Cladistics and population structure analysis of Anaplasma marginale (Rickettsiales: Anaplasmataceae) in Haryana, India based on genes encoding the major surface proteins.

Anaplasma marginale, a tick-borne obligate intracellular rickettsia is incriminated to cause heavy economic losses throughout the tropical and subtropical regions, including India. However, studies highlighting the phylogeography and demographic dynamics of A. marginale are very scant from India. Thus, the present study assessed the cladistics and population structure of Anaplasma marginale based on the genes encoding the major surface proteins (MSP) 4 and 5. The cladistics based on phylogenetic tree including the sequences generated herein with the GenBank archived sequences of A. marginale was performed. The relationship between A. marginale haplotypes based on both the genetic markers was estimated by performing median joining (MJ) haplotype network analysis. Demographic dynamics involving population diversity indices and neutrality indices was also performed. The cladistics and MJ haplotype network analysis corresponding to both the markers demonstrated the presence of three distinct clades (1-3) of A. marginale. Population structure analysis revealed low nucleotide (0.00236 ± 0.00064 and 0.00955 ± 0.00101) and haplotype (0.321 ± 0.073 and 0.493 ± 0.083) diversities for the MSP4 and MSP5 genes, respectively. High genetic structuring and low gene flow [Nm values ranging between 0.044481 and 0.208337 for the MSP4 gene and 0.032735 (clades 1 and 2) for the MSP5 gene] was also recorded among the different clades of A. marginale, based on both genetic markers. The present study highlighted the presence of different clades of A. marginale distributed worldwide. The isolates circulating in north India belonged to the dominant clade prevalent throughout the globe.