In a group of 32 adult volunteers given subunit influenza virus vaccine containing 250 international units (i.u.) of A/Victoria/3/75, 250 i.u. of A/Scotland/ 840/74 and 300 i.u. of B/Hong Kong/8/73, there were substantial increases in the geometric mean homologous haemagglutination-inhibiting (HI) antibody titres. There was also substantial boosting of the antibodies to the earlier variants of the Hong Kong (H3N2) series and to a later variant of the Asian (H2N2) series. There was no boosting of antibodies to the A/FM/1/47 strain, a representative member of the H1N1 series, but two individuals showed substantial rises to A/PR/8/34 (H0N1).

There were increases in the HI titre of antibodies cross reactive with two recent isolations, A/Texas/1/77, and A/Victoria/35/77, but the majority of vaccinees failed to reach antibody titres likely to be protective against such strains.

The relative immunogenicity in mice of whole influenza virus, and virus split with different disrupting agents, was compared. Using the single radial immunodiffusion test to estimate the haemagglutinin antigen concentration in different virus preparations, it was found that, in general, split virus preparations induced substantially lower titres of HI antibody in mice than whole virus after one or two injections of the antigen.

Samonella johannesburg has been prevalent in Hong Kong since 1973 and most strains were resistant to a multiplicity of antibiotics. The susceptibility of S. johannesburg strains isolated in a 5-year period from 1973 to 1977 to eight antimicrobial drugs including ampicillin (A), streptomycin (S), tetracycline (T), chloramphenicol (C), Kanamycin (K), sulphadiazine (Su), trimethoprim (Tm) and gentamicin (G) was tested by the agar dilution method. The proportion of strains resistant to chloramphenicol and ampicillin increased steadily during the 5-year period while those resistant to tetracycline decreased dramatically. This change was associated with an alteration of predominant patterns of antibiotic resistance: strains with the resistance pattern A.S.T.C.K.Su predominated in years 1973, 1974 and 1975 while those with the resistance pattern A.S.C.K.Su predominated in years 1976 and 1977. Analysis of the resistance patterns of S. johannesburg strains isolated from the same cases showed that the resistance pattern A.S.C.K.Su was more stable, and changed less frequently to other patterns of resistance than strains with the resistance pattern A.S.T.C.K.Su. In donor salmonella strains with the A.S.T.C.K.Su resistance pattern, transmissible factorscarrying resistance to A.S.T.C.K.Su in to to, to A.S.T.C.Su, A.T.C.K.Su and to A or T alone were demonstrated. In donor salmonella strains with the A.S.C.K.Su resistance pattern, transmissible factors carrying resistance to A.S.C.K.Su in toto and to A.S.K.Su were detected. The significance of the carriage of such transmissible resistance factors by this Salmonella is briefly discussed.

Summary Surface waters in 14 selected sites were examined for the presence of salmonella using modified Moore's swabs. The sites included an upland impounding reservoir, 3 rivers and 10 streams within Lancashire and Cheshire, selected because of their accessibility to farm livestock. Salmonellas were isolated from 22 out of the 57 swabs examined representing 10 sites. The probable source of pollution was shown to be sewage or farm effluent and an examination of sites over a wider area may be expected to produce similar results.

The significance of these findings is discussed in relation to the epidemiology of salmonella infections and the possible disinfection of effluent discharges.

This paper presents the hypothesis that some cases of cholera might be due to effluent discharge from aircraft. The theoretical case is borne out by inspection of data on the physical conditions pertaining between high altitudes and ground level. A study of the distribution of isolated outbreaks and single cases of disease and their relation to major airline routes showed a reasonable correspondence. Sporadic outbreaks of cholera in Europe between 1970 and 1975 were found to lie within the flight paths of regular airline services from Calcutta, where cholera is endemic, to the Northern Hemisphere. Laboratory studies on the stability of Vibrio cholerae to conditions likely to be encountered in droplets falling from high altitude to the ground suggested that significant numbers of organisms might survive. It should be noted that in this study no account was taken of the effect of ultra-violet light on viability and it is known that at high altitudes the ultraviolet light component of solar radiation is much higher than at ground level. Results of experiments where small numbers of organisms were inoculated into relatively poor media showed that rapid growth ensued and that sufficient organisms were produced to give an infective dose of Vibrio cholerae in 1–10 ml/fluid. It could be concluded that human infection could easily occur by ingestion of fluids such as milk or soup which had some time earlier received a fortuitous but slight contamination from the air. Investigation of one disinfectant (chloramine T) showed that it reacted rapidly and in a complex manner with peptone. One effect of this reaction was the elimination of bactericidal activity and it seems likely that, as at present employed, chloramine T is of doubtful value in aeroplanehygiene. One important conclusion that arises from this work is that if cholera can be spread, even only occasionally, by effluent from aircraft then close investigation should be made of the possibility of other bacteria and viruses being spread in a similar way.

Between 1969 and 1972 three quality control studies were set up to investigate the variation in results that was occurring between and within laboratories performing routine tests for the diagnosis of rubella infection. No attempt was made to standardize the test in these studies, and a wide range in titres of sera was reported. The aims of the present studies were:

(i) to investigate in greater detail whether results were more reproducible between laboratories if test sera were compared with control sera of known potency and the results given in international units of activity, and

(ii) to ascertain whether results between laboratories would be more reproducible if a standard test procedure was used.

Eleven laboratories participated in testing 38 sera on three separate occasions by a prescribed standard technique and by that used routinely in each laboratory. Eight of the 38 sera consisted of four pairs of duplicate samples.

Analysis of results of the study showed that the reproducibility between laboratories was substantially improved when the test sera were compared with a control serum of known potency and when a standard test procedure was used.

Variation in results between laboratories was least when a control serum of low rather than high potency was used. Variation within laboratories can be reduced by increasing the number of times the control and test sera are tested.

Since the rubella antibody content of the British Standard anti-rubella serum is expressed in international units, the potency of the control and results of test sera should also be expressed in such units.

Ten laboratories collaborated in a study of minimum immune titre (MIT) of rubella haemagglutination-inhibiting (HI) antibody with one laboratory acting as a reference laboratory to provide a uniform basis for comparison of the HI results. The international unitage equivalent to the MIT used by the ten laboratories was found to vary from 24 to 98 units. Testing of the sera by immunofluorescence and by HI after flotation centrifugation indicated that residual non-specific inhibitors may interfere with HI antibody testing to an extent equivalent to 12–15 units. An acceptable MIT would therefore be equivalent to 24–48 units of rubella HI antibody. The single radial haemolysis (SRH) results on the sera indicate that this is a sensitive and specific test for rubella antibody.

Coxsackievirus B5 in the presence of fetal calf serum was exposed to six commonly used disinfectants for times of 10, 20 and 30 s. At the end of exposure times skim milk neutralized the disinfectant activity, with residual virus assayed by the plaque technique. The six disinfectants considered were Javex, sodium hydroxide, ethanol, Wescodyne, One Stroke Ves-Phene and Sonacide. Although 95% (v/v) ethanol was significantly more virucidal than dilutions of the other five disinfectants tested causing a 106 reduction in 20 s, it may not be practical to use in many instances. Next to 95% (v/v) ethanol, 1/75 (800 parts/b6) Javex, 0·25% (w7/v) sodium hydroxide and 1/200 Wescodyne were the most effective virucides. These disinfectants were equal in effectiveness causing a 105 reduction of coxsackievirus B5 in 30 s. Of these three disinfectants Javex is the most practical to use since sodium hydroxide is caustic and Wescodyne is selective in its virucidal action. Undiluted Sonacide was a less effective virucide causing a less than 10-fold reduction of coxsackievirus B5 in 30 s. A 1/50 dilution of One Stroke Ves-Phene was the least effective virucide tested since it did not significantly inactivate coxsackievirus B5 in 30 s.

Outbreaks of myxomatosis during the winter or spring have coincided with the establishment of the European rabbit flea in the Mallee region. The severity of these outbreaks has varied from causing complete suppression of the normal spring increase in rabbit numbers to being completely ineffective in a year in which late spring rains allowed rabbit breeding to extend into the early summer.

In 1973 and 1974 effective spring myxomatosis caused heavy mortality in kittens before they emerged from the warrens. The age of the population increased as the result of few young rabbits coming into the population and of the lessened stress on old rabbits in a low summer-autumn population. This effect was reversed in the late-breeding year, 1976, when flea numbers were apparently too low to maintain a spring outbreak and rabbit numbers increased rapidly.

In a study of the distribution of e-antigen and anti-e in subjects whose blood was positive for hepatitis B surface antigen (HBsAg), patients with acute hepatitis B who were tested during the incubation period were all e-antigen-positive but after the onset of illness e-antigen was detected in only 11%. Persistence, and in some instances reappearance of e-antigen in those who became long-term carriers of HBsAg was associated with high titres of HBsAg. There was a high incidence of e-antigen in those conditions in which cell-mediated immunity may be depressed, including Down's syndrome and chronic renal failure.

The majority of HBsAg carriers identified as sources of infection were e-antigen-positive. A positive reaction for e-antigen is evidently associated with a defective immune response to hepatitis B virus infection which permits continued replication of virus in liver cells accompanied by high titres of HBsAg, numerous Dane particles and detectable DNA polymerase in the blood with consequently a greater likelihood of transmitting infection.

Although it cannot be assumed that anti-e positive carriers of HBsAg are not infective, it may be necessary, in the assessment of passive or active immunization for the control of hepatitis B, to take into account the e-antigen/antibody status of possible sources of infection.

The virus growth in the pharyngeal area and the virus excretion in milk of susceptible and vaccinated dairy cows after intranasal instillation of foot-and-mouth disease (FMD) virus type O1 were examined. Ten vaccinated cows were purchased through a market. Of these, nine had delivered their first calf. The cows were inoculated 2–9 months after having received the last dose of vaccine. All vaccinated cows resisted the intranasal challenge. The virus multiplied in the pharyngeal area but, compared with two susceptible controls, to a limited extent. No clear relation was found between virus growth and the titre of circulating neutralizing antibody at the time of challenge.

Virus was first detected in milk samples of the susceptible cows when generalized FMD lesions had developed on day four; the excretion lasted for 3–4 days.

Up to 19 days after inoculation untreated milk of the vaccinated cows was examined for the presence of infectious FMD virus. Samples were inoculated onto cell cultures, fed to susceptible pigs and calves and injected intramuscularly and/or intradermolingually into susceptible steers. No infectious FMD virus could be detected, either in cell cultures or in susceptible animals. The animals did not develop neutralizing antibody against FMD virus and were subsequently shown to be fully susceptible to challenge. The results are discussed with particular reference to current problems regarding the export of milk products from countries where vaccination against FMD is practised to countries free of the disease.

Feeding tests were carried out in the laboratory to obtain basic data on the susceptibility of wild Norway rats to difenacoum. The results were used to derive a standard test procedure for the identification of difenacoum resistance in warfarin-susceptible and resistant rats. Details are given of tests on rats from suspected difenacoum-resistant infestations on farms.

Eleven fabrics selected to provide a representative range of yarns and weaves have been examined microscopically and subjected to a series of tests. The observations were directed towards assessing the potential ability of each fabric to resist penetration by particles, such as skin scales, which might carry micro-organisms. The number, size and shape of pores penetrating through the material were estimated and the penetration of test dusts assessed in several ways. While, generally, the relative merits of the fabrics are similar whatever test or measurement is considered there are a number of significant exceptions which reflect peculiarities of the test system or of a fabric. Comparison with the results of dispersal experiments with volunteers wearing garments made of the fabrics is made in a following paper.

The effectiveness of a representative range of fabrics in restricting dispersal through them of dry skin-borne bacteria has been examined. The fabrics were tested made up into trousers which were worn by volunteers during standardized exercise in a test chamber operated within a unidirectional flow clean-air room. Under these conditions, with careful attention to sealing at ankles and waist, it was possible to estimate penetration as low as 0·3%. Penetrations as low as 1% were observed with some synthetic fabrics. These had a relatively high surface resistivity and developed significant electrostatic charges.

When the observed values for penetration were compared with the results of a series of measurements and tests made on the fabrics it was clear that the correlation between these values and the other results was in every case very close for all the five woven cotton or cotton terylene fabrics but that no measurement or test was capable of predicting the behaviour of all the other materials in dispersal experiments. The inherent variability of dispersal experiments seems to be very great. With a standard deviation of the approximately log-normal distribution of the experimental values as high as about 2 times the mean, it is necessary to carry out as many as 20 replicate experiments in order to differentiate with certainty between garments with a two-fold difference in penetration.

There was a 1000-fold difference between the highest and the lowest mean rate of dispersal of bacteria-carrying particles during exercise among a group of three male and three female subjects. Differences in the numbers of skin fragments dispersed and in the proportion of these carrying bacteria were almost equally responsible for this. Since there is little difference between individuals in the rate of skin replacement the differences in the rates of dispersal of skin fragments during exercise must reflect large variations in the amount of skin surface removed in other ways. The skin fragments dispersed had a wide size range extending below 5 μm for the minimum projected diameter (MPD). The median MPD was about 20 μm with 7–10% less than 10 μm. Many of the particles could therefore pass freely through tightly woven fabrics with pores up to 10–15 μm which might seem to be impenetrable to whole corneocytes, typically larger than 30 × 40 μm in the hydrated state.

In a study on the serotypes of Escherichia coli which are present in the faeces of students travelling from many parts of the world to Dublin, a great variety of types was found. It was not possible to relate certain types to the various parts of the world where the students came from. There was no decrease in variety of serotypes after the students had been in Dublin for a few months and no distinctive ‘Dublin’ types were acquired. Serological variation of the E. coli was suggested as partially explaining some of the variety of the serotypes found. Although eight students developed diarrhoea without an aetiological agent being isolated after arrival in Dublin, no distinct pattern of E. coli could be related to this.