1. A complement fixation test has been developed to measure the minor antigenic differences which occur between strains of the virus of foot-and-mouth disease of the same immunological type.

2. Strain-specific sera were prepared from each of the virus strains examined and then titrated with each of the antigens.

3. The amounts of complement fixed in each reaction were measured in the region of maximal fixation where the antigen and antibody were present in optimal proportions.

4. Heterologous antigen-antibody reactions were compared with the homologous reaction in each test and expressed as cross-fixation ratios.

5. Pairs of antigens could then be compared by taking the product of their cross-fixation ratios one with the other. The values of cross-fixation product so obtained ranged from 1·0 between identical strains to 0·01 between strains of different immunological type.

6. Strains of virus which exhibit cross-fixation products of 0·5 or more with one another have been classified within subtype groups.

I wish to acknowledge the guidance and encouragement of Dr J. B. Brooksby, Director of the Animal Virus Research Institute, Pirbright, and the technical assistance of Mr E. Scoates.

1. Modifications of the technique of colicine typing are reported which allow more rapid and economical identification of Shigella sonnei for epidemiological purposes without loss of accuracy.

2. The technique is epidemiologically valid as judged by the constancy of type in repeated isolations from individuals and the uniformity of type in epidemics; it is considered that the few instances of lack of uniformity in these indices are probably examples of true mixed type infection. There is no evidence of type instability in vitro.

3. Type incidence differs significantly from that reported in two other centres; a new colicine type (Type 14) is described which brings the total of recognizable types to 16. It is considered that in addition to the five types which were previously thought distinctive, three other Types, 6, 11 and 14, can now be so regarded.

4. There is a need for continued studies to resolve the few discrepancies associated with infection by more than one type either in the individual or in an epidemic; it is hoped that colicine typing will reawaken interest in Sonne dysentery.

This investigation was supported (in part) by Public Health Service Research Grant AI– 04833–01.from the National Institute of Allergy and Infectious Diseases.

In 1961 and 1962 a Working Party of the Public Health Laboratory Service, in which twenty-two laboratories participated, investigated the occurrence of salmonellae in abattoirs, meat factories, butchers' shops and meat products, and their association with human infections.

Thirty-two abattoirs were studied. Salmonellae were isolated from 930 (21%) of 4496 swabs of abattoir drains. There was great variation between different abattoirs, but in general salmonellae were found most frequently in those which slaughtered a high proportion of cattle and a low proportion of sheep; more sero-types were isolated from bacon factories than from abattoirs which slaughtered more than one species of animal. Of 11,347 tissue specimens collected at abattoirs, 218 (1·92%) yielded salmonellae.

Drain swabs from butchers' shops were examined and 73 (6·5%) of 1117 swabs were positive. Meat and meat products were less commonly contaminated but 0·8% of 4127 samples yielded salmonellae.

Salmonella typhimurium was the serotype isolated most frequently from all sources. It was often shown that the same serotypes or phage-types were occurring in abattoirs and in human cases in an area at the same time. In eight food-poisoning incidents, involving a total of 281 cases and excreters, there was convincing evidence that meat or a meat product was the vehicle of infection; in a further twenty-three incidents the organisms causing disease were isolated from sources which suggested that infection might have been meat-borne.

The evidence collected suggests that cattle introduce salmonellae into abattoirs more often than other species of animals. The importance of pigs as a source of human infection is confirmed. Sheep are not a source of salmonella infection in man from meat and meat products, whereas meat from pigs, cattle and calves is a source of infection and is responsible for both sporadic cases and outbreaks of disease.

We wish to thank the many medical officers of health who co-operated in this study. The public health inspectors and abattoir staffs who collected the specimens are too numerous to mention by name, but their invaluable assistance is most gratefully acknowledged. Among the medical officers who assisted us in the survey were: Dr A. Armit (Bridport M.B. and R.D.), Prof. D. B. Bradshaw (Leeds C.B.), Dr C. B. Crane (York C.B.), Dr J. Douglas (Bradford C.B.), Dr A. B. R. Finn (Guildford M.B.), Dr R. A. Good (Winchester M.B.), Dr G. B. Hopkins (Wimborne and Cranborne R.D.), Dr E. W. Kinsey (Caernarvon M.B.), Dr I. B. Lawrence (Dorchester M.B. and R.D.), Dr R. A. Leader (Ipswich C.B.), Dr Mary Lennox (Barry M.B.), Dr V. P. McDonagh (Keighley M.B.), Dr H. E. Nutten (Beccles M.B.), Dr G. O'Donnell (Worcester C.B.), Dr E. J. O'Keeffe (Wareham M.B. and Wareham and Purbeck R.D.), Dr N. F. Pearson (Sturminster Newton R.D.), Dr W. P. Phillips (Cardiff C.B.), Dr T. H. Pierce (Llandudno U.D.), Dr J. L. Rennie (Carlisle C.B.), Dr C. L. Sharp (Bedford M.B.), Dr E. F. Shennan (Evesham U.D.), Dr J. Stevenson-Logan (Southend-on-Sea C.B.), Dr D. W. Wauchob (Blackpool C.B.), Dr J. Walker (Lancashire C.C.), Dr J. V. Walker (Darlington C.B.), Dr R. B. Walker (Kingsbridge R.D.), Dr E. J. Gordon Wallace (Weymouth M.B.), Dr C. Robertson Wilson (Lancashire C.C.), Dr E. M. Wright (Salisbury M.B.), Dr Alfred Yarrow (South East Essex).

Haemagglutination-inhibiting antibodies against A, A′ and A2 strains of influenza virus and against one strain of influenza B were estimated in sera from blood donors in Sydney in February 1958 and in April and October 1961.

The A2 antibody increased substantially while both A and A′ antibodies declined slightly. There was a great decline in influenza B antibody during the same period.

Thanks are due to Dr Phyllis M. Rountree who suggested this study. Miss Patricia Taylor gave excellent technical assistance in the early part of this work.

A simple method for the isolation of pox virus hybrids on the C.A.M. has been described. One parental virus was used as a heat-inactivated suspension. The other parent was used in the active state, but at a temperature higher than its ceiling temperature. Under these conditions the inactive parent was reactivated so that pocks resulted only from the cells infected with both parental viruses. Many of these pocks were unlike those of either parent. Such lesions were found to contain a high proportion of hybrids. In these experiments, alastrim was crossed with rabbit pox and variola major with cowpox.

The term ‘heat-tethered’ has been used to describe virus whose intracellular cycle of development has been arrested by incubation at too high a temperature. Heat-tethered virus has interesting properties and two of these have been described. When the temperature is lowered, heat-tethered virus will start to grow again. Its reactivating potential has been mentioned above. A more detailed account of the properties of heat-tethered virus is being prepared.

Infected human thyroid tissue cultures have been found to yield free V-Z virus on ultrasonic disintegration and some virus is also present in the fluid phase of intact tissue cultures, while the yield of virus from infected human amnion cells is very low and no free virus is found in the fluid phase. Thyroid cultures are more susceptible to infection with V-Z virus, and the infected cultures are a better source of complement-fixing antigen, than are amnion cultures.

The lack of free virus in infected amnion tissue cultures cannot be attributed to protection by interferon. It also seems likely that if any infectious virus were released it would be more likely to be adsorbed to normal cells than to be inactivated, but as no secondary foci appear in amnion monolayers we conclude that infective virus is not released into the medium.

It is suggested that the virus in thyroid cells is present in a more complete form than that in amnion cells.

We are grateful to Dr R. M. Rawcliffe of Birkenhead General Hospital and Dr F. Whitwell of Broadgreen Hospital, Liverpool, for arranging the supply of thyroid tissue.

The protection afforded by cholera vaccine administered by the intradermal route, and demonstrated by active and passive mouse protection tests, active guinea-pig protection tests, and agglutination titres, is excellent and equal to that given by subcutaneous inoculation.

It is suggested that cholera vaccine administered by the intradermal route would greatly reduce the incidence of reactions which occur when the vaccine is given subcutaneously.

The survival and persistence of Shigella sonnei and S. flexneri in various food preparations were studied. The length of survival and the rate of decrease in surviving fractions varied considerably depending upon the menstruum and the holding temperature. This study points out the potential hazards involved in consuming food products that may be contaminated by shigellae.

A new enrichment medium for the isolation of salmonella types from faeces is described.

The inhibitory substances for coliform organisms and enterococci in this medium are magnesium chloride and sodium hydrogen selenite.

The new medium was found in routine diagnostic work to be superior to the Mueller–Kauffmann medium in the isolation of Salmonella typhi and only a little inferior in the isolation of other salmonella types.

When used in addition to the standard media the new medium increases the number of positive results.

I am indebted to Dr Jadranka Zajc-Satler for the identification of the salmonella types isolated and to Mrs I. Mamilovič, Miss P. Ferbežar, and Mrs D. Zavodnik for technical assistance.

1. An outbreak of food poisoning due to Salmonella typhi-murium phage-type la is described.

2. Bread and (or) bakery confectionery eaten by all but two of the victims, had originated from a particular bakery firm.

3. S. typhi-murium phage-type 1a was found in the stools of an apprentice baker, a female packer of cakes and bread, and in three female counter-hands. The apprentice baker was responsible for the preparation and decoration of the confectionery which was distributed to the branch-shops and other establishments throughout the area.

4. S. typhi-murium was not found in any of the raw materials used at the bakehouse.

5. The cases which arose at a residential school for cripples gave a ratio of six cases to eight symptomless excretors.

6. Seven weeks after the start of the outbreak the last of the infected food-handlers was considered to be free from infection and fit to return to work.

Twelve weeks later the last member of the public was declared to be negative.

Thanks are expressed to Dr Joan Taylor of the Salmonella Reference Laboratory for her advice and assistance in the preparation of this paper, and to the staffs of the Public Health Laboratory and Public Health Department, Edmonton, N. 9, for their help and co-operation during the investigation.

The characters of seven clones of virus derived from mixed infections with alastrim and rabbit pox have been described. One clone was shown to behave as rabbit pox in respect of all its markers. The other six were found to be distinct new types of virus, each having a different combination of the parental characters. The reasons for accepting these viruses as hybrids have been discussed. An analysis of the pairwise crosses between individual markers suggested that each of the nine markers was capable of segregating independently.

A virus was isolated from fifteen of nineteen children living in an infants' home during an outbreak of diarrhoea. The virus possesses many of the characteristics of the enterovirus group but is serologically distinct from any of the accepted members of this group. It is non-pathogenic for unweaned mice, non-cytopathic in tissue cultures of monkey kidney, but is rapidly cytopathic for tissue-cultured cells of human origin. It is serologically similar to virus Hu 659 isolated by Abrahams in the United States (personal communication).

I should like to thank the Director-General of Public Health and State Psychiatric Services, New South Wales, for permission to publish.

The characterization of 16 clones of virus derived from mixed infections with variola major and cowpox has been described. This work has involved the description of the plaques produced by variola major in chick embryo monolayers, and a more detailed study of the effects of raised temperature on pock production by pox viruses on the C.A.M.

Two of the variola major—cowpox clones were found to correspond to cowpox virus, while the other 14 shared various combinations of parental characters. Among them there were 10 distinct new types of virus. Evidence of the stability of these viruses has been presented.

Analysis of the combination of characters encountered among the hybrids has given good evidence that all the eight marker characters used segregate independently. A particular instance of this was the character of chick embryo virulence which, among the hybrid viruses, was shown to be unrelated either to ceiling temperature or speed of plaque formation.

The significance of these findings in relation to the general problem of virulence has been briefly discussed. The possibility that vaccinia may have originated as a hybrid of variola and cowpox has lso been considered.

The efficiencies of bactericides in destroying bacteria on woollen blanket were investigated on a laboratory scale. The bactericides were not effective when tested with new blanket; this low efficiency was found to be related to the rapid adsorption of the bactericides by the wool. Pretreatment of the wool with concentrated solutions of bactericides depressed the rate of depletion of the bactericides from subsequent washing liquors with bactericides at customary concentrations, and led to more satisfactory rates of kill (inactivation factors about 106).

The test organisms, Staphylococcus aureus and Escherichia coli, were applied to the blanket as a powder, and the relative densities of bacteria on the blanket were determined using a procedure based on maceration of the fabric. The bactericides, 4-chloro-3, 5-xylenol (P.C.M.X.), cetyl trimethyl ammonium bromide (C.T.A.B.) and bis-(4-chlorophenyl diguanido)-hexane diacetate (chlorhexidine diacetate) were tested in the presence of appropriate detergents.

Cultures were kindly supplied by Dr Hildred Butler of the Royal Women's Hospital, Melbourne.

Since the original epizootic of myxomatosis in this country (1953–55) carcasses of rabbits from outbreaks of the disease have been sent regularly to the Central Veterinary Laboratory, Weybridge, but no detailed investigations have been carried out on outbreaks of disease in natural populations in Great Britain since 1954 (Armour & Thompson, 1955). In July 1962 a rabbit was sent from the East Riding of Yorkshire and as a matter of routine this establishment was informed of the outbreak. The population of rabbits concerned was large and occupied an area of approximately 200 acres. The strain of virus causing the outbreak was attenuated and when this was discovered efforts were made to secure samples for as long as the outbreak lasted.

A rapid 18 hr. technique has been developed for detecting salmonella contaminated carcass and boneless meats. It is based on 43° C. selenite enrichment of samples, followed by immunofluorescent detection of salmonella cells in the enrichment. In tests with 286 meat samples the rapid and conventional techniques agreed in the detection of 93 positive and 149 negative samples. The two tests failed to agree for the remaining 44 samples. The rapid technique thus lacks precision, but could be used as a rapid ‘presumptive’ salmonella test, so that contaminated material could be prevented from reaching the processing lines of food factories.

We thank Dr Betty Hobbs of the Food Hygiene Laboratory for kindly sup plying the meat samples used in this investigation, Dr Patricia Bradstreet of the Standards Laboratory for Serological Reagents for the salmonella diagnostic antisera and Mr R. Kenworthy for performing the goat injections.

Eight carriers of intestinal pathogens (5 Salm. typhi-murium, 2 Sh. sonnei, 1 E. coli 026) were given their own coliforms, rendered drug-resistant in vitro to neomycin or paromomycin, together with one of these drugs. In seven cases, the drug-resistant coliform flora established itself, while the natural coliform flora and the pathogen were suppressed. In four cases only (2 Sh. sonnei, 2 Salm. typhi-murium) the pathogen was eliminated in the course of this procedure.

Virological and serological studies on an outbreak of aseptic meningitis in association with Coxsackie B5 virus, and Coxsackie A9 virus to a lesser extent, are reported. Coxsackie B5 virus was isolated from spinal fluids of 60 patients and Coxsackie A 9 virus from one spinal fluid. Fifty Coxsackie B 5 and 13 Coxsackie A 9 viruses were recovered from patients' faeces. The evidence that the epidemic was caused by these viruses was confirmed by determination of neutralizing antibody in paired sera.

The plaque variants of Coxsackie B5 virus isolated from the faecal specimens and the poor antibody response in Coxsackie A 9 infection were reported as points of virological and serological interest.

1. The first chronic carrier in western Norway was discovered in 1918. Since then 147 individuals have been found to be chronic carriers, 84 being carriers of S. typhi and 63 of S. paratyphi B.

2. Of the 147 chronic carriers 23 were males and 124 females. Most of the carriers were elderly folk, 96 over the age of 50 and 37 over the age of 70 when their carrier state was discovered. There is a considerable rise in the incidence of gall-stones among women around the age of 50, while a similar rise comes at a higher age in men. This sex difference may be a contributory cause of the larger number of female carriers.

3. Operations were performed on 66 chronic carriers with a view to curing the carrier state. In 2 cases, only cystotomy could be performed because of the state of the gall-bladder. In one of these the carrier state was cured, while it persisted in the other.

4. The gall-bladders of 64 chronic carriers were removed by operation with the following results: 2 died as a result of the operation, 9 remained carriers, and 53 are considered cured. The operation was therefore successful in four-fifths of the cases.

The gall-bladders of 2 individuals who remained carriers were found at operation to be sterile and perfectly normal, without stone formation. Two other individuals who remained carriers have later died, 1½ and 7 years after their operations. In both cases S. paratyphi B was cultivated from the common bile duct and the hepatic duct. The specific process may therefore in a few cases be situated at a higher level in the bile passages of the liver.

5. The interval between infection and operation varied from 3 months to 50 years. The 2 carriers who had the longest interval are both cured.

6. Indications for operation are given on the basis of the experiences provided by the present material.

A survey of rinderpest-neutralizing antibody was carried out on the sera of 315 hippopotamuses which were shot in the Queen Elizabeth Park, Uganda. No serological positives were found in animals aged 11 years or less but about 4% were detected in the age class 13–25 years. In the 28–41 years age class the proportion of positives rose to about 36%. All except one of the positive sera were titrated, the figures obtained being comparable to those in other recently infected species of wild ungulates.

It was concluded that the heat-stable antibody in hippopotamuses resulted from inapparent infections with rinderpest virus during epizootics which passed through the areas of Lake George and Lake Albert in the years 1920/21, 1931/33 and 1944/45. No record was available of clinically recognizable rinderpest in the hippopotamus population but deaths due to other causes were mentioned briefly.

Comment was made on the stability of rinderpest-neutralizing antibody over periods of about 30 years.

One of us (R. M. L) is grateful to the Nuffield Foundation for financial support. Thanks are due to Drs S. S. Stone and W. P. Heuschele (Agricultural Research Service, United States Department of Agriculture) for their assistance in organizing the collection of serum samples.

This paper is published by permission of Mr H. R. Binns, C.M.G., O.B.E., Director, E.A.V.R.O.