Developments in biologicals最新文献

Bats are important reservoir hosts of RNA viruses, including lyssaviruses, which can cross the species barrier to infect humans and other domestic and wild non-flying mammals. Six of the seven Lyssavirus genotypes described to date infect bats. In Europe, two genotypes of Lyssavirus, European bat Lyssavirus types 1 and 2 (EBLV-1 and EBLV-2), circulate among several bat species and numerous bats are found infected every year. To provide epidemiologists and public health officials with data to effectively implement public health measures, we have undertaken field studies to identify the temporal dynamics of virus infection in bat colonies by combining multidisciplinary approaches. We have focused our work on a long-term longitudinal survey of different bat colonies in the Balearic Islands. The prevalence of virus RNA and neutralizing antibodies were analysed in captured bats. The bats were banded to allow for individual monitoring of infection and movements between colonies. The results show different lyssavirus infection episodes across the twelve years of study and provide the first evidence that mortality of the mouse-eared bat (Myotis myotis) in their natural environment does not increase significantly after episodes of EBLV-1 infection.

Haptoglobin (Hp) is an acute phase protein that is a marker in blood for clinical and subclinical disease in the pig. The aim of this study was to identify single nucleotide polymorphisms (SNPs) in the Hp gene and analyse their influence on baseline serum levels. DNA samples and serum were collected from 345 boars. Of 13 SNPs identified, 5 were genotyped using PCR-RFLP and Pyrosequencing. Serum Hp levels were measured using a biochemical assay. A general linear model was fitted with line and genotype as fixed effects. In addition, linkage disequilibrium (LD) was estimated between the 5 SNPs using r-square and D prime. Serum Hp concentrations in the population showed a skewed distribution with a mean of 0.34 g/L (range 0-2.65 g/L). Three SNPs were found to be associated with baseline Hp levels (p-value = 0.0093, 0.0051 and 0.0094). These 3 SNPs were also found to be in high LD with each other. This is the first study to find associations between polymorphisms in the porcine Hp gene and baseline Hp serum levels. The results have implications for breeding for resistance to infection.

In Thailand, the animal most reported rabid is the stray dog. Dog bite related rabies cases in humans account for 70-95% of rabies related deaths. The reported incidence of dog bites is highest in the central part of the country, especially in Bangkok. This epidemiological survey shows that at least five different canine rabies virus types are present in Bangkok. Rabies antigen and antibody prevalence in stray dogs in Bangkok was also investigated. Saliva and serum samples were taken from 3,314 stray dogs, captured between December 2003 and June 2004. One two year-old female was antigen positive by latex agglutination test and the result was confirmed by reverse transcription-polymerase chain reaction (RT-PCR). The overall antibody seroprevalence by enzyme-linked immunosorbent assay was 62% (95% CI: 54, 70%). Antibody seroprevalence was higherfor dogs captured within central Bangkok (86% of 1,208 dogs captured) than in the dogs captured on the outskirts of the greater metropolitan area (49% of 2,106 dogs captured). If our sample of stray dogs is representative, then the seroprevalence achieved from previous vaccination campaigns is insufficient in order to break the rabies transmission cycle among stray and feral dogs.

The United Kingdom has performed passive surveillance for European bat lyssaviruses (EBLVs) since 1987, and species-targeted surveillance since 2003. One critical component of these studies is the accurate identification of bats either submitted for testing or sampled in the field. Identification is dependent on numerous morphological characteristics. Whilst this is an effective means of bat identification, a number of problems remain with this approach. It relies on the experience of bat specialists and can lead to problems in differentiating members of the Myotis genus, particularly between Myotis mystacinus (whiskered bat) and Myotis brandtii (Brandt's bat), and between the most common species of the genus Pipistrellus. Furthermore, degradation of bats submitted for testing can also lead to problems in making an accurate species identification. Comparison of genetic sequence data could offer an alternative approach to differentiating bat species when morphological characterisation is not possible. Using tissue samples from UK resident bat species, sequence analysis of the mitochondrial DNA cytochrome b gene, and the beta-actin gene allowed for identification of many of the most common bat species in the UK, and genetic separation of two morphologically cryptic species. Application of this approach identified the species of a bat infected with EBLV-2 in Surrey as Myotis daubentoni (Daubenton's bat).

Health is one of the most important contributors to animal welfare, productivity and profitability in pig production today. For the past 30 years, pig breeders have focused on genetic improvement of lean growth, feed efficiency, meat quality and reproduction. However, in recent years, selection objectives have been broadened to include livability, robustness and disease resistance. A DNA marker for selection of resistance to F18+ E. coli has been available for several years. This marker decreases mortality and improves growth on farms experiencing post-weaning scours and/or oedema disease. However, for most diseases affecting intensive production systems such as porcine reproductive and respiratory syndrome (PRRS), porcine circovirus type 2-associated diseases (PCVAD), Haemophilus parasuis, and swine influenza virus, resistance is a complex and polygenic trait. Selection for improved resistance to these diseases will be incremental and require use of multiple markers in complex breeding schemes. Novel technologies such as pig gene microarrays, single nucleotide polymorphism (SNP) panels and advanced bioinformatics are being used to identify new health candidate genes for these economically important diseases. Lagging behind, however, is availability of large DNAdatasets from pedigreed populations with accurately measured health phenotypes that are needed to identify associations between SNPs and health traits. Increased focus on datasets with health traits will be the key to finding useable discoveries with new genomics technologies. Currently, the industry uses dozens of SNP markers to increase the accuracy of selection for complex breeding objectives, including disease resistance. As the pig genome is sequenced and barriers to genotyping thousand of markers are eliminated, genomic selection for health traits will receive increasing attention from commercial breeders.

Resistance to infection takes place at many levels, and involves both non-specific and specific immune mechanisms. The chicken has a different repertoire of immune genes, molecules, cells and organs compared to mammals. To understand the role of any disease resistance gene(s), it is therefore important to understand these different repertoires, and the bird's response to a particular pathogen. Our studies focus on the innate immune response, as responses of macrophages from inbred lines of chickens, and heterophils from commercial birds, correlate with resistance or susceptibility to Salmonella infection with a variety of Salmonella serovars and infection models. To map disease resistance genes, we are using a combination of expression quantitative trait loci (eQTLs) from microarray studies, allied with whole genome SNP arrays (WGA) and a candidate gene approach. There are over 500 human genes with the Gene Ontology term "innate immunity". We have identified over 400 of these genes in the chicken genome, and are actively identifying informative SNPs in them. The segregation of 6000 WGA SNPs across all of our inbred lines was also assessed, which should yield approximately 900 informative SNPs for a cross between any two lines. The initial focus of these studies is on mapping resistance genes in our inbred lines, but the studies will be extended to commercial flocks.

A major challenge for the commercial poultry production is controlling enteric disease-causing pathogens in the absence of prophylactic drugs. Although traditional genetic approaches have contributed to enhanced efficiency of poultry production and increased the ability of the industry to provide safe, high quality, and low cost meat products to consumers, economic losses due to enteric diseases remains a significant problem. Therefore, there is a need to develop alternative control strategies against poultry enteric pathogens of economic importance. Recent advances in molecular genetics and functional genomics are now allowing for rapid progress in understanding the molecular mechanisms of disease resistance against major infectious agents of poultry. It is anticipated that identifying the nature of host-pathogen interactions will facilitate the development of novel vaccines and therapeutics. In this paper, recent progress in identifying genes that influence resistance to avian coccidiosis, the most economically important disease of poultry, will be discussed. This work provides an excellent example of how the integration of new molecular genetic and functional genomics tools increases our knowledge of the mechanism of genetic resistance to complex diseases.