Four litters of newborn piglets suffering from haemolytic disease of four different grades of severity, were observed clinically. Pallor and mild jaundice were evident in some cases, but the activity of the piglets was not reduced except in the terminal stages of fatal cases. Malnutrition affected a number of piglets sometimes from fortuitous factors. In mild cases there were no clinical symptoms, and the disease could be detected only by demonstrating a fall in haemoglobin level or sensitization of the red cells.

Several blood group systems were concerned in the genesis of the disease in these piglets and both agglutinating and incomplete antibodies were shown to be present in the piglets' circulations; in one case antibody was found in the piglet's circulation only 3½ hr. after suckling started, and by 4 hr. the titre of free antibody was 256. The antibodies did not pass the placenta.

In severe cases a rapid fall in haemoglobin, interrupted by a sharp, transient rise, and accompanied by reticulocytosis and erythroblastaemia, was characteristic of the first 24 hr.; this was followed in some cases by a prolonged low level of haemoglobin before recovery started.

In some of the animals that died, severe and widespread focal necrosis of the liver, together with degeneration and necrosis in the kidney, were marked. Pigment deposits and erythrophagocytosis were common in nearly all organs but abnormal extramedullary erythropoiesis was not observed.

A number of haematological, serological and biochemical findings are recorded.

1. The protection afforded by glycine and other amino-acids to guinea-pig complement against heat-inactivation is increased in the presence of sugars, although the latter are not themselves protective.

2. No significant increase in protective activity occurs in the presence of the alcohols derived from some of the sugars tested.

3. A marked exception amongst the alcohols is inositol, which reinforces the protective power of glycine at least as much as do the sugars.

4. The fourth component of complement is destroyed by heating at 63° C. for 30 min. It is, however, protected against heat-inactivation by glycine, and this protective effect is intensified in the presence of glucose and inositol.

5. The protection afforded to serum by the presence of glycine or glycine dissolved in glucose is removed when the system is dialysed, indicating that if a complex is formed it is readily dissociable.

This report on a large outbreak of disease, known locally as ‘Chikungunya’, in the Newala district of Tanganyika concerns the circumstances of isolation of strains of virus, some of their properties, and their relation to the epidemic. The work, reported here, started in Newala from 18 February to 10 March, 1953, and continued thereafter in Entebbe.

To show that blood-sucking insects can transmit viruses which cause human diseases, human beings themselves must be used for experiments, or, as this is rarely possible, their place must be taken by suitable laboratory animals. For this purpose an animal species must be available with the following attributes: it must regularly circulate much virus in its blood after infection, and it must be susceptible to infection by the intracutaneous inoculation of a small dose of virus. None of the animal species available possess these attributes during experimentation with many human viruses. Insect transmission can often then be demonstrated by using the indirect method described in this paper.

The preparation of purified influenza virus from infected allantoic fluid is described, and its fractionation by ether treatment with the production of pure samples of soluble antigen and haemagglutinin.

Chemical analysis of intact infective virus showed it to have a nitrogen content of 9.3%, a carbohydrate content of 3.5%, and a content of ribonucleic acid of 0.7–0.74%.

Purified soluble antigen derived from the infective virus particle was shown to be a ribonucleoprotein containing 5.3% RNA. No carbohydrate other than ribose was found. Purified haemagglutinin was shown to be a mucoprotein containing 4.2% of a polysaccharide possibly composed of galactose and mannose in equimolar proportions.

Staphylococcal phages may be divided into three broad divisions:

(1) Phages lysing coagulase-positive staphylococci with a restricted host range. Phages in this division may be further divided into five lytic groups I, II, III, IV and Miscellaneous.

(2) ‘Polyvalent’ phages; phages with a wide host range among coagulase-positive cocci, and sometimes also active on coagulase-negative strains.

(3) Phages lysing only coagulase-negative staphylococci.

Within each division the phages can be further grouped by their serological reactions. Nine serological groups have been defined. Phages of any single serological group also share other characteristics, e.g. stability, and the ability to form lysogenic systems.

An interference phenomenon was produced by the intraperitoneal injection of broth culture dilutions of Pasteurella pestis grown at 28° C. into small white rats.

At a critical level of approximately 106Past. pestis L37 marked interference was produced. Doses of 104 or 107 killed rats readily.

Interference was produced by the addition of killed organisms, a cell-free vaccine or a live vaccine, to small lethal doses of L37.

Non-specific interference was produced by the intravenous injection of Indian ink prior to the intraperitoneal challenge with Past. pestis L37.

The biological characters of eight strains of the Newcastle disease virus, isolated in different parts of the world between 1933 and 1951, have been studied and compared in detail.

Two types of the virus have been distinguished, one from the Newcastle disease prevalent in Europe and Australia, the other from that occurring in the United States of America.

Viruses of the first type are highly virulent, multiply rapidly and successively develop the properties of infectivity, haemagglutination and haemolysis. Their haemagglutination pattern is constant and wide; they profoundly modify human group O erythrocytes, and they are antigenically homogeneous.

Viruses of the second type are of weaker virulence. They grow at a slower rate in the allantoic cavity of the chick embryo, and the development of their characters is retarded; they have a reduced haemagglutination pattern and only a minimum capacity to modify human group O cells. Antigenically strains of the second type are homogeneous.

From haemagglutination inhibition and absorption studies it is concluded that major antigens are shared by both types, and that the first type possesses one or more antigens lacking in the second.

The highly virulent Canadian TWISS strain possesses the characters of the first type and an antigenic constitution with features of both types.

The significance of the results is discussed in relation to the ecology of Newcastle disease.

Titrations of the same preparations of myxoma virus have been made on the chorioallantoic membranes of developing chick embryos and by the intradermal inoculation of rabbits. Six strains of widely differing virulence for the rabbit were used.

No differences were found in the infectivity of different strains for either the rabbit or the egg, even though the severity of the symptoms produced in the rabbit varied greatly with different strains; and although some had never previously been inoculated in eggs and one had been subjected to seventy-five serial passages on the chorioallantoic membrane.

The egg was less sensitive than the rabbit, the mean number of infections per dose for rabbits relative to eggs being 2.46, taken over all strains. This ratio did not differ significantly between strains of myxoma virus.

There was evidence of some host variation in rabbit susceptibility and a great deal of variation in egg susceptibility. The maximum value for the average probability that an infectious unit would produce a lesion in the rabbit skin was about 0.6, and the maximum value for the average probability that an infectious unit would produce a pock on the chorioallantoic membrane was 0.25.

Titration of several closely spaced dilutions of different strains of the virus on the chorioallantoic membrane showed a reasonably close approximation to a proportional relationship between the pock count and the virus dilution. The change with dilution in the proportion of failures to infect rabbits approximated to expectation. Both lines of evidence are consistent with the hypothesis that a pock or skin lesion is initiated by one infective unit of virus, and that the infective unit is stable with dilution.

Proof of the existence of multiplication of myxoma virus in mosquitoes has been sought by a variety of experiments with Aedes aegypti and Anopheles annulipes. All were completely negative. All features of transmission are compatible with a purely mechanical and none is compatible with a ‘biological’ mechanism.

In mechanical transmission important features of the infected animal host are the number and accessibility of viruliferous skin lesions, and the location and concentration of virus in these lesions.

By inducing mosquitoes to probe through infectious skin lesions and subsequently permitting them to make many successive probes on marked skin sites on the backs of susceptible rabbits, it has been possible to obtain quantitative information on the median minimum virus load of probing mosquitoes, and the rates of loss due to probing and the passage of time.

A preparation of myxoma virus suspended in normal rabbit serum had a half-lifetime of 11 days at 4° C., 5 days at 18–20° C., and 31 hr. at 27–28° C. Apart from losses due to probing (about 12% of the virus load per probe) viable virus on the proboscis of the mosquito probably disappears at about the same rates.

When examined under similar conditions in the laboratory, the two strains of myxoma virus used to initiate the Australian and European epizootics, and three somewhat attenuated strains recovered in the field in Australia and France, were found to produce lesions containing approximately the same amount of virus, and were transmitted by mosquitoes with approximately equal efficiency. The laboratory variant neuromyxoma multiplied poorly in the skin and was very rarely transmitted by mosquitoes.

The survival potential of different virus strains in the field is correlated with the length of time during which rabbits infected with different strains present to biting mosquitoes lesions containing high concentrations of virus. Sickness of the infected rabbit, and extensive viruliferous skin lesions, will increase its suitability as a source of virus for mosquitoes. These considerations explain the dominance of slightly attenuated strains of myxoma virus in the field in Australia.

Species of mosquitoes, when tested under standard conditions in the laboratory, differ in their efficiency as vectors of myxomatosis. These differences may be related to differences in the method of feeding, and to structural differences in the mouthparts.

Engorgement on an immune rabbit after probing through myxomatous skin lesions had no greater effect on the subsequent ability of mosquitoes to transmit myxomatosis than a similar blood feed on a normal rabbit.

Nine serial mosquito-bite passages of the standard laboratory strain of virus, each involving one week in the rabbit and two weeks in the mosquito, had no effect on its pathogenic behaviour.

Methods are proposed for measuring the constants of an exponentially declining population under conditions in which the least-squares method is unsuitable. A table is given to facilitate the calculations.

1. One per cent of samples of farm milk were found to contain pathogenic varieties of Bacterium coli of the O groups associated with infantile gastroenteritis.

2. Unheated cows' milk is a dangerous food for babies.

3. Summer diarrhoea was probably, for the most part, milk-borne infection by special O groups of Bact. coli.

4. Thirteen per cent of chickens on farms were found to be excreting Bact. coli of the O groups associated with infantile gastro-enteritis but only a few of the strains possessed H antigens of varieties known to have an association with human disease.

5. Possible reservoirs of infection cannot be adequately searched for until a selective method is devised to aid the separation of pathogenic O groups of Bact. coli from the non-pathogenic.