First molecular evidence of equine granulocytic anaplasmosis in Pakistan

Anaplasma phagocytophilum (A. phagocytophilum) is an obligate intracellular bacterium that causes equine granulocytic anaplasmosis (EGA) disease in equines. This pathogen has zoonotic potential, which makes it very important to be detected and controlled as early as possible. This study was aimed to assess the molecular prevalence, associated risk factors of EGA along with its effects on various hematological parameters. This study revealed an overall 10.67% prevalence in equine. Horses showed highest prevalence followed by mules and donkeys presenting 11.86, 10.53 and 9.43% prevalence, respectively. The samples were confirmed for anaplasmosis through sequencing. The BLAST queries confirmed very high homology of our isolates with Chinese and Japanese isolates of A. phagocytophilum (Accession no's; KX505303, KY242456 and LC002836). The phylogenetic analysis found the study isolates clustered with each other and this cluster closely resembled Chinese isolate of A. bovis (FJ169957), A. phagocytophilum (HQ872464) and A. phagocytophilum (NR_044762) human isolate from northern Minnesota and Wisconsin. The key risk factors identified for occurrence of EGA in equine species on the basis of univariable analysis were sex of animal, housing type, tick infestation, previous tick history and tick control status, type of acaricides used, rearing system and farm hygiene, respectively. The hematological parameters like Hemoglobin (Hb), Total Leukocyte Count (TLC), Total Erythrocytes Count (TEC), and granulocytes were decreased in diseased animals. The mules showed no typical hematological variations which make sense for its nature as carrier of infection to the susceptible species. This is the first molecular evidence of EGA in Pakistan. The disease needs to be handled seriously as it has zoonotic potential. The animals should be properly attended in disease conditions as leukopenia, neutropenia and lymphopenia can aggravate the condition by making the animal prone to secondary infections.