Using MALDI-TOF mass spectrometry to identify ticks collected on domestic and wild animals from the Democratic Republic of the Congo

Steve Ngoy,Sylvestre Gambalemoke Mbalitini,Maureen Laroche,Philippe Parola,Guy-Crispin Gembu,Anne Laudisoit,Adama Zan Diarra,Pascal Baelo,Erik Verheyen,Onésime Mubenga

doi:10.1007/s10493-021-00629-z

Abstract

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) has recently emerged as an alternative to morphological and molecular tools to identify tick species. In this study, we set out to evaluate and confirm the ability of MALDI-TOF MS to identify different species of ticks collected in the Democratic Republic of the Congo and preserved in 70% ethanol. A total of 575 ticks, of which 530 were collected from domestic pigs and 45 from wild animals, were subjected to MALDI-TOF MS analysis to evaluate the intraspecies reproducibility and interspecies specificity of MS profiles obtained from the different species. Morphologically, the ticks belonged to seven different species, namely Rhipicephalus complanatus, Rhipicephalus congolensis, Haemaphysalis muhsamae, Ixodes cumulatimpunctatus, Amblyomma exornatum, Amblyomma compressum and an unidentified Rhipicephalus sp. A total of 535/575 (93%) of the spectra obtained were of good enough quality to be used for our analyses. Our home-made MALDI-TOF MS arthropod database was upgraded with spectra obtained from between one and five randomly selected specimens per species. For these reference specimens, molecular identification of the ticks was also made using 16S, 12S rDNA genes and the Cox1 mtDNA gene sequencing. The remaining good quality spectra were then queried against the upgraded MALDI-TOF MS database, showing that 100% were in agreement with the morphological identification, with logarithmic score values (LSVs) between 1.813 and 2.51. The consistency between our morphological, molecular and MALDI-TOF MS identification confirms the capability and precision of MALDI-TOF MS for tick identification.

Highlights

Ticks are obligate blood-feeding arthropods that parasitise a large number of vertebrates, including mammals, birds, reptiles and amphibians (Mediannikov and Fenollar 2014; Parola and Raoult 2001)
A total of 575 ticks were collected, including 530 (92.2%) which were collected from 191 domestic pigs and 45 (7.8%) which were collected from five wild animals
The morphological identification performed by the Democratic Republic of the Congo (DRC) team initially identified four tick species; namely Rhipicephalus complanatus (456; 79.3%), Rhipicephalus congolensis (61; 10.6%), Haemaphysalis muhsamae, and Ixodes cumulatimpunctatus (12; 2.1%)

Summary

Introduction

Ticks are obligate blood-feeding arthropods that parasitise a large number of vertebrates, including mammals, birds, reptiles and amphibians (Mediannikov and Fenollar 2014; Parola and Raoult 2001) They are distributed into three families: Argasidae (soft ticks), Ixodidae (hard ticks) and Nuttalliellidae, representing a total of at least 898 recognised species (Dantas-Torres et al 2012). Some agents of tick-borne diseases such as Crimean-Congo haemorrhagic fever virus (CCHFV), Anaplasma, Rickettsia, Theileria and Babesia have been reported in the DRC in humans (Grard et al 2011; Simpson et al 1967; Woodall et al 1967), domestic animals (Dahmana et al 2019; Kalume et al 2009, 2013; Sas et al 2017) and tick vectors (Rhipicephalus sanguineus s.l. and Amblyomma compressum) (Mediannikov et al 2012; Sanogo et al 2003)

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