Tick-borne viruses

Abstract

Tick-borne viruses (TBVs) belong to the largest biological group known as arboviruses with unique mode of transmission by blood-feeding arthropods (ticks, mosquitoes, sand flies, biting midges, etc.) to a susceptible vertebrate host. Taxonomically, it is a heterogenous group of vertebrate viruses found in several viral families. With only one exception, African swine fever virus, all TBVs have a RNA genome. To date, at least 160 tick-borne viruses are known, some of them pose a significant threat to human and animal health worldwide. Recently, a number of established TBVs has re-emerged and spread to new geographic locations due to the influence of anthropogenic activities and few available vaccines. Moreover, new emerging tick-borne diseases are constantly being reported. Major advances in molecular biotechnologies have led to discoveries of new TBVs and further genetic characterization of unclassified viruses resulting in changes in TBVs classification created by the International Committee for the Taxonomy of Viruses. Although TBVs spend over 95% of their life cycle within tick vectors and the role of ticks as vectors has been known for over 100 years, our knowledge about TBVs and molecular processes involved in the virus-tick interactions is scarce.

Murine Gammaherpesvirus 68 (MHV-68), a Newly Discovered Tick Borne Virus

“…With two exceptions, all arboviruses are RNA viruses. The only established DNA tick-borne virus, African swine fever virus (ASFV), belongs to the Asfarviridae family with a single genus Asfivirus [47]. The ASFV genome consists of a single molecule of linear, covalently close-ended, dsDNA varying in length from 170 to 190 kbp.…”

“…In Slovakia, the D. reticulatus tick had a focal distribution in Slovakia in the past [62], occurring mainly in the southwest and southeast along the Morava, Dunaj, and Latorica rivers. Of late, D. reticulatus has extended its former geographical distribution by at least 200 km further to the north and by approximately 300 m into higher altitudes up to 520 m above sea D. reticulatus tick is associated with a number of different pathogens and currently considered the second most significant reservoir and vector of numerous pathogens causing bacterial, protozoal, rickettsial, and viral diseases in its hosts [38,43,[64][65][66][67][68]. Its role in the transmission of disease to humans is currently small; however, it might play an important role in the maintenance of pathogens in enzootic cycles [69][70][71][72].…”

“…In Dermacentor sp. several other tick-borne viruses were identified such as Colorado tick fever virus, Burana orthonairovirus, Lanjan virus, Razdan virus, Dhori virus, and Sawgrass virus (reviewed in [64]).…”

“…In Haemaphysalis spp. also other viruses were identified such as Kyasanur Forest disease virus, three strains of Burana orthonairovirus, Nairobi sheep disease orthonairovirus, SFTS phlebovirus, Barur ledantevirus, Yongjia ledantevirus, New Minto virus, and to-date ungrouped viruses (Bhanja virus, Kaisodi virus, Silverwater virus, and Kwatta) [64]. In 2016, MHV-68 was firstly identified in adult H. concinna ticks collected in Gabčíkovo from May 2013 to May 2014.…”

“…Besides TBEV, several viruses were identified in I. ricinus ticks (e.g., Louping ill virus, Langat virus, Eyach virus, and at least 20 other viruses in Ixodes sp. ticks) [64,92].…”