Molecular characterization and pathogen detection in Amblyomma gervaisi and Amblyomma varanense collected from snakes of India

Abstract

The main objective of this study was to underscore detail gross and ultra-structural morphology, molecular characterization of ticks found on snakes and their ability to carry zoonotic pathogens. The investigation was carried out throughout the North-Eastern states of India during different seasons from March, 2020 to February, 2021. The outer surface of different species of snakes that were either kept in zoos or captured or killed by local people were thoroughly examined for presence of any ticks. Some of the collected ticks were preserved in absolute alcohol for molecular study while rest was kept in 70% alcohol for Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Light microscopy, SEM and TEM revealed specific morphological features through which the collected ticks were identified as Amblyomma gervaisi and Amblyomma varanense and further confirmation was revalidated by molecular detection. The ticks were commonly found during the rainy season (July to October) and Indian 2021 42(4 ) 80 black cobra (Naja naja) was found more commonly infested with both genera than that of other three species of snakes. The existence of tick-associated pathogens in A. gervaisi and A. varanense were determined by molecular and bioinformatics techniques. DNA isolated from snake ticks yielded products by the tick mitochondrial 16S rRNA PCR. Sequence homology and phylogenetic analysis of amplified PCR product revealed that the pathogen infecting Amblyomma ticks was a member of the genus Coxiella. The partial sequence of the Coxiella agent of A. gervaisi and A. varanense grouped with Coxiella symbionts of other hard tick species (Ixodidae). Additionally, present study suggests a very long period of coevolution between ticks and Coxiella symbionts and suggests that the original infection might have occurred in an ancestor common to the 2 main tick families, Argasidae (soft ticks) and Ixodidae (hard ticks). However, further extensive study of additional tick species and expanded host populations must be required to conclude this evolutionary relationship between ticks and Coxiella symbionts.