Rapid evolution of virulence and drug resistance in the emerging zoonotic pathogen Streptococcus suis

Background: Streptococcus suis is a zoonotic pathogen that infects pigs and can occasionally cause serious infections in humans. S. suis infections occur sporadically in human Europe and North America, but a recent major outbreak has been described in China with high levels of mortality. The mechanisms of S. suis pathogenesis in humans and pigs are poorly understood. Methodology/Principal Findings: The sequencing of whole genomes of S. suis isolates provides opportunities to investigate the genetic basis of infection. Here we describe whole genome sequences of three S. suis strains from the same lineage: one from European pigs, and two from human cases from China and Vietnam. Comparative genomic analysis was used to investigate the variability of these strains. S. suis is phylogenetically distinct from other Streptococcus species for which genome sequences are currently available. Accordingly, ,40% of the ,2 Mb genome is unique in comparison to other Streptococcus species. Finer genomic comparisons within the species showed a high level of sequence conservation; virtually all of the genome is common to the S. suis strains. The only exceptions are three ,90 kb regions, present in the two isolates from humans, composed of integrative conjugative elements and transposons. Carried in these regions are coding sequences associated with drug resistance. In addition, small-scale sequence variation has generated pseudogenes in putative virulence and colonization factors. Conclusions/Significance: The genomic inventories of genetically related S. suis strains, isolated from distinct hosts and diseases, exhibit high levels of conservation. However, the genomes provide evidence that horizontal gene transfer has contributed to the evolution of drug resistance

Simulated hazards of loosing infection-free status in a Dutch BHV1 model

A compulsory eradication programme for bovine herpesvirus 1 (BHV1) was implemented in the Netherlands in 1998. At the start of the programme, about 25% of the dairy herds were certified BHV1-free. Simulation models have played an important role in the decision-making process associated with BHV1 eradication. Our objective in this study was to improve understanding of model behaviour (as part of internal validation) regarding loss by herds of the BHV1-free certificate. Using a Cox proportional hazards model, the association between farm characteristics and the risk of certificate loss during simulation was quantified. The overall fraction of herds experiencing certificate loss amongst initially certified during simulation was 3.0% in 6.5 years. Factors that increased risk for earlier certificate loss in the final multivariable Cox model were higher 'yearly number of cattle purchased', 'farm density within a 1 km radius' and 'cattle density within a 1 km radius'. Qualitative behaviour of risk factors we found agreed with observations in field studies. (C) 2003 Elsevier B.V. All rights reserved

Evaluating Animal Health Investments Évaluer les investissements dans la santé animale Investitionen in Tiergesundheit evaluieren.

Economic evaluation of livestock diseases can either estimate their impact in terms of disease losses and treatment costs or it can examine the value of investments in coordinated disease control or eradication programmes. The latter evaluations can be ex ante and ex post and are useful in determining future strategy and learning lessons from past programmes. The paper discusses how to approach economic evaluations of livestock disease and the applications to different disease situations in Europe. An ex ante evaluation of options to control foot-and-mouth disease in the Netherlands is presented to examine the use of vaccination and culling methods with results that are dependent on the context of the disease epidemic. An evaluation of French animal health delivery systems is presented that emphasises the need to understand the economic, social and legal relationships between people caring for animals. Finally an ex ante analysis of blue tongue in the Netherlands is presented that demonstrates different levels of cost effectiveness of vaccination and other control measures. Economic analysis improves our understanding of the trade-offs we need to make when prioritising diseases to be controlled, and on what methods to employ in controlling the prioritised disease. © 2012 The Agricultural Economics Society and the European Association of Agricultural Economists

Quantification of Eimeria acervulina in faeces of broilers: comparison of McMaster oocyst counts from 24 hour faecal collections and single droppings to real-time PCR from cloacal swabs

Coccidiosis is an economically important disease in chickens, caused by infection with Eimeria species parasites. Diagnosis of coccidiosis is frequently based on oocyst enumeration in pooled faecal samples or litter. In studies on infection dynamics and for monitoring in the field, samples from individual chickens may be more appropriate as these support the determination of infection status of individual birds and more accurately reflect oocyst output at time of sampling. Faecal samples from individual birds can be collected, but the counting procedure limits the number of samples that can be processed and unequivocal microscopic differentiation between Eimeria species is very difficult. A test that overcomes these drawbacks would improve efficiency and quality of the diagnosis. The aim of this study was to compare two methods for Eimeria oocyst quantification in samples from individual birds. A real-time PCR that quantifies oocysts in cloacal swabs (qPCR) and oocyst counts in single droppings were compared to the standard procedure of oocyst counts in bulked 24 h faeces. Faecal samples were collected daily from 30 broiler chickens, inoculated with different doses of Eimeria acervulina. The three techniques produced comparable oocyst counts for all inoculation doses. Single dropping counts are applicable for small sample sizes and when a single Eimeria species is used. For larger sample sizes qPCR is preferable as it can be carried out on samples that have been frozen for storage. Furthermore, qPCR can identify and quantify different Eimeria species, which makes it a valuable diagnostic tool for field or experimental wor