Identification of tick species and disseminate pathogen using hemolymph by MALDI-TOF MS

Matrix Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) is increasingly emerging tool for identification of arthropods including tick vectors using whole or body part of specimens. The challenges of the present study were to assess MALDI-TOF MS profiling for the both identification of tick species and Rickettsia spp. in infected ticks using hemolymph as protein mixture.

Firstly, hemolymph protein mixture from legs of 5 tick species, Rhipicephalus sanguineus, Rhipicephalus bursa, Dermacentor marginatus, Hyalomma marginatum rufipes and Amblyomma variegatum infected by Rickettsia africae were submitted to MALDI-TOF MS to assess tick species identification ability. Secondly, hemolymph MS spectra from Rh. sanguineus infected or not by Rickettsia c. conorii were compared to detect protein profiles changes. Finally, leg hemolymph MS spectra from new specimens of the 5 tick species were tested blindly including ticks infected by R. c. conorii. Discriminating mass peaks distinguishing the R. c. conorii infected and non-infected Rh sanguineus were determined.

Consistent and reproducible MS profiles were obtained into each tick species. Comparison of MS spectra revealed distinct hemolymph protein profiles according to tick species. MS spectra changes were observed between hemolymphs from R. c. conorii-infected and non-infected Rh. sanguineus specimens, revealing 17 discriminating mass peaks. Clustering analysis based on MS protein profiles highlighted that hemolymph samples were grouped according to tick species. All tick hemolymph samples blindly tested against our home-made arthropod MS reference database were correctly identified at the species distinguishing also R. c. conorii-infected from Rickettsia-free Rh. sanguineus specimens.

The present study demonstrated the use of hemolymph MS profiles for dual identification of tick species and associated pathogens. This concomitant identification could be helpful for tick entomological diagnosis, notably for specimens removed directly on patients.