Abstract
Ixodid ticks represent vectors and reservoirs for a broad range of zoonotic pathogens. Collected ticks from field studies are therefore usually stored in ethanol, which in higher concentrations effectively inactivates most of the known tick-borne pathogens. Although commonly practiced as gold standard for inactivation, hardly any scientific data demonstrate that ethanol sufficiently penetrates the comparatively thick cuticula of ticks. Therefore, Amblyomma hebraeum tick pools were stored for 21 days in ethanol (96%). Afterwards, the ethanol was removed and the ticks were homogenized. Quantitative 1H-NMR spectroscopic analysis was applied to determine the residual concentration of ethanol inside the ticks. 1H-NMR spectroscopic analysis revealed that ethanol constituted 28.3–42.6 mg of the total weight of three ticks in the pools (89.9–121.5 mg). In addition, the low-pathogenic Hazara orthonairovirus (HAZV) was used as a cell culture model for this study. The virus was exposed to ethanol concentrations between 0 and 60% and incubated under various temperature conditions for four time periods. Afterwards, the residual virus infectivity was determined by titration. Following ethanol exposure, HAZV did not grow in cells after 9 h of exposure to an ethanol concentration of 25%. These results demonstrate an extremely low ethanol resistance of the virus, which was generally in line with previously reported ethanol inactivation data for Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV). After prolonged storage and impregnation, comparable ethanol concentrations are achieved in the ticks, indicating the suitability of this inactivation method also for Bunyaviruses in ticks. At the very least, a massive virus inactivation can be assumed. Definitive proof of virus inactivation would require a bioassay of ethanol-treated infected ticks under appropriate biosafety conditions.
Highlights
Ixodid ticks are vectors and reservoirs for a broad variety of highly pathogenic zoonotic bacteria and viruses potentially causing life-threatening diseases
1H-NMR spectroscopic analysis revealed that the tick pools (1000 μl) contained 28.3–42.6 mg pure ethanol (Table 1)
A significant virus reduction started already at concentrations above 15% and a complete inactivation was observed with 20% ethanol (Fig. 1)
Summary
Ixodid ticks are vectors and reservoirs for a broad variety of highly pathogenic zoonotic bacteria and viruses potentially causing life-threatening diseases (bacteria: Anaplasmosis, Babesiosis, Borreliosis, etc.; viruses: Tick borne Encephalitis, Omsk hemorrhagic fever, Crimean-Congo hemorrhagic fever, Severe Febrile Thrombocytopenia Syndrome, etc. (for a more extensive list, see https://www.cdc.gov/ticks/diseases/index.html). Ixodid ticks are vectors and reservoirs for a broad variety of highly pathogenic zoonotic bacteria and viruses potentially causing life-threatening diseases One of the most grievous tick-borne viruses, classified as biosafety level 4 pathogen, is Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV). This virus belongs to the Nairovididae family in the Orthonairovirus genus and is transmitted by ticks of the genus Hyalomma, being its main vector and reservoir (Bente et al 2013; Gargili et al 2017). Studying and diagnostic screening of ixodid ticks and their zoonotic pathogens has become an essential part of modern public health research. In order to safely handle and taxonomically identify tick species possibly infected with CCHFV at a lower biosafety level, the virus must be reliably inactivated
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