Prevalence of Toxoplasma gondii antibodies in wild red deer, roe deer, moose, and reindeer from Norway

Serum samples from 4339 wild cervids collected in Norway were tested for antibodies against Toxoplasma gondii using the direct agglutination test. The association between seroprevalence and species, sex, age, and geographic region was investigated. Positive titers (> or =1:40) were found in 33.9% of 760 roe deer (Capreolus capreolus); 12.6% of 2142 moose (Alces alces); 7.7% of 571 red deer (Cervus elaphus); and 1.0% of 866 reindeer (Rangifer tarandus). The seroprevalences were significantly different between the species. There was a significant increase in prevalence with age in roe deer, moose, and red deer, except from yearling to adult in red deer. A significant age-sex interaction was found in moose, and the effect of age was most distinct for females. No association between seropositive animals and sex was found for roe deer and red deer. There were significant differences in prevalence between geographic regions in roe deer and male moose. A widespread exposure to T. gondii in Norwegian cervids is documented, and meat from Norwegian cervids, particularly roe deer, should be regarded a potential source of infection for humans.     

Prevalence of Cryptosporidium and Giardia in free-ranging wild cervids in Norway

Faecal samples were collected from 1,190 wild cervids in Norway and analyzed for cysts/oocysts of the protozoan parasites Giardia and Cryptosporidium. Samples were from calves, yearlings and adults of moose (Alces alces), red deer (Cervus elaphus), roe deer (Capreolus capreolus) and reindeer (Rangifer tarandus) shot during the hunting season. Cryptosporidium was found in 15 (3.3%) of 455 moose, 1 (0.3%) of 289 red deer, 18 (6.2%) of 291 roe deer, but was not found in any of 155 reindeer. Giardia was found in 56 (12.3%) moose, 5 (1.7%) red deer, 45 (15.5%) roe deer and 11 (7.1%) reindeer. The calves had the highest prevalence of infection, but this was only statistically significant for Giardia in moose and for Cryptosporidium and Giardia in roe deer. Calves generally had the highest intensity of infection, but this difference was only statistically significant for calves with Giarda and the highest intensity of infection. Both Giardia and Cryptosporidium were found in samples from several geographical areas, indicating that these parasites are distributed among the cervid population in all parts of Norway, especially in moose and roe deer. This is the first published report of Cryptosporidium in moose and of Giardia in reindeer.     

Confirmed Exposure to Tick‐Borne Encephalitis Virus and Probable Human Cases of Tick‐Borne Encephalitis in Central/Northern Anatolia,Turkey

Tick‐borne encephalitis virus (TBEV) is the aetiological agent of tick‐borne encephalitis (TBE), a potentially fatal central nervous system infection of humans. TBE is endemic in many areas of Europe and Asia; however, very scarce data on TBEV activity are available from Turkey. We aimed to identify TBEV exposure in healthy blood donors and the impact of TBEV in central nervous system infections in Central/Northern Anatolia. Two‐thousand four hundred and fifty four sera, collected from blood donors at Ankara, Konya, Eski?ehir and Zonguldak branches of the Turkish Red Crescent Middle Anatolia Regional Blood Center, were analysed for TBEV serosurveillance. Paired serum and cerebrospinal fluid samples from 108 patients with the diagnosis of aseptic meningitis/encephalitis of unknown aetiology were also evaluated to identify TBE and neuroborreliosis cases. Commercial enzyme‐linked immunosorbent assays and indirect immunofluorescence tests were employed for antibody detection. Forty‐seven donor samples (1.9%) were reactive for TBEV IgG. In 25 persons with IgG reactivity (53.1%), risk factors for tick‐borne infections were revealed. One sample from Zonguldak province (1/198; 0.5%) in the Black Sea region of Turkey was confirmed to possess neutralizing antibodies via plaque reduction neutralization test. TBEV IgM was detected in 9.2% (8/108) of the patients. IgM was accompanied by IgG reactivity in two persons where, in one, recent history of a tick bite was also identified. Intrathecal antibody production for TBEV could not be demonstrated. No evidence for Borrelia infections could be found. Confirmed exposure to TBEV and/or an antigenically similar tick‐borne flavivirus is documented for the first time in blood donors in Zonguldak in Northern Anatolia. Probable cases of TBE have also been identified from Central Anatolia. The epidemiology of TBEV activity in Turkey needs to be assessed and benefits of vaccination for general population, risk groups or travellers must be considered.     

Virus Detection in Questing Ticks is not a Sensitive Indicator for Risk Assessment of Tick‐Borne Encephalitis in Humans

Tick‐borne encephalitis virus (TBEV) is the most important tick‐transmitted arbovirus causing human disease in Europe, but information on its endemic occurrence varies between countries because of differences in surveillance systems. Objective data are necessary to ascertain the disease risk for vaccination recommendations and other public health interventions. In two independent, separately planned projects, we used real‐time RT‐PCR to detect TBE virus in questing ticks. In Poland, 32 sampling sites were selected in 10 administrative districts located in regions where sporadic TBE cases were reported. In Germany, 18 sampling sites were selected in two districts located in a region with high TBE incidence. Altogether, >16 000 ticks were tested by real‐time RT‐PCR, with no sample testing positive for TBEV. A systematic search for published studies on TBEV prevalence in ticks in Poland and Germany also suggested that testing large numbers of collected ticks could not consistently assure virus detection in known endemic foci. Although assignment of results to administrative regions is essential for TBE risk mapping, this was possible in only 10 (investigating 22 417 ticks) of 15 published studies (>50 000 ticks) identified. We conclude that the collection and screening of ticks by real‐time RT‐PCR cannot be recommended for assessment of human TBE risk. Alternative methods of environmental TBEV monitoring should be considered, such as serological monitoring of rodents or other wildlife.     

Prevalence of antibodies against Toxoplasma gondii and Neospora caninum in moose (Alces alces) and roe deer (Capreolus capreolus) in Sweden

Toxoplasma gondii and Neospora caninum are two coccidian parasites with a worldwide distribution. T. gondii is one of the more common parasitic zoonoses in the world and in young children and immunocompromised persons, infection can lead to severe disease and death. N. caninum is an important cause of abortions in cattle. Wildlife have been identified as reservoirs and transmitters for both parasites. The purpose of this study was to investigate the seroprevalences of T. gondii, and N. caninum in moose (Alces alces), and roe deer (Capreolus capreolus) in Sweden. Blood samples were collected from 417 moose during 2000-2005 and from 199 roe deer during 1990-2007. The samples were investigated for presence of antibodies by a T. gondii direct agglutination test and a N. caninum iscom ELISA. Because the iscom ELISA has not been validated for moose or roe deer, sera that gave a positive result were further investigated by immunoblot analysis to verify presence of antibodies. Antibodies to T. gondii were detected in 85 (20%) and 68 (34%) moose and roe deer sera, respectively. In moose the seroprevalence was higher in south and central Sweden than in the north, whereas there was no difference between the regions for roe deer. Adult moose and roe deer had higher odds of being seropositive than young animals but there were no difference in seroprevalence between males and females. One roe deer was positive by immunoblotting and was regarded as N. caninum positive, whereas all moose sera were negative. The results show that T. gondii infection is widely spread in the Swedish moose and roe deer populations. Precautions should therefore be taken when handling internal organs and carcasses of harvested cervids. Proper handling and cooking of game meat also is important to prevent toxoplasmosis in humans.     

Geographical distribution and prevalence of tick‐borne encephalitis virus in questing Ixodes ricinus ticks and phylogeographic structure of the Ixodes ricinus vector in Norway

The tick‐borne encephalitis virus (TBEV), a zoonotic flaviviral infection, is endemic in large parts of Norway and Eurasia. Humans are mainly infected with TBEV via bites from infected ticks. In Norway, the main geographical distribution of ticks is along the Norwegian coastline from southeast (~59°N) and up to the southern parts of Nordland County (~65°N). In this study, we collected ticks by flagging along the coast from Østfold County to Nordland County. By whole‐genome sequencing of the mitochondrial genome of Ixodes ricinus, the phylogenetic tree suggests that there is limited phylogeographic structure both in Norway and in Europe. The overall TBEV prevalence is 0.3% for nymphs and 4.3% for adults. The highest estimated TBEV prevalence in adult ticks was detected in Rogaland and Vestfold County, while for nymphs it is highest in Vestfold, Vest‐Agder and Rogaland. The present work is one of the largest studies on distribution and prevalence of TBEV in ticks in Scandinavia, showing that the virus is wider distributed in Norway than previously anticipated.     

Campylobacter spp., Salmonella spp., verocytotoxic Escherichia coli, and antibiotic resistance in indicator organisms in wild cervids

Faecal samples were collected, as part of the National Health Surveillance Program for Cervids (HOP) in Norway, from wild red deer, roe deer, moose and reindeer during ordinary hunting seasons from 2001 to 2003. Samples from a total of 618 animals were examined for verocytotoxic E. coli (VTEC); 611 animals for Salmonella and 324 animals for Campylobacter. A total of 50 samples were cultivated from each cervid species in order to isolate the indicator bacterial species E. coli and Enterococcus faecalis / E. faecium for antibiotic resistance pattern studies. Salmonella and the potentially human pathogenic verocytotoxic E. coli were not isolated, while Campylobacter jejuni jejuni was found in one roe deer sample only. Antibiotic resistance was found in 13 (7.3%) of the 179 E. coli isolates tested, eight of these being resistant against one type of antibiotic only. The proportion of resistant E. coli isolates was higher in wild reindeer (24%) than in the other cervids (2.2%). E. faecalis or E. faecium were isolated from 19 of the samples, none of these being reindeer. All the strains isolated were resistant against one (84%) or more (16%) antibiotics. A total of 14 E. faecalis-strains were resistant to virginiamycin only. The results indicate that the cervid species studied do not constitute an important infectious reservoir for either the human pathogens or the antibiotic resistant microorganisms included in the study.     

Tick-borne encephalitis (TBE) with special emphasis on infection in horses

The tick-borne encephalitis (TBE), also known as early summer meningo-encephalitis, is a geographically limited virus infection transmitted mainly by ticks. The importance of TBE is largely underestimated. The causative agent TBE-Virus (TBEV) is grouped into the genus Flavivirus of the virus family Flaviviridae. Clinical disease including fatal outcomes has been described for men and dogs. With regard to horses only a limited number of case reports is available. In a study performed at the Institute of Virology, Justus-Liebig-University Giessen serum samples from the German endemic region of Marburg-Biedenkopf were tested for antibodies against TBEV. From 240 sera tested 7 (2.9%) were regarded as positive in a serum neutralization test (SNT). In an ELISA, performed in parallel to confirm the SNT results, 5 out of 7 positive sera from the SNT were also positive. The remaining two samples with low SNT-titres and all sera from horses negative in the SNT were also negative in the ELISA. This article is focussed on TBE of horses. In this context different aspects of TBE are included such as properties of the causative agent, interactions between causative agent, host animals and environment, spread of TBEV, pathogenesis, clinical symptoms, diagnosis and control.     

Campylobacter spp., Salmonella spp., Verocytotoxic Escherichia coli,and Antibiotic Resistance in Indicator Organisms in Wild Cervids

Faecal samples were collected, as part of the National Health Surveillance Program for Cervids (HOP) in Norway, from wild red deer, roe deer, moose and reindeer during ordinary hunting seasons from 2001 to 2003. Samples from a total of 618 animals were examined for verocytotoxic E. coli (VTEC); 611 animals for Salmonella and 324 animals for Campylobacter. A total of 50 samples were cultivated from each cervid species in order to isolate the indicator bacterial species E. coli and Enterococcus faecalis/E. faecium for antibiotic resistance pattern studies. Salmonella and the potentially human pathogenic verocytotoxic E. coli were not isolated, while Campylobacter jejuni jejuni was found in one roe deer sample only. Antibiotic resistance was found in 13 (7.3%) of the 179 E. coli isolates tested, eight of these being resistant against one type of antibiotic only. The proportion of resistant E. coli isolates was higher in wild reindeer (24%) than in the other cervids (2.2%). E. faecalis or E. faecium were isolated from 19 of the samples, none of these being reindeer. All the strains isolated were resistant against one (84%) or more (16%) antibiotics. A total of 14 E. faecalis-strains were resistant to virginiamycin only. The results indicate that the cervid species studied do not constitute an important infectious reservoir for either the human pathogens or the antibiotic resistant microorganisms included in the study.     

Serological Investigations of Red Foxes (Vulpes vulpes L.) for Determination of the Spread of Tick‐borne Encephalitis in Northrhine‐Westphalia

Serum samples from 786 red foxes shot between January 1995 and August 1996 in the southern half of Northrhine‐Westphalia, located in western Germany, were tested for the presence of antibodies against tick‐borne encephalitis (TBE) virus using the Immunozym FSME IgG All Species‐ELISA^® (Immuno, Heidelberg, Germany) as a screening test: 759 sera were negative, 23 (2.9 %) were borderline, and four (0.5 %) were positive. Nine of the 27 ELISA reactive sera were confirmed by the TBE Western‐Blot (Immuno, Heidelberg, Germany). Furthermore these 27 sera were tested for neutralizing antibodies by means of a plaque reduction neutralization test (PRNT) against TBE and West Nile viruses. Only one single serum was found to have a neutralization titre (+ 1 : 800 PRNT₈₀) against TBE virus. All other 26 sera were negative for neutralizing antibodies against TBE or West Nile virus. Since the titre of the single serum is low, it can be interpreted that if TBE virus is present, its prevalence is extremely low. Northrhine‐Westphalia is not classified as a TBE‐endemic area. Further calculated serological testing of game and virological investigation of collected ticks in the affected area seem to be meaningful and necessary.     

COMPARISON BETWEEN PROTON MAGNETIC RESONANCE SPECTROSCOPY FINDINGS IN DOGS WITH TICK‐BORNE ENCEPHALITIS AND CLINICALLY NORMAL DOGS

In vivo diagnosis of tick‐borne encephalitis is difficult due to high seroprevalence and rapid viral clearance, limiting detection of antibodies in blood and cerebrospinal fluid. Magnetic resonance imaging (MRI) characteristics of tick‐borne encephalitis have been reported, however MRI studies can also be negative despite the presence of neurologic signs. Magnetic resonance spectroscopy (¹H MRS) is an imaging method that provides additional information about the metabolic characteristics of brain tissues. The purpose of this retrospective cross‐sectional study was to describe brain metabolites using short echo time single‐voxel ¹H MRS in dogs with confirmed tick‐borne encephalitis and compare them with healthy dogs. Inclusion criteria for the affected dogs were neurological symptoms suggestive of tick‐borne encephalitis, previous endemic stay and tick‐bite, diagnostic quality brain MRI and ¹H MRS studies, and positive antibody titers or confirmation of tick‐borne encephalitis with necropsy. Control dogs were 10, clinically normal beagles that had been used in a previous study. A total of six affected dogs met inclusion criteria. All dogs affected with tick‐borne encephalitis had ¹H MRS metabolite concentration alterations versus control dogs. These changes included mild to moderate decreases in N‐acetyl aspartate and creatine peaks, and mild increases in glutamate/glutamine peaks. No lactate or lipid signal was detected in any dog. Myoinositol and choline signals did not differ between affected and control dogs. In conclusion, findings supported the use of ¹H MRS as an adjunctive imaging method for dogs with suspected tick‐borne encephalitis and inconclusive conventional MRI findings.     

Evidence of Powassan/deer tick virus in adult black‐legged ticks (Ixodes scapularis) recovered from hunter‐harvested white‐tailed deer (Odocoileus virginianus) in Pennsylvania: A public health perspective

Studies reporting tick infection rates for Powassan virus (POWV), an emerging zoonotic arthropod‐borne pathogen responsible for POWV disease in the Commonwealth of Pennsylvania, are limited. To determine the presence and ascertain a statewide prevalence of POWV, ticks were collected from 9,912 hunter‐harvested white‐tailed deer (Odocoileus virginianus) heads presented to six regional Pennsylvania Game Commission Chronic Wasting Disease sampling stations in early December of 2013, 2014 and 2015. Of the 2,973 ticks recovered, 1,990 (66.9%) were identified as adult Ixodes scapularis (black‐legged tick). The 1,990 I. scapularis ticks were PCR‐tested for the presence of POWV. The ticks had a statewide Powassan/deer tick virus infection rate of 0.05%, providing evidence of this pathogen in Pennsylvania's adult I. scapularis ticks and supporting the need for more comprehensive pathogen prevalence assessment strategies, as well as increased public health awareness for this emerging zoonotic arthropod‐borne pathogen of public health concern.     

Discrepancies between self‐reported tick bites and evidence of tick‐borne disease exposure among nomadic Mongolian herders

Twenty‐six per cent of Mongolians live pastoral lifestyles, increasing their likelihood of exposure to ticks and placing them at a higher risk for contracting tick‐borne diseases (TBDs). Anaplasma spp. and Rickettsia spp. have been identified in ticks, livestock and humans in Mongolia, but no known qualitative research has been conducted investigating the association between nomadic herder characteristics, tick bite history and exposure to TBDs. To better understand the association between self‐reported tick bites and symptoms versus actual exposure to TBDs, this study paired serological data with 335 surveys administered to Mongolian herders, ages 12–69, from 2014 to 2015. Logistic regression results identified no significant associations between reported tick bites or symptoms with serological evidence of Anaplasma spp. and Rickettsia spp. controlling for age, gender and aimag. Among the 335 respondents who were seropositive to either Anaplasma spp. or Rickettsia spp., 32.9% self‐reported experiencing abnormal symptoms such as redness, inflammation, headache, arthritis or fever after being bitten. Alternatively, 17.3% (58/335) of individuals reported experiencing symptoms following a tick bite in instances where serological results indicated no exposure to Anaplasma spp. or Rickettsia spp. Results also identified inconsistencies in reporting and seroprevalence among different age groups, with children having the highest reporting and treatment seeking rates but low levels of exposure in comparison with other groups. While survey results showed that individuals were aware of peak tick seasons and tick species that inhabit specific areas, 58% of heads of households (49/84) were unaware that ticks can cause disease in livestock or dogs. This study suggests that herders are an at‐risk population in Mongolia with gaps in awareness of TBD risk. Increased surveillance paired with focused outreach to prevent TBDs targeted to the herder population is encouraged.     

东北地区三种鹿科动物潜在栖息地预测与保护空缺分析

栖息地是野生动物赖以生存的根本,掌握物种潜在栖息地的空间分布及其与环境因子的关系可以加强对物种的保护。鹿科(Cervidae)动物是东北地区森林等生态系统不可或缺的一部分,本研究选取东北地区3种鹿科动物马鹿(Cervus elaphus)、梅花鹿(Cervus nippon)、驼鹿(Alces alces)为研究对象,通过查阅文献、全球生物多样性信息网络数据库(GBIF)以及部分外业数据得到物种分布点,运用MaxEnt软件对3种鹿科动物进行潜在栖息地预测,模型AUC值如下:马鹿0.939,梅花鹿0.991以及驼鹿0.861。将模拟得到的潜在栖息地与东北地区保护区叠加进行保护空缺分析。模型模拟得出的潜在栖息地占整个东北地区面积:马鹿(25.85%)、梅花鹿(0.99%)以及驼鹿(13.83%);潜在栖息地被现有保护区覆盖率:马鹿(10.03%)、梅花鹿(21.70%)、驼鹿(8.85%),尚有大部分潜在栖息地未得到自然保护区覆盖。上述研究结果对这3种国家级保护鹿科动物的保护管理规划的制定提供了有益参考。     

Role of wild ruminants in the epidemiology of bluetongue virus serotypes 1, 4 and 8 in Spain

ABSTRACT: Although the importance of wild ruminants as potential reservoirs of bluetongue virus (BTV) has been suggested, the role played by these species in the epidemiology of BT in Europe is still unclear. We carried out a serologic and virologic survey to assess the role of wild ruminants in the transmission and maintenance of BTV in Andalusia (southern Spain) between 2006 and 2010.A total of 473 out of 1339 (35.3%) wild ruminants analyzed showed antibodies against BTV by both ELISA and serum neutralization test (SNT). The presence of neutralizing antibodies to BTV-1 and BTV-4 were detected in the four species analyzed (red deer, roe deer, fallow deer and mouflon), while seropositivity against BTV-8 was found in red deer, fallow deer and mouflon but not in roe deer. Statistically significant differences were found among species, ages and sampling regions. BTV RNA was detected in twenty-one out of 1013 wild ruminants (2.1%) tested. BTV-1 and BTV-4 RNA were confirmed in red deer and mouflon by specific rRT-PCR.BTV-1 and BTV-4 seropositive and RNA positive wild ruminants, including juveniles and sub-adults, were detected years after the last outbreak was reported in livestock. In addition, between the 2008/2009 and the 2010/2011 hunting seasons, the seroprevalence against BTV-1, BTV-4 and BTV-8 increased in the majority of provinces, and these serotypes were detected in many areas where BTV outbreaks were not reported in domestic ruminants. The results indicate that wild ruminants seem to be implicated in the dissemination and persistence of BTV in Spain.     

Levels of trace elements in liver from Norwegian moose, reindeer and red deer in relation to atmospheric deposition

The levels of antimony, arsenic, cadmium, copper, lead, mercury, molybdenum, selenium and zinc were determined in liver of moose, reindeer and red deer from differen localities in Norway. Reindeer had considerably higher levels of mercury, lead and arsenic than moose and red deer. These findings are considered to be related to differences in feeding habits since reindeer on highland plateaus feed mainly on lichens which have been shown to accumulate trace elements. The levels of arsenic, and to some extent also selenium and cadmium, in moose and reindeer liver showed a north-south gradient closely related to the regional distribution of these elements in the forest moss. As regards lead, a north-south gradient and a relationship to moss levels, were found in moose liver only. It therefore seems that atmospheric deposition of the elements mercury, lead, arsenic, cadmium and selenium contribute to the body burden of these elements in cervides in Norway. There was no evidence of these elements accumulating to toxic levels.     

Pestivirus and alphaherpesvirus infections in Swedish reindeer (Rangifer tarandus tarandus L.)

Herding semi-domesticated reindeer has economic and social value for Sami people in the northern territories of Fennoscandia. However, with the intensification of reindeer husbandry, interspecies transmission of pathogens between reindeer and domestic animals may become a problem, especially for countries such as Sweden, Norway, and Finland where pestivirus and alphaherpesvirus have been eradicated in domestic ruminants. This study, which included 1158 Swedish reindeer, showed relatively high prevalence of antibodies against bovine viral diarrhoea virus (BVDV) (32%) and bovine herpesvirus-1 (BoHV-1) (53%). Adult animals were more often seropositive for BVDV and BoHV-1 (50% and 78%, respectively) than were calves (18 and 11%, respectively). While the seroprevalence of alphaherpesvirus was similar in different herding districts, pestivirus seropositivity was highest in the South and diminished towards the North of the Swedish reindeer herding area. High correlation of the seropositivity against both pathogens at both individual and herd levels may indicate possible mutual synergetic effects and may be explained by the immunosuppressive nature of the viruses. While alphaherpesvirus seroprevalence was probably related to putative cervid herpesvirus 2 (CvHV-2), the pestivirus infecting reindeer remains undefined. The virus neutralisation test of reindeer sera using different pestivirus strains, revealed higher titres against Border disease virus strains like 137/4 (BDV-1) and Reindeer-1 (BDV-2) than against BVDV-1. However, the virus was not identified by real time RT-PCR in any of the samples (n=276) from seronegative reindeers. The study showed that pestivirus and alphaherpesvirus infections are endemic in the Swedish reindeer population.     

Evaluation of serological tests for detecting tick-borne encephalitis virus (TBEV) antibodies in animals

Tick-borne encephalitis (TBE) in animals is not well understood yet. TBE virus (TBEV) serology in several host species could be valuable for epidemiological analyses in the field as well as for the detection of clinical cases. However, performance and suitability of the available test systems are not well assessed. Therefore, we evaluated two commercial TBEV-ELISA kits in a pilot study and compared them for their suitability in veterinary applications. For this purpose, we tested 163 field collected goat sera and evaluated the results by serum neutralization test (SNT) as "gold standard". Twenty-eight SNT positive sera (17.2%) were detected. The best suited ELISA kit was used for determination of a species-specific cutoff for horses, cattle, sheep, goats, pigs, mice, dogs, rabbits and monkeys with defined sera from animals without known or with improbable contact to TBEV. The level of non-specific ELISA results does not only differ between animal species but may also be influenced by the age of the tested animals. The number of sera which tested false positive by ELISA was higher in older than in young sheep. In order to obtain defined polyclonal sera as references, two dogs, cattle, goats, sheep, rabbits and pigs each, as well as one horse and 90 mice were immunized four times with a commercially available TBEV vaccine. In conclusion, our results demonstrated that commercial TBEV-ELISA kits are suitable for application in veterinary medicine for both, verification of clinical TBE cases and epidemiological screening. However, positive ELISA results should be verified by SNT. Only a very low number of false negative ELISA-results were found.     

Epizootiologic background of dissimilar distribution of human cases of Lyme borreliosis and tick-borne encephalitis in a joint endemic area

Lyme borreliosis (LB) and tick-borne encephalitis (TBE) are co-endemic in some parts of Europe, however, their distribution differs despite a common tick vector and comparable animal hosts. A serosurvey of game and small mammals was made in a highly endemic area and compared with historical data in human cases; the epidemiologic risk and the population density of game were modelled using a geographic information system. While LB-risk corresponded with an overall population density of game (red deer, roe deer, mouflon, wild boar) regardless of mouse abundance, TBE-risk suggested a dependence on the abundance of mice on the one hand, and game, particularly roe deer, on the other. While the prevalence of TBE-antibodies generally grew with the game’s age, it was virtually constant at about 65% in LB irrespective of species. It implies a cumulation of scarce TBE-infection histories during the game’s lifetime, and thus a limited size of TBE-foci relative to the living space of these animals, as well as omnipresent LB-foci, in which the animals became continuously re-infected. More ecological prerequisites seem necessary to keep TBE circulating in nature which may be responsible for its confined distribution.