Two strains of myxoma virus isolated from naturally infected wild rabbits have been described. They showed similar clinical symptoms, the most striking feature being the flat primary lesion. In fifteen rabbits the Brecon strain gave a mean survival time of 26·3 days with a range of 17–47 days, and one recovery. Of 5 rabbits inoculated with the Durham strain three became clinically infected and two remained healthy, the latter were found to be fully susceptible on reinoculation. The three infected rabbits all recovered.

The field strains of virus were compared with known myxoma strains—Glenfield, Cornwall, A & H and KM 13. The first three are fully virulent, while KM 13 is attenuated and characteristic of the field strains now being isolated in Australia. The similarity between the clinical symptoms and mean survival time of KM 13 and the Brecon strain was noted.

It is suggested that the two field strains described in this paper may be the first indication that the evolution of myxoma virus in this country is similar to the evolution of the virus in Australia.

One of us (P.J.C.) is greatly indebted to the Director for allowing this work to be carried out at M.R.E. whilst laboratory accomodation was being prepared at Worplesdon. We are grateful for the help and encouragement of Dr J. C. N. Westwood of M.R.E. To Prof. F. Fenner who gave us the Australian strains of myxoma virus and to Mr J. H. Darbyshire of the Central Veterinary Laboratory who supplied the tissues from which the two attenuated strains were isolated, we extend our thanks.

1. A food store infested with house-mice (Mus musculus L.) was treated with boxes containing 1% warfarin dust surrounding a solution containing 0·005% sodium warfarin and 5% sugar. The boxes were placed around the bases of the stacks, in the air-lanes between stacks and at eaves height at the gable ends of the store.

2. Census baitings with counted numbers of wheat grains showed that the mouse population was reduced by about 95% after 5 weeks of the poison treatment and by almost 100% after 20 weeks.

3. The field trial suggests that the combined use of rodenticidal dust and poison solution baiting points is a useful additional method of controlling M. musculus and is most effectively employed against mice living in warm, dry environments.

Thanks are expressed to our colleague Mr E. W. Powell, who co-operated in this work.

A milk-borne outbreak of Salm. heidelberg infection due to unpasteurized milk from tuberculin-tested cows is described. There were 77 cases and 46 symptomless excreters of the organism. There were no deaths. The infection was traced to a cow with a symptomless salmonella mastitis and the origin of the organism was thought to be contaminated animal feeding stuffs.

We are indebted to Dr Joan Taylor, Colindale, for the identification of the salmonella serotypes; to Dr H. R. Cayton, Bristol, for assistance in the examination of animal feeding stuffs; to Dr E. N. Davey, Gloucester, for permission to include his results of milk examinations; and to the following public health inspectors who assisted in the field investigation—Mr A. Furniss, Mr G. Baillie and Mr M. V. Smith, Cirencester Urban District; Mr H. Wheeler and Mr R. Hayward, Cirencester Rural District; Mr P. Hayter, Bristol; and Mr D. S. Smith, Trowbridge.

Data are presented which amplify previously published work on the additive antiseptic effect of Roccal as follows:

1. Smallpox calf pulp derived from animals whose skin is treated with Roccal during the viral incubation period apparently adsorbs sufficient concentration of the reagent to produce a measurable bactericidal effect.

2. The adsorbed antiseptic induces a significant additive effect well beyond that of the action of stated concentrations of phenol and ether alone, as evidenced by the fact that this combination produces rapid diminution of the bacterial flora in highly contaminated calf lymph.

3. Vaccines containing the combination of antiseptics described caused no dermatitis or other untoward reactions in rabbits and humans and their viral potency was not affected.

4. The use of the antiseptic reagents makes possible the rapid preparation of smallpox vaccines for human use. Acceptable bacterial flora levels are obtained usually within 24 hr. of preparation.

The author is indebted to Magda Gagliardi, Marie Mazzochi and Izola Prunty for their assistance in the performance of the many bacterial counts, toxicity tests and other technical work.

A survey embracing all cattle vaccinated in Kenya with lapinized rinderpest virus between 1 January 1954 and 30 June 1956 revealed an over-all incidence rate of adverse reactions of 0·09 %. The real incidence rate approached 3 per 1000 cattle because only susceptible cattle were at risk. Four types of reactions were recognized. The most serious, because of the attendant high case mortality rate, was aggravation of latent protozoal infections. The commonest reactions were rinderpest-like without serious sequelae except in pregnant cows, many of which aborted. Transient spermatolysis was observed in six vaccinated bulls and anaphylaxis was recorded rarely.

The incidence of rinderpest-like reactions was primarily influenced by the innate resistance of the cattle. The viral strains recovered from reacting cattle were genotypically unchanged.

I am grateful to Mr J. W. Macaulay, B.Sc., F.R.C.V.S., D.V.S.M., Chief Veterinary Research Officer, Kabete, Kenya, for his encouragement, advice and counsel. This paper is published by permission of the Director of Veterinary Services, Kenya.

The pH-stability of three strains of rinderpest virus, propagated in tissue cultures, was investigated at 4°C. in veronal-acetate buffers (Michaelis) of pH 3·0–10·7.

An attenuated laboratory strain, in its 95th culture passage (RBOK), showed maximal stability in the pH range 7·2–8·0, the half-life being about 3·7 days. It was relatively stable from pH 4·0 to 10·2, the half-life at the extremes of this range being over 2 hr. At pH 3·0 the infectivity declined very rapidly, the half-life period being 24·0 sec.

One virulent strain (RGK/1) showed a significantly lower resistance than strain RBOK at pH 3/0, probably also at pH 5·0. The inactivation rates for these two strains were, however, not greatly different at pH 10·7. The other virulent strain (RBT/1) was even less stable than RGK/1 at pH 4·0 or 5·0 but of a comparable stability at pH 9·0 and 10·2.

These findings are discussed in comparison with published data on the related viruses of measles and canine distemper. The importance of strain differences in studies of this kind is stressed.

We are grateful to Mr C. S. Rampton, A.I.M.L.T., and Mr L. W. Rowe, F.I.M.L.T., for help in the preparation of the diagrams. This paper is published with the permission of Mr H. R. Binns, C.M.G., O.B.E., Director, E.A.V.R.O.

Presence of natural Cl. welchii α-antitoxin in 65 Indian equines was observed. All the 65 equines had 1 unit or more of circulating natural antitoxin per ml. of serum. The maximum titre observed was 4 units/ml. in about 8% of the animals. These figures are very much higher than the figures obtained in other countries. Such a high incidence of natural immunity indicates frequent natural contact with the antigen concerned.

Results of hyperimmunization of 7 equines are recorded and discussed.

Our thanks are due to the authorities of Bengal Immunity Laboratory for permission to publish these observations and to Sri M. Pal for useful technical assistance.

Antigenic differences between the strains RV 11 and SA 13/61 of foot-and-mouth disease virus (type SAT 1) were studied in vivo by cross-protection tests. Cattle inoculated with formolized antigen of either strain developed good immunity to experimental infection with the identical strain but little resistance to the other strain.

In vitro the results of complement fixation tests and of serum-virus neutralization tests in tissue culture were consistent with the observations made in vivo. The results of studies on the serological relationships between four strains of type SAT 1 are presented.

The importance of strain differences in the epizootiology and control of the disease is discussed briefly.

The authors wish to thank Dr I. A. Galloway and Dr J. B. Brooksby for their advice and criticism, and to acknowledge the valuable technical assistance of Mr K. Herniman, Mr R. L. G. King and Mr E. Scoates.

An analysis has been made of the records of 5290 attendances at the Common Cold Research Unit, Salisbury, during the years 1946 to 1957. Materials prepared from the nasal washings of persons suffering from colds were administered to 993 volunteers, of whom 386 (38·9 %) showed definite evidence of infection within a few days. The attack rate of these experimentally induced colds was lower during the months October to March than from April to September. The difference was statistically significant as regards male but not as regards female volunteers.

Six strains of virus were propagated by passage from volunteer to volunteer, in one instance up to the eighth serial transfer from the original material, without apparent loss of pathogenic properties. Comparison of the clinical effects of these strains, and of a number of miscellaneous strains, revealed several differences which were minor in character but, statistically, highly significant. These comprised differences in attack rate, severity, incubation period, duration and relative frequency of symptoms, which could not be ascribed to seasonal or other influences.

It was concluded that the observed variations in the clinical pattern of the experimentally induced colds were attributable to qualitative differences in the strains of virus used.

I wish to thank Sir Christopher Andrewes, F.R.S., for his unfailing help and encouragement at every stage of this investigation and all my colleagues at the Common Cold Research Unit for much useful comment and discussion. I am indebted to the Statistics Department of the Ministry of Labour and National Service for processing the records and to Mr R. G. Carpenter for assistance with some of the statistical analyses.

H.influenzae type b, the sero-type which causes meningitis, was isolated from 3 (2·4 %) of 127 naso-pharyngeal swabs from white non-Jamaican children resident in Jamaica, and from 14 (2·9 %) of 473 such swabs from a mixed group of Jamaican children. Much higher frequencies were found in households in which cases of haemophilus meningitis had recently occurred (41 %), in the nursery of an orphan home (up to 70%) and in a day-nursery. In the orphan home nursery the high frequency persisted over a number of months, but no case of meningitis or other relevant disease occurred. A high concentration of this organism is therefore compatible with normal health, and the significance of high concentrations in the homes of meningitis patients is not certain.

I am indebted to the Standing Advisory Committee for Medical Research in the British Caribbean for a grant towards the cost of materials; to a number of colleagues at the University College of the West Indies, notably Dr E. H. Back, Senior Lecturer in Paediatrics, and the staff of the Department of Social and Preventive Medicine; to those in charge of the orphan home, the day-nursery, the play-school and the other institutions visited; to many cooperative parents and children and to my wife for help in the collection of specimens.

1. Faeces from apparently healthy Bantu school children of a periurban district of Johannesburg were examined eight times at regular intervals over a period of 1 year.

2. Of 75 children, 29·3 % experienced at least one salmonella infection and 2·7 % one shigella infection. It is suggested that over a year nearly all children will have one, and many of them several, infections with these pathogens. The infections occurred at a low rate throughout the year.

3. In most cases the infections were asymptomatic. A few of the children showed evidence of being salmonella carriers of long standing.

4. Eighteen different salmonella types were recovered. Salmonella typhi, S. paratyphi B and S. paratyphi C were absent. The organisms were highly resistant to penicillin, erythromycin and novobiocin and a few strains were also resistant to chloramphenicol and tetracycline.

5. The drinking water was of poor quality and may well be implicated in the transmission of the infections.

Our thanks are due to the Director of this Institute, Dr J. H. S. Gear, for permission to publish this paper; to Mr R. G. Robinson for assessing the microorganisms'sensitivity to antibiotics; and to the South African Council of Scientific and Industrial Research, Pretoria, for a grant enabling us to meet the transport expenses.