Experiments in the quality control of water samples are being conducted in the Public Health Laboratory Service and the water industry in the United Kingdom. The number of distributions which have been made is 7 and 92 laboratories are now participating. The methods used for preparing and distributing samples are described. Some participating laboratories use the multiple tube method and some use membrane filtration to assess the presence of coliforms and Escherichia coli. The results are, therefore, a mixture of estimated numbers and direct colony counts.

A comparison of five methods of cleaning Formica surfaces contaminated with bacteria dried in milk has been carried out. A standardized procedure was developed, and impression plates were found to be at least as sensitive as a swab-rinse method for detecting bacteria on the surfaces. The most satisfactory results were obtained with one type of disposable alcohol-impregnated wipe and with a detergent/hypochlorite solution applied with paper. A reusable cloth impregnated with disinfectant initially performed well against all test organisms, but was less reliable against Staphylococcus aureus and Streptococcus faecalis after the cloth had been used and rinsed several times. The importance of introducing methods to reduce the high risk of cross–contamination presently associated with the use of wiping cloths in catering premises is stressed.

A seroepidemiological survey has shown a remarkable shift in the previously reported regular cyclic pattern of Mycoplasma pneumoniae epidemics which culminated every 4·5 years during the period 1958–74. The last of four regular epidemics occurred in 1972. It was followed by ‘premature’ epidemics in 1975 and 1977/8 which inaugurated a change from an epidemic to an endemic pattern of the infection in Denmark. Over the following 9 years (1978–86) there has been an irregular but significant decrease in the annual number of seropositive samples with the usual high incidence during winter seasons. This endemic period terminated in the fourth trimester of 1987 with the development of a new epidemic. The hypothesis is advanced that a sixfold increase of children in day care may have influenced the change from an epidemic to an endemic situation which after 9 years led to a new epidemic of M. pneumoniae infection.

A μ-capture enzyme-linked immunosorbent assay (ELISA) for detecting chlamydia-specific IgM was developed by use of the heat stable, lipopolysaccharide group-specific antigen and an alkaline phosphatase-labelled anti-chlamydia group-specific monoclonal antibody conjugate. The test was used to study the serological response in chlamydial respiratory tract infection among patients with acute respiratory tract symptoms in Cambridgeshire during the past 7 years. Results were compared with those of the complement fixation test (CFT) in routine use as well as those of a whole inclusion indirect immunofluorescence (WIF) test for IgM. Correlation between results of the μ-capture ELISA and those of the WIF test was 87·5%.

Because of recent reports of abortion in farmers' wives following infection with ovine strains of Chlamydia psittaci during pregnancy, the distribution of chlamydial antibodies was studied in rural populations in north-west England, where endemic chalamydial infection with abortion in common in sheep. Immunoperoxidase assays with C. treachomatis and ovine C. psittaci showed no significant differences in either the frequency or titres of antibodies between sheep farmers and other types of farmer or non-farming adults living in the same areas. The frequency and titers of antibodies in farmers' wives were no greater than in farmers, and were unrelated to their previous obstetric history or type of farming. Overall, 62/255 (24%) of this rural population had antibody detected by C. trachomatis antigen and only 30/255 (13%) detected by C.Psittaci antigen. The possible significance of these findings is discussed. This survey does not suggest that the risk of infection with C.psittaci is especially high in people working with sheep, but the complications following infection during pregnancy deserve the specific instructions that have been given to pregnant women to avoid exposure, especially during lambing, in farming and veterinary work.

Enzyme-linked immunosorbent assay (ELISA) tests were used to measure IgG antibody levels in 2638 New Zealand children who had been immunized with the triple vaccine DTP. The percentage of children immune to diphtheria decreased with age. The percentage of children immune to tetanus varied from 67.1 to 55.0%. The percentage of children with measurable antibody to pertussis increased with age. The mean percentages of children with measurable antibody or immunity to one or more DTP components were 34.2% (with 3 components), 34.4% (2 components), and 78.1% (1 component). It appears the immunization strategy for diphtheria and tetanus is satisfactory for herd immunity in New Zealand children. However, the current pertussis strategy may not be providing adequate immunity to 5-year-olds in this country.

Amongst 1267 healthy children 6 months to 4.5 years of age in Adelaide, the pneumococcal carriage rate from a single nasal swab sampling was 29% in the period 1980–1. Of 269 children, sampled monthly on five occasions, 91% carried a pneumococcus on one or more occasions: 55% carried a single type, 33% carried two types, 2% carried three types and 1% carried four types; 18% carried a pneumococcus on either 4 or 5 occasions. The commonest types encountered were types 6, 19 and 23 in that order, and these three types constituted 57% of the total: other common types(> 5% of the total) were types 14, 15 and 11, and the six commonest types constituted 77% of the total. Of these, types 6, 14, 19 and 23 commonly cause systemic disease in children; on the other hand types 11 and 15 cause disease infrequently. The number of strains showing antimicrobial drug resistance was low: on quantitative testing 0.7%of 291 isolates examined showed relative resistance to benzylpenicillin and 0.7% were resistant to tetracycline; 10.9% of 230 isolates examined showed resistance to co-trimoxazole; dual or multiple drug resistance was not detected, and all isolates tested were susceptible to chloramphenicol, erythromycin, lincomycin and rifampicin.

Two incidents of toxin-type food poisoning in N.E. Scotland associated with the consumption of red whelks (Neptunea antiqua) are described. Four patients developed symptoms within 1 h of consuming whole whelks. These included visual distrubances—double vision and difficulty in focusing-ingling of the fingers, prostration and in one subject nausea, vomiting, diarrhoea and ataxia. In all cases recovery was complete in 24 h. Using a newly developed analytical technique the concentration of the causative toxin, tetramine, in the salivary glands of the whelks consumed was estimated at 0.07%, equivalent to a content of 3.75mg/100g of the shellfish.

Faecal excretion of enteropathogens was studied in newborns in their first week of life. Rotavirus was investigated in 225 neonates, of whom 107 belonged to the low socio-economic stratum (SES) and 118 to the high SES. Half of each group were delivered by caesarean section. Rotavirus was detected in 10 infants (4.4%). Eight of them had been in the same ward and excreted the same viral electrophoretype. Enteropathogenic bacteria were isolated from 8 out of 57 (14–0%) newborns. Positive cultures were equally distributed by SES and route of delivery. Giardia lamblia was the only parasite detected, in one infant (2–6%) of the high SES. None of the children developed symptoms. Faecal excretion of enteropathogens ended spontaneously within a week in all cases. It is suggested that the lack of symptomatology and the spontaneous termination of the faecal excretion are related to immaturity of the small intestinal mucosa, that does not allow the completion of the steps that must take place during a successful infectious event.

Two live attenuated measles vaccines developed in baby calf kidney cells, a similar vaccine produced in chick embryo chorioallantoic cells and five vaccines prepared from human diploid cells (HDC) have been studied by subcutaneous injection in groups of susceptible and immune children in three field trials. The results indicated that the vaccine developed in chick embryo cells which caused mild clinical reactions, had induced a lower seroprotection rate in susceptible children and only a low rise in hemagglutination-inhibition (HI) antibody titre in previously immunized children. The serological responses induced by vaccines developed in HDC or in calf kidney cells were satisfactory in both susceptible and immune children. The superiority of HDC grown measles vaccine for revaccination is discussed.

Adenovirus DNA was isolated directly from virus-containing stools and digested with restriction endonucleases. The resulting fragments were separated by polyacrylamide gel electrophoresis (PAGE) and visualized by silver staining. This enabled us to assign most of the viruses detected to subgenus, serotype and, sometimes, unique strains. Although less sensitive than electron microscopy, the method allowed more information about the infecting virus to be obtained and no cultivation was necessary. Comparison with culture also allowed dual infections to be recognized.

A 2-year survey of faecal adenoviruses in Newcastle upon Tyne showed that type 41 (strain 41a) was the predominant type and strain 41p was not recorded. Heterogeneity in strain 41a was also noted as found elsewhere. Adenovirus type 40 was common prior to 1985 but was absent during the last 2 years.

The potential for hantaviral transmission among wild Norway rats by wounding associated with aggressive interactions was evaluated using a prospective sero-epidemiological study coupled with a mark-release-recapture survey. There was a significant association between an animal's serological status and the presence of wounds. Longitudinal studies of marked and released animals showed sero-conversion between captures was associated with wounding between captures more often (33%) than expected by chance, while unwounded animals seroconverted less often (8%) than expected. Typically, less than a 5% difference was found when comparing the incidence of seroconversion with the predicted rate based on wounding and seroprevalence. Infection was highly associated with the onset of sexual maturity and aggression but decoupled from rat age and the length of environmental exposure. Seroconversions occurred at times most associated with aggressive encounters and least associated with amicable behaviours that could lead to aerosol transmission.

Measles antibody titres were established in three groups of infants: children of vaccinated mothers, children of unvaccinated mothers and neonates born after different gestational periods.

Reactions so far reported after the use of oil emulsion (OE) foot-and-mouth disease (FMD) vaccines in pigs have been infrequent and quick to resolve themselves. Although tentatively ascribed to anaphylaxis, these reactions have received little attention and their mechanism of causation has not been established conclusively.

Epidem. Inf. 100 (1988), 175

T. J. Humphrey, G. C. Mead and B. Rowe

Poultry meat as a source of human salmonellosis in England and Wales

Epidemiological overview

line 22: ‘PTs 43a,’ should read ‘PTs 49a,’

line 24: ‘PTs 43,’ should read ‘PTs 49,’