Dermacentor reticulatus: a vector on the rise.

Dermacentor reticulatus is a hard tick species with extraordinary biological features. It has a high reproduction rate, a rapid developmental cycle, and is also able to overcome years of unfavourable conditions. Dermacentor reticulatus can survive under water for several months and is cold-hardy even compared to other tick species. It has a wide host range: over 60 different wild and domesticated hosts are known for the three active developmental stages. Its high adaptiveness gives an edge to this tick species as shown by new data on the emergence and establishment of D. reticulatus populations throughout Europe. The tick has been the research focus of a growing number of scientists, physicians and veterinarians. Within the Web of Science database, more than a fifth of the over 700 items published on this species between 1897 and 2015 appeared in the last three years (2013-2015). Here we attempt to synthesize current knowledge on the systematics, ecology, geographical distribution and recent spread of the species and to highlight the great spectrum of possible veterinary and public health threats it poses. Canine babesiosis caused by Babesia canis is a severe leading canine vector-borne disease in many endemic areas. Although less frequently than Ixodes ricinus, D. reticulatus adults bite humans and transmit several Rickettsia spp., Omsk haemorrhagic fever virus or Tick-borne encephalitis virus. We have not solely collected and reviewed the latest and fundamental scientific papers available in primary databases but also widened our scope to books, theses, conference papers and specialists colleagues' experience where needed. Besides the dominant literature available in English, we also tried to access scientific literature in German, Russian and eastern European languages as well. We hope to inspire future research projects that are necessary to understand the basic life-cycle and ecology of this vector in order to understand and prevent disease threats. We conclude that although great strides have been made in our knowledge of the eco-epidemiology of this species, several gaps still need to be filled with basic research, targeting possible reservoir and vector roles and the key factors resulting in the observed geographical spread of D. reticulatus.

[The Omsk hemorrhagic fever: research results (1946-2013)].

The main aspects of epidemiology and epizootology of the Omsk hemorrhagic fever (OHF) are analyzed. The discovery of the virus OHF in 1947, as well as the first outbreak of new diseases in the districts of the Omsk region, is described. Comprehensive work for decryption of the etiology of the OHF by specialists from the Omsk and Moscow Institutes is carried out. Long-term dynamics of activity of natural foci of OHF contains four periods of variable intensity of epidemic and epizootic processes. The main reservoir of the virus OHF in natural foci and the source of human infection is muskrat. Metaxenosis provides maintaining of the population of the virus, which is of some significance for hosts. Independent position of the virus OHF in the group of the Flaviviruses of mammals transmitted by ticks is established. There are two aenovariants of the virus OHF.

Omsk haemorrhagic fever.

Omsk haemorrhagic fever is an acute viral disease prevalent in some regions of western Siberia in Russia. The symptoms of this disease include fever, headache, nausea, severe muscle pain, cough, and moderately severe haemorrhagic manifestations. A third of patients develop pneumonia, nephrosis, meningitis, or a combination of these complications. The only treatments available are for control of symptoms. No specific vaccine has been developed, although the vaccine against tick-borne encephalitis might provide a degree of protection against Omsk haemorrhagic fever virus. The virus is transmitted mainly by Dermacentor reticulatus ticks, but people are mainly infected after contact with infected muskrats (Ondatra zibethicus). Muskrats are very sensitive to Omsk haemorrhagic fever virus. The introduction of this species to Siberia in the 1930s probably led to viral emergence in this area, which had previously seemed free from the disease. Omsk haemorrhagic fever is, therefore, an example of a human disease that emerged owing to human-mediated disturbance of an ecological niche. We review the biological properties of the virus, and the epidemiological and clinical characteristics of Omsk haemorrhagic fever.

Comparative analysis of immune responses to Russian spring-summer encephalitis and Omsk hemorrhagic fever viruses in mouse models.

Omsk hemorrhagic fever virus (OHFV) and Russian spring-summer encephalitis virus (RSSEV) are tick-borne flaviviruses that have close homology but different pathology and disease outcomes. Previously, we reported that C57BL/6 and BALB/c mice were excellent models to study the pathology and clinical signs of human RSSEV and OHFV infection. In the study described here, we found that RSSEV infection induced robust release of proinflammatory cytokines (IL-1α, IL-1ß, IL-6 and TNF-α) and chemokines (MCP-1, MIP-1ß, RANTES and KC) in the brain at 9 and 11dpi, together with moderate to low Th1 and Th2 cytokines. In contrast, OHFV infection stimulated an early and prominent induction of IL-1α, TNF-α, IL-12p70, MCP-1, MIP-1α and MIP-1ß in the spleen of infected mice. Collectively our data suggest that a differential host response to infection may lead to the alternate disease outcomes seen following OHFV or RSSEV infection.

[Tick-borne human pathogenic microorganisms found in Europe and those considered nonpathogenic. Part I: Ticks and Viruses]. / Durch Zecken übertragene humanpathogene und bisher als apathogen geltende Mikroorganismen in Europa. Teil I: Zecken und Viren.

The importance of tick-borne encephalitis (TBE) and Lyme borreliosis-the main European tick-borne diseases-is steadily growing. This fact is due to many different factors including climate changes. However, across Europe many other human pathogenic viruses, bacteria, and parasites are found in ticks. This article gives an overview of tick-borne human pathogenic viruses present in Europe as well as those considered nonpathogenic. It also deals with the various species of vector-competent ticks. Among these ticks, viruses from 6 families encompassing 8 genera and 35 species are found,whereby the families Flaviviridae, Bunyaviridae, and Reoviridae with the genera flavivirus, nairovirus, and orbivirus are the most prevalent. Because of their special importance Omsk hemorrhagic fever, louping-ill disease, tick-borne encephalitis, and Crimean-Congo hemorrhagic fever are discussed in detail. Although West Nile virus is mainly transmitted to man by mosquitoes, it is discussed in detail, because West Nile fever has become a good example for a new and rapidly spreading vector-borne disease in the USA and for a recurrent one in Europe. Secondly, besides the mosquito-bird cycle an interesting tick--bird cycle is emerging. The overview clearly demonstrates that in Europe (particularly in Germany) tick-borne viruses, with the exception of TBE, constitute an extremely ignored research subject. This lack of attention is in contrast to their importance and results in a lack of necessary scientific data.