Search Results (4)

Botulinum neurotoxins (BoNTs) are highly toxic proteins that require high-affinity immunocapture reagents for use in endopeptidase-based assays. Here, 30 novel and 2 earlier published llama single-domain antibodies (VHHs) against the veterinary-relevant BoNT serotypes C and D were yeast-produced. These VHHs recognized 10 independent antigenic sites, and many cross-reacted with the BoNT/DC and CD mosaic variants. As VHHs are highly suitable for genetically linking to increase antigen-binding affinity, 52 VHH multimers were produced and their affinity for BoNT/C, D, DC, and CD was determined. A selection of 15 multimers with high affinity (K_D < 0.1 nM) was further shown to be resilient to a high salt wash that is used for samples from complex matrices and bound native BoNTs from culture supernatants as shown by Endopep-MS. High-affinity multimers suitable for further development of a highly sensitive Endopep-MS assay include four multimers that bind both BoNT/D and CD with K_D of 14–99 pM, one multimer for BoNT/DC (65 pM) that also binds BoNT/C (75 pM), and seven multimers for BoNT/C (<1–19 pM), six of which also bind BoNT/DC with lower affinity (93–508 pM). In addition to application in diagnostic tests, these VHHs could be used for the development of novel therapeutics for animals or humans. Full article

Salmonellosis is the second most commonly reported foodborne gastrointestinal infection in humans in the European Union (EU). Most outbreaks are caused by Salmonella Enteritidis, present in contaminated food products, particularly in egg and egg products. In recent years, an increase in the prevalence of Salmonella in laying hen flocks in the EU has been observed. For the effective control of infection, adequate detection is key. In laying hen flocks, the occurrence of Salmonella in the EU is monitored by the culture of environmental samples (dust, faeces, and boot swabs). The performance of sampling procedures described in the literature for the detection of Salmonella in laying hens was reviewed. In total, 924 abstracts were screened, resulting in the selection of 87 abstracts and 18 publications for qualitative and quantitative analyses, respectively. Sample sizes and sampling locations of faecal material and dust were variable and poorly described. Microbiological culture methods used to detect Salmonella were variably described in the literature and were often incomplete. Overall, the available literature indicates higher sensitivity of environmental versus individual hen matrices and points to differences in sensitivity between environmental matrices. For non-cage housing systems, boot swabs are the preferred samples, while for cage housing systems dust might be a more reliable sample. Full article

Wind-supported transport of particle matter (PM) contaminated with excreta from highly pathogenic avian influenza virus (HPAIv)-infected wild birds may be a HPAIv-introduction pathway, which may explain infections in indoor-housed poultry. The primary objective of our study was therefore to measure the nature and quantity of PM entering poultry houses via air-inlets. The air-inlets of two recently HPAIv-infected poultry farms (a broiler farm and a layer farm) were equipped with mosquito-net collection bags. PM was harvested every 5 days for 25 days. Video-camera monitoring registered wild bird visits. PM was tested for avian influenza viruses (AIV), Campylobacter and Salmonella with PCR. Insects, predominantly mosquitoes, were tested for AIV, West Nile, Usutu and Schmallenberg virus. A considerable number of mosquitoes and small PM amounts entered the air-inlets, mostly cobweb and plant material, but no wild bird feathers. Substantial variation in PM entering between air-inlets existed. In stormy periods, significantly larger PM amounts may enter wind-directed air-inlets. PM samples were AIV and Salmonella negative and insect samples were negative for all viruses and bacteria, but several broiler and layer farm PM samples tested Campylobacter positive. Regular wild (water) bird visits were observed near to the poultry houses. Air-borne PM and insects—potentially contaminated with HPAIv or other pathogens—can enter poultry air-inlets. Implementation of measures limiting this potential introduction route are recommended. Full article

The Salmonella monitoring program, as outlined in the EU Commission regulation 200/2010, asks for repeated sampling in order to ascertain progress in achievement of the EU target. According to Article 2.2.2.2.c of this regulation, the competent authority may decide to do a resample and retest when it has reasons to question the results of initial testing. In the Netherlands, the competent authorities have been resampling and retesting all initial positive samplings for several years because of doubts about false positive initial test results. An analysis of population data in the period 2015–2019 indicates that 48% of initial samplings at the farm were classified as false positive after resampling and retesting by the competent authorities. A qualitative analysis, assessing factors that could be associated with the occurrence of false positives, indicates that cross-contamination during the sampling process by the poultry farmer is probably the most likely source. Cross-contamination of samples during transport from the farm to the laboratory and/or cross-contamination at the laboratory are also considered possible sources. Given the slightly non-optimal system-specificity of the Salmonella monitoring program, there is good reason to make, or consider, standard resampling and retesting of initial positive results by the competent veterinary authorities possible within the EU. Full article