Alasdair J. C. Cook

Intestinal carriage of verocytotoxigenic Escherichia coli O157, Salmonella, thermophilic Campylobacter and Yersinia enterocolitica, in cattle, sheep and pigs at slaughter in Great Britain during 2003.

An abattoir survey was undertaken to determine the prevalence of foodborne zoonotic organisms colonizing cattle, sheep and pigs at slaughter in Great Britain. The study ran for 12 months from January 2003, involved 93 abattoirs and collected 7703 intestinal samples. The design was similar to two previous abattoir surveys undertaken in 1999-2000 allowing comparisons. Samples were examined for VTEC O157, Salmonella, thermophilic Campylobacter and Yersinia enterocolitica. The prevalence of VTEC O157 faecal carriage was 4.7% in cattle, 0.7% in sheep and 0.3% in pigs. A significant decrease in sheep was detected from the previous survey (1.7%). Salmonella carriage was 1.4% in cattle, a significant increase from the previous survey of 0.2%. In sheep, faecal carriage was 1.1% a significant increase from the previous survey (0.1%). In pigs, carriage was 23.4%, consistent with the previous study. Thermophilic Campylobacter spp. were isolated from 54.6% of cattle, 43.8% of sheep and 69.3% of pigs. Y. enterocolitica was isolated from 4.5% of cattle, 8.0% of sheep and 10.2% of pigs.

Avian influenza surveillance in wild birds in the European Union in 2006

Background  Infections of wild birds with highly pathogenic avian influenza (AI) subtype H5N1 virus were reported for the first time in the European Union in 2006.

Evaluation of animal and public health surveillance systems: a systematic review

Disease surveillance programmes ought to be evaluated regularly to ensure they provide valuable information in an efficient manner. Evaluation of human and animal health surveillance programmes around the world is currently not standardized and therefore inconsistent. The aim of this systematic review was to review surveillance system attributes and the methods used for their assessment, together with the strengths and weaknesses of existing frameworks for evaluating surveillance in animal health, public health and allied disciplines. Information from 99 articles describing the evaluation of 101 surveillance systems was examined. A wide range of approaches for assessing 23 different system attributes was identified although most evaluations addressed only one or two attributes and comprehensive evaluations were uncommon. Surveillance objectives were often not stated in the articles reviewed and so the reasons for choosing certain attributes for assessment were not always apparent. This has the potential to introduce misleading results in surveillance evaluation. Due to the wide range of system attributes that may be assessed, methods should be explored which collapse these down into a small number of grouped characteristics by focusing on the relationships between attributes and their links to the objectives of the surveillance system and the evaluation. A generic and comprehensive evaluation framework could then be developed consisting of a limited number of common attributes together with several sets of secondary attributes which could be selected depending on the disease or range of diseases under surveillance and the purpose of the surveillance. Economic evaluation should be an integral part of the surveillance evaluation process. This would provide a significant benefit to decision-makers who often need to make choices based on limited or diminishing resources.

A modelling approach to estimate the sensitivity of pooled faecal samples for isolation of Salmonella in pigs

The objective of this study was to develop and parametrize a mathematical model of the sensitivity of pooled sampling of faeces to detect Salmonella infection in pigs. A mathematical model was developed to represent the effect of pooling on the probability of Salmonella isolation. Parameters for the model were estimated using data obtained by collecting 50 faecal samples from each of two pig farms. Each sample was tested for Salmonella at individual sample weights of 0.1, 0.5, 1, 10 and 25 g and pools of 5, 10 and 20 samples were created from the individual samples. The highest test sensitivity for individual samples was found at 10 g (90% sensitivity), with the 25 g test sensitivity equal to 83%. For samples of less than 10 g, sensitivity was found to reduce with sample weight. Incubation for 48 h was found to produce a more sensitive test than incubation for 24 h. Model results found increasing sensitivity with more samples in the pool, with the pools of 5, 10 and 20 being more sensitive than individual sampling, and the pools of 20 being the most sensitive of those considered.

Factors related to the carriage of Verocytotoxigenic E. coli, Salmonella, thermophilic Campylobacter and Yersinia enterocolitica in cattle, sheep and pigs at slaughter.

A 12-month abattoir study was undertaken from January 2003. We collected 7492 intestinal samples from cattle, sheep and pigs at slaughter. Rectal samples were taken from cattle and sheep and caecal samples from pigs. They were examined for verocytotoxigenic E. coli (VTEC) O157, Salmonella, thermophilic Campylobacter and Yersinia enterocolitica. Data were collected on the animal from which the sample came and this information was analysed to look at potential risk factors for carriage of these organisms. Logistic regression models were run where an adequate number of positive results were available. This revealed that VTEC O157 carriage in cattle was associated with the summer period and that age was a protective factor. Salmonella carriage in pigs was associated with lairage times >12 h, the North East and not feeding when there was no bedding available. In cattle, carriage was associated with the summer period, the Eastern region of GB and dairy animals. In sheep a spring seasonal effect was seen, which coincided with the lambing period. The carriage of thermophilic Campylobacter in cattle was associated with single-species abattoirs, with age a protective factor. In sheep, winter was a risk period with lairage management influential. For pigs, lairage times of <12 h were found to be associated with carriage. A seasonal trend for carriage of Y. enterocolitica in all species was demonstrated with the period December-May a risk. For cattle, age was also a risk factor; for sheep feeding in the lairage and for pigs being held overnight were risk factors.

Flock Health Indicators and Campylobacter spp. in Commercial Housed Broilers Reared in Great Britain

ABSTRACT This study investigated the relationship between flock health and Campylobacter infection of housed commercial broilers in Great Britain. Thirty ceca were collected at slaughter from batches of broilers from 789 flocks, at either full or partial depopulation, between December 2003 and March 2006 and examined individually for Campylobacter by direct plating onto selective media. Management and health data were collected from each flock and included information on mortality or culling during rearing, the number of birds rejected for infectious or noninfectious causes at slaughter, the proportion of birds with digital dermatitis (also termed hock burn), and other general characteristics of the flock. Campylobacter spp. were isolated from 280 (35%) flocks. The relationship between bird health and welfare and Campylobacter status of flocks was assessed using random-effects logistic regression models, adjusting for region, month, year, and rearing regime. Campylobacter-positive batches of ceca were associated with higher levels of rejection due to infection (odds ratio [OR], 1.5; 95% confidence interval [CI95%], 0.98 to 2.30) and digital dermatitis (OR, 2.08; CI95%, 1.20 to 3.61). Furthermore, higher levels of these conditions were also associated with the highest-level category of within-flock Campylobacter prevalence (70 to 100%). These results could indicate that improving health and welfare may also reduce Campylobacter in broilers.

Temporal patterns and risk factors for Escherichia coli O157 and Campylobacter spp. in young cattle.

Escherichia coli O157 and Campylobacter jejuni and Campylobacter coli are zoonotic pathogens originating from farm animals. Cattle are the main reservoir for E. coli O157 and also contribute to human cases of campylobacteriosis through contaminated milk, direct contact, and environmental contamination. Thirty groups of young cattle on 30 farms were observed for 7 months and sampled on 4 to 6 separate occasions for E. coli O157 and C. jejuni/coli to characterize shedding patterns and identify risk factors. The within herd prevalence of E. coli O157 per sampling occasion ranged from 0 to 60% (mean = 24%) and average Campylobacter spp. within herd prevalence was 47% ranging from 0 to 100%. The prevalence of E. coli O157-positive herds declined with a linear trend throughout the study from 100 to 38% (OR: 0.5, P < 0.01), whereas time in the study was not significantly associated with Campylobacter prevalence (P = 0.13). Larger herds were more likely to be positive with either or both agents, whereas the number of suckler calves on the farm reduced the risk of both organisms (OR: 0.4/0.6, P < 0.01). Poultry on the premises reduced the risk of E. coli O157, but was not associated with Campylobacter. Emptying and cleaning the water troughs more often than once monthly reduced the risk of detecting Campylobacter and cattle sourced by private water supplies were more likely to be Campylobacter positive. No drinking water management practices were associated with E. coli O157. The risk of detecting both organisms were almost five times higher when the cattle were housed indoors (OR: 4.9, P = 0.03).

Surveillance for Avian Influenza in Wild Birds in the European Union in 2007

Abstract Surveillance of wild birds for avian influenza viruses has been compulsory in the European Union (EU) since 2005, primarily as a means of detecting H5N1 highly pathogenic avian influenza (HPAI) virus and of monitoring the circulation of low pathogenicity avian influenza (LPAI) virus H5 and H7 strains. In 2007, 79,392 wild birds were tested throughout the EU. H5N1 HPAI was detected in 329 birds from four Member States (MS); affected birds were almost entirely of the orders Podicipediformes (grebes) and Anseriformes (waterfowl) during the summer months. LPAI was detected in 1485 wild birds among 21 MS. A total of 1250 birds were positive for influenza A but were not discriminated any further; LPAI H5 was detected in 105 birds, exclusively of the order Anseriformes. LPAI H7 was detected in seven birds. LPAI of other subtypes was found in 123 birds. Epidemiologic evidence and phylogenetic analysis of H5N1 viruses indicate that H5N1 did not appear to persist in the EU from 2006 but was reintroduced, probably from the Middle East.

A mathematical model for the transmission of Salmonella Typhimurium within a grower-finisher pig herd in Great Britain.

In a study of pigs slaughtered at British abattoirs, approximately 23% carried Salmonella in their cecal (large intestine) contents. The most frequent serotype was Salmonella Typhimurium (STM), which was the second most common cause of human salmonellosis in Great Britain. A pig industry-monitoring program was developed to reduce Salmonella infection on British farms. The control of STM infection on the farm requires an understanding of STM transmission dynamics within the herd, and a mathematical model has been developed for an infected grower-finisher farm. The model estimates the probability of a random pig being infected with STM. There are three broad categories of STM infection in pigs: pigs that are infected but unable to transmit the infection (latent); pigs that are infectious, i.e., able to transmit the infection (shedders); and pigs that have stopped shedding but harbor STM in their internal organs (carriers). The model estimates that 21.0% (5th and 95th percentiles, 0.05 to 77.5%) of slaughter-age pigs on an infected farm are likely to be shedding STM. Although this range is wide, it is biologically plausible. Sensitivity analysis of the total number of infected pigs revealed that the most significant input parameters are the probability of effective contact between a specific infectious and susceptible pig and the duration of shedding. The model predicted that 11.5% of pigs would be shedding STM at slaughter age. This value is close to the estimate obtained from a British abattoir survey that 11. 1% of pigs carried STM in their ceca, indicating that the model has reasonable validity.

Risk factors for transmission of foot-and-mouth disease during an outbreak in southern England in 2007

During an outbreak of foot-and-mouth disease (FMD) in southern England in 2007, a case-control study was conducted to identify risk factors for infection and to investigate the relative impact of risk factors on transmission between the infected farms. Seven of the eight case farms in the outbreak and 22 control farms participated. Data were collected via questionnaires and subjected to comparative statistical analysis. Case farms were further classified as primary or secondary according to the likely source of infection during the study. On primary case farms, it was plausible that infection had been introduced directly from the original source. On secondary case farms, FMD infection was more likely to have originated from another infected premises. Calving occurred more frequently on case farms than on control farms during the risk period, and the two primary case farms had a larger proportion of youngstock than the other farms. Secondary case farms (n=5) had a higher composite environmental risk score and a lower biosecurity score than control farms.