Molecular epidemiology, phylogenetic analysis and risk assessment of Anaplasma marginale from naturally infected bovines of Punjab (India)

Abstract

Anaplasmosis, an infectious vector borne rickettsial disease caused by different species of Anaplasma transmitted through mechanical and biological (tick) processes has a great concern to livestock industry due to its associated economic losses. The current cross sectional comprehensive epidemiological study was conducted from August 2020 to November 2021 on 391 (277 cattle and 114 buffaloes) bovines from different districts of five agro climatic zones of Punjab state. Classical microscopic examination of Romanowsky stained blood smears showed an occurrence of 13.00%, while DNA amplification targeting major surface protein (msp5) of Anaplasma marginale revealed the 382 bp amplicon in 32.48% samples. Zone based molecular prevalence of A. marginale was highest in the Undulating zone (41.93%) and least in the Sub-Mountain zone (18.84%). The prevalence in Central plain zone, Western plain zone, and Western zone were 40.15, 30.95 and 29.91%, respectively. An overall molecular prevalence of A. marginale was 34.52, 32.75 and 20.0% in young, adults and calves, respectively, the difference being non-significant. Anaplsma marginale was more prevalent in unorganized farms (38.22%; 60/157) than organized farms (28.63%; 66/234). Risk factors analysis revealed young, female cattle at unorganized farms were more prone to anaplasmosis. Out of 127 positive samples, four samples were customed to sequencing revealed 98–99% homology with published sequences for other available global isolates. Multi-single nucleotide polymorphisms (SNP) were observed in the sequence of two samples when aligned with the reference sequence from the NCBI database (CP023731).