Sharp decline in scrapie prevalence in the Netherlands after breeding for resistance: Are we close to achieving eradication?

Introduction. In the Netherlands an ambitious scrapie control program was started at the national level in 1998, based on genetic selection of animals for breeding. From 2002 onwards EU regulations required intensive active scrapie surveillance as well as certain control measures in affected flocks. Materials and Methods. Here we use standard statistical methods as well as mathematical modeling to analyze (1) data on genotype frequencies and scrapie prevalence in the Dutch sheep population obtained from both surveillance and affected flocks; (2) data on PrP genotype frequencies in a random sample of flocks; (3) postal survey results on between-flock differences in breeding strategy and flock management. Results and Conclusions. Analyzing the data (1) we find that the breeding program has produced a steady increase in the level of genetic scrapie resistance in the Dutch sheep population. We also found that a few years later this was followed by a sharp decline in the prevalence of classical scrapie in tested animals. Notably, the estimated classical scrapie prevalence level per head of susceptible genotype declined significantly as well. This indicates that selective breeding has a disproportionate effect on infection prevalence, reminiscent of the well-known population effect of vaccination against a transmissible disease. The overall recent decline in classical scrapie prevalence in Dutch sheep suggests that eradication of the disease in The Netherlands may be within reach. However, a subset of farms may still continue to act as a core group for scrapie transmission for some time, as we show by analyzing between-flock heterogeneities using the data (2) and (3). In addition, genetic resistance levels may decline again in future as participation to the selective breeding program has recently become voluntary

The Atacama Cosmology Telescope: A Catalog of >4000 Sunyaev–Zel’dovich Galaxy Clusters

We present a catalog of 4195 optically confirmed Sunyaev–Zel'dovich (SZ) selected galaxy clusters detected with signal-to-noise ratio >4 in 13,211 deg2 of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multifrequency matched filter to 98 and 150 GHz maps constructed from ACT observations obtained from 2008 to 2018 and confirmed using deep, wide-area optical surveys. The clusters span the redshift range 0.04 1 clusters, and a total of 868 systems are new discoveries. Assuming an SZ signal versus mass-scaling relation calibrated from X-ray observations, the sample has a 90% completeness mass limit of M500c > 3.8 × 1014 M⊙, evaluated at z = 0.5, for clusters detected at signal-to-noise ratio >5 in maps filtered at an angular scale of 2farcm4. The survey has a large overlap with deep optical weak-lensing surveys that are being used to calibrate the SZ signal mass-scaling relation, such as the Dark Energy Survey (4566 deg2), the Hyper Suprime-Cam Subaru Strategic Program (469 deg2), and the Kilo Degree Survey (825 deg2). We highlight some noteworthy objects in the sample, including potentially projected systems, clusters with strong lensing features, clusters with active central galaxies or star formation, and systems of multiple clusters that may be physically associated. The cluster catalog will be a useful resource for future cosmological analyses and studying the evolution of the intracluster medium and galaxies in massive clusters over the past 10 Gyr

The effect of diet composition on tryptophan requirement of young piglets

The aim of the study was to evaluate the requirement for Trp in relation to diet composition in piglets in the period after weaning (BW range of 9 to 24 kg). Two Trp deficient (relative to the Dutch (CVB, 1996) and NRC (NRC, 1998) requirement values for piglets of 10 to 20 kg BW) basal diets were formulated; one based on corn and soybean meal and a second one based on wheat, barley, soybean meal, peas and whey powder (10.0 g/kg apparent ileal digestible (AID) Lys; 1.4 g/kg AID Trp; 1.5 g/kg standardised ileal digestible (SID) Trp). Both basal diets were supplemented with 0.3, 0.6 and 0.9 g L-Trp per kg diet to obtain diets with 1.7, 2.0 and 2.3 g AID Trp per kg (1.8, 2.1 and 2.4 g SID Trp per kg), respectively. Each of the 8 treatments was evaluated in 8 replicates (pens with eight male or female piglets). Average daily feed intake, ADG, and G:F were measured as response criteria. Over the 28-d experimental period, ADG and G:F were greater for the treatments on the wheat/barley diet compared to those on the corn/soybean meal and were increased by the level of Trp in the diet (P <0.05). Average daily feed intake was only increased by the level of Trp supplementation (P <0.05). Increasing the Trp level increased ADFI for the corn/soybean meal diet up to 2.3 g AID Trp per kg (2.4 g SID Trp per kg) and up to 2.0 g AID Trp per kg (2.1 g SID Trp per kg) in the wheat/barley diet (P <0.05). For both diets types supplementation of free L-Trp increased the G:F up to 1.7 g AID Trp per kg (1.8 g SID Trp per kg). Non-linear regression analysis of the response curves for ADFI using an exponential model for estimating a requirement value for Trp (defined as the Trp level resulting in 95% of the maximum response) revealed a requirement estimate of 2.3 g AID Trp per kg for the corn/soybean meal based diet and 2.1 g AID Trp per kg for the wheat/barley based diet, equivalent to 2.4 and 2.2 g SID Trp per kg diet, respectively. For ADG, a requirement estimate of 2.1 g AID Trp per kg for both types of diets was derived, equivalent to 2.2 g SID Trp per kg diet. The Trp requirement for young piglets seems to be greater than indicated by some commonly used recommendations and does not seem largely dependent on diet ingredient compositio

Sharp decline in scrapie prevalence in the Netherlands after breeding for resistance: Are we close to achieving eradication?

Introduction. In the Netherlands an ambitious scrapie control program was started at the national level in 1998, based on genetic selection of animals for breeding. From 2002 onwards EU regulations required intensive active scrapie surveillance as well as certain control measures in affected flocks. Materials and Methods. Here we use standard statistical methods as well as mathematical modeling to analyze (1) data on genotype frequencies and scrapie prevalence in the Dutch sheep population obtained from both surveillance and affected flocks; (2) data on PrP genotype frequencies in a random sample of flocks; (3) postal survey results on between-flock differences in breeding strategy and flock management. Results and Conclusions. Analyzing the data (1) we find that the breeding program has produced a steady increase in the level of genetic scrapie resistance in the Dutch sheep population. We also found that a few years later this was followed by a sharp decline in the prevalence of classical scrapie in tested animals. Notably, the estimated classical scrapie prevalence level per head of susceptible genotype declined significantly as well. This indicates that selective breeding has a disproportionate effect on infection prevalence, reminiscent of the well-known population effect of vaccination against a transmissible disease. The overall recent decline in classical scrapie prevalence in Dutch sheep suggests that eradication of the disease in The Netherlands may be within reach. However, a subset of farms may still continue to act as a core group for scrapie transmission for some time, as we show by analyzing between-flock heterogeneities using the data (2) and (3). In addition, genetic resistance levels may decline again in future as participation to the selective breeding program has recently become voluntary

Active surveillance for scrapie in the Netherlands: effect of a breeding programme on the prevalence of scrapie in sheep (2002-2010)? = Acht jaar actieve scrapie-surveillance in Nederland: het effect van het fokprogramma op de prevalentie van schrapie bij het schaap (2002-2010)

The susceptibility of sheep to scrapie is modulated by the prion protein (PrP) genotype of the animal. An ambitious voluntary scrapie control programme was started in the Netherlands in 1998, based on selection of rams with theARR/ARR genotype for breeding. This programme was followed by an obligatory programme in 2004; the programme has been voluntary since 2007. We monitored the prevalence of PrP genotype frequencies and the prevalence of scrapie in the Dutch sheep population between 2002 and June 2010. Results showed that selection for scrapie-resistant sheep resulted in an increase in the ARR allele frequency in the Dutch national flock from 37.5% in 2005 to 61.4% in 2009. Moreover, surveillance data showed that there was a significant decrease in the prevalence of scrapie a few years after the start of the obligatory breeding programme, from more than 0.2% in 2004 to 0.015% in 2009. This decrease is a consequence of the increased number of scrapie-resistant sheep in the Dutch sheep population. To date, the results and the models based on the data show that the selective breeding programme should be continued for several years in order to successfully eradicate scrapie. It will be important to monitor the PrP frequency and scrapie prevalence in the Dutch sheep population in the coming years