Delimitation of the Tick-Borne Flaviviruses. Resolving the Tick-Borne Encephalitis and Louping-Ill Virus Paraphyletic Taxa

The tick-borne flavivirus (TBFV) group contains at least 12 members where five of them are important pathogens of humans inducing diseases with varying severity (from mild fever forms to acute encephalitis). The taxonomy structure of TBFV is not fully clarified at present. In particular, there is a number of paraphyletic issues of tick-borne encephalitis virus (TBEV) and louping-ill virus (LIV). In this study, we aimed to apply different bioinformatic approaches to analyze all available complete genome amino acid sequences to delineate TBFV members at the species level. Results showed that the European subtype of TBEV (TBEV-E) is a distinct species unit. LIV, in turn, should be separated into two species. Additional analysis of the diversity of TBEV and LIV antigenic determinants also demonstrate that TBEV-E and LIV are significantly different from other TBEV subtypes. The analysis of available literature provided data on other virus phenotypic particularities that supported our hypothesis. So, within the TBEV+LIV paraphyletic group, we offer to assign four species to get a more accurate understanding of the TBFV interspecies structure according to the modern monophyletic conception.

TBE in United Kingdom

Until 2019, TBE was considered only to be an imported disease to the United Kingdom. In that year, evidence became available that the TBEV is likely circulating in the country1,2 and a first “probable case” of TBE originating in the UK was reported.3 In addition to TBEV, louping ill virus (LIV), a member of the TBEV-serocomplex, is also endemic in parts of the UK. Reports of clinical disease caused by LIV in livestock are mainly from Scotland, parts of North and South West England and Wales.4

DIAGNOSIS AND TREATMENT OF TICK-BORNE DISEASES OF PETS

In recent years, there has been an increase in the number of tick-borne diseases around the world, especially borreliosis, rickettsiosis (anaplasmosis, ehrlichiosis), tick-borne encephalitis and others. Climate and environmental changes, migration (movement) of domestic animals lead to changes in the epizootiological situation regarding communicable diseases. The analysis of epizootological, clinical, laboratory data is carried out. The data of scientific researches concerning tick-borne diseases, namely borreliosis, ehrlichiosis, tick-borne encephalitis, louping-ill infection are generalized. In recent years, infectious and invasive animal diseases caused by viruses, bacteria and protozoa transmitted by ticks have become a new challenge in health and veterinary practice. Many such diseases are zoonoses and lead to disability and mortality in humans and animals. Ixodid ticks often attack animals and humans and are widespread throughout Europe, as well as being involved in the transmission of a large number of tick-borne diseases. Currently, one of the biggest threats is the pathogens of the complex Borrelia burgdorferi s. l., which belong to the spirochetes and affect various species of mammals and birds and are transmitted by ticks (Ixodes ricinus, Ixodes hexagonus and Ixodes persulcatus). The disease is of great epidemiological importance for human health. Diagnosis and treatment are insufficiently developed. Ehrlichia spp. are gramnegative, obligate intracellular bacteria from the family Anaplasmataceae. In Europe, Ehrlichia canis is the etiological agent of monocytic ehrlichiosis in dogs. The main host of E. canis is a dog (other dogs can serve as reservoir hosts); vector - Rhipicephalus sanguineus. Tick-borne encephalitis, as well as louping-ill infection, are diseases transmitted by Ixodid ticks and pose a danger to dogs, cats and other animals, as well as people in Europe. At present, all these diseases acquire important epizootological significance, as diagnosis and treatment are complicated. The main measure of disease prevention among dogs is the effective protection of animals from tick attack. Tick-borne diseases are a type of infectious and invasive diseases of animals and humans, the causative agents of which spread from one susceptible subject to another with the participation of blood-sucking arthropods. The most common and clinically significant diseases are: borreliosis, ehrlichiosis, tick-borne encephalitis and other. Systematic studies of zoonotic diseases have not been conducted in Ukraine. Systematic monitoring of pathogens and effective control of communicable diseases of animals are the basis for improving the epidemiological situation among the population.