INTRODUCTION
Crimean-Congo hemorrhagic fever virus (CCHFV), a orthonairovirus of theNairoviridae family is the causative agent of a severe human
hemorrhagic fever disease characterized by fever, weakness, myalgia, and
hemorrhagic signs (Bente et al., 2013).
The disease, named Crimean hemorrhagic fever was first observed in the
Crimean Peninsula in 1944, and the causative agent which was isolated in
1967, was found to be identical to Congo virus isolated in 1956 from a
febrile child in the Belgian Congo hence the names Crimean and Congo are
used in combination (Casals, 1969). The
mean of CCHF fatality rates in Africa (22.0%) is lower than Asia
(33.5%) and Europe (33.8%) (Nasirian,
2020). The natural vector and reservoir have been identified
as Hyalomma sp. ticks, and the distribution of human cases
closely mirrors vector distribution CCHFV has been detected in more than
30 species of ticks, including Dermacentor sp . andRiphicephalus sp . ticks (Mehravaran
et al., 2013). Studies conducted since then have consistently found a
relationship between various tick species (Hyalomma,
Rhipicephalus, Boophilus, Dermacentor and Ixodes ) and the
presence of CCHFV in ticks are believed to be the principal means of
viral transmission and persistence in nature
(Drosten, Kummerer, Schmitz, & Gunther,
2003; Wolfel et al., 2007).
Nevertheless, the ability to transmit infection has been demonstrated
for ixodid ticks of several genera, and transovarial transmission of the
virus from adult females to the succeeding generation of larval ticks
has been shown to occur in a few members of the Hyalomma,
Dermacentor, and Rhipicephalus genera
(Zeller, Cornet, Diop, & Camicas, 1997).
In south-eastern Romania, the presence of Hyalomma was confirmed
in 2014 (Dumitrescu et al., 2014). The
coincidence in distribution of CCHF virus and Hyalomma ticks
implies that members of this genus are important vectors of the virus
(Shepherd, Swanepoel, Cornel, & Mathee,
1989). Arboviruses usually show low levels of genome diversity, perhaps
since they have to be adapted both to an arthropod vector and a
vertebrate host species, but CCHFV does not follow this rule and shows a
high nucleic acid diversity (Weaver,
2006). This virus is a negative-sense, single-stranded RNA virus with a
genome of approximative 19.2 kb in length. The genome contains three
segments: small (S), medium (M) and large (L). The L segment encodes the
RNA-dependent RNA polymerase, the M segment encodes the precursor of the
two envelope glycoproteins Gn and Gc, and the S segment encodes the
nucleocapsid protein (Aitichou, Saleh,
McElroy, Schmaljohn, & Ibrahim, 2005;
Estrada & De Guzman, 2011;
Honig, Osborne, & Nichol, 2004). CCHFV
is an enveloped virus characterized by a degree of sequence diversity of
20%, 22%, and 31% among the S-, L-, and M-segments of the virus
genome (Bente et al., 2013). M and L RNA
segments of nairoviruses are larger than other bunyaviruses
(hantaviruses and phleboviruses)
(Estrada-Pena et al., 2007;
Hoogstraal, 1979). As other members of
the family Bunyaviridae , CCHFV glycoproteins target the Golgi
apparatus, where most viral assembly takes place. Recent studies have
revealed a new strain which shows unique S-segment phylogenies and which
constitutes a unique clade (provisionally identified as clade VII)
(Chinikar et al., 2010). Crimean-Congo
hemorrhagic virus circulates in nature in unnoticed enzootic
tick–vertebrate–tick cycles. Asymptomatic CCHFV infection has been
reported in numerous vertebrate species and appears to be pervasive in
both wild and domestic animals. Asymptomatic viremia last up to 7–15
days in several vertebrate animal species, and CCHFV has been isolated
from livestock and small mammals (horses, donkeys, goats, cattle, sheep,
and pigs (Ergonul, 2006).
In Romania there is still not sufficient data concerning CCHFV and the
virus has never been detected in ticks. Virus detection by real-time
quantitative reverse transcription polymerase chain reaction (RT-qPCR)
is essential to prove an actual circulation of CCHFV in a country and
can be used to identify animals and humans CCHFV infections, together
with viral detection in ticks. The predominant problem in CCHFV RT-qPCR
development has always been the high genetic diversity of the virus
(Deyde, Khristova, Rollin, Ksiazek, &
Nichol, 2006).
The aim of this study was to assess the prevalence of CCHFV inDermacentor sp . and Rhipicephalus sp . ticks collected from
Romania, more precisely in Tulcea county, where in previous studies IgG
antibodies anti-CCHFV were found in sheep and goats
(Ceianu, Panculescu-Gatej, Coudrier, &
Bouloy, 2012; Răileanu, Anită, Porea, &
Savuta, 2015).