TSE pathogenesis in cattle and sheep

Many studies have been undertaken in rodents to study the pathogenesis of transmissible spongiform encephalopathies (TSE). Only a few studies have focused on the pathogenesis of bovine spongiform encephalopathy (BSE) and scrapie in their natural hosts. In this review, we summarize the most recent insights into the pathogenesis of BSE and scrapie starting from the initial uptake of TSE agents and crossing of the gut epithelium. Following replication in the gut-associated lymphoid tissues (GALT), TSE agents spread to the enteric nervous system (ENS) of the gut. Infection is then carried through the efferent fibers of the post-ganglionic neurons of the parasympathetic and sympathetic nervous system to the pre-ganglionic neurons in the medulla oblongata of the brain and the thoracic segments of the spinal cord. The differences between the pathogenesis of BSE in cattle and scrapie in sheep are discussed as well as the possible existence of additional pathogenetic routes

Minder BSE en scrapie

De dierziekte BSE is gevaarlijk voor de mens. Onderzoekers van het Central Veterinary Institute (CVI) hebben daarom snelle diagnostische tests ontwikkeld en ingezet bij rundvee, schapen en geiten. Ook hebben ze ervoor gezorgd dat schapen minder vatbaar zijn voor de verwante prionziekte scrapie

Transmission and quantification of verocytotoxin-producing Escherichia coli O157 in dairy cattle and calves

Data from a field study of 14 months duration in a naturally colonized dairy herd and data from an experiment with calves were used to quantify transmission of verocytotoxin-producing Escherichia coli (VTEC O157) in cattle. For the latter, two groups of 10 calves were randomly assigned and put out in one of two pastures. From each group, five animals were experimentally inoculated with 109 c.f.u. O157 VTEC and, considered infectious, put back in their group. Each of the susceptible contact calves became positive within 6 days of being reunited. The estimate of the basic reproduction ratio (R0) in the experiment was 7·3 (95% CI 3·92¿11·5), indicating that each infectious calf will infect seven other calves on average during an assumed infectious period of 28 days in a fully susceptible population. The R0 among dairy cows appeared to be about 10 times lower (0·70, 95% CI 0·48¿1·04). After the transmission experiment, six contact-infected animals that were shedding continuously during the experiment were housed in a tie stall during winter. After 40 days, all six tested negative for O157 VTEC. In June, after a period of 34 weeks in which the heifers remained negative, they were put out in a clean and isolated pasture to observe whether they started shedding again. On each pasture that was infected with O157 VTEC during the transmission experiment the previous summer, newly purchased susceptible calves were placed. None of the heifers or calves started shedding during 14 weeks, indicating that both the heifers and the previously contaminated pasture did not function as reservoir of O157 VTE

Relationships between methane production and milk fatty acid profiles in dairy cattle

There is a need to develop simple ways of quantifying and estimating CH4 production in cattle. Our aim was to evaluate the relationship between CH4 production and milk fatty acid (FA) profile in order to use milk FA profiles to predict CH4 production in dairy cattle. Data from 3 experiments with dairy cattle with a total of 10 dietary treatments and 50 observations were used. Dietary treatments included supplementation with calcium fumarate, diallyldisulfide, caprylic acid, capric acid, lauric acid, myristic acid, extruded linseed, linseed oil and yucca powder. Methane was measured using open circuit indirect respiration calorimetry chambers and expressed as g/kg dry matter (DM) intake. Milk FA were analyzed by gas chromatography and individual FA expressed as a fraction of total FA. To determine relationships between milk FA profile and CH4 production, univariate mixed model regression techniques were applied including a random experiment effect. A multivariate model was developed using a stepwise procedure with selection of FA based on the Schwarz Bayesian Information Criterion. Dry matter intake was 17.7 ± 1.83 kg/day, milk production was 27.0 ± 4.64 kg/day, and methane production was 21.5 ± 1.69 g/kg DM. Milk C8:0, C10:0, C11:0, C14:0 iso, C15:0 iso, C16:0 and C17:0 anteiso were positively related (

Risicobeoordeling schapenscheren en schapenwol voor mens en dier in de Nederlandse wolproductieketen

Het doel van dit onderzoek is een risicobeoordeling van de microbiologische risico's voor mens en dier van het schapenscheren, transport en het bewerken van schapenwol in de wolproductieketen in Nederland, inclusief de opties voor eventueel noodzakelijke risicoreducerende maatregelen. De VWA wilde de volgende vragen beantwoord hebben: 1. Welke microbiologische gevaren vormen in Nederland een risico voor infectie van en verspreiding onder mensen en dieren naar aanleiding van directe en indirecte contacten met het product wol in de wolproductieketen? 2. Kunt u deze microbiologische risico's in prioritaire volgorde plaatsen (kwalitatieve of indien mogelijk semikwantitatieve risicobeoordeling)? 3. Als er risico's aanwezig zijn, die op basis van een expertmening niet verwaarloosbaar klein zijn, welke risicoreducerende maatregelen kunnen mogelijk worden toegepast in de productieketen en op welk moment

Selection and optimization of proteolytically stable llama single-domain antibody fragments for oral immunotherapy

We previously demonstrated that oral application of the recombinant single-domain antibody fragment (VHH) clone K609, directed against Escherichia coli F4 fimbriae, reduced E. coli-induced diarrhoea in piglets, but only at high VHH doses. We have now shown that a large portion of the orally applied K609 VHH is proteolytically degraded in the stomach. Stringent selection for proteolytic stability identified seven VHHs with 7- to 138-fold increased stability after in vitro incubation in gastric fluid. By DNA shuffling we obtained four clones with a further 1.5- to 3-fold increased in vitro stability. These VHHs differed by at most ten amino acid residues from each other and K609 that were scattered over the VHH sequence and did not overlap with predicted protease cleavage sites. The most stable clone, K922, retained 41% activity after incubation in gastric fluid and 90% in jejunal fluid. Oral application of K922 to piglets confirmed its improved proteolytic stability. In addition, K922 bound to F4 fimbriae with higher affinity and inhibited fimbrial adhesion at lower VHH concentrations. K922 is thus a promising candidate for prevention of piglet diarrhoea. Furthermore, our findings could guide selection and improvement by genetic engineering of other recombinant antibody fragments for oral use

Godenzonen, het heilige gras en de verlosser: voetbal is een religie

De Volkskran

Rapid and discriminatory diagnosis of scrapie and BSE in retro-pharyngeal lymph nodes of sheep

BACKGROUND: Diagnosis based on prion detection in lymph nodes of sheep and goats can improve active surveillance for scrapie and, if it were circulating, for bovine spongiform encephalopathy (BSE). With sizes that allow repetitive testing and a location that is easily accessible at slaughter, retropharyngeal lymph nodes (RLN) are considered suitable organs for testing. Western blotting (WB) of brain homogenates is, in principle, a technique well suited to both detect and discriminate between scrapie and BSE. In this report, WB is developed for rapid diagnosis in RLN and to study biochemical characteristics of PrP(res). RESULTS: Optimal PrP(res )detection in RLN by WB was achieved by proper tissue processing, antibody choice and inclusion of a step for PrP(res)concentration. The analyses were performed on three different sheep sources. Firstly, in a study with preclinical scrapie cases, WB of RLN from infected sheep of VRQ/VRQ genotype – VRQ represents, respectively, polymorphic PrP amino acids 136, 154, and 171 – allowed a diagnosis 14 mo earlier compared to WB of brain stem. Secondly, samples collected from sheep with confirmed scrapie in the course of passive and active surveillance programmes in the period 2002–2003 yielded positive results depending on genotype: all sheep with genotypes ARH/VRQ, VRQ/VRQ, and ARQ/VRQ scored positive for PrP(res), but ARQ/ARQ and ARR/VRQ were not all positive. Thirdly, in an experimental BSE study, detection of PrP(res )in all 11 ARQ/ARQ sheep, including 7 preclinical cases, was possible. In all instances, WB and IHC were almost as sensitive. Moreover, BSE infection could be discriminated from scrapie infection by faster electrophoretic migration of the PrP(res )bands. Using dual antibody staining with selected monoclonal antibodies like 12B2 and L42, these differences in migration could be employed for an unequivocal differentiation between BSE and scrapie. With respect to glycosylation of PrP(res), BSE cases exhibited a greater diglycosylated fraction than scrapie cases. Furthermore, a slight time dependent increase of diglycosylated PrP(res )was noted between individual sheep, which was remarkable in that it occurred in both scrapie and BSE study. CONCLUSION: The present data indicate that, used in conjunction with testing in brain, WB of RLN can be a sensitive tool for improving surveillance of scrapie and BSE, allowing early detection of BSE and scrapie and thereby ensuring safer sheep and goat products