Usutu virus, Belgium, 2016.

During late summer 2016, in a northwest European region extending over Belgium, the Netherlands and the eastern border of the German state of North Rhine Westphalia, an outbreak of wild bird deaths occurred similar to those reported on the continent since 1996. Dead birds were necropsied and examined by complementary methods. Pathologic and immunohistological investigations strongly suggested an infection by Usutu virus. Subsequently, genomic segments of the said virus were detected, the virus was isolated and its complete genome was sequenced. The strain, designated Usutu-LIEGE, is a close phylogenetic relative of those isolated in Germany which form a distinct group within the USUV phylogeny, the so-called Europe_3 lineage. Should this outbreak recapitulate the characteristics of those in southwest Germany in 2011 and in/around Vienna (Austria) in 2001, it is expected that specific avian populations in the affected area will face a significant reduction in size for a few years.

Risk factors and effect of selective removal on retroviral infections prevalence in Belgian stray cats.

The aim of this study was to evaluate the effect of several risk/protective factors and predictors on the prevalence of feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) infections in 302 stray cats captured during a trap-neuter-release programme in a mixed urban-rural area from Belgium, from 2010 to 2012. The impact of selective removal of FIV-positive cats on the apparent prevalence in the remaining population over this three-year period was also assessed. The seroprevalences over three years were 18.8 per cent for FIV and 0.7 per cent for FeLV. For FIV, the seroprevalence decreased significantly from the first year of the programme (2010; 30.5 per cent) to the last (2012; 13.1 per cent). Sex (male) and age (adult and old cats) were risk factors, while the year of sampling (years 2011 and 2012) was a protective factor. Age, sex and location were the most relevant predictors of FIV status. The data presented in this study revealed a very high FIV seroprevalence in Belgian stray cats, while FeLV was almost absent. The selective removal of positive cats had a drastic effect on the FIV seroprevalence in the remaining cat population.

Bluetongue virus RNA detection by real-time rt-PCR in post-vaccination samples from cattle.

Bluetongue virus serotype 8 (BTV-8) was responsible for a large outbreak among European ruminant populations in 2006-2009. In spring 2008, a massive vaccination campaign was undertaken, leading to the progressive disappearance of the virus. During surveillance programmes in Western Europe in 2010-2011, a low but significant number of animals were found weakly positive using BTV-specific real-time RT-PCR, raising questions about a possible low level of virus circulation. An interference of the BTV-8 inactivated vaccine on the result of the real-time RT-PCR was also hypothesized. Several studies specifically addressed the potential association between a recent vaccination and BTV-8 RNA detection in the blood of sheep. Results were contradictory and cattles were not investigated. To enlighten this point, a large study was performed to determine the risks of detection of bluetongue vaccine-associated RNA in the blood and spleen of cattle using real-time RT-PCR. Overall, the results presented clearly demonstrate that vaccine viral RNA can reach the blood circulation in sufficient amounts to be detected by real-time RT-PCR in cattle. This BTV-8 vaccine RNA carriage appears as short lasting.

No serologic evidence for emerging Schmallenberg virus infection in dogs (Canis domesticus).

Schmallenberg virus, a novel orthobunyavirus, is spreading among ruminants, especially sheep and cattle, throughout Europe. To determine the risk for domestic dog infection, we conducted a survey among cases referred to the university Companion Animal Clinic to assess possible seroconversion. No evidence of transmission to dogs was detected.

The presence of bluetongue virus serotype 8 RNA in Belgian cattle since 2008.

After a short winter break, bluetongue virus serotype 8 was responsible in 2007 for a large-scale epidemic among ruminant populations in Western Europe. Little is known about the mechanisms allowing the virus to survive winter conditions. A yearly mass vaccination of cattle and sheep started in spring 2008, which was recognized as successful in terms of clinical protection, but occult circulation of the bluetongue virus has not been adequately addressed. We studied the carriage of bluetongue RNA in the spleen of cattle in the vector-free period and the circulation of bluetongue virus in cattle populations in Belgium since the introduction of vaccination programmes. Overall, the results presented here show evidence for the long-term carriage of bluetongue virus RNA in the spleen of cattle and demonstrated a low but significant circulation and transplacental transmission of bluetongue virus in Belgian cattle in 2009, with apparent disappearance in 2010.

Modulating mouse innate immunity to RNA viruses by expressing the Bos taurus Mx system.

Mx proteins are interferon-induced members of the dynamin superfamily of large guanosine triphosphatases. These proteins have attracted much attention because some display antiviral activity against pathogenic RNA viruses, such as members of the orthomyxoviridae, bunyaviridae, and rhabdoviridae families. Among the diverse mammalian Mx proteins examined so far, we have recently demonstrated in vitro that the Bos taurus isoform 1 (boMx1) is endowed with exceptional anti-rabies-virus activity. This finding has prompted us to seek an appropriate in vivo model for confirming and evaluating gene therapy strategies. Using a BAC transgene, we have generated transgenic mouse lines expressing the antiviral boMx1 protein and boMx2 proteins under the control of their natural promoter and short- and long-range regulatory elements. Expressed boMx1 and boMx2 are correctly assembled, as deduced from mRNA sequencing and western blotting. Poly-I/C-subordinated expression of boMx1 was detected in various organs by immunohistochemistry, and transgenic lines were readily classified as high- or low-expression lines on the basis of tissue boMx1 concentrations measured by ELISA. Poly-I/C-induced Madin-Darby bovine kidney cells, bovine turbinate cells, and cultured cells from high-expression line of transgenic mice were found to contain about the same concentration of boMx1, suggesting that this protein is produced at near-physiological levels. Furthermore, insertion of the bovine Mx system rendered transgenic mice resistant to vesicular-stomatitis-virus-associated morbidity and mortality, and embryonic fibroblasts derived from high-expression transgenic mice were far less permissive to the virus. These results demonstrate that the Bos taurus Mx system is a powerful anti-VSV agent in vivo and suggest that the transgenic mouse lines generated here constitute a good model for studying in vivo the various antiviral functions-known and yet to be discovered-exerted by bovine Mx proteins, with priority emphasis on the antirabic function of boMx1.