Tick-borne encephalitis virus (TBEV) can cause severe meningitis, encephalitis, and meningoencephalitis. TBEV represents a pathogen of high zoonotic potential and an emerging global threat. There are three known subtypes of TBEV: Far-Eastern, Siberian and European. Since 2001 there have been suggestions that two new subtypes may be distinguished: "178-79" and "886-84". These assumptions are based on the results of the envelope gene fragment sequencing (Zlobin et al., 2001; Kovalev and Mukhacheva, 2017) and genotype-specific probes molecular hybridization (Demina et al., 2010). There is only one full-genome sequence of "178-79" strain and two identical ones of "886-84" strain can be found in GenBank. For clarification of the intraspecific position of the "886-84-like" strains group we completely sequenced six previously unknown "886-84-like" strains isolated in Eastern Siberia. As a result of applying different bioinformatics approaches, we can confirm that "886-84-like" strains group is a distinct subtype of TBEV.
1. Pathogens often cause detrimental effects to their hosts and, consequently, may influence host population dynamics that may, in turn, feed back to pathogen transmission dynamics. Understanding fitness effects of pathogens upon animal host populations can help to predict the risks that zoonotic pathogens pose to humans. 2. Here we determine whether chronic infection by Puumala hantavirus (PUUV) affects important fitness-related traits, namely the probability of breeding, reproductive effort and mother and offspring condition, in the bank vole (Myodes glareolus). Using 9 years empirical data in a PUUV endemic area in Central Finland, we found differences between reproductive characteristics of PUUV-infected and uninfected female bank voles. 3. Young infected females had a significantly higher, and old individuals lower, likelihood of reproducing than uninfected animals during the middle of the breeding season. The implication is that PUUV infection may have long-term deleterious effects that are observed at old age, while in young individuals, the infection may enhance breeding probability by directing resources towards current breeding. 4. Moreover, PUUV infection was related with the mother's body condition. Infected mothers were in poorer condition than uninfected mothers in the early breeding season, but were in better condition than uninfected mothers during the middle of the breeding season. Offspring body condition was positively associated with mother's body condition, which, in turn, was related to the PUUV infection status of the mother. 5. Our findings indicate that chronic infection may affect the reproduction of female hosts, but the effect is dependent on the host age. The effect of chronic hantavirus infection was small and density-independent and hence unlikely to contribute to the cyclic population dynamics of the host. However, the effects on a female's reproductive output might affect the abundance of young susceptible individuals in the population and hence influence the transmission and persistence of the pathogen. Although experimental and long-term capture-mark-recapture studies are required to further clarify the fitness effects of hantavirus infection and their consequences for pathogen dynamics, this study shows that the infection may have complex effects that are dependent on the age of the individual and the time of the breeding season.
An active natural focus of icterohemorrhagic leptospirosis has been detected in the area of fish-breeding ponds in Rostov Province, where the intensive epizootic among the population of Norway rats is observed the whole year round (574 animals have been examined, 56 cultures have been isolated). The epizootic process reaches its highest intensity in autumn (the proportion of infected animals exceeds 50%). This natural focus in the area of fish-breeding ponds is epidemiologically dangerous. The limitation of its infectious potential is possible by means of poisoned baits.
The incidence and antibody prevalence of hemorrhagic fever with renal syndrome (HFRS) in Bashkirtostan (European part of Russia) and northern Sweden was compared with the abundance of Clethrionomys glareolus (bank voles) in the two areas. In Bashkirtostan, 10% of the women and 15% of the men were found to be antibody positive. The corresponding figures for Sweden were 8% and 16% for women and men, respectively. The annual incidence of HFRS in Bashkirtostan was 50 cases per 100,000 inhabitants, with a male:female ratio of 4.6:1. The incidence in the endemic area of Sweden was seven cases per 100,000 inhabitants, with a male:female ratio of 1.8:1. A similar age distribution of cases, with a peak in the middle age groups, especially in men, was found in both Bashkirtostan and Sweden. The incidence of HFRS in humans and the abundance of bank voles varied with time in both Bashkirtostan and Sweden, but the study failed to find any significant correlation between the two variables. The study showed that HFRS causes significant human morbidity in the areas studied but that both incidence and possibly bank vole abundance was higher in Bashkirtostan than in northern Sweden.
BACKGROUND: It has recently been shown that Ljungan virus (LV) is associated with disease in its wild rodent reservoir. In addition, it has been demonstrated that LV causes malformations and perinatal death in a mouse model. The question was therefore raised whether LV is a zoonotic agent in humans. METHODS: Population fluctuations of native rodents in Sweden were compared to the incidence of intrauterine fetal deaths (IUFDs) using the Swedish national hospitalization database. Formalin-fixed tissues from cases of IUFD were investigated using LV-specific immunohistochemistry. RESULTS: Variation in the incidence of IUFDs closely tracked the fluctuations in native rodent populations. LV was detected in the brain tissue in 4 of 10 cases of IUFDs investigated by immunochemistry. LV was also detected in the placenta in 5 of the 10 IUFD cases, but in none of 20 placentas from normal pregnancies. CONCLUSIONS: LV may play an important role in IUFDs.