Impact of Age, Season, and Flowing vs. Stagnant Water Habitat on Avian Influenza Prevalence in Mute Swan (Cygnus olor) in Belgium.

Due to their probable role in the spread of Asian highly pathogenic avian influenza (HPAI) H5N1 virus, and in order to explore its implication in the low pathogenic avian influenza (LPAI) virus epidemiology, mute swans represent one particular wild bird species specifically targeted in the avian influenza (AI) surveillance elaborated in Belgium. A total of 640 individual mute swans have been sampled during a 4-yr AI surveillance program (2007-2010) to determine the AI seroprevalence and viroprevalence in this species; all were analyzed through age, temporal, and habitat (flowing and stagnant water) factors. Using a nucleoprotein (NP)-based ELISA, a global antibody prevalence of 35% has been found and was characterized by two peaks in the winter and the summer that might be indicative of a greater LPAI virus circulation in the autumn than in the spring. A significantly higher antibody prevalence was detected in adult swans (53.8%) as compared to juveniles (15.5%). In contrast, a low prevalence of infection (2.7%) was found, mainly in juvenile mute swans and only during the autumn migration period. Interestingly, an impact of water habitat was observed based on the comparison of the antibody prevalence and prevalence of infection from swan populations living on stagnant water vs. flowing water, suggesting that stagnant water provides a more-favorable environment for LPAI persistence and transmission.

Chasing notifiable avian influenza in domestic poultry: a case report of low-pathogenic avian influenza h5 viruses in two Belgian holdings.

In December 2008, bird species in two geographically distant holdings were found positive for H5 viruses following the annual Avian influenza serological screening in Belgium. The virological tests performed identified in one holding a low-pathogenic avian influenza (LPAI) virus subtype H5N2, and a H5 LPAI virus was identified by real-time PCR and direct sequencing at the second holding. The first farm was an outdoor mixed holding housing ornamental birds and poultry (n = 6000) and the second a free-range geese breeding farm (n = 1500). No clinical signs or mortalities were reported. Control measures defined by Council Directive 2005/94/EC were followed, including notification to the European Commission via the Animal Disease Notification System and to the World Organization for Animal Health, and poultry were killed, while ornamental bird species were quarantined. Partial sequencing of the H5N2 virus haemagglutinin and neuraminidase N2 gene sequences revealed a close homology to some recent LPAI isolates identified from wild birds in Germany and Italy and from wild birds in Eurasia and Africa, respectively. It is noteworthy that, these two holdings were already H5 positive based on HI test results carried out during the previous serological screening; however, no virus was detected at that time. To have a better understanding of the potential 'silent' circulation of the H5N2 isolate in the field, experimental infections of chickens and turkeys were performed. The low excretion detected might in part explain viral persistence not associated with spread between gallinaceous birds in the same holding, indicating that the H5N2 LPAI isolate was not fully adapted to these two poultry species. Our results highlighted limitations to only using serological screening for the early detection of LPAI in an 'at-risk farm', suggesting that virological and serological monitoring tests be applied simultaneously as a means of testing animals in 'at-risk farms'.

Molecular epidemiological analysis of the transboundary transmission of 2003 highly pathogenic avian influenza H7N7 outbreaks between the Netherlands and Belgium.

The 2003 outbreak of Highly pathogenic avian influenza (HPAI) A(H7N7) in the Netherlands, Belgium and Germany resulted in significant genetic diversification that proved informative for tracing transmission events. Building on previous investigations on the Dutch outbreak, we focused on the potential transnational transmissions between the Netherlands and Belgium. Although no clear epidemiological links could be identified from the tracing data, the transmission network based on concatenated HA-NA-PB2 sequences supports at least three independent introductions from the Netherlands to Belgium and suggests one possible introduction form Belgium back to the Netherlands. Two introductions in the Belgian province of Limburg occurred from nearby farms in the Dutch province of Limburg. One introduction resulted in three secondary infected farms, while a second introduction did not cause secondary infections. The third introduction into Belgium occurred in the north of the Antwerp province, very close to the national border, and originated from the North of the Dutch province Brabant (long distance transmission, >65 km). The virus spread to two additional Belgian farms, one of which may be the source of a secondarily infected farm in the Netherlands. One infected turkey farm in the province of Antwerp (Westmalle) was geographically close to the latter introduction, but genetically clustered with the first introduction event in the Limburg province. Epidemiological tracing data could neither confirm nor exclude whether this outbreak was a result from long distance contacts within Belgium or whether this farm presented a fourth independent transboundary introduction. These multiple transnational transmissions of HPAI in spite of reinforced biosecurity measures and trade restrictions illustrate the importance of international cooperation, legislation and standardization of tools to combat transboundary diseases.

Bluetongue sentinel surveillance program and cross-sectional serological survey in cattle in Belgium in 2010-2011.

Bluetongue virus serotype 8 (BTV-8) emerged in Central Western Europe in 2006 causing a large scale epidemic in 2007 that involved several European Union (EU) countries including Belgium. As in several other EU member states, vaccination against BTV-8 with inactivated vaccines was initiated in Belgium in spring 2008 and appeared to be successful. Since 2009, no clinical cases of Bluetongue (BT) have been reported in Belgium and BTV-8 circulation seemed to have completely disappeared by spring 2010. Therefore, a series of repeated cross-sectional surveys, the BT sentinel surveillance program, based on virus detection in blood samples by means of real-time RT-PCR (RT-qPCR) were carried out in dairy cattle from the end of 2010 onwards with the aim to demonstrate the absence of BTV circulation in Belgium. This paper describes the results of the first two sampling rounds of this BT sentinel surveillance program carried out in October-November 2010 and January-February 2011. In addition, the level of BTV-specific maternal antibodies in young non-vaccinated animals was monitored and the level of herd immunity against BTV-8 after 3 consecutive years of compulsory BTV-8 vaccination was measured by ELISA. During the 1st sampling round of the BT sentinel surveillance program, 15 animals tested positive and 2 animals tested doubtful for BTV RNA by RT-qPCR. During the 2nd round, 17 animals tested positive and 5 animals tested doubtful. The positive/doubtful animals in both rounds were re-sampled 2-4 weeks after the original sampling and then all tested negative by RT-qPCR. These results demonstrate the absence of BTV circulation in Belgium in 2010 at a minimum expected prevalence of 2% and 95% confidence level. The study of the maternal antibodies in non-vaccinated animals showed that by the age of 7 months maternal antibodies against BTV had disappeared in most animals. The BTV seroprevalence at herd level after 3 years of compulsory BTV-8 vaccination was very high (97.4% [95% CI: 96.2-98.2]). The overall true within-herd BTV seroprevalence in 6-24 month old Belgian cattle in early 2011 was estimated at 73.4% (95% CI: 71.3-75.4).

Emergence of bluetongue serotypes in Europe, part 2: the occurrence of a BTV-11 strain in Belgium.

An EDTA-blood sample from a cow without clinical signs, which gave early birth to a newborn calf that died soon after delivery, was shown to be positive for bluetongue virus (BTV)-RNA using a group-specific real-time RT-PCR (RT-qPCR). In-house serotype-specific RT-qPCR assays for bluetongue virus serotype 1 (BTV-1), -6 and -8 all gave negative results. Subsequent assays were carried out using conventional (gel-based) RT-PCR primers for all 25 BTV serotypes and only two primer sets, both specific for BTV-11, gave bands of the expected size. The cDNAs generated were sequenced and comparisons of the genome segment 2 sequence with that of the modified 'live' vaccine strain of BTV-11 from South Africa showed 100% identity. A survey of all ruminants in a 1-km area around the first positive farm using a BTV-11 serotype-specific RT-qPCR revealed five other holdings with in total nine BTV-11 positive animals. A cross-sectional monitoring of dairy cattle in Belgium showed an overall prevalence of 3.8% on herd level and 0.2% on animal level. A BTV-11 has been introduced into the Belgian cattle herd during the 2008 vector season. The source of the infection and the way by which the virus was introduced are unknown.

Bluetongue in Belgium: episode II.

Bluetongue (BT) is an arthropod-borne viral disease of ruminants. In August 2006, domestic ruminant populations in Northern Europe became infected with BT virus serotype 8 (BTV-8). The first BTV-8-case of the year 2007 in Belgium was notified in July. This case was the starting point of a second wave of BT outbreaks. The main objective of this study was to describe the evolution and the clinical impact of the second episode of BT in Belgium. In addition, the main differences with the previous episode (August-December 2006) are reported. Both outbreak and rendering plant data were analysed. Overall cumulative incidence at herd level was estimated at 11.5 (11.2-11.8) and 7.5 (7.3-7.8) per cent in cattle and sheep populations respectively. The findings went in favour of a negative association between within-herd prevalence in 2006 and the risk of showing clinical signs of BT in 2007 (via protective immunity). A high level of correlation was demonstrated between BT incidence and small ruminant mortality data when shifting the latter of 1-week backwards. This result supports the hypothesis that the high increase in small ruminant mortality observed in 2007 was the consequence of the presence of BT. For cattle, the correlation was not as high. An increase in cattle foetal mortality was also observed during the year 2007 and a fair correlation was found between BT incidence and foetal mortality.

Transplacental infection and apparently immunotolerance induced by a wild-type bluetongue virus serotype 8 natural infection.

Until recently, bluetongue (BT) virus (BTV) serotypes reportedly causing transplacental infections were all ascribed to the use of modified live virus strains. During the 2007 BT epidemic in Belgium, a significant increase in the incidence of abortions was reported. A study including 1348 foetuses, newborns and young animals with or without suspicion of BTV infection, was conducted to investigate the occurrence of natural transplacental infection caused by wild-type BTV-8 and to check the immunocompetence of newborns. BTV RNA was present in 41% and 18.5% of aborted foetuses from dams with or without suspected BTV involvement during pregnancy, respectively. The results of dam/calf pairs sampled before colostrum uptake provide evidence of almost 10% transplacental BTV infection in newborns. Apparently immunotolerant calves were found at a level of 2.4%. The current study concludes that the combined serological and real-time PCR (RT-qPCR) result of pregnant dams gives no indication of the infection status of the offspring except in the case of a double negative result. In a group of 109 calves with clinical suspicion of BT, born during the vector-free period, 11% were found to be RT-qPCR positive. The true prevalence was estimated to be 2.3%, indicating the extent of transplacental infection in a group of 733 calves of one to 4 months of age without BT suspicion. Moreover, virus isolation was successful for two newborn calves, emphasizing the need for restricting trade to BT-free regions of pregnant dams possibly infected during gestation, even if they are BTV RT-qPCR negative.

Avian influenza outbreak management: action at time of confirmation, depopulation and disposal methods; the 'Belgian experience' during the H7N7 highly pathogenic avian influenza epidemic in 2003.

Eradication of H5 and H7 influenza in a positive flock will include mass depopulation of birds, containment and inactivation of the virus in the carcasses and litter, and decontamination of the facility. A quick response is desired in the event of a disease outbreak. Ideally, birds should be depopulated within 24 h after detecting the virus. Mass depopulation of birds must be performed in a humane manner while minimizing human health and biosecurity risks. In the framework of the European legislation, a number of methods are authorized for the killing of poultry for processing prior to marketing. However, during emergencies such as a disease outbreak, there are fewer options. The current most commonly used procedures for large-scale emergency depopulation of birds consist of exposing poultry to CO or CO(2) gas. Both gasses have been used in Belgium during the H7N7 crisis in 2003. The gassing procedures include whole house gassing, portable panel enclosures, cage cabinets, containers and polyethylene tent method. Whole house gassing requires sealing the house to prevent gas leakage and, using specialized equipment, introducing large volumes of gas evenly over the birds. All procedures are very labour intensive, create a biosecurity risk and require a large number of personnel. There are considerable region-to-region differences in emergency depopulation techniques and disposal of carcasses and infected material. Because of the differences in bird type and species, management, housing and stocking density, it is difficult to propose a depopulation technique that will be suitable for all circumstances. Safety of the human operators is an increasing concern with all H5 and H7 strains and in particular with the highly pathogenic H5N1 strain. Researchers and commercial poultry companies in the United States recently established that non-toxic water-based foam with a certain bubble size presents a practicable, effective and humane method for mass depopulation. Foam of the right bubble size creates an occlusion in the trachea of birds, causing a rapid onset of hypoxia. The foam that blankets the broiler house induces physical hypoxia - the same cause of death as the approved method using carbon dioxide gas (CO(2)). The article illustrates the different culling and disposal methods with a focus on the methods used during the 2003 H7N7 crisis in Belgium.

Tomographic measurements of regional cerebral blood flow in progressive supranuclear palsy and Parkinson's disease.

Intellectual changes observed in progressive supranuclear palsy (PSP) are sometimes seen with lesser intensity in Parkinson's disease (PD). Cognitive impairment of PSP has been attributed to a frontal lobe dysfunction explaining the frontal cortex hypometabolism detected by PET. To establish whether this frontal hypometabolism is more pronounced in PSP than in PD, we compared frontal and temporo-parietal cerebral blood flow (CBF) indexes studied by SPECT using Tc99m HmPAO in 18 PSP, 18 PD and 8 control subjects. For each patient neuropsychological performances were also assessed. A significant left frontal hypoperfusion was observed in PSP (mean index value: 0.78 +/- 0.03, p < 0.01) and PD (0.78 +/- 0.04, p < 0.05) as compared to controls (0.84 +/- 0.03), whereas there was no difference between PSP and PD. No correlation was discovered between neuropsychological performances and frontal cortical index changes. This frontal uptake reduction of Tc99m HmPAO in PSP and PD could result from a disconnection phenomenon secondary to subcortical lesions. In both groups mean frontal indexes showed only a left frontal hypoperfusion suggesting that subcortical structures might be asymmetrically involved in early stages of the diseases. The lack of difference for indexe values between PSP and PD might be explained by the difference between the mean disease duration: 4.3 years for the PSP and 7.8 years for the PD. It might also suggest that frontal CBF reduction exists in the same proportions in PD and PSP, but at a later stage in the former case.

[Memory disorders in chickenpox encephalitis]. / Troubles de la mémoire dans une encéphalite de la varicelle.

A 31-year old man with chicken-pox encephalitis presented with a cerebellar syndrome and disorders of memory. The latter consisted of severe anterograde amnesia with normal retrograde memory, without confabulation or anosognosia. This suggested that the hippocampus was involved, probably functionally, since the outcome was rapidly favourable and the MRI was normal.

[Painless apoplectiform paralysis of the brachial plexus]. / Paralysie plexique apoplectiforme non douloureuse.

A 40 year-old glass-blower suddenly experienced a painless weakness of his left shoulder and arm, more severe in C5 and C6 territories. The disorders regressed. Il was suspected that this brachial plexus neuropathy was of ischemic origin. However the absence of pain was surprising.