Characterization of Hemorrhagic Fever with Renal Syndrome Caused by Hantaviruses, Estonia

Thirty cases of hemorrhagic fever with renal syndrome (HFRS) due to Puumala virus (PUUV), Saaremaa virus (SAAV), and Dobrava virus infection were confirmed in Estonia. Except for the levels of serum creatinine, no remarkable differences were found in the clinical course of HFRS caused by PUUV and SAAV

Tickborne Encephalitis Virus, Norway and Denmark

Serum from 2 Norwegians with tickborne encephalitis (TBE) (1 of whom was infected in Denmark) and 810 Norwegian ticks were tested for TBE virus (TBEV) RNA by reverse transcription–polymerase chain reaction. Sequencing and phylogenetic analysis were performed. This is the first genome detection of TBEV in serum from Norwegian patients

First evidence of established populations of the taiga tick Ixodes persulcatus (Acari: Ixodidae) in Sweden

Background: The tick species Ixodes ricinus and I. persulcatus are of exceptional medical importance in the western and eastern parts, respectively, of the Palaearctic region. In Russia and Finland the range of I. persulcatus has recently increased. In Finland the first records of I. persulcatus are from 2004. The apparent expansion of its range in Finland prompted us to investigate if I. persulcatus also occurs in Sweden. Methods: Dog owners and hunters in the coastal areas of northern Sweden provided information about localities where ticks could be present. In May-August 2015 we used the cloth-dragging method in 36 localities potentially harbouring ticks in the Bothnian Bay area, province Norrbotten (NB) of northern Sweden. Further to the south in the provinces Vasterbotten (VB) and Uppland (UP) eight localities were similarly investigated. Results: Ixodes persulcatus was detected in 9 of 36 field localities in the Bothnian Bay area. Nymphs, adult males and adult females (n = 46 ticks) of I. persulcatus were present mainly in Alnus incana - Sorbus aucuparia - Picea abies - Pinus sylvestris vegetation communities on islands in the Bothnian Bay. Some of these I. persulcatus populations seem to be the most northerly populations so far recorded of this species. Dog owners asserted that their dogs became tick-infested on these islands for the first time 7-8 years ago. Moose (Alces alces), hares (Lepus timidus), domestic dogs (Canis lupus familiaris) and ground-feeding birds are the most likely carriers dispersing I. persulcatus in this area. All ticks (n = 124) from the more southern provinces of VB and UP were identified as I. ricinus. Conclusions: The geographical range of the taiga tick has recently expanded into northern Sweden. Increased information about prophylactic, anti-tick measures should be directed to people living in or visiting the coastal areas and islands of the Baltic Bay.Peer reviewe

Hantaviirusinfektsioonid Eestis

Hantaviirusnakkused on zoonootilised – viirused tsirkuleerivad looduses ilma inimese osaluseta, neid levib näriliste vahendusel. Tuntud on kaks kliiniliselt erinevat haigusvormi – neerusündroomiga hemorraagiline palavik (levinud Aasias ja Euroopas) ning hantaviiruse pulmonaalne sündroom (levinud Ameerikas). Sõltuvalt viirustüübist võib letaalsus haigestumuse korral ulatuda kuni 40%-ni. Eestis on isoleeritud Dobrava genotüüp viirus. Saaremaal püütud juttselg hiirtel on isoleeritud viirus osutunud aga omaette genotüüpi kuuluvaks ja on nimetatud saaremaa hantaviiruseks. Hantaviirusnakkus on levinud ka Eestis – aastal 2001 esines 12 seroloogiliselt kinnitatud haigusjuht

Serological Evidence of Exposure to Globally Relevant Zoonotic Parasites in the Estonian Population

We investigated Estonian population and its selected subgroups for serological evidence of exposure to Ascaris lumbricoides, Echinococcus spp., Taenia solium, Toxocara canis, Toxoplasma gondii, and Trichinella spiralis. Serum samples from 999 adults representing general population, 248 children aged 14-18, 158 veterinarians, 375 animal caretakers, and 144 hunters were tested for specific immunoglobulin G antibodies against the selected parasites using commercial enzyme immunoassays (ELISA). Sera yielding positive or twice grey zone Echinococcus spp, T. solium, T. canis, and T. spiralis results were subjected to western blot (WB) analysis. In the general population, based on the ELISA results, the A. lumbricoides seroprevalence was 12.7%, Echinococcus spp. seroprevalence was 3.3%, T. solium seroprevalence was 0.7%, T. canis seroprevalence was 12.1%, T. gondii seroprevalence was 55.8%, and T. spiralis seroprevalence was 3.1%. Ascaris lumbricoides seroprevalences were higher in children and in animal caretakers than in the general population, and T. canis seroprevalence was higher in animal caretakers than in the general population. Compared with the general population, Echinococcus spp. seroprevalence was higher in children. By contrast, T. gondii seroprevalence was higher in animal caretakers, and lower in children, than in the general population. In the general population, the WB-confirmed Echinococcus spp. seroprevalence was 0.5%, T. solium cysticercosis seroprevalence was 0.0%, Toxocara spp. seroprevalence was 14.5%, and Trichinella spp. seroprevalence was 2.7%. WB-confirmed Toxocara spp. seroprevalence was higher in animal caretakers than in the general population. We found serological evidence of exposure to zoonotic parasites in all tested groups. This calls for higher awareness of zoonotic parasitic infections in Estonia.Peer reviewe

Multi-laboratory evaluation of ReaScan TBE IgM rapid test, 2016 to 2017

Tick-borne encephalitis (TBE) is a potentially severe neurological disease caused by TBE virus (TBEV). In Europe and Asia, TBEV infection has become a growing public health concern and requires fast and specific detection. Aim: In this observational study, we evaluated a rapid TBE IgM test, ReaScan TBE, for usage in a clinical laboratory setting. Methods: Patient sera found negative or positive for TBEV by serological and/or molecular methods in diagnostic laboratories of five European countries endemic for TBEV (Estonia, Finland, Slovenia, the Netherlands and Sweden) were used to assess the sensitivity and specificity of the test. The patients' diagnoses were based on other commercial or quality assured in-house assays, i.e. each laboratory's conventional routine methods. For specificity analysis, serum samples from patients with infections known to cause problems in serology were employed. These samples tested positive for e.g. Epstein-Barr virus, cytomegalovirus and Anaplasma phagocytophilum, or for flaviviruses other than TBEV, i.e. dengue, Japanese encephalitis, West Nile and Zika viruses. Samples from individuals vaccinated against flaviviruses other than TBEV were also included. Altogether, 172 serum samples from patients with acute TBE and 306 TBE IgM negative samples were analysed. Results: Compared with each laboratory's conventional methods, the tested assay had similar sensitivity and specificity (99.4% and 97.7%, respectively). Samples containing potentially interfering antibodies did not cause specificity problems. Conclusion: Regarding diagnosis of acute TBEV infections, ReaScan TBE offers rapid and convenient complementary IgM detection. If used as a stand-alone, it can provide preliminary results in a laboratory or point of care setting.Peer reviewe

Viral zoonoses in Estonia : hantaviruses and tick-borne encephalitis virus : Identification, prevalence, serological and genetic relationships

Hantaviruses and tick-borne encephalitis virus (TBEV) cause serious human infections. Hantaviruses are transmitted to humans by wild rodents and cause hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome. Two clinical courses of HERS are recognized in Europe: a severe, with a reported mortality rate up to 14%, and a milder with a mortality rate of approx. 0,1%. The more severe form is associated with Dobrava virus (DOBV), transmitted by Apodemus flavicollis, and the milder one with Puumala virus (PUUV), transmitted by Clethrionomys glareolus, and probably also with Saaremaa (SAAV) transmitted by Apodemus agrarius. In Estonia, only a few cases of HERS are officially registered each year, in contrast to a large number of patients in the neighbouring countries, Finland, Sweden and Russia. Therefore, one of our goals was to study the presence and distribution of hantaviruses in Estonia and their significance for human morbidity. We described the first serologically confirmed cases of HFRS in Estonia, with evidence of PUUV and SAAV as the causative agents. In general, a mild clinical course was observed in the patients. The most common symptoms were fever, headache, microscopic hematuria and backache. Laboratory findings included elevated serum creatinine concentrations and proteinuria. Antibodies to PUUV as well as to SAAV, were found in the human population throughout Estonia. Our studies revealed highly variable hantavirus seroprevalence rates. The highest prevalence rates to SAAV were found on Saaremaa and Vormsi islands (23,1% and 7,3% respectively) and to PUUV in the central/south-western parts of Estonia (up to 18,4% in Raplamaa county). The relatively high prevalence suggested that a significant number of HERS cases remain undiagnosed. Our studies showed that SAAV and DOBV represent distinct serotypes within the genus Hantavirus. We revealed a clear serological distinction between SAAV and DOBV as 23 human sera reacted with at least fourfold higher neutralizing end-point titers to one of the two viruses. These findings, together with the facts that SAAV and DOBV are carried by different rodent hosts (A. agrarius and A. flavicollis) and that the two viruses possess different pathogenicity for humans, suggested that SAAV and DOBV represent distinct hantaviruses. Two rodent species, C. glareolus and A. agrarius, were found positive for hantavirus antigen at rates of 13,7% and 4,5% of the investigated rodents, respectively. Analysis of viral sequences recovered from infected C. glareolus tissue samples showed that the infecting virus belonged to the PUUV genotype, confirming circulation of this hantavirus in mainland Estonia. Together with earlier findings on SAAV in A. agrarius, the results revealed that both hantaviruses, PUUV and SAAV, are common in Estonia. Phylogenetic analysis revealed that the Estonian PUUV strains formed a distinct genetic lineage placed in the closest proximity to Russian strains. TBEV is an arthropod-borne virus, which is transmitted to vertebrates by chronically infected ticks. Tick-borne encephalitis (TBE), caused by TBEV is a well recognized serious health problem in Estonia. At the beginning of the 1990s, the TBE morbidity increased continuously, with a sharp rise in 1997, and remains to date at one of the highest levels in Europe. Before our study very little was known about the circulation of TBEV and the reasons for the high TBE morbidity in Estonia. Therefore, another important goal was to isolate and analyze TBEV strains circulating in the country. The results of our studies show that all three known TBEV subtypes: Western (W-TBEV), Siberian (S-TBEV) and FarEastern (FE-TBEV) are co-circulating in Estonia. Phylogenetic analysis showed clustering of the Estonian strains of S-T13EV and W-T13EV subtypes with the strains from Latvia and Lithuania, which is in agreement with the geographical clustering of TBEV variants. Within the S-TBEV subtype, the Baltic strains form a well supported lineage of their own. This new lineage is distinguished from the lineages that include strains from Siberia and the Far East. We also found an additional signature amino acid residue at position 175 of the E protein sequence, which is unique for all Baltic S-T13EV strains. In contrast, within the FE-T13EV subtype, the Baltic strains from Estonia and Latvia do not cluster together as expected, but instead share the most recent common respective ancestors with strains from the Far-East and Ural