Epidemiological surveillance on natural-borne infections in the Ulyanovsk region

The analysis of natural foci of haemorrhagic fever with renal syndrome (HFRS) and tick-borne borreliosis on the territory of the Ulyanovsk region is presented. Reduced rat control interventions result in a wide spread of these and other infections with natural focality. Monitoring of natural foci of HFRS, tick-borne borreliosis and arbovirus infections, their typing and determination of main reservoirs are the most promising among epidemiological surveillance methods.     

Combined focus of tick-borne encephalitis, tick-borne rickettsiosis and tularemia in the habitat of Haemaphysalis concinna in south central Siberia

For the first time in the Krasnoyarsk region the population Haemaphysalis concinna ticks were found to be infected with the causative agents of three natural focal tick-borne infections--tick-borne encephalitis, tick-borne rickettsiosis and tularemia. The existence of the combined natural focus of these three infections has been confirmed by epidemiological data. Ticks Dermacentor nuttalli also play a similar role in combined foci of tick-borne encephalitis and tick-borne rickettsiosis in these focal territories.     

Infectious diseases in natural reservoirs: epidemic situation and morbidity in the Russian Federation and prophylactic measures

The analysis of morbidity in infections with natural foci in Russia for the period of 1999-2000 indicates that a rise in the number of cases of hemorrhagic fever with the renal syndrome, tick-borne encephalitis, Crimean hemorrhagic fever and West Nile fever with a high proportion of urban population among the patients is registered annually. An increase in the epizootic activity of the natural foci of plague is noted in the absence of morbidity among humans. The appearance of the outbreaks of tularemia is linked nor only with the increased activity of the natural foci, but also with the reduced coverage of the population with prophylactic immunization in endemic regions. This analysis infers that morbidity prognosis in infections with natural foci for 2001 remains unfavorable. The growth of morbidity in these infections is mainly due to the reduction of measures for controlling their vectors both is open nature and in settlements, as well as to low coverage with prophylactic immunization. Urgent complex measures which may ensure effective antiepidemic and prophylactic work for controlling infections with natural foci are presented.     

Tick–Host–Borrelia Population Interactions: Long-Term Records in Eastern Europe

During 10 spring and summer seasons (1992–2001), the dynamics of the epizootic process in natural foci were studied in taiga forests of the Pre-Ural region, Russia. In these foci, Borrelia garinii, Borrelia afzelii and tick-borne encephalitis (TBE) virus circulate transmitted by their main vector tick, Ixodes persulcatus. Main parameters of the epizootic process were calculated for each season. In three seasons (1993, 1996, and 1999) all parameters characterizing the abundance of unfed nymphs and adult ticks, as well as the prevalence of Borrelia and TBE virus in them, increased sharply and simultaneously. These seasons were preceded by years of population peaks in forest rodents (1992, 1995, and 1998), especially Clethrionomys glareolus voles, the dominant species in the local mammalian fauna. Apparently, the possibility of horizontal transmission of the agents of tick-borne infections sharply increases in such years and this results in the intensification of their dissemination. This revised version was published online in July 2006 with corrections to the Cover Date.     

Complex method for epizootiological and epidemiological surveillance

A complex method for the epizootological and epidemiological surveillance of a number of bacterial and viral infections on the territories inside and outside their natural foci has been developed. The investigation techniques are described and the data on the isolation rate of each causative agent in different geographical zones are presented. In the natural foci of plague and tularemia, as well as on the territories outside such foci, the causative agents of intestinal yersiniosis, pseudotuberculosis, salmonellosis, erysipeloid, staphylococci and streptococci, arena- and arboviruses have been isolated from the rodents and ectoparasites under study. The results of this investigation suggest that the method may be recommended for use in medical institutions dealing with the problems of infections originating from natural foci.     

Correlation of TBE Incidence with Red Deer and Roe Deer Abundance in Slovenia

Tick-borne encephalitis (TBE) is a virus infection which sometimes causes human disease. The TBE virus is found in ticks and certain vertebrate tick hosts in restricted endemic localities termed TBE foci. The formation of natural foci is a combination of several factors: the vectors, a suitable and numerous enough number of hosts and in a habitat with suitable vegetation and climate. The present study investigated the influence of deer on the incidence of tick-borne encephalitis. We were able to obtain data from deer culls. Using this data, the abundance of deer was estimated and temporal and spatial analysis was performed. The abundance of deer has increased in the past decades, as well as the incidence of tick-borne encephalitis. Temporal analysis confirmed a correlation between red deer abundance and tick-borne encephalitis occurrence. Additionally, spatial analysis established, that in areas with high incidence of tick-borne encephalitis red deer density is higher, compared to areas with no or few human cases of tick-borne encephalitis. However, such correlation could not be confirmed between roe deer density and the incidence of tick-borne encephalitis. This is presumably due to roe deer density being above a certain threshold so that availability of tick reproduction hosts has no apparent effect on ticks'' host finding and consequently may not be possible to correlate with incidence of human TBE.     

The immune status of the population of the Crimea to the tick-borne encephalitis virus]

The immune status of the Crimean population with respect to tick-borne encephalitis (TBE) virus has been studied. The results of the study confirm the existence of natural foci of TBE in the Crimea. The most active and potentially dangerous foci are located in forests of the mountain area of the peninsula. The study has revealed that humans are mainly exposed to the risk of contacting TBE virus infection during their work and rest in the forest.     

New findings concerning the spread of natural foci of infection in the transpolar region of eastern Siberia]

New materials are presented on the presence of the foci of anthropozoonozes in the Extreme North. For the first time there was established the existence in the subarctic tundra of the Taimyr peninsula of the arbovirus foci of the tick-borne encephalitis complex. A virus of the tick-borne encephalitis complex was isolated in 1973 from the gamasida ticks Haemogamasus ambulans Thorel. and Hirstionyssus isabellinus Oudms. and the nests of the Siberian lemming Lemmus lemmus L. This pointed to the existence in the Transpolar region of the foci or arboviruses in the nest-hole biocenoses of the lemmings outside the bird colonies. Cultures of tularemia bacilli (which proved the etiology of the epizootic among the lemmings observed in 1973 and also the presence of the lemming natural foci of tularemia and their combination with the arbovirus foci) were isolated from the lemmings at the same territory. The results of serological examination of the local population and of the animals pointed to the circulation in the Transpolar region of the causative agents of leptospirosis, toxoplasmosis, Q-fever and of the Asian tick-borne rickettsiosis.     

Forest tick Ixodes ricinus (Ixodidae) in the foci of tick-borne borreliosis of the northwestern part of the Moscow region

Monitoring studies during 1996-2001 have shown a natural foci of tick-borne borreliosis with high abundance of Ixodes ricinus and high infection rate with an agent: 19.5-38.4 tick individuals per 1 km of route, infection rate 18.0 +/- 1.7-22.5 +/- 1.5%. A risk to be infected with the Lyme disease in the ricinus focus of the tick-borne borreliosis during the epizootic season did not vary much during the period of study, 3.5-8.2 in different year, mean 6.0 infected ticks per 1 km of route.     

Effectiveness of the seroprophylaxis of tick-borne encephalitis depending on the titer of homologous gamma-globulin antihemagglutinins

To give a rationale for using homologous gamma globulin with antihemagglutinin titers of 1 : 20 to 1 : 80 for the prophylaxis of tick-borne encephalitis, 5-year observations covering all persons attacked by ticks in one of the intensive natural foci of the disease in the Western Urals have been made. The threefold statistically significant difference in the morbidity rate of tick-borne encephalitis between groups of persons immunized and not immunized with gamma globulin has been shown.     

Main features of natural focality of ixodid tick-borne borreliosis in Russia

In a general form the "key" data on natural focality of ixodid tick-borne borrelioses and ecology of their agents--B. burgdorferi s. 1. in Russia, which have been accumulated by now, are presented. Vectors and reservoir hosts of different species of Borrelia, as well as a landscape preference of natural foci and ecological factors, determining risk of human infection, are characterized.     

Epidemiological characterization of Ixodes tick-borne borreliosis in the Krasnoyarsk territory

The analysis of morbidity in tick-borne infections for many years indicates that in the 1960s-1990s in the total structure of the clinical forms of tick-borne encephalitis the erythematic form amounted to 1.4-20.9, which 1.9- to 3.1-fold exceeded the morbidity characteristics for the whole of Russia. The epidemiological analysis of morbidity at the territory for the period of 1992-2001 is indicative of the presence of the combined foci of tick-borne encephalitis and Ixodes tick-born borrelioses (TBB) in 42 regions of the territory. The cyclic character of morbidity and the irregularity of its spread in different regions of the territory can be observed. Among the TBB patients, town dwellers constitute, on the average, 75.8%. These tick-born infections exhibit regional differences connected with landscape variations and the patients age. However official statistics does not reflect the real epidemic situation at the territory: hypodiagnostics is primarily due to the absence of reliable laboratory confirmation in remote regions of the Krasnoyarsk territory.     

Biological properties of strains of tick-borne encephalitis virus isolated in the natural foci of the eastern part of the Russian plain

Strains of tick-borne encephalitis virus isolated in the natural foci of infection in the eastern part of the Russian Plain (the Kirov region) were examined for their biological properties. The strains examined were 69 strains isolated from ticks Ixodes persulcatus, 62 strains obtained from patients with the clinically manifest form of tick-borne encephalitis and 56 strains isolated from the blood of patients with the inapparent form of infection. Comparative studies on laboratory animals (albino mice, golden hamsters, suckling guinea pigs and other mammals) as well as comparative serologic studies provided evidence which suggested that all virus isolates from the Kirov region were antigenically identical with the strain "Sofin" isolated in the Far East and represent thus a single causative agent of the tick-borne encephalitis virus infection. This strain of virus is supposed to exist in two variants, in dependence on ecological conditions: one of these variants is the eastern variant (strain Sofin and strains from the Kirov region) and the other one is the western variant of tick-borne encephalitis virus.     

Study data on ornithosis infection in the Azerbaijan SSR]

Data are presented on the study of epizootology and epidemiology of ornithosis. There were revealed natural foci of ornithosis in the Kyzyl-Agach preserve, at the Sary-Su lakes and at the Glinyany island; these foci were dihostal and polyhostal, as well as conjointed (ornithosis, arboviruses, Q-fever, Asian tick-borne typhus, leptospirosis). Anthropurgic foci were found in 12 populated localities, semi-wild dove serving as the main component. Fowl was found to be infected in 12 poultry-farms; occupational ornithosis was present among the bird-rearers. Immunological structure of the population in respect to ornithosis was studied. Patients with various diagnoses showed positive serological reactions retrospectively; there were 155 cases of ornithosis among them.     

The 70th anniversary of E.N. Pavlovsky’s concept of natural nidality of human diseases

The concept of the natural nidality of human diseases has significantly changed during the last 70 years, but its essence is preserved. Many “new” infections with natural foci were discovered and their geographical distribution was investigated in detail, and the classification of natural foci was developed. It has been established that epidemic features of transmissible infections depend mainly on types of parasitism of insect, tick and mite vectors.     

Tick-borne encephalitis in the Maritime Territory

On the basis of epidemiological analysis carried out at the period of 1940-1987, a decrease in tick-borne encephalitis (TBE) morbidity was registered; at the same time time the disease invariably took, as before, a clinically severe course. The most dangerous foci of TBE were found to be located in the southern Okhotsk region grown with dark coniferous forests. The subsiding and activation of the natural foci of TBE in different regions of the territory were established and some heretofore unknown foci in southern regions of the Maritime Territory were found. Ixodes mites inhabiting the Maritime Territory were shown to have a low level of virus carriership, thus causing the low level of population immunity to TBE virus. Combined foci of TBE and Powassan encephalitis were found.     

Natural focal infections in the north of the Far East. I. The detection of natural foci of infections in Chukot]

Results of a 3-year complex (zoo-parasitological, viral, bacteriological, and serological) studies of mammals and birds in Chukotka demonstrated the presence of natural foci of pseudo-tuberculosis, intestinal yersinosis, salmonellosis (heidelberg), and of tick-borne encephalitis. The existence of natural foci of tularemia and endemic rickettsioses is supposed on the basis of serological data.     

A Review of Studies on the Transmission of Anaplasma phagocytophilum from Sheep: Implications for the Force of Infection in Endemic Cycles

We review the findings of a longitudinal study of transmission of the intracellular tick-borne bacterium Anaplasma phagocytophilum from sheep to Ixodes ricinus ticks under natural conditions of tick attachment in the UK. In this study, sheep-to-tick transmission efficiency varied in a quadratic relationship with the number of adult ticks that were feeding on the sheep. We raise the hypothesis that this relationship may be due to conflicting effects of the density of ticks on bacterial survival and target cell (neutrophil) fluxes at the tick-host interface: in the same sheep at the same time, resistance to ticks was progressively inhibited with increasing number of feeding adult ticks, and investigation of serological responses to tick antigens suggesting loss of resistance may be associated with polarisation of host Th1 to Th2 type responses to ticks. We also raise the hypothesis that these properties, with superimposed effects on tick survival, may mean that variation in tick density is an important causal factor of observed variations in the force of A. phagocytophilum infection amongst different geographic foci. This revised version was published online in July 2006 with corrections to the Cover Date.     

Multi-Year Monitoring of the Tick–Pathogen System in Natural Foci of Tick-Borne Encephalitis in the Suburbs of Irkutsk

Entomological Review - The state of the natural foci of tick-borne encephalitis (TBE) was monitored during 15 seasons (2005–2019) in several key plots within a popular recreational and...