of Theileria species, 16SrRNA genes of Anaplasma and

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... Mycoplasma species, 16SrRNA gene of Candidatus Mycoplasma haemobos, MPSP gene of T. orientalis and RoTaT1.2 VSG gene of Trypanosoma evansi, in sixty-one (61) Kedah-Kelantan X Brahman cattle from Pahang, Malaysia. Haemato-biochemical analyses were performed using automated analysers while EOF was determined with the aid of saline solutions. Results: PCR amplification produced the expected fragment sizes for MPSP gene of T. orientalis, msp4 gene of Anaplasma marginale, 16S rRNA gene of C. M. haemobos, RoTaT1.2VSG gene of T. evansi. Nucleotide blast demonstrated that sequences of the PCR amplicons showed a high degree of molecular similarity in comparison with reference sequences. Analysis of 18SrRNA gene sequences of Theileria species and 16S rRNA gene sequences of Anaplasma species revealed Theileria sinensis and Anaplasma platys as additional species detected in these cattle. Theileria species was the most detected blood pathogen in the sampled cattle. The blood picture of all cattle group revealed poikilocytosis, anisocytosis, rouleaux formation and degenerative left shift. Erythrocyte fragility values of all the cattle groups were above the reference range. Anaemia of the macrocytic normochromic type was observed in the Trypanosoma evansi; and Anaplasma platys + Theileria sinensis double species co-infected cattle. Normocytic normochromic anaemia was observed in the T. sinensis infected cattle group. Significant (p<0.05) increases in serum liver and kidney parameters, total protein, globulin, total and unconjugated bilirubin and decreased albumin was observed in the Trypanosoma evansi infected cattle. Conclusion: We present the first report of anaemia associated with Theileria sinensis infection in Malaysian cattle. Because of the high occurrence of bovine theileriosis and detection of Anaplasma