A quantitative method for testing serum diphtheria antitoxin levels was set up using a diphtheria antitoxin radioimmunoassay (RIA). The results of this RIA correlated well with the Schick test in 554 subjects and with intradermal neutralization tests in guinea-pigs in a small group of subjects. The RIA was suitable for use on blood collected by fingerprick on to a disc of standard chromatography paper. These discs could be stored at room temperature for at least 1 month. If storage for more than 6 months was required –20 °C was found to be better. Experience with this RIA in a total of 2349 subjects indicated that it is more accurate, rapid and less costly than Schick testing. The RIA should prove to be the preferred method for testing diphtheria immunity in population surveys.

The presence of genetic resistance to myxomatosis in a sample of wild rabbits from one area in England was reported in 1977. Rabbits from three other areas in Great Britain have been tested subsequently, and all cases showed similar resistance to a moderately virulent strain of myxoma virus. Rabbits from one area also showed a significant degree of resistance to a fully virulent strain of virus.

It is concluded that genetic resistance to myxomatosis is widespread in wild rabbit populations in Britain. The implications of the results are discussed in relation to the co-evolution of the disease and its host.

An outbreak of tuberculosis caused by Mycobacterium avium type 2 is described which resulted in the total condemnation of 26 carcasses and partial condemnation of tissues and organs of a further 200 animals. Circumstantial evidence is presented that hens running in the farmyard were the source of the infection.

Examinations of the carcasses and organs of the diseased pigs suggested that the accepted pathogenesis of the disease is incorrect and a new hypothesis is presented. The problems for the meat inspector in differentiating tuberculosis from ‘milk-spot liver’ are discussed and recommendations made.

The findings of the study are discussed in the light of ‘The Meat Inspection Regulations 1963’ and it is recommended that where tuberculosis is suspected there is no longer any necessity to split the carcasses. The public health implications of this study are discussed.

In a population of approximately 300000 there were 150 illnesses attributable to chlamydial infection from January 1975 to June 1983 and nearly all were presumed due to Chlamydia psittaci. Diagnosis was based on the complementfixation (CF) test, the disadvantages of which are discussed, especially anamnestic responses.

There were 73 cases of pneumonia, 37 febrile respiratory infections, 35 miscellaneous conditions and five asymptomatic seropositive contacts.

The annual number of cases was lowest in 1976 (3) and increased to a maximum in 1980 (28) followed by a sustained high level. No seasonal variation was observed.

A presumptive bird source was present in only 17% and detailed consideration of cases in one rural practice suggests that the infection may possibly be more endemic than zoonotic.

Experimental infection of the vagina of TO and CBA mice with Mycoplasma pulmonis was enchanced greatly by progesterone treatment. Almost all treated animals became infected, whereas only two-thirds of the untreated TO mice and less than half of the untreated CBA mice did so. Almost 1000-fold more organisms were recovered from treated than from untreated mice and the duration of infection was more than doubled. The enhanced infection in the hormone-treated animals was accompanied by a more severe vaginal polymorphonuclear leucocyte response which reached a maximum two weeks after inoculation of M. pulmonis. In the to mice the eventual decline in cellular response coincided with the gradual disappearance of the mycoplasmal infection. The implications of these findings for genital infections of other animal species are discussed.

Three hundred volunteers were divided into two age groups, 14–30 years and 31–60 years. Each participant was immunized intramuscularly with a subunit, whole virus or adsorbed whole virus vaccine, containing A/Bangkok/I/79 (H3N2), A/Brazil/ 11/78 (H1N1)and B/Singapore/222/79 influenza virus. Serum haemagglutination-inhibition (HI) antibody response, protection, and reactogenicity were studied after one and two doses of the vaccines. Primary immunization induced much higher percentages of HI antibody titres ≥ 100 against all three vaccine viruses and much higher geometric mean titres (GMT) in volunteers with pre-immunization titres ≥ 18 as compared to those with pre-immunization titres < 18. Secondary immunization did not result in an increase of GMTs or antibody titres ≥ 100 in volunteers with pre-immunization titres < 18. On the whole, the response to the subunit vaccine was similar to that to the other two vaccines. To influenza B/Singapore/222/79 virus the response was lowest after administration of the whole virus vaccine in the age group 31–60 years. Over 50% of the HI titres ≥ 100 found after immunization in the different vaccine and age groups were still present after one year. Serologically established infections during the winter months following immunization amounted to 15% in the subunit vaccine group, 6% in the whole virus vaccine group, and 10% in the adsorbed whole virus vaccine group. Local and systemic reactions to all three vaccines were mild in nature. Local reactions after primary immunization were much less frequent following administration of the subunit vaccine as compared to the other two vaccines, especially in the younger age group. In comparison to primary immunization, after booster immunization the incidence of local reactions was higher for the subunit vaccine and lower for the adsorbed whole virus vaccine. In the age group 14–30 years the incidence of local reactions after primary as well as booster immunization was much greater in females than in males, especially when the adsorbed whole virus vaccine was used.

This paper presents three different methods of estimating the number and age distribution of individuals susceptible to pertussis in England and Wales. The first approach is an extrapolation from data in the prevaccine era, the second is based upon theoretical consideration of the transmission dynamics of pertussis, and the third is a detailed cohort analysis of available notification and vaccination data. Each of these analyses suggests that the total number of people susceptible to pertussis infection in England and Wales has remained at 3–4 million for the past 40 years, despite the increase and changes in numbers vaccinated. The effect of vaccination has been to reduce the incidence of infection and disease, but not to reduce the number of susceptibles. These findings, which are consistent with ‘mass action theory’, could be tested by an appropriately designed seroepidemiological survey.

Rubella vaccination histories were taken from 333 young women working in the head office of a retail organization: 29% said they had had vaccine and 47% said they had not. The remainder did not know. Forty-six per cent of those ≤ 25 years old (who should have been offered vaccine at school), and 6% of those > 25 years old, said they had been vaccinated. When screened for immunity to rubella by radial haemolysis (RH) 3% had a low level of antibody (< 15 i.u./ml) and 11% had no antibody. After immunization with Cendevax the specific rubella IgM response was measured by an IgM antibody capture radioimmunassay (MACRIA). It was only detectable in the group without RH antibody, and was present in 26/31 of them. The Ig M response to Cendevax was strongest in specimens taken 20–39 days after immunization, but in 10 out of 11 cases tested was still present at around 71 days. The specific Ig M responses to Cendevax were very similar to those in women given Almevax in an earlier study, when measured in parallel tests.

Taking both vaccines together, specific Ig M was present in 35 out of 36 vaccinees without pre-existing antibody tested between 40 and 77 days post-immunization. Detection of specific IgM by MACRIA would therefore be an effective means of determining susceptibility retrospectively in rubella vaccinees found to be pregnant.

Two solid selective media, xylose deoxycholate citrate agar (XDCA) and bile salts brilliant green agar (BBG) and an enrichment broth–alkaline peptone water, were evaluated for the isolation of Aeromonas hydrophila and Plesiomonas shigelloides. Alkaline peptone water and XDCA are useful for recovery of Aeromonas but not Plesiomonas, whereas BBG is satisfactory for both organisms.

The duration of immunity following a single administration of rinderpest cell culture vaccine, of 90 or more monolayer passages, was studied in E. African zebu (Boran) and grade (cross-bred European) cattle. All animals were kept for periods of 6–11 years in rinderpest-free environments; groups of them (in all 23 Borans and 10 grades) were then challenged by parenteral or intranasal inoculation of virulent virus or by contact exposure to reacting cattle. Nasal excretion of virus was studied daily over the 10-to 14-day period following challenge, and simultaneous attempts were made to detect viraemia. The neutralizing antibody response was followed at 6-month intervals over the whole post-vaccination period and then daily for 10 days and at longer intervals to 3 weeks after challenge.

All 33 animals which were exposed by various routes failed to react clinically and a rinderpest viraemia was never detected. No transmission of virus from the vaccinates to susceptible in-contact controls occurred within 14 or more days, from the 20 animals which could be so tested. Clearcut serological responses to challenge were seen in six cattle (four Borans and two grades) which were challenged after 7 years or more; these reactions were all delayed to the 9th or 10th days, i.e. they were not typically ‘anamnestic’.

These results are discussed in relation to mass vaccination campaigns for the control of rinderpest and from the comparative viewpoint of measles vaccination in man.

The prevalence of scropositivity to Legionella spp. was studied in inmates and staff members of two geriatric hospitals (Rahel and Sinai); attendants to a geriatric Day Club; and 26 old people with entirely independent households. The sera were examined by indirect immunofluorescence with antigens of six Legionella species (L. pneumophila, L. longbeachae, L. micdadei, L. gormanii, L. dumoffii and L. bozemanii). A titre of ≥ 256 to at least one antigen was obtained in 30·5% of patients and 35·7% of staff members from Rahel; 12·1% of patients and 17·2% of staff members from Sinai; 9·1% of attendants to the Day Club; and none of 26 old people with their own households. All the positive patients from Rahel reacted with L. pneumophila, but only four of seven of the positive patients from Sinai did so; none of the seropositive subjects from the Day Club reacted with this agent.

The results indicate intramural exposure to agents of legionellosis, at least for the Rahel Hospital.

The majority (85%) of shigella isolated in 1980 and 1981 in Korea were Shigella flexneri, the others were Sh. sonnei (14%) with only a small number of Sh. dysenteriae. Only 14 of the 459 strains of shigella isolated were susceptible to all 12 drugs tested, and 445 were resistant to three or more drugs. Strains multiply resistant to the six drugs, chloramphenicol (Cm), tetracycline (Tc), streptomycin (Sm), sulfisomidine (Su), ampicillin (Ap) and trimethoprim (Tp) were most frequently encountered, followed by those resistant to Cm, Tc, Sm, Su and Tp. The complete patterns of resistance to drugs except nalidixic acid and rifampin in approximately 73% of drug-resistant strains were co-transferred to Escherichia coli by conjugation, indicating that the resistance was R plasmid-mediated. Randomly selected R plasmids conferring various patterns of resistance markers were tested for the incompatibility groups, and almost all of them were classified into Inc FII. Two of three R plasmids conferring resistance to Cm, Tc, Sm and Su were classified into Inc B and one to Inc FII. Two R types with resistance markers of Cm, Tc, Sm and Ap were not classified with our standard plasmids used.

A case of Corynebacterium ulcerans sore throat in a community that drank raw milk from its own farm led to the discovery of another symptomless human infection. Eight cows in the herd were found to be infected and the intermittent pattern of excretion was demonstrated in another cow followed through its lactation. Further evidence of milk infected by C. ulcerans was found by examining all raw milk samples submitted to the laboratory. Two other human cases were diagnosed in Devon during the period of this investigation.

The application of Preston enrichment broth to isolation of ‘thermophilic’ campylobacters from water has been investigated. Enrichment substantially increased the yield of such organisms. The optimum timing for subculturing the broth was after 48 h incubation. Despite the addition of aerotolerant supplement to the broth the number and variety of isolates was greater when the broth was incubated microaerically than when it was incubated in air.

Pregnancies were identified in which maternal IgG antibodies against rubella virus were not detectable by single radial haemolysis. Twenty paired maternal/cord sera were then tested for haemagglutination-inhibiting (HI) activity against rubella virus without kaolin pretreatment of the sera. In the absence of specific antibody, the HI activity observed could thus be ascribed to the effect of non-specific inhibitors. The HI activity in maternal sera was significantly (P < 0·001) higher than that in cord sera. The 20 pairs of sera were similarly tested against a bunyavirus, an alphavirus and a flavivirus, both with and without kaolin pretreatment. The results showed non-specific inhibitors were found to higher titre in maternal sera, with the difference being statistically significant (P < 0·001) for each of the three viruses.

Growth and survival of four Campylobacter jejuni strains in yolk, in liquid whole egg and in white during aerobic storage at 37, 20 and 4 °C was followed. In 48 h at 37 °C the coll counts of C. jejuni increased by about 3 log10 units in yolk and 1·60–3·3510 log units in liquid whole egg. The growth of C. jejuni was slightly better in yolk than in liquid whole egg. At 20 °C during 48 h the cell counts decreased by about 0·5–1·5 log10 units in yolk and in liquid whole egg. At 4 °C the decrease in cell counts after 21 days ranged from 1 to 2 log10 units, except for one strain, KH 3, which could not be detected after 14 days storage in yolk. In liquid whole egg the cell counts of this strain also decreased considerably during storage.

In white the number of inoculated C. jejuni cells decreased rapidly. The killing effect of white was shown to be temperature-dependent; at 37 and 20 °C no positive samples were detected after 24 h and at 4 °C no positive samples were found after 48 h.

A general practice population of around 3900, under continuous clinical and laboratory surveillance, experienced 20 outbreaks of influenza between March 1960 and March 1976. Four epidemics were caused by subtype H2N2 type A viruses, seven by subtype H3N2 type A viruses and nine outbreaks by type B viruses. The age of every person proved virologically to have influenza is related to the age structure of the community and to the phase of the epidemic in which the virus-positive specimens were collected. Children 0–15 years old suffered a higher incidence rate than adults 16–90±. Pre-school children 0–4 suffered the highest rate of infection by viruses of both influenza A subtypes, whereas older schoolchildren 10–15 suffered the highest rate of type B infections. Despite these high incidence rates neither pre-school nor schoolchildren appear to have been the major disseminators of any of these influenza viruses in the community.

Adults of all ages suffered a high rate of infection even into extreme old age, and the indiscriminate age distribution among adults was sustained in the successive epidemics. Such age-patterns are not those caused by a highly infectious immunizing virus surviving by means of direct transmissions from the sick, whose prompt development of the disease continues endless chains of transmissions. An alternative epidemic mechanism – whereby the virus does not spread from the sick but becomes latent in them, reactivating seasonally so that they later infect their companions – would produce age patterns similar to those recorded here for influenza patients. The suggested mechanism is illustrated by a simple conceptual model and the influenzal age patterns are discussed in relation to the recycling of influenza A subtypes.

Intracerebral inoculation was more effective than intraperitoneal, intravenous or subcutaneous inoculation as a means of producing lethal infections with Fusobacterium necrophorum in mice. Strains varied in virulence but, of five examined, two had LD50 values as low as ca. 8000 and 14000 viable organisms. Profuse bacterial multiplication in the brain was demonstrated. Intravenous vaccination with a single large dose of heat-killed whole culture or washed bacterial cells failed to protect against intracerebral challenge.

Intracerebral injection of other fusobacteria (F. nucleatum, F. varium and F. necrogenes) and of 22 strains belonging to 10 Bacteroides spp. was without apparent effect on mice, except for a slight transient illness in some animals given B. fragilis. This organism (five strains) differed from the other Bacteroides spp. tested, which included eight strains belonging to the fragilis group, in being eliminated more slowly from the mouse brain – a point that may be relevant to the special pathogenicity of B. fragilis in endogenous infections in man. There was no evidence that B. fragilis multiplied in the brain or that intravenous vaccination with a large dose of heat-killed homologous culture affected the rate at which it was eliminated.

A total of 289 non-O1 Vibrio cholerae (NVC) strains and 20 rough V. cholerae (RVC) strains isolated in an endemic area were tested for antibiotic resistance and for transferable R-plasmids. Twenty three per cent of NVC and 40% of the RVC isolates were found to be resistant to one or more drugs. Eight NVC and four RVC strains possessed multiple drug resistance, varying from four to eight drugs. The common spectrum found in NVC isolates were chloramphenicol and streptomycin (CS) or chloramphenicol, streptomycin, tetracycline and ampicillin (CSTA). Resistance to sulphamethoxazole (Su) and to trimethoprim (Tm) was encountered infrequently. In RVC isolates in addition CSTASuTm determinants, resistance markers to aminoglycosides kanamycin, gentamicin and neomycin were also found. Eighteen of the 27 V. cholerae strains with two or more resistance determinants transferred them en bloc to Escherichia coli K12. The level of resistance in the recipient strain was equal to or greater than that of the donor vibrio strains. Most of the strains possessing solitary resistance markers were unable to transfer them. βlactamase production could be demonstrated in 92·8% of the ampicillin resistant strains. None of the strains was resistant to nalidixic acid or furazolidone. The results emphasize the importance of antimicrobic susceptibility determination of V. cholerae isolates, regardless of the serotypes, before commencing chemotherapy.

The distribution of specific phage types of Salmonella typhimurium within the Australian chicken industry has been studied and documented on an Australia wide and state-by-state basis. A total of 1799 strains of S. typhimurium were obtained from Australia-wide sources and phage typing categorized 1498 of these isolates into 30 distinct phage types, with the remaining 301 strains untypable. Five phage types, 6, 26, 31, 135 and 179, accounted for 76% of the total strains typed, with the remaining 24% of strains being distributed among 25 phage types.

Of the major phage types, type 31 was restricted to Victoria and Western Australia, but the other types were distributed throughout Australia.

In addition, the antibiotic resistance pattern of the various phage types was determined and only five of the 30 phage types showed appreciable levels of resistance.