No virological evidence for an influenza A - like virus in European bats

New members of the influenza A virus genus have been detected recently in bats from South America. By molecular investigations, using a generic real-time RT-PCR (RT-qPCR) that detects all previously known influenza A virus subtypes (H1-H16) and a newly developed RT-qPCR specific for the South American bat influenza-like virus of subtype H17, a total of 1571 samples obtained from 1369 individual bats of 26 species from Central Europe were examined. No evidence for the occurrence of such influenza viruses was found. Further attempts towards a more comprehensive evaluation of the role of bats in the ecology and epidemiology of influenza viruses should be based on more intense monitoring efforts. However, given the protected status of bats, not only in Europe, such activities need to be embedded into existing pathogen-monitoring programs.

Virological monitoring of white storks (Ciconia ciconia) for avian influenza

Between 2003 and 2008, more than 600 white stork (Ciconia ciconia) nestlings in the German federal state of Brandenburg were ringed and examined for influenza A viruses. With the spread of highly pathogenic avian influenza virus (HPAIV) of subtype H5N1 among wild birds in Germany in spring 2006, dead wild birds, including 88 white storks, were tested for infection with HPAIV. Furthermore, fresh fecal samples were examined by RT-PCR to monitor the occurrence of HPAIV in adult storks. While the monitoring of nestlings and adult white storks failed to yield evidence of influenza A virus infections in these birds, two storks found dead in April 2006 in the same location tested positive for HPAIV H5N1. Sequence analysis revealed that the virus isolated from one of the storks belonged to clade 2.2, which was commonly found in wild birds in the north of Germany and other European countries during the epidemic in 2006. Despite these two cases, white storks seemed to serve as neither a vector nor as a reservoir for HPAIV in Germany. The risk of white storks transmitting HPAIV to domestic poultry and humans is low.

Human rabies due to lyssavirus infection of bat origin

Rabies is a fatal viral encephalitis and results from infection with viruses belonging to the genus Lyssavirus. Infection usually results from a bite from a dog infected with classical rabies virus. However, a small number of cases result from contact with bats. It is within bats that most lyssavirus variants, referred to as genotypes, are found. The lyssaviruses found in bats have a distinct geographical distribution and are often restricted to specific bat species. Most have been associated with rabies in humans and in some cases spill-over to domestic animals. Many diagnostic techniques are unable to differentiate rabies virus from other genotypes so it is possible that some human and animal cases go unreported. Furthermore, current vaccines have limited efficacy against some genotypes.

Phylogenetic analysis of rabies viruses from Sudan provides evidence of a viral clade with a unique molecular signature

Rabies is endemic in Sudan and remains a continual threat to public health as transmission to humans is principally dog-mediated. Additionally, large-scale losses of livestock occur each year causing economic and social dilemmas. In this study, we analysed a cohort of 143 rabies viruses circulating in Sudan collected from 10 different animal species between 1992 and 2006. Partial nucleoprotein sequence data (400 bp) were obtained and compared to available sequence data of African classical rabies virus (RABV) isolates. The Sudanese sequences formed a discrete cluster within the Africa 1a group, including a small number of sequences that clustered with sequences from Ethiopian RABV. These latter sequences share an Aspartic Acid at position 106 (Asp(106)) with all other Africa 1a group members, in contrast to the remaining Sudanese strains, which encode Glutamic Acid at this position (Glu(106)). Furthermore, when representatives of other African and European lineages were aligned, Glu(106) is unique to Sudan, which supports the concept of a single distinct virus strain circulating in Sudan. The high sequence identity in all Sudanese isolates studied, demonstrates the presence of a single rabies virus biotype for which the principal reservoir is the domestic dog.

Experimental infection of serotine bats (Eptesicus serotinus) with European bat lyssavirus type 1a

The serotine bat (Eptesicus serotinus) accounts for the vast majority of bat rabies cases in Europe and is considered the main reservoir for European bat lyssavirus type 1 (EBLV-1, genotype 5). However, so far the disease has not been investigated in its native host under experimental conditions. To assess viral virulence, dissemination and probable means of transmission, captive bats were infected experimentally with an EBLV-1a virus isolated from a naturally infected conspecific from Germany. Twenty-nine wild caught bats were divided into five groups and inoculated by intracranial (i.c.), intramuscular (i.m.) or subcutaneous (s.c.) injection or by intranasal (i.n.) inoculation to mimic the various potential routes of infection. One group of bats was maintained as uninfected controls. Mortality was highest in the i.c.-infected animals, followed by the s.c. and i.m. groups. Incubation periods varied from 7 to 26 days depending on the route of infection. Rabies did not develop in the i.n. group or in the negative-control group. None of the infected bats seroconverted. Viral antigen was detected in more than 50% of the taste buds of an i.c.-infected animal. Shedding of viable virus was measured by virus isolation in cell culture for one bat from the s.c. group at 13 and 14 days post-inoculation, i.e. 7 days before death. In conclusion, it is postulated that s.c. inoculation, in nature caused by bites, may be an efficient way of transmitting EBLV-1 among free-living serotine bats.

Detection of high levels of European bat lyssavirus type-1 viral RNA in the thyroid gland of experimentally-infected Eptesicus fuscus bats

Two common bat lyssavirus species have been identified in many European countries: European bat lyssavirus type-1 and -2 (EBLV-1 and EBLV-2). Only limited knowledge on the susceptibility of the natural EBLV-hosts, insectivorous bats, to lyssavirus infection is available. Our study was undertaken to evaluate the susceptibility and pathology associated with an EBLV-1 infection in Eptesicus fuscus following different routes of virus inoculation including intracranial (n = 6), intramuscular (n = 14), oral (n = 7) and intranasal (n = 7). Blood and saliva samples were collected from all bats on a monthly basis. Four bats inoculated intracranially developed rabies with a mean of 11 days to death, whilst seven bats inoculated intramuscularly developed rabies, with an extended incubation period prior to death. We did not observe any mortality in the oral (p.o.) or intranasal (i.n.) groups and both groups had detectable levels of virus neutralizing antibodies (data not shown). Virus shedding was demonstrated in the saliva by virus isolation and the detection of viral RNA in ill bats, particularly immediately prior to the development of disease. In addition, the presence of virus and viral RNA was detected in the thyroid gland in bats challenged experimentally with EBLV-1, which exceeded that detected in all other extra-neural tissue. The significance of detecting EBLV-1 in the thyroid gland of rabid bats is not well understood. We speculate that the infection of the thyroid gland may cause subacute thyroiditis, a transient form of thyroiditis causing hyperthyroidism, resulting in changes in adrenocortical activity that could lead to hormonal dysfunction, thereby distinguishing the clinical presentation of rabies in the rabid host.

Susceptibility of North American big brown bats (Eptesicus fuscus) to infection with European bat lyssavirus type 1

The aim of this study was to determine the susceptibility of insectivorous bats (using the big brown bat as a model) to infection with European bat lyssavirus type 1a (EBLV-1a), to assess the dynamics of host immune responses and to evaluate the opportunity for horizontal viral transmission within colonies. Two isolates of EBLV-1a, originating from Slovakia (EBLV-1aSK) and Germany (EBLV-1aGE), were tested. Four different routes of inoculation were used with isolate EBLV-1aSK [10(4.8) mouse intracerebral median lethal dose (MICLD(50)) in 50 mul]: intramuscular (i.m.) in the deltoid area or masseter region, per os (p.o.) and intradermal (i.d.) scratches. Isolate EBLV-1aGE (10(3.2) and 10(2.2) MICLD(50) in 20 mul) was inoculated via the intranasal (i.n.), i.m. (low- and high-dose groups, into pectoral muscles); p.o. and intracerebral (i.c.) routes. None of the bats infected by the i.n., p.o. or i.d. route with either virus isolate developed disease during the experiments (91 or 120 days, respectively). Incubation periods were 9-12 days for i.c.-inoculated bats (66 % mortality), 12-33 days for bats inoculated i.m. with the higher dose (23-50 % mortality) and 21-58 days in bats inoculated i.m. with the lower dose of virus (57 % mortality). Virus or viral RNA in bat saliva was detected occasionally, as early as 37 days before death. All i.d.-inoculated and the majority of i.m.-inoculated bats seroconverted within 7-10 days of inoculation. These observations suggest that exposure of bats to varying doses of EBLV-1 from rabid conspecifics via natural (i.d.) routes could lead to an abortive infection and serve as a natural mode of immunization resulting in the presence of virus-neutralizing antibodies in free-ranging bats.

A random grid based molecular epidemiological study on EBLV isolates from Germany

Germany has reported one of the highest levels of EBLV cases in bats in Europe. So far, all isolates originating from Germany have been identified as EBLV-1, using monoclonal antibodies, and a preliminary epidemiological study has indicated that there is a distinct geographical distribution of EBLV-1 in Germany. To further investigate the spatial and temporal distribution of EBLV-1 variants in Germany and their impact on molecular epidemiology, isolates were selected using a random grid sampling procedure based on GIS. Agrid layer 30 km long over the entire area of Germany was applied to 120 geo-referenced isolates and one isolate of each grid cell containing EBLV isolates was randomly chosen. Once selected, the nucleoprotein (N) plus parts of the phosphoprotein (P) gene of each isolate were sequenced using direct cycle sequencing. Results of the subsequent phylogenetic analysis of the N-gene confirmed previous studies on European EBLVs, showing a high sequence homology between German EBLV-1 isolates. Almost identical sequence homologies within certain geographical regions indicate genomic stability during the transmission cycle of EBLV-1, with little geographic spread or intermixing. Interestingly, a 6 bp insertion as well as a single nucleotide insertion, detected in the N-P intergenic region, has been found in EBLV-1 isolates from Germany.

Epidemiology of rabies in Southeast Europe

Rabies remains endemic within a number of countries in Southeast Europe including Romania, Bulgaria and Turkey. With the probable expansion of the European Union eastwards, it is likely that rabies elimination programs will be increased to reduce the burden of disease in new accession countries. A clear understanding of the epidemiology of the virus in this area of Europe is vital before such programs are introduced. With the exception of Turkey, the red fox (Vulpes vulpes) is the principal disease reservoir in Southeastern Europe. However, cases of rabies in the dog (Canis familiaris) are regularly reported. In contrast to Northern Europe, the raccoon dog (Nyctereutes procyonoides) does not appear to be a vector in the south. This study summarises the current rabies situation in Southeast Europe and demonstrates the phylogenetic relationships between the viruses in a number of the countries within the region. Rabies virus RNA was extracted from original samples and a fragment of the nucleoprotein gene amplified by reverse-transcriptase PCR. Automated sequencing was used to derive nucleoprotein gene sequences and these were used to prepare a molecular phylogeny of rabies viruses in Southeast Europe. In Bulgaria, the dog is the main vector bringing rabies into contact with humans and livestock. However, other species may also act as reservoirs for the disease, complicating the development of elimination strategies. The fox is the principal reservoir species for rabies in Romania although cases in dogs are regularly reported. Despite a gradual decline in dog rabies, urban pockets of the disease remain in many regions of Turkey. Furthermore, there is some evidence that the fox has been a significant vectorfor rabies and may be responsible for increases in rabies in cattle in the Aegean region of the country. Throughout the region there is evidence for cross-border movement of rabies by both wildlife and canine vectors.

The financial challenge of keeping a large region rabies-free--the EU example

Following the implementation of oral rabies vaccination of foxes (ORV) in Western Europe, a continuous decrease in rabies incidence was reported, and eventually rabies was eliminated. Once fox rabies is eliminated in a given area, re-infection from neighbouring infected countries is a permanent threat. As a result, countries need to maintain a vaccination belt along common borders until rabies is also eliminated in sufficiently large border regions of neighbouring infected countries. In a theoretical approach EU member states were taken as a prime example, assuming that they were rabies-free but that neighbouring countries were still infected. Using GIS, a 50 km deep vaccination belt beyond the front of the rabies endemic zone was installed in countries bordering those regions. The annual cost for the prevention of re-infection of the EU territory was calculated considering current EU recommendations (vaccination twice per year, aerial and complementary hand distribution, bait density of 30 baits per km2). Minimum and maximum prices for commercial available oral rabies vaccine baits, aircraft and rabies surveillance were considered for the calculation of costs. The total vaccination area which needed to be established was about 251,000 km2. Using mainly fixed-wing aircraft, the annual cost for ORV including rabies surveillance varied between a minimum of 10 and a maximum of 16M Euro, depending on the cost of vaccine bait. If helicopters were used exclusively, the maximum cost increased to about 32M Euro. Depending on the length of the border to infected regions, countries will have to pay up to 25% of the total cost. Countries which need to install a vaccination belt will never have a rabies-free status because of the likely occurrence of rabies cases in border zones.