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R L Salmon

Publications and source records attributed to R L Salmon.

At least 37 records · Page 2Linked to original sources
PubMed1998

Risk factors for and prevention of sporadic infections with vero cytotoxin (shiga toxin) producing Escherichia coli O157.

BACKGROUND: Recent outbreaks of vero cytotoxin (shiga toxin) producing Escherichia coli O157 (VTEC O157) infection have stimulated debate on food safety. However, 90% of cases in England and Wales are sporadic. We report a case-control study of sporadic VTEC O157 infection. METHODS: We compared 85 sporadic cases of VTEC O157 infection, identified through population surveillance, with 142 controls, randomly selected from general practitioners' lists. We matched cases and controls for age, sex, and family doctor's practice. Exposures to foods, water, animals, farms, and environmental factors were recorded. We visited the premises concerned when cases had eaten beefburgers or cooked sliced meats from caterers or had had contact with a farm. FINDINGS: Consumption of a beefburger from a catering premises other than from a fast-food chain A (a national chain) and consumption of cold cooked sliced meat (eg, in a salad or sandwich) from caterers, but not butchers, was associated with VTEC O157 infection (odds ratios 4.63 [95% CI 1.33-30.14] and 3.36 [1.04-12.74], respectively). Policies for ensuring thorough cooking of burgers by one national fast-food chain differed from the other catering premises we visited. There was evidence of person-to-person spread and transmission of VTEC O157 infection from animals. INTERPRETATION: Local inspection of catering establishments that serve cooked meats together with public education to prevent spread on farms and in houses would reduce the burden of VTEC O157 infection by about 10% for each risk factor.

Agriculture↗
PubMed1998

Low rates of ehrlichiosis and Lyme borreliosis in English farmworkers.

To determine the occupational significance of tick-borne zoonoses we sought serological evidence of Lyme borreliosis, human monocytic ehrlichiosis (HME) and human granulocytic ehrlichiosis (HGE) in a representative sample of farmworkers. Although around 20% reported ticks on their domestic and companion animals, few (< 2% per year) reported being bitten by ticks. Seroprevalence of Lyme borreliosis (0.2%), HME (0.2%) and HGE (1.5%) was low. Those seropositive for HGE were no more likely to report tick bites nor more likely to report ticks on their animals. This study provides evidence that farmworkers in England are exposed to tick-borne zoonoses but that they are uncommon. Since the severity of these diseases is linked to delays in diagnosis and treatment, clinicians should be aware of these diagnoses in patients from rural communities, with or without a self-reported history of tick bite.

Adult↗
PubMed1998

Escherichia coli O157 serology: false-positive ELISA results caused by human antibodies binding to bovine serum albumin.

An analysis of farm workers and rural dwellers for serum antibodies to the lipopolysaccharide (LPS) of Escherichia coli O157 detected sera with antibodies binding to bovine serum albumin (BSA) by ELISA. These antibodies were not specific for BSA when examined by immunoblotting, and the ELISA values were reduced to a background level when plates were blocked with normal rabbit serum.

Animals↗
PubMed1998

Uptake of measles containing vaccines in the measles, mumps, and rubella second dose catch-up programme in Wales.

A two dose schedule for measles, mumps, and rubella (MMR) vaccination was introduced in England and Wales on 1 October 1996 in order to prevent the accumulation of susceptible individuals and thus prevent future epidemics. A routine second dose of MMR vaccine is now offered with the diphtheria, tetanus and polio (DTPol) preschool booster. In addition a second dose of MMR is being offered to all children born since 1 January 1990 without documented histories of two doses of measles containing vaccine in a catch up programme due to end in March 1998. Progress in the catch up programme in Wales was assessed by examining uptake of all possible combinations of measles containing vaccines in four birth cohorts by 1 May 1997. Of 126,550 children born between January 1990 and March 1993 (aged 4 years, 1 month to 7 years, 3 months) and living in Wales on 1 May 1997, 63,855 (50.5%) had received two doses of measles containing vaccine and 120,668 (95.4%) had received at least one dose, but 5882 children (4.6%) had no record of having received any measles containing vaccine. Uptake of the preschool DTPol booster in the same cohort was 87.2%. Uptake of two measles containing vaccines varied between health authority (range: 35.4-58.3%) and between birth cohorts (range: 40.0-81.8%). Few (18.4%) previously unimmunised children had attended for the MMR catch-up dose. Successful elimination of measles may depend on targeting this group in order to improve coverage. Although this analysis was carried out during the catch-up programme, these data suggest that the programme may not reach the children who most need to be immunised.

Child↗
PubMed1998

Surveillance of influenza in Wales: interpreting sentinel general practice rates using contemporaneous laboratory data. Opportunities and limitations.

OBJECTIVES: To evaluate the opportunities and limitations of using laboratory data to enhance sentinel general practice surveillance of influenza. DESIGN: Descriptive study of active sentinel surveillance of clinically diagnosed influenza in general practice and passive total population surveillance of laboratory reports of influenza A, influenza B, Mycoplasma pneumoniae, and respiratory syncitial virus infections. SETTING: Wales. SUBJECTS: Total sentinel practices population (currently 228,130); population of Wales (2,913,000, 1994 mid-year estimate). MAIN OUTCOME MEASURES: Simplicity, flexibility, acceptability, sensitivity, predictive value positive, representativeness, and timeliness of a surveillance system. Rate of influenza and other respiratory infections. RESULTS: Sentinel general practice surveillance of influenza in Wales is simple, flexible, acceptable, timely, representative, and relatively sensitive. Current laboratory surveillance is complex and less timely than sentinel practice surveillance but is complete and has a relatively high positive predictive value. For the period January 1993 to September 1996, peaks in rates of influenza reported by sentinel practices during winters 1993/94 and 1995/96 were temporally associated with increased rates of laboratory confirmed influenza A and respiratory syncitial virus, whereas the peak in 1994/95 was associated with increased rates of laboratory confirmed influenza B, M pneumoniae, and respiratory syncitial virus. CONCLUSIONS: Timely laboratory data can add value to influenza data already obtained from sentinel general practice surveillance. However continuous audit is essential to resolve the possible limitations of either surveillance system.

Evaluation Studies as Topic↗
PubMed1996

Risk factors for Neisseria meningitidis carriage in a school during a community outbreak of meningococcal infection.

As part of the management of an outbreak of meningococcal infection, 119 school contacts of an index case were swabbed for nasopharyngeal carriage. In a cohort study, risk factors for Neisseria meningitidis carriage were ascertained by means of a questionnaire, completed by 114 (96%) of those swabbed. Twenty five (21%) cultures were identified as "neisseria positive'; of which there were 18 (15%) Neisseria meningitidis isolates, 2 (2%) Neisseria lactamica isolates and 5 (4%) showed contaminants only. Two (2%) carriers were identified as harbouring the implicated outbreak strain. Single variable analysis identified six statistically significant risk factors for meningococcal carriage; increasing age, female sex, manual social class, personal smoking, regular attendance at a discotheque and rhinorrhoea. Multivariate analysis, using logistic regression modelling, found that of these six variables only age, sex and social class remained statistically significant when the other factors were controlled for. Nevertheless the role of smoking, social events and respiratory/viral infections in nasopharyngeal carriage, and other plausible mechanisms whereby age, sex and social class might exert their effect, could usefully be investigated further.

Adolescent↗
PubMed1996

Marine waters contaminated with domestic sewage: nonenteric illnesses associated with bather exposure in the United Kingdom.

OBJECTIVES: This study identified possible dose-response relationships among bathers exposed to marine waters contaminated with domestic sewage and subsequent risk of nonenteric illness. METHODS: Four intervention follow-up studies were conducted within the United Kingdom. Healthy volunteers (n = 1273) were randomized into bather and nonbather groups. Intensive water-quality monitoring was used to assign five bacteriological indices of water quality to individual bathers. Illnesses studied were acute febrile respiratory illness, and eye, ear, and skin ailments. RESULTS: Fecal streptococci exposure was predictive of acute febrile respiratory illness, while fecal coliform exposure was predictive of ear ailments. Estimated thresholds of effect occurred at bather exposures above 60 fecal streptococci and 100 fecal coliform per 100 ml of water, respectively. Although no relationship was found between eye ailments and indicator organism exposure, compared with nonbathers, bathers were at higher risk for eye ailments. CONCLUSIONS: Nonenteric illness can be transmitted via recreational contact with marine waters contaminated with sewage. These results argue against the use of a single indicator to establish water quality standards.

Adult↗
PubMed1995

The risk of acquiring Q fever on farms: a seroepidemiological study.

OBJECTIVES: To determine the occupational risk of Q fever. DESIGN: Cohort study. SETTING: Community: five English local authority districts. SUBJECTS AND METHODS: Prevalence and incidence of immunoglobulin G (IgG) specific antibody to Coxiella burnetii phase II antigen was measured in a representative (study) cohort of farm workers in the United Kingdom, and detailed exposure data were collected. Also seroprevalence of Q fever in a (control) cohort of police and emergency service personnel was measured. RESULTS: Prevalence was significantly (P < 0.01) higher in the study cohort (105/385 v 43/395). During the first 12 month period after enrollment no seroconversions were found (upper 95% confidence limit: 1318/100,000/year). During the second 12 month period after enrollment two seroconversions were found, equalling an incidence of 813/100,000/year (95% confidence interval (95% CI) 98-2937/100,000/year). No association was found between seroprevalence and age. In the study cohort, extent of total contact with farm animals seemed more important than exposure to any specific animal: full time employees were more than four times more likely to be antibody positive than part time employees (P < 0.05). Exposure to cattle, but not sheep, goats, cats, raw milk, and hay (all reported sources of Q fever) was associated with being positive to Coxiella burnetii IgG by univariate analysis but this association was not independent of total farm animal contact. CONCLUSIONS: The risk of Q fever on livestock farms is related to contact with the farm environment rather than any specific animal exposure. The absence of an increasing prevalence with age suggests that exposure may occur as clusters in space and time (outbreaks).

Adolescent↗
PubMed1994

Predicting likelihood of gastroenteritis from sea bathing: results from randomised exposure.

The health effects of bathing in coastal waters is an area of scientific controversy. We conducted the first ever randomised "trial" of an environmental exposure to measure the health effects of this activity. The trial was spread over four summers in four UK resorts and 1216 adults took part. Detailed interviews were used to collect data on potential confounding factors and intensive water quality monitoring was used to provide more precise indices of exposure. 548 people were randomised to bathing, and the exposure included total immersion of the head. Crude rates of gastroenteritis were significantly higher in the exposed group (14.8 per 100) than the unexposed group (9.7 per 100; p = 0.01). Linear trend and multiple logistic regression techniques were used to establish relations between gastroenteritis and microbiological water quality. Of a range of microbiological indicators assayed only faecal streptococci concentration, measured at chest depth, showed a significant dose-response relation with gastroenteritis. Adverse health effects were identified when faecal streptococci concentrations exceeded 32 per 100 mL. This relation was independent of non-water-related predictors of gastroenteritis. We do not suggest that faecal streptococci caused the excess of gastrointestinal symptoms in sea bathers but these microorganisms do seem to be a better indicator of water quality than the traditional coliform counts. Bathing water standards should be revised with these findings in mind.

Adult↗
PubMed1994

Successful control of a school based measles outbreak by immunization.

In an outbreak of measles in North Wales centred on a secondary school in 1991, 74 cases occurred over a period of 51 days. Before the outbreak started, 27% pupils did not have a history of measles or immunization and were considered susceptible. Active case finding and identification and vaccination of susceptible contacts commenced after the fourth generation of cases and further reduced the pool of susceptible schoolchildren from 17%, at the onset of the vaccination campaign, to 8%. A fifth generation of cases did not occur. Delays in diagnosis (mean 2.8 days) and notification (mean 6.1 days) hampered control. There was no evidence of primary vaccine failure (observed vaccine efficacy 97%). Sixty-nine (93%) cases were considered preventable. Reasons for the apparent success of the intervention are discussed.

Adolescent↗
PubMed1994

Vero cytotoxin-producing Escherichia coli O157 in beefburgers linked to an outbreak of diarrhoea, haemorrhagic colitis and haemolytic uraemic syndrome in Britain.

Vero cytotoxin (VT)-producing Escherichia coli O157 (O157 VTEC) were isolated from a raw beefburger obtained from a retail source linked to a small community outbreak of O157 VTEC infection in Wales. Strains from the meat and from seven of eight patients belonged to phage type 49 and were indistinguishable by their VT-type, plasmid content and hybridization with DNA of a VT-encoding phage from an O157 VTEC strain. This first report of the isolation of O157 VTEC from a beef product in Britain supports the view that there is a bovine reservoir for this organism.

Adolescent↗
PubMed1994

Zoonotic illness--determining risks and measuring effects: association between current animal exposure and a history of illness in a well characterised rural population in the UK.

STUDY OBJECTIVES: To recruit a representative sample of farmworkers, accurately quantify the range and extent of their animal exposures, and measure the associated risks of illness. DESIGN: Inception cohort. SETTING: The study was undertaken among farmworkers living in five local authority areas in the catchment of Hereford and Preston Public Health Laboratories, England. PARTICIPANTS: A quota sample of 404 people on 255 agricultural holdings took part. The holdings were selected at random from the Ministry of Agriculture, Fisheries and Food register. Altogether 58% of eligible subjects approached agreed to participate. MEASUREMENTS AND MAIN RESULTS: The sample had the same sex distribution as the 1991 census for those giving their occupation as agriculture. The mean age was significantly (p < 0.01) higher (44.6 years v 42.2 years) than that of those giving their occupation as agriculture, forestry or fishing in the census, although the modal range (45-59 years) was the same. At enrollment interviews, subjects individually reported contact with up to nine animal species (mode 4) out of 26 reported in all. Based on the numbers contacted and the frequency and intimacy of contact, scores on a ranked ordinal scale from 0-5 were constructed for each species and frequencies for each score were plotted. Subjects also reported past operations and serious illness. A history of pneumonia was significantly (p < 0.05) associated with a pigeon loft on the farm (relative risk (RR) 7.3) and attending farrowing pigs (RR 6.6), and one of leptospirosis with a rat problem on the farm (RR 28.1). Cattle contact was associated with a significantly lower likelihood (protective) of glandular fever (RR 0.19) and rheumatic or scarlet fever (RR 0.12). These effects were significantly related to rankings of the extent of exposure. CONCLUSIONS: It is possible to recruit a representative sample of farmworkers and measure their animal exposures in great detail. Among these exposures, associations with plausible risk factors for pneumonia and leptospirosis and apparently protective factors for glandular fever, scarlet fever, and rheumatic fever have been demonstrated, which further show a relationship between the extent of exposure and response. These findings can be tested further by examining the relationship of exposures to serological evidence of illness or by further prospective follow up of this and similarly well characterised cohorts, or both.

Adult↗
PubMed1993

What are the complications of influenza and can they be prevented? Experience from the 1989 epidemic of H3N2 influenza A in general practice.

OBJECTIVES: In an epidemic: to measure the incidence and risk of complications of influenza; to determine the effect of pre-existing disease on complications; to estimate vaccine uptake and efficacy. DESIGN: Case-control study. SETTING: Primary care: two group practices. SUBJECTS: 342 of the 395 cases of clinically diagnosed influenza reported to the general practice surveillance of infectious diseases scheme of the Public Health Laboratory Service during the 1989 epidemic, and 342 age and sex matched controls. INTERVENTIONS: Examination of records. MAIN OUTCOME MEASURES: Documented recognised complications; hospital admission; previous vaccination. RESULTS: Of 15 recognised complications, bronchitis was the commonest (rate 190.1/1000 cases) and significantly commoner in cases (summary odds ratio 9.7) after adjusting for higher consultation rates (mean 6.1 per annum v 4.2 among controls; p < 0.0001). No deaths were recorded. The risk of bronchitis complicating influenza was higher in patients with pre-existing illnesses regarded as an indication for vaccination (odds ratio 3.3; p < 0.0001). Observed vaccination efficacy in those with pre-existing illnesses and in elderly subjects was high (63% and 77% respectively) but uptake was low (4.5% and 6.1% respectively). CONCLUSIONS: Bronchitis complicates about one fifth of all cases of influenza presenting to general practitioners. Patients with pre-existing illnesses regarded as an indication for vaccination are particularly at risk. Vaccine uptake is extremely low, precluding an unequivocal demonstration of a protective effect.

Adolescent↗
PubMed1993

The problems of tracing a geographically widespread outbreak of salmonellosis from a commonly eaten food: Salmonella typhimurium DT193 in north west England and north Wales in 1991.

Geographically widespread outbreaks involving commonly isolated organisms and where the vehicles of infection are commonly eaten foodstuffs pose particular difficulties at a technical and organizational level. An outbreak of Salmonella typhimurium infection, affecting 39 people, spread over a wide area in North West England and North Wales in April and May 1991, was detected thanks to the practice of sending specimens to the national reference laboratory where phage typing and characterizing of antibiotic resistance patterns enabled the identification of a cluster of distinctive isolates (S. typhimurium DT193 resistant to sulphonamides, trimethoprim and furazolidone). An investigation, involving twenty environmental health departments in addition to health authorities and the Public Health Laboratory Service, showed an association between the illness and eating loose sliced cooked ham (P = 0.004). Detailed tracing of the chain of supply of the ham showed this to be particularly cooked ham originating from a single small local producer (P = 0.00003). Further investigation of that producer revealed that a batch of ham distributed on one day in early April was undercooked due to a malfunction in cooking equipment.

Adolescent↗