Novel Flavi-like virus in ixodid ticks and patients in Russia

Novel Haseki tick virus (HSTV) was detected in ixodid ticks and patients in the Asian part of Russia. Sequencing of the genome fragments corresponding whole polyprotein and viral RdRp demonstrated that HSTV is genetically close to unclassified Flavi-like viruses. Phylogenetic analysis of HSTV sequences showed that these viruses were close to Bole tick virus 4 (BLTV 4), which was detected early in Asia, Europe, Africa and the Caribbean region. The organization of the genome predicts that HSTV and BLTV 4 may also be classified as putative new genera within Flaviviridae with enlarged Flavi-like positive-sense ssRNA viral genomes. Cases of HSTV putative human incidents after Ixodes persulcatus attack were discovered in hospital patients with tick-borne infections in Vladivostok (Russia). The illness was associated with 3-5 days of fever, accompanied by acute respiratory lesions. Mixed human tick-borne infections (TBIs) were also detected for these patients as dual or triple coinfections for tick-borne encephalitis virus, Borrelia spp., Anaplasma spp., and HSTV. Thus, it is necessary to study HSTV antibody tests, virus isolation, and surveillance for HSTV sequences in different species of ticks, different geographical regions and patients after tick attacks.

Detection of tick-borne pathogens in wild birds and their ticks in Western Siberia and high level of their mismatch

The Tomsk region located in the south of Western Siberia is one of the most high-risk areas for tick-borne diseases due to elevated incidence of tick-borne encephalitis and Lyme disease in humans. Wild birds may be considered as one of the reservoirs for tick-borne pathogens and hosts for infected ticks. A high mobility of wild birds leads to unpredictable possibilities for the dissemination of tick-borne pathogens into new geographical regions. The primary goal of this study was to evaluate the prevalence of tick-borne pathogens in wild birds and ticks that feed on them as well as to determine the role of different species of birds in maintaining the tick-borne infectious foci. We analysed the samples of 443 wild birds (60 species) and 378 ticks belonging to the genus Ixodes Latraille, 1795 collected from the wild birds, for detecting occurrence of eight tick-borne pathogens, the namely tick-borne encephalitis virus (TBEV), West Nile virus (WNV), and species of Borrelia, Rickettsia, Ehrlichia, Anaplasma, Bartonella and Babesia Starcovici, 1893, using RT-PCR/or PCR and enzyme immunoassay. One or more tick-borne infection markers were detected in 43 species of birds. All markers were detected in samples collected from fieldfare Turdus pilaris Linnaeus, Blyth's reed warbler Acrocephalus dumetorum Blyth, common redstart Phoenicurus phoenicurus (Linnaeus), and common chaffinch Fringilla coelebs Linnaeus. Although all pathogens have been identified in birds and ticks, we found that in the majority of cases (75.5 %), there were mismatches of pathogens in birds and ticks collected from them. Wild birds and their ticks may play an extremely important role in the dissemination of tick-borne pathogens into different geographical regions.

Powassan virus, a scoping review of the global evidence

BACKGROUND

Powassan virus (POWV), a flavivirus discovered in 1958, causes sporadic but severe cases of encephalitis in humans. Since 2007, the number of human Powassan cases diagnosed each year in the USA has steadily increased. This is in agreement with predictions that Powassan cases may increase in North America as a result of increased exposure to infected ticks. However, the increase may also reflect improved diagnostics and reporting among other factors.

METHODS

A scoping review was prioritized to identify and characterize the global literature on POWV. Following an a priori developed protocol, a comprehensive search strategy was implemented. Two reviewers screened titles and abstracts for relevant research and the identified full papers were used to characterize the POWV literature using a predetermined data characterization tool.

RESULTS

One hundred and seventy-eight articles were included. The majority of the studies were conducted in North America (88.2%) between 1958 and 2017. Both genotypes of POWV (Powassan lineage 1 and Deer Tick virus) were isolated or studied in vitro, in vectors, nonhuman hosts and human populations. To date, POWV has been reported in 147 humans in North America. The virus has also been isolated from five tick species, and several animals have tested positive for exposure to the virus. The relevant articles identified in this review cover the following eight topics: epidemiology (123 studies), pathogenesis (66), surveillance (33), virus characterization (22), POWV transmission (8), diagnostic test accuracy (8), treatment (4) and mitigation strategies (3).

CONCLUSION

The literature on POWV is relatively small compared with other vector-borne diseases, likely because POWV has not been prioritized due to the small number of severe sporadic human cases. With the projected impact of climate change on tick populations, increases in the number of human cases are expected. It is recommended that future research efforts focus on closing some of the important knowledge gaps identified in this scoping review.

The epidemiology and geographic distribution of relapsing fever borreliosis in West and North Africa, with a review of the Ornithodoros erraticus complex (Acari: Ixodida)

BACKGROUND

Relapsing fever is the most frequent bacterial disease in Africa. Four main vector / pathogen complexes are classically recognized, with the louse Pediculus humanus acting as vector for B. recurrentis and the soft ticks Ornithodoros sonrai, O. erraticus and O. moubata acting as vectors for Borrelia crocidurae, B. hispanica and B. duttonii, respectively. Our aim was to investigate the epidemiology of the disease in West, North and Central Africa.

METHODS AND FINDINGS

From 2002 to 2012, we conducted field surveys in 17 African countries and in Spain. We investigated the occurrence of Ornithodoros ticks in rodent burrows in 282 study sites. We collected 1,629 small mammals that may act as reservoir for Borrelia infections. Using molecular methods we studied genetic diversity among Ornithodoros ticks and Borrelia infections in ticks and small mammals. Of 9,870 burrows investigated, 1,196 (12.1%) were inhabited by Ornithodoros ticks. In West Africa, the southern and eastern limits of the vectors and Borrelia infections in ticks and small mammals were 13°N and 01°E, respectively. Molecular studies revealed the occurrence of nine different Ornithodoros species, including five species new for science, with six of them harboring Borrelia infections. Only B. crocidurae was found in West Africa and three Borrelia species were identified in North Africa: B. crocidurae, B. hispanica, and B. merionesi.

CONCLUSIONS

Borrelia Spirochetes responsible for relapsing fever in humans are highly prevalent both in Ornithodoros ticks and small mammals in North and West Africa but Ornithodoros ticks seem absent south of 13°N and small mammals are not infected in these regions. The number of Ornithodoros species acting as vector of relapsing fever is much higher than previously known.