Ethanol inactivation of orthonairoviruses in ixodid ticks

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.

Detection of Crimean-Congo hemorrhagic fever virus in blood-fed Hyalomma ticks collected from Mauritanian livestock

Background

Crimean-Congo hemorrhagic fever virus (CCHFV) belongs to the genus Orthonairovirus (Nairovididae) and is a (re)emerging tick-borne pathogen. It is endemic in most parts of Africa, Asia and southern Europe, and can cause severe hemorrhagic symptoms in humans, with high fatality rates (5–30%).

Methods

Hyalomma ticks were collected from four different livestock herds (cattle and camels) in Mauritania in 2018. The tick species were determined morphologically and confirmed molecularly by using the cytochrome oxidase 1 gene marker. For the detection of CCHFV, ticks were tested individually by one-step multiplex real-time reverse-transcriptase quantitative polymerase chain reaction. The small segment of all positive samples was sequenced to determine the CCHFV genotype.

Results

In total, 39 of the 1523 ticks (2.56%) collected from 63 cattles and 28 camels tested positive for CCHFV. Three Hyalomma species were identified. Hyalomma rufipes had the largest proportion of positivity (5.67%; 16/282), followed by Hyalomma dromedarii (1.89%; 23/1214). No Hyalomma impeltatum tested positive (0%; 0/21). Positive ticks were found in only six out of 91 host animals. Viral sequence analysis revealed the presence of two different CCHFV lineages (Africa I and Africa III).

Conclusions

In this study, 2.56% of Hyalomma ticks collected from camels and cattle in Mauritania tested positive for CCHFV. However, the true prevalence of CCHFV in unfed ticks may be lower, as a considerable number of ticks may have been passively infected during blood-feeding by co-feeding ticks or due to viremia of the host. The results indicate the need to track the actual area of circulation of this virus.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04819-x.

Molecular discrimination of Hyalomma tick species serving as reservoirs and vectors for Crimean-Congo hemorrhagic fever virus in sub-Saharan Africa

The species identification of tick vectors of Crimean-Congo hemorrhagic fever virus (CCHFV), especially Hyalomma (H.) species, is a prerequisite to understand the eco-epidemiology of this disease and to reveal vector and virus reservoir species. However, the morphologic species discrimination can be difficult for damaged or blood-fed ticks and in case of species intercrosses. Therefore, we used matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and restriction fragment length polymorphism (RFLP) analysis to distinguish the most common Hyalomma species from sub-Saharan Africa (H. truncatum, H. rufipes and H. dromedarii). Within the last years, MALDI-TOF MS analysis based on tick leg proteins has been shown to be a reliable method to distinguish several tick species. For this purpose, a reference spectral library of several European, American and African tick species was established. In this study, six different Hyalomma species were tested, all of which were all clearly distinguishable by mass spectrometric analyses. Moreover, MALDI TOF- MS was able to confirm morphologic findings where sequencing provided ambiguous results. In addition, a polymerase chain reaction (PCR) based on the CO1 gene amplification of ticks has been developed for the unequivocal species identification by amplicon sequencing and specific restriction endonuclease cleavage pattern analysis. RFLP proved to be a feasible auxiliary discrimination tool for selected Hyalomma species when access to sequencing methods is not available, as for instance during field studies.

[Evaluation of atrial septum defects in adulthood using echocardiography methods]

Two-dimensional and Doppler echocardiographic methods are used to noninvasively detect atrial septal defects. The value of these methods to predict the magnitude of intracardiac left-to-right shunts has not been thoroughly investigated. In this study, we derived right ventricular (RV) and septal defect dimensions, and Qp/Qs-ratios from two-dimensional and Doppler echocardiography in 30 consecutive patients (17 females, 3 males, age 37 +/- 17 years) with invasively confirmed atrial septal defects. Noninvasively obtained parameters were compared to atrial shunt size as measured by oxymetry. RV dimensions correlated only poorly (RV length: r = 0.53, p < 0.005; RV-diameter r = 0.45 p < 0.05), but septal defect dimensions (r = 0.67, p < 0.001) and Qp/Qs-index (r = 0.65, p < 0.05) correlated fairly with shunt size. RV dilatation was highly sensitive (100%) but only moderately specific (67%) as an indicator of shunts > 30%. A defect length > or = 15 mm was moderately sensitive (81%) but highly specific (100%) and a Qp/Qs-index > or = 1.45 was highly sensitive (100%) and specific (76%) to detect shunts > 30%. None of the noninvasive parameters investigated in this study was able to differentiate moderate (> 30% but < 50%) from large ( > or = 50%) intracardiac left-to-right shunts.