The effect of actinomycin D on the growth of African horse sickness virus in monkey kidney cells was studied. It was found that actinomycin D inhibited the yield of virus. It is suggested that African horse sickness virus is either a DNA containing virus or an RNA virus whose replication is DNA-dependent.

The comparative efficiency of cultures of rectal swabs and faecal specimens in detecting salmonellas in asymptomatic carriers was determined and then correlated with the number of salmonellas excreted per g. of faeces (wet weight). In six short-term salmonella carriers, 82% of rectal swab cultures taken daily for 11 consecutive days were positive for salmonellas, whereas 94% of faecal specimens cultured were positive. Similarily, in 8 long-term carriers, 58% of the rectal swab cultures were positive as compared with 91% of faecal specimens. The inferiority of the results of rectal swab cultures correlated with their inefficiency in detecting salmonellas when fewer than 1000 salmonellas per g. of faeces were present.

The patterns of salmonella excretion as depicted by estimated salmonella content of faecal specimens showed that all carriers had irregular day-to-day variations. The average number of salmonellas excreted per g. of faeces by short-term carriers was greater than that by long-term carriers, although both groups revealed the same wide variations in number of organisms excreted.

The effect of delayed processing and shipment of specimens upon recovery of salmonellas was also studied. No deleterious effects were noted when specimens were shipped and processing was delayed for up to 3 days.

Using Moore's swabs in four abattoirs, six strains of subgenus III salmonellas were isolated—four diphasic strains belonging to one serotype and two monophasic strains belonging to another. The serotypes differed in the length of time needed to ferment lactose. There was some evidence that the diphasic serotype could have had an ovine origin.

The median lethal dose of orally administered norbormide for wild Rattus norvegicus found to be 9·0 mg./kg. of body weight and the LD 95 about 17·0 mg./kg.

In tests in which various concentrations of norbormide or zine phosphide were added to the food of individually caged wild rats, mortality increased with concentration of poison, though more slowly with norbormide than with zine phosphide. The mortality that occurred among rats offered a choice between unpoisoned food and the same food with added norbormide or zinc phosphide indicates that in control treatments in the field the optimum concentration of norbormide in bait would be about 0·;5% and that this might be expected to give results comparable with those obtainable with 2·;5% or 5·0% zine phosphide. Other methods of estimating suitable field strengths indicate that concentrations of norbormide higher than 0·;5% may be preferable.

Some animals that survived exposure to a choice of plain food and the same Food poisoned with norbormide or zine phosphide at field concentrations avoided mating lethal amounts by reacting to the taste of the poison. Others learned to use the taste of the food, not that of the poison as a cue and later avoided eating the food when it contained no poison.

When either poison was presented to rats in the more palatable of two foods in the choice situation mortality was relatively high. Some of the surviving animals subsequently rejected the more palatable food in preference to the normally less palatable alternative.

The colicine type and antibiotic resistance have been determined on strains of Sh. sonnei derived from 9419 incidents of Sonne dysentery in London between October 1956 and March 1965.

The most striking observation has been the appearance of strains with patterns of colicine production and antibiotic resistance new to the area. These changes are best regarded as a result of the interaction and transfer of characters between Sh. sonnei and other intestinal organisms.

The general tendency has been for strains of Sh. sonnei to become increasingly resistant to antibiotics but this has not been an uninterrupted process. The proportion of drug-resistant strains at any one time depended on the properties of the current epidemic strain.

Spread of Sonne dysentery was essentially local, but some strains of Sh. sonnei were found to spread much more widely than others. Most, but not all, of the strains resistant to streptomycin and tetracycline possessed only limited powers of spreading.

1. A new colicine type (type 15) of Shigella sonnei is described.

2. The epidemiological circumstances associated with its appearance in Edinburgh and Glasgow are summarized.

3. Our indices of reliability as an epidemiological marker are fulfilled by this new type.

The aetiological agent of an epizootic among Common Terns (Sterna hirundo) in South Africa in 1961 was isolated from several sick birds and named Tern virus. It was classified on the basis of antigenic and morphological properties as a strain of avian influenza virus, Myxovirus influenzae A/Tern/South Africa/1961. The strain-specific antigen of Tern virus was unrelated to all known influenza strains with the single exception of Chicken/Scotland/1959 virus and the two viruses may be regarded as variants of the same strain. This relationship raised the interesting epidemiological possibility of the spread of infection between sea-birds and domestic poultry because the Common Tern migrates between Europe and South Africa.

We studied the incidence of staphylococcal infection in a thoracic surgery ward which consisted of a number of separate rooms, and inquired whether the subdivision of the ward was responsible for the unusually low sepsis-rate.

The airborne dissemination of Staphylococcus aureus from one room to another appeared to be little less than that in an open ward; but the total number of Staph. aureus in the air was very low.

Most of the patients received prophylactic antibiotics. The nasal carrier-rate of Staph. aureus by patients fell greatly during their stay in the ward. There was a progressive disappearance of sensitive organisms and little acquisition of multiple-resistant organisms.

When there are urgent clinical grounds for the lavish use of antibiotics, the dangers appear to be reduced by effective segregation of the patients from each other.

Bluetongue virus was found to be resistant to ether, chloroform and sodium deoxycholate under a variety of conditions but sensitive to treatment with trypsin. The virus had a narrow zone of pH stability between pH 6 and 8 in Michaelis buffer. Below pH 6 bluetongue was irreversibly inactivated within 1 min. at 37° C. In many of its characteristics, bluetongue virus appears to be closely related to the reoviruses.

1. An incomplete field study in Lincolnshire, England, suggested that toxoplasmosis might be transmitted from pig to man by mosquitoes. Although the results were inconclusive they suggested the experimental work recorded in this paper.

2. Trophozoites of the Beverley strain were obtained in increased yield from the peritoneal fluid of Mastomys treated with hydrocortisone. Cysts were obtained in increased yield by passage of the brain of Sigmodon into laboratory mice.

3. Four species of mosquitoes were fed through a membrane or on sucrose solution on media containing either cysts or trophozoites of Toxoplasma gondii. In some experiments blood was added to ensure passage of the feed to the mosquito stomach, in others it was excluded so that at least part would pass to the crop.

4. A spurious ‘cyst’ resembling but distinguishable from Toxoplasma was noted in the homogenate of mouse brain.

5. In no instance did mosquitoes retain infectivity as demonstrated by injection into mice, beyond the third day, but since experiments were not carried on beyond the fourteenth day the existence of an occult form cannot be excluded.

Vaccination with a rough variant of Salmonella dublin had no observable harmful effect on guinea-pigs. It conferred a good immunity against S. typhimurium and S. choleraesuis var kunzendorf infections.

A method of secondary enrichment is described suitable for the isolation of a wide range of salmonella serotypes from abattoir swabs and polluted river water. The technique does not employ selectively toxic chemicals.

A method of doing viable counts of Cl. welchii has been described that gives reproducible results from faeces. By this method counts were carried out on the faeces of persons in the general population, and those associated with an outbreak of food poisoning due to Cl. welchii. There was a significant increase in viable count in those with symptoms of food poisoning. Owing to many variables, single viable counts do not appear to be useful in the laboratory diagnosis of food poisoning, but the detection of heat-resistant spores, by direct culture after boiling, may be of some use. More work must be carried out to substantiate this point.

1. Features in the epidemiology of a spontaneous enteric gangrene in the Highlands of New Guinea are described.

2. The disease has been called pig-bel because of its firm association with the pig-feasting practices of the people, which occur in 3–7 year cycles.

3. Cl. welchii type C is believed to play an important role in the pathogenesis of the condition. Strains isolated were strongly toxigenic and uniform in their toxin production.

4. A food poisoning aetiology was not proved but circumstantial and immunological evidence suggest that pork may be a vector of the disease.

5. The source of Cl. welchii type C was not established.