Risk factors for hide contamination of Scottish cattle at slaughter with Escherichia coli O157.

In the slaughter processing of cattle, contaminated hides have been identified as one of the major sources of Escherichia coli O157 carcase contamination. Logistic regression analysis was applied to data collected in a large scale study in Scotland involving 222 cattle forming 34 groups sent for slaughter from 30 farms to 10 slaughterhouses. Aspects of individual animal characteristics, farm management practices and slaughterhouse features were examined to identify potential risk factors for hide contamination at harvest. Two models were developed, the first in which slaughterhouse was modelled as a fixed effect, and a second model where slaughterhouse and farm groups were modelled as random effects. In the first model, there was a significantly increased risk of a carcase testing positive for E. coli O157 on the hide if either the hide of the carcase immediately before or after it on the line was contaminated (OR 3.6; 95% CI: 1.4-9.9). If both adjacent carcases had contaminated hides, the odds ratio for the study carcase having a contaminated hide rose to 11.5 (95% CI: 4.4-32.5). If animals were held in lairage, receiving hay as feed appeared to have a protective effect on hide contamination. Transportation to the slaughterhouse by haulier, as opposed to transport by the farmer, was associated with a 5.4 increase in the odds of E. coli O157 contamination. The use of a crush in the lairage, often employed when reading ear tags, was also found to significantly increase the odds of hide contamination with E. coli O157. In the second model, the inclusion of slaughterhouse and farm group as random effects resulted in two of the previously identified factors being associated with hide contamination. If at least one of the adjacent carcases on the line had a contaminated hide, the associated odds ratio was 6.6 (95% CI: 2.8-15.9), which rose to 22.7 (95% CI: 9.3-55.5) if both adjacent hides were contaminated. Receiving hay in lairage was found to be important to the model, although not significant in itself (OR 0.005; 95% CI: 1.2e(-6)-20.7). These results suggest that modifiable risk factors for hide contamination exist. However, in order best to reduce the prevalence of hide contamination at slaughter, individual slaughterhouse risk assessment and intervention strategies are appropriate.

Spatial and temporal epidemiology of sporadic human cases of Escherichia coli O157 in Scotland, 1996-1999.

In Scotland, between 1995 and 2000 there were between 4 and 10 cases of illness per 100000 population per year identified as being caused by Escherichia coli O157, whereas in England and Wales there were between 1 and 2 cases per 100000 population per year. Within Scotland there is significant regional variation. A cluster of high rate areas was identified in the Northeast of Scotland and a cluster of low rate areas in central-west Scotland. Temporal trends follow a seasonal pattern whilst spatial effects appeared to be distant rather than local. The best-fit model identified a significant spatial trend with case rate increasing from West to East, and from South to North. No statistically significant spatial interaction term was found. In the models fitted, the cattle population density, the human population density, and the number of cattle per person were variously significant. The findings suggest that rural/urban exposures are important in sporadic infections.

Survey of zoonoses recorded in Scotland between 1993 and 2002.

All the human and animal laboratory reports of zoonoses sent to Health Protection Scotland between 1993 and 2002 were identified. There were 24,946 reports from veterinary laboratories, and 94,718 (20 per cent) of the 468,214 reports from medical laboratories were considered to be zoonotic. The most common reports of zoonoses from people were Campylobacter, Salmonella, Cryptosporidium and Giardia species and Escherichia coli o157. The most common reports of zoonoses from animals were Salmonella, Cryptosporidium, Chlamydia and Campylobacter species and Mycobacterium avium paratuberculosis. For all the zoonoses in people, the National Health Service Board areas Borders, Dumfries and Galloway, Forth Valley, Grampian, Lanarkshire and Lothian had a higher than expected standardised incidence rate of infection, whereas Ayrshire and Arran, Fife, Greater Glasgow, Shetland, Tayside and Western Isles had a lower than expected rate. The organisms and diseases considered to be new and emerging were Rhodococcus species, Cyclospora cayetanensis, Leishmania species, Pneumocystis carinii (jiroveci) and bovine spongiform encephalopathy/variant Creutzfeldt-Jakob disease.

Frozen storage of Escherichia coli O157 in buffered peptone water and its detection on bovine carcasses.

The adaptation of a standard Escherichia coli O157 isolation method involving immunomagnetic separation and a period of frozen storage was investigated. A series of experiments was designed to test the recovery of a bovine strain of E. coli O157 from buffered peptone water after a period of frozen storage at -80 degrees C. The effects of the addition of glycerol at 5 and 10%, freezing time, the number of freeze-thaw cycles, the method of freezing and the method of thawing, the inclusion of a resuscitation-and-incubation step, and the sensitivity of the isolation method were investigated. The most effective method of storing frozen samples for 6 months and recovering strains of E. coli O157 after storage was found to involve 6 h of incubation of sample material in buffered peptone water at 37 degrees C before frozen storage at -80 degrees C with 10% glycerol, a rapid thaw after frozen storage, and resuscitation at 27 degrees C for 1 h and incubation at 37 degrees C for 1 h to allow freeze-injured and stressed bacteria to recover with a period of growth prior to immunomagnetic separation isolation. There was no significant decrease in log counts of a bovine strain E. coli O157 over 6 months of frozen storage in buffered peptone water with 10% glycerol. With this method, it was possible to isolate E. coli O157 from naturally infected bovine carcasses after a period of frozen storage.

Epidemiology of Salmonella enterica serovars enteritidis and Typhimurium in animals and people in Scotland between 1990 and 2001.

Two serovars of salmonella which are currently of particular importance in both human and animal infections are Salmonella enterica serovars Enteritidis phage type 4 (PT4) and Typhimurium definitive type 104 (DT104). This paper describes the trends in the relationships between the levels of infection of people and a range of farm animal species with these two serovars and explores some of the reasons behind them. In 1996, there was a peak of 520 reports of S Typhimurium DT104 infection in people in Scotland, but the number has decreased every year since, to 96 in 2001. In cattle the incidence of S Typhimurium DT104 also peaked in 1996, with 138 incidents, and it has similarly decreased every year to 2001 when there were 10 reported incidents. Similar declines have been observed in its incidence in sheep and pigs. In people the number of reports of S Enteritidis PT4 peaked in 1997 at 1684 and then declined to 457 in 2001. In chickens, the number of reports of S Enteritidis PT4 peaked in 1998 at 34 incidents, but no incidents were reported in the following three years.

Cryptosporidium in farmed animals: the detection of a novel isolate in sheep.

We describe the discovery of polymorphisms in the Cryptosporidium oocyst wall protein (COWP) gene conferring a novel restriction fragment length polymorphism (RFLP) pattern in 26/60 (43%) isolates from a flock of sheep sampled following a waterborne outbreak of human cryptosporidiosis. The sheep isolates showed identical PCR-RFLP patterns to each other by COWP genotyping but different from those of most currently recognised genotypes, including the major Cryptosporidium parvum genotypes 1 and 2. Sequence analysis of the 550bp amplicon from the COWP gene was compared with a DNA coding region employed in previous studies and showed the novel isolate to differ from other Cryptosporidium species and C. parvum isolates by 7-21%. The sheep-derived isolates were compared at this and further three Cryptosporidium gene loci with isolates from other farmed animals. The loci employed were one in the thrombospondin related adhesive protein (TRAP-C2) gene and two in the 70kDa heat shock protein (HSP70) gene (CPHSP1 and 2). Other animal samples tested in our laboratory were from clinically ill animals and all contained C. parvum genotype 2. The sheep in which the novel isolate was identified were healthy and showed no symptoms of cryptosporidiosis, and the novel sheep isolate could represent a non-pathogenic strain. Our studies suggest that a previously undetected Cryptosporidium sub-type may exist in sheep populations, reflecting the increasingly recognised diversity within the parasite genus.

Risk factors for sporadic cases of Escherichia coli O157 infection: the importance of contact with animal excreta.

To determine environmental risk factors for sporadic E. coli O157 infection in Scotland we undertook a prospective, matched case-control study between 1 October 1996 and 31 March 1999. One hundred and eighty-three cases and 545 matched controls were recruited. Contact with animal faeces (OR = 3.65; 95% CI 1.81, 7.34: P < 0.0005) and likely contact with animal faeces (OR = 4.8; 95% CI 2.42, 9.48; P < 0.0005) emerged as strong risk factors for infection. Certain exposures (mainly food-related) were inversely associated with infection i.e. were statistically protective. Most striking was the consumption of bottled water (OR = 0.28; 95% CI 0.15, 0.52; P < 0.0005). Transmission of E. coli O157 does not occur simply through contaminated food. Members of the public need to be aware of the potential for acquiring E. coli O157 through contamination of the environment with animal faeces so that they may take measures to mitigate their risk.

A foodborne outbreak of Vero cytotoxin-producing Escherichia coli O157:H-phage type 8 in hospital.

This paper describes the epidemiological and microbiological aspects of the largest outbreak of Vero cytotoxin-producing Escherichia coli O157 (VTEC O157) infection in a hospital setting in which the route of transmission was foodborne. The outbreak, which was caused by a relatively uncommon phage type of VTEC O157, occurred in four geriatric continuing care wards in May 1997. The total number of people found to be excreting the organism was 37, of whom 16 were inpatients and 11 were staff. Twelve people displayed enteric symptoms. In addition, all but two of 10 cases identified in the local community were thought to be associated with the outbreak. An epidemiological investigation amongst the hospital patients revealed a statistically significant association between VTEC O157 infection and attendance at a concert party on the continuing care wards on 17 May 1997 (relative risk = 3.22;P= 0.006). There was an even stronger relationship between consumption of home-baked cream-filled cakes brought to that party and evidence of infection (relative risk = 19.35;P= 0.00002). Further investigations in the local community, coupled with microbiological evidence, supported the epidemiological finding that homemade cream cakes brought into the hospital were the vehicle of infection for the outbreak. There was no secondary spread within the hospital. The outbreak serves as a reminder of the hazard posed by foodstuffs brought into a hospital from outside.

Salmonella typhimurium DT104 infection in people and animals in Scotland: a collaborative epidemiological study 1993-96.

This paper describes a comparative analysis of human and farm animal salmonellosis in Scotland between 1993 and 1996, with particular reference to Salmonella typhimurium definitive type 104 (DT104). Cattle were the main reservoir, accounting for 73.1 per cent of incidents involving all salmonellae and 69.5 per cent of those involving S typhimurium DT104. The annual rates of incidence in people and cattle were recorded in each Health Board area. Dumfries and Galloway had the highest rate of incidence in cattle for all salmonellae (19.0 per 100,000) but people were affected uniformly across mainland Scotland. However, the rate of incidence of S typhimurium DT104 was highest in Dumfries and Galloway for both people (10.1 per 100,000) and cattle (13.0 per 100,000). In Dumfries and Galloway, Wigtownshire had the highest rates for all salmonellae and for S typhimurium DT104 in both people and cattle. In Dumfries and Galloway, 37.8 per cent of the adult cases of S typhimurium DT104 in people were among those known to have had regular contact with animals, and children under six years of age accounted for 36.3 per cent of the human infections in this region.

Weak substrate binding to transport proteins studied by NMR.

The weak binding of sugar substrates fails to induce any quantifiable physical changes in the L-fucose-H+ symport protein, FucP, from Escherichia coli, and this protein lacks any strongly binding ligands for competitive binding assays. Access to substrate binding behavior is however possible using NMR methods which rely on substrate immobiliza-tion for detection. Cross-polarization from proton to carbon spins could detect the portion of 13C-labeled substrate associated with 0.2 micromol of the functional transport system overexpressed in the native membranes. The detected substrate was shown to be in the FucP binding site because its signal was diminished by the unlabeled substrates L-fucose and L-galactose but was unaffected by a three- to fivefold molar excess of the non-transportable stereoisomer D-fucose. FucP appeared to bind both anomers of its substrates equally well. An NMR method, designed to measure the rate of substrate exchange, could show that substrate exchanged slowly with the carrier center (>10(-1) s), although its dynamics are not necessarily coupled strongly to this site within the protein. Relaxation measurements support this view that fluctuations in the interaction with substrate would be confined to the binding site in this transport system.

Epidemiological aspects of outbreaks of food-borne salmonellosis in Scotland between 1980 and 1989.

Between 1980 and 1989, 2,212 outbreaks of food-borne infection were reported in Scotland. Of 2,073 episodes for which a causative agent was established, 1,732 (84%) were caused by salmonellae. An average of 980 people were affected each year, while the average number of individuals infected per general outbreak was 16.8. The infected foods were consumed outside Scotland in 25% of the outbreaks. In 75% of 1,107 episodes where the location was specified, the implicated foods were consumed in the home; hotels and restaurants accounted for 15%. Specific food items were identified in 603 (35%) of the 1,732 outbreaks; poultry meat was responsible for 332 (55%) and milk 49 (8%), while eggs accounted for 23 (4%) outbreaks.

Human hydatid disease leading to hospital admission in Scotland 1968-1989.

An attempt to estimate the impact of hydatid disease upon human health in Scotland between 1968-89 was made by examining Scottish hospital discharge statistics, and death statistics. Because hydatid disease may be asymptomatic, and coding errors are more likely to occur with rare diseases, an assessment was made as to the likelihood of hydatid disease having been responsible for hospital admission. Over the 22 year period a total of 110 hospitalised individuals with a diagnosis of hydatid disease were identified; no deaths were recorded. Inspection of the other diagnoses and operations recorded for each case suggested that hydatid disease was responsible for hospital admission in only 65 individuals (59%). One further individual, who had been admitted to a hospital outside Scotland, was identified from a Western Isles register of cases receiving surgery for hydatid disease. This register was used to assess the completeness of the Scottish hospital statistics; 10/11 Western Isles cases were identified using hospital statistics. Local case registers seem essential for accurate estimates of incidence and prevalence, and to evaluate the need for control programmes. The median age of the 66 individuals considered to have been admitted to hospital because of hydatid disease was 49 years (range 4-85); 38 (58%) were male. A total of 36 cases were managed surgically (55%), and there was a tendency for the use of surgery to increase over the 22 year period. The Health Boards with the highest incidence of clinically apparent infection leading to hospital admission were: Western Isles, Shetland and Highland; with 2.53, 1.23, and 0.21 cases per 100,000 population per year respectively.