Tick-borne encephalitis virus in horses, Austria, 2011.

An unexpectedly high infection rate (26.1%) of tick-borne encephalitis virus (TBEV) was identified in a herd of 257 horses of the same breed distributed among 3 federal states in Austria. Young age (p<0.001) and male sex (p=0.001) were positively associated with infection.

Low Usutu virus seroprevalence in four zoological gardens in central Europe.

BACKGROUND: Usutu virus (USUV), a mosquito-borne flavivirus of the Japanese encephalitis virus antigenic group, caused bird die-offs in Austria, Hungary and Switzerland between 2001 and 2009. While the zoological gardens of Vienna and Zurich recorded USUV-associated mortality in different species of birds during this period, incidences in Budapest were limited to areas outside the zoo, and in the greater Basel area avian mortality due to USUV infection was not observed at all. The objectives of this investigation were to gain insight into USUV infection dynamics in captive birds in zoos with varying degrees of virus exposure and to study differences in susceptibility to USUV of different species of birds. RESULTS: 372 bird sera were collected between October 2006 and August 2007. The samples were tested in parallel by hemagglutination inhibition (HI) and 90% plaque reduction neutralization tests (PRNT-90). 8.75%, 5.3% and 6.59% of birds in the zoos of Vienna, Zurich and Basel, respectively, showed USUV-specific antibodies by PRNT-90. No antibodies to USUV were detected in birds of the Budapest zoo. The order Strigiformes (owls) exhibited the highest USUV-seroprevalence, compared to other orders of birds. CONCLUSIONS: USUV seems not to pose an imminent threat to zoo bird populations in central Europe at the moment. Depending on a variety of especially environmental factors, however, this may change at any time in the (near) future, as experienced with West Nile virus (WNV). It is therefore strongly suggested to continue with combined WNV and USUV surveillance activities in affected areas.

Antibody prevalence to avian influenza virus subtypes H5, H7 and H9 in falcons, captive and wild birds, United Arab Emirates, 2003-2006.

BACKGROUND: Avian influenza viruses (AIV) may cause enormous economic losses in the poultry industry and sporadically severe disease in humans. Falconry is a tradition of great importance in the Arabian Peninsula. Falcons may catch AIV through contact with infected quarry species. OBJECTIVES: Falcons together with other bird species are the focus of this seroprevalence study, carried out on sera collected in the United Arab Emirates (UAE). AIV with the haemagglutinin subtypes H5, H7 and possibly H9 may infect humans. METHODS: We investigated the antibody prevalence to these subtypes in falcons and other birds by haemagglutination inhibition test. 617 sera of falcons and 429 sera of 46 wild/captive bird species were tested. RESULTS: From the falcons, only one was positive for H5 antibodies (0.2%), none contained antibodies to H7, but 78 had antibodies to H9 (13.2%). Regarding other birds, eight were positive for antibodies to H5 (2.1%), none had antibodies to H7, but 55 sera from 17 species contained antibodies to H9 (14.4%). CONCLUSIONS: In contrast to H5 and H7 infections, H9N2 is widespread worldwide. Its ability to reassort, thereby creating possibly pathogenic strains for humans, should remind us of the potential risk that close contact with birds entails.

Serological evidence of continuing high Usutu virus (Flaviviridae) activity and establishment of herd immunity in wild birds in Austria.

Usutu virus (USUV), family Flaviviridae, has been responsible for avian mortality in Austria from 2001 to 2006. The proportion of USUV-positive individuals among the investigated dead birds decreased dramatically after 2004. To test the hypothesis that establishment of herd immunity might be responsible, serological examinations of susceptible wild birds were performed. Blood samples of 442 wild birds of 55 species were collected in 4 consecutive years (2003--2006). In addition, 86 individuals from a birds of prey rehabilitation centre were bled before, at the peak, and after the 2005 USUV transmission season in order to identify titre dynamics and seroconversions. The haemagglutination inhibition test was used for screening and the plaque reduction neutralization test for confirmation. While in the years 2003 and 2004 the proportion of seropositive wild birds was <10%, the percentage of seroreactors raised to >50% in 2005 and 2006. At the birds of prey centre, almost three quarters of the owls and raptors exhibited antibodies before the 2005 transmission season; this percentage dropped to less than half at the peak of USUV transmission and raised again to almost two thirds after the transmission season. These data show a from year to year continuously increasing proportion of seropositive wild birds. The owl and raptor data indicate significant viral exposure in the previous season(s), but also a number of new infections during the current season, despite the presence of antibodies in some of these birds. Herd immunity is a possible explanation for the significant decrease in USUV-associated bird mortalities in Austria during the recent years.

Amplification and sequencing of Brachyspira spp. specific portions of nox using paraffin-embedded tissue samples from clinical colitis in Austrian pigs shows frequent solitary presence of Brachyspiramurdochii.

Brachyspira infections are significant causes of enterocolitis in pigs. In order to differentiate pathogenic species (Brachyspira (Br.) hyodysenteriae, Brachyspira pilosicoli) from less pathogenic or non-pathogenic species (Brachyspira intermedia, Brachyspira innocens, Brachyspira murdochii) in paraffin-embedded tissue samples a polymerase chain reaction (PCR) protocol allowing identification of Brachyspira at species level in archival material was developed. This approach was complemented by sequencing of the PCR amplification products. All seven cases presented with clinical and morphological Brachyspira-associated enterocolitis. Br. hyodysenteriae was not identified in any of the cases, while Br. pilosicoli was identified in a single case in conjunction with Br. murdochii. One case each was found positive for Br. innocens and Br. intermedia. Interestingly, the majority of cases presented as single or double infections with Br. murdochii. In some of the pigs other pathogens, like porcine circovirus-2 or Lawsonia intracellularis were present. These observations point at the possibility that under certain conditions even Brachyspira species of low pathogenicity can multiplicate extensively and lead to Brachyspira-associated enterocolitis.

Emergence of Usutu virus in Hungary.

In 2001, Usutu virus (USUV), a mosquito-borne flavivirus of the Japanese encephalitis virus serogroup related to West Nile virus and previously restricted to sub-Saharan Africa, emerged in wild and zoo birds in and around Vienna, Austria. In order to monitor the spread of the infection, a dead bird surveillance program was established in Austria and in neighboring Hungary. In Hungary, 332 dead birds belonging to 52 species were tested for USUV infection between 2003 and 2006. In the first 2 years, all birds investigated were negative. In August 2005, however, USUV was detected in organ samples of a blackbird (Turdus merula), which was found dead in Budapest, Hungary, by reverse transcription-PCR, immunohistochemistry, and in situ hybridization. In July and August 2006, a further six dead blackbirds tested positive for USUV, and the virus was isolated from organ samples of one bird. These birds were also found in urban areas of Budapest. The nearly complete genomic sequence of one Hungarian USUV strain was determined; it was found to share 99.9% identity with the strain that has been circulating in Austria since 2001. This result indicates that the USUV strain responsible for the blackbird die-off in Budapest most likely spread from Austria to Hungary instead of being independently introduced from Africa.

In vitro host-cell susceptibility to Usutu virus.

We investigated the susceptibility to Usutu virus (Flavivirus) of 13 permanent cell lines, 3 primary cell cultures, and chicken embryos. Vero, PK-15, and goose embryo fibroblast cells developed cytopathic effects; however, viral multiplication was detected in all mammalian cell types by immunohistochemical tests. Chicken embryo fibroblast cells and chicken embryos were resistant.

Genetic clustering of Borna disease virus natural animal isolates, laboratory and vaccine strains strongly reflects their regional geographical origin.

The aim of this study was to gain more detailed insights into the genetic evolution and variability of Borna disease virus (BDV). Phylogenetic analyses were performed on field viruses originating from naturally infected animals, the BDV vaccine strain 'Dessau', four widely used laboratory strains and the novel BDV subtype No/98. Four regions of the BDV genome were analysed: the complete p40, p10 and p24 genes and the 5'-untranslated region of the X/P transcript. BDV isolates from the same geographical area exhibited a clearly higher degree of identity to each other than to BDV isolates from other regions, independent of host species and year of isolation. Five different clusters could be established within endemic areas, corresponding to the geographical regions from which the viruses originated: (i) a Swiss, Austrian and Liechtenstein Rhine valley group, related closely to the geographically bordering Baden-Wurttemberg and Bavaria II group (ii) in the western part of Germany; (iii) a third group, called Bavaria I group, limited in occurrence to Bavaria; (iv) a southern Saxony-Anhalt and bordering northern Saxony group, bound to the territories of these federal states in the eastern part of Germany; and (v) a mixed group, consisting of samples from different areas of Germany; however, these were mainly from the federal states of Thuringia and Lower Saxony. The laboratory strains and the vaccine strain clustered within these groups according to their geographical origins. All field and laboratory strains, as well as the vaccine strain, clearly segregated from the recently described and highly divergent BDV strain No/98, which originated from an area in Austria where Borna disease is not endemic.

Emergence of Usutu virus, an African mosquito-borne flavivirus of the Japanese encephalitis virus group, central Europe.

During late summer 2001 in Austria, a series of deaths in several species of birds occurred, similar to the beginning of the West Nile virus (WNV) epidemic in the United States. We necropsied the dead birds and examined them by various methods; pathologic and immunohistologic investigations suggested a WNV infection. Subsequently, the virus was isolated, identified, partially sequenced, and subjected to phylogenetic analysis. The isolates exhibited 97% identity to Usutu virus (USUV), a mosquito-borne Flavivirus of the Japanese encephalitis virus group; USUV has never previously been observed outside Africa nor associated with fatal disease in animals or humans. If established in central Europe, this virus may have considerable effects on avian populations; whether USUV has the potential to cause severe human disease is unknown.

[Screening for antibodies against zoonotic agents among employees of the Zoological Garden of Vienna, Schönbrunn, Austria]. / Untersuchungen auf Antikörper gegen Zoonoseerreger bei Angestellten des Wiener Tiergartens Schönbrunn.

The aim of this study was to investigate the prevalence of antibodies against zoonotic agents in employees of the zoological garden of Vienna, Schönbrunn, Austria. Sixty out of 120 employees participated in the study. In 97% of them antibodies to at least one zoonotic agent were identified. Only two participants were free of antibodies to the zoonotic agents tested. The following seroprevalences (in brackets) were obtained: Viral zoonotic (and potentially zoonotic) agents: Influenzavirus A/H1N1 (58%), Influenzavirus A/H3N2 (85%), Lymphocytic choriomeningitis virus (13%), Encephalomyocarditis virus (5%), Orthopox- (Cowpox-) virus and Hantavirus type Puumala (3%). Hantavirus type Hantaan and Borna disease virus (all negative). Bacterial zoonotic agents: Bartonella henselae (65 %), Borrelia burgdorferi (10%), Leptospira interrogans serovar copenhageni and serovar icterohaemorrhagiae as well as Chlamydophila psittoci (2% each). Brucella spp., Coxiella bumetii, and Francisella tularensis (all negative). Parasitic zoonotic agents: Toxoplasma gondii (53%), Toxocara spp. (21%), Capillaria hepatica (2%), Fasciola hepatica, Schistosoma mansoni, E. multilocularis, and E. granulosus (all negative). The remarkably high seroprevalence to the causative agent of cat scratch disease, Bartonella henselae, is probably due to the private contact of the employees to cats. Regarding viral zoonotic agents it has to be mentioned that Influenzavirus vaccination and/or human-to-human transmission of especially A/H3N2 Influenzaviruses probably attributed significantly to the very high seroprevalence to both Influenzavirus types A/H1N1 and A/H3N2. When investigating parasitic zoonotic agents, high prevalence rates were found against Toxoplasma gondii and Toxocara spp., however, it was not possible to establish a causal link between seropositivity and the professional activity in the zoo. Interestingly, in the case of antibodies to T. gondii, the typical correlation with age was not found in this study, while in the case of the Toxocara spp. positive subjects a correlation was identified with both age and duration of employment in the zoo. Regarding the later two zoonotic parasites, employees of the zoological garden showed significantly higher seroprevalences than the average Austrian population. Antibodies to Capillaria hepatica, a hepatic-parasite in rodents which is diagnosed in humans rarely, were identified in one employee and another one showed a questionable positive result. Further investigations did not exhibit clinical infestations with the parasite in these two individuals so far.