Rainbow trout and specimens of pond mud were collected from three fish farms and examined for the presence of Clostridium botulinum. Two of the farms were constructed with concrete channels and one was mud-bottomed.

Cl. botulinum was isolated only from the mud-bottomed farm (24% of muds), and the isolates were all non-proteolytic type B. The implications of the presence of Cl. botulinum spores in the mud of fish farms is discussed.

The preparation of a skin test antigen from Mycobacterium ulcerans by ultrasonic disintegration and filtration is described. The reagent, called Burulin, was tested in Africa in normal school children, and in patients with leprosy, tuberculosis or M. ulcerans disease. Those with tuberculosis or M. ulcerans disease were simultaneously tested with Tuberculin PPD. Burulin was found to be highly specific for patients in the reactive stage of M. ulcerans disease, and there was no cross-reaction in patients with other mycobacterioses. On the other hand, the majority of patients with M. ulcerans disease reacting to Burulin also produce positive reactions to Tuberculin PPD.

The addition of dehydrated broth powder to a random selection of bottles from each batch of infusion fluids before sterilization, followed by incubation of the bottles after sterilization, provides a method of sterility testing which possesses many advantages over the traditional method of culturing small samples from bottles after sterilization.

The serum antibody titres in 62 cases of acute brucellosis are presented. The antibody persisting after infection and the appearance of non-agglutinating antihuman globulin titres were investigated. The criteria for the serological diagnosis of acute and chronic brucellosis are discussed.

The conglutinating complement fixation test was compared with the haemolytic complement fixation test for the detection of brucella antibodies in human sera. Conglutinating-complement-fixation antibodies were detectable during the early stages of acute brucellosis and persisted for approximately 1 year after the infection.

A serological analysis of mycelial antigens of Thermoactinomyces vulgaris in immunodiffusion with human sera revealed five individual antigens. Three antigens were proteins, sensitive to pronase and soluble in phenol. Two were cationic polysaccharides, sensitive to sodium periodate, and containing glucosamine and muramic acid.

Latex coated with mycelial antigens was compared with precipitin tests in detecting antibodies to T. vulgaris; the number of positive results detected by each test differed slightly, and a combination of the two tests detected the highest number. Counterimmunoelectrophoresis (CIE) was shown to be a very sensitive method for detecting precipitins, but not for their measurement. A prospective evaluation of immunodiffusion, latex agglutination and CIE as potential serodiagnostic techniques for farmer's lung disease is suggested.

Kittens with maternal antibodies to myxoma virus, the offspring of rabbits which had recovered from myxomatosis, were exposed to fleas contaminated with myxoma virus and/or contact with infected rabbits from birth. All kittens died or became infected before 8 weeks of age. When compared with adult animals similarly infected the kittens showed no advantage in terms of survival time or recovery rate attributable to maternal antibodies. Flea transmission of virus was found more effective than contact transmissions.

One hundred and eighty-seven samples of slurry from cattle were examined for the presence of salmonellas, pathogenic leptospires and brucellas. Small numbers of salmonellas, generally less than 1/g., were isolated from 20 samples (11%). These were S. dublin (12), S. typhimurium (4), S. indiana (1), S. bredeney (1), S. cerro (1) and S. unnamed 4,12: d:—(1).

Leptospires were isolated from 56 samples (30%) but none was pathogenic for hamsters. No brucellas were isolated. The results of this survey are discussed in relation to the epidemiology of salmonellosis.

The mouse was used as a model to determine whether storage of Salmonella dublin in slurry and in broth reduces the virulence of the organism. No reduction in virulence of S. dublin stored in slurry for 36 days or in maintenance broth for 70 days was observed. The disease hazard involved in pasture-spreading of slurry contaminated with salmonellas is related to factors other than virulence.

The effect of antigens of Bordetella pertussis and their antibodies on brain infections by B. pertussis in mice are suppression of an infection immediately, so that the initial 90 % loss due to leakage from the brain is maintained or the numbers of bacteria are reduced even further, sometimes with complete sterilization particularly after a small lethal challenge of 10 LD 50 (mechanism 1), and a delayed antibacterial activity in vivo which does not begin until 3 days after challenge (mechanism 2). The first, immediate reaction is over in 2–3 days; the second is maintained from 3–4 days onwards, and results in elimination of the bacteria and protection of mice.

The parts played in vivo in overcoming infection in these two ways by two antigens and their respective antibodies have been investigated. These antigens are a lipopolysaccharide capable of eliciting an antibody which is bactericidal in vitro in the presence of complement called the ‘bactericidal antigen’, and the mouse protective antigen.

Considering first passive immunity, bactericidal antibody elicited by isolated antigen, and of high titre in vitro, is only very weakly active by mechanism (1) in vivo. Brains are seldom sterilized and mice not therefore protected. Antisera to whole cell vaccines whether they contain the ‘bactericidal antigen’ or not, or the protective antigen or not can more easily reduce infections by mechanism (1), eliminating small lethal challenges in some mice which are protected. A passive, intracerebrally protective antibody (PIPA) different from other known antibodies, has been postulated to account for this. Antisera to whole cell vaccine which is protective as denned in the potency assay, can, in additon to this, protect mice by mechanism (2) not only against 10 LD 50 but also 100 LD 50 challenge, and is the only antibody which can do this.

These antibodies have been investigated by injecting them with the challenging organisms. The antibody effects described above are given by antisera stimulated by several injections and also by the concentrated serum immunoglobulins of once vaccinated mice. The antibody, which is bactericidal in vitro only, is in the 7 S globulin fraction of the serum of once vaccinated mice. The protective antibody capable of overcoming small and large challenges is in the 19 S and 11 S globulins. The antibody, PIPA, protecting against small lethal challenges only is in the fraction A2 containing mainly 11 S globulin.

In active immunization experiments the suppression of infection which immediately follows intracerebral vaccination, but which only lasts 2–3 days (mechanism 1), is not dependent on either ‘bactericidal’ or protective antigens but on a component present in all our whole cell vaccines. Vaccines which also had protective antigen eliminated the remaining infection at 4–6 days after challenge by mechanism (2).

As in passive immunity, only the protective antigen can completely overcome 100 LD 50. Suppression of a small, lethal, intracerebral infection given 14 days after intraperitoneal vaccination by mechanism (1) may however be correlated with protective antigen.

When mice were injected intracerebrally with doses of Bordetella pertussis vaccine greater than 5 ImD50 and challenged intracerebrally 14 days later with virulent B. pertussis there was an immediate reduction in the numbers of organisms. An analysis of this in vivo bactericidal effect has shown that large doses of an unrelated vaccine, Salmonella typhosa, equivalent in cell mass to about 50 ImD 50 of B. pertussis vaccine can achieve this effect, so for such doses the effect must be partly non-specific. This action is not maintained and so is not ultimately protective. Local immunoglobulin was also demonstrable 14 days after 300 ImD 50 of B. pertussis vaccine but following smaller doses of 10–20 ImD 50 it could not be found until after the mice had been infected and the blood–brain barrier impaired.

A similar immediate reduction in the numbers of infecting organisms inoculated 1 day after vaccination has been shown to follow very small, non-protective doses of vaccines unrelated to B. pertussis and to be achieved with lipopolysaccharide and endotoxin isolated from B. pertussis. Brains were not sterilized and only in mice receiving protective B. pertussis vaccine was the lowering of infection maintained beyond 2 days and the brains eventually sterilized.

The antibody passively protecting mice against intracerebral infection was found in the 19 S and 11 S globulin fractions of the serum of once-vaccinated mice and in the 11 S and 7 S fractions of the serum of rabbits and ascitic fluid of mice receiving repeated doses of vaccine. The IgM probably eliminated infections by immediate sterilization but had to be present locally to do so since it was unable to pass from the circulation into the brain, and was therefore inactive when injected intraperitoneally. The IgA and IgG were not so restricted and both the 11 S and 7 S globulins were capable of exerting an immediate suppressive effect on infecting organisms. The 7 S globulin was also capable of a maintained or delayed suppressive effect.

Lymphocytes from fully protected once-vaccinated mice, transferred 2–3 weeks after intraperitoneal vaccination, were able to confer some protection when injected intraperitoneally or intracerebrally into recipient mice infected 2 weeks after transfer. Homologous, non-concentrated antiserum from once-vaccinated mice, injected intraperitoneally 1 hr. before infection sometimes augmented the transferred immunity, whereas alone it was inactive.

Laboratory tests were carried out to assess the efficacy of gophacide as a rodenticide against the Norway rat (Rattus norvegicus) and the house mouse (Mus musculus). Results of feeding tests with wild animals suggest that the compound would be more useful against mice than rats, and that 0.3% would be a near optimal concentration for field trials for both species.

The hazards of using gophacide as a rodenticide are discussed.

The acute rodenticide gophacide was tested against urban infestations of the house mouse (Mus musculus L.) and treatment success was assessed from the results of census baitings conducted before and after each treatment. Seven of eight populations of mice living in premises where alternative food supplies were limited were successfully controlled when medium oatmeal bait containing gophacide at 0.1% was laid directly for 4 days. In further treatments against mice inhabiting more complex environments and having greater access to other foods, the performance of gophacide at 0.1% and at 0.25% in a wholemeal flour/pinhead oatmeal/corn oil bait was compared with that of zinc phosphide at 3.0% in the same bait-base. The poison treatments were conducted for 1 or 4 days and always after 3 days pre-baiting. Treatment success varied considerably irrespective of the type of treatment or of the poison used. In general, however, gophacide proved to be as effective as zinc phosphide for the control of mice.

Two strains of type SAT 2 foot-and-mouth disease virus which gave high titres of haemagglutinin activity reacted type-specifically in direct haemagglutinationinhibition tests with reference, bovine convalescent antisera. Comparisons of the haemagglutination-inhibition and the serum neutralization tests using cattle sera showed that both were equally specific and sensitive for detecting virus antibody.

A study of the distribution of subtypes ad and ay among sera from hepatitis B antigen-positive subjects in North West England and North Wales revealed a marked contrast between symptomless carriers among whom ad predominated and patients with acute hepatitis the majority of whom were ay. Those with hepatitis associated with drug addiction or other forms of ‘needle transmission’ were almost all of subtype ay. On the other hand in cases of ‘sporadic’ hepatitis without evidence of parenteral exposure subtypes ad and ay are about equally distributed.

These findings are similar to those reported from other countries in Northern Europe and North America. Although geographical and social factors clearly affect the distribution of the two subtypes it is suggested that the virus of subtype ay may be more readily transmitted than subtype ad by parenteral routes involving small amounts of blood.

To assess the relative importance of different postulated modes of spread of hepatitis B in dialysis units, blood charged with various tracer organisms was used in simulated haemodialysis runs in four laboratories, and the resulting contamination of equipment and environment was measured semi-quantitatively.

Some airborne spread of the tracer organism occurred when tubing containing contaminated blood was needled as the ‘patient’ went on and came off the dialyser. Virtually no small airborne particles could be demonstrated however in simulated emergencies in which a blood line was disconnected, or even when bottles of blood were dropped on to a hard floor from a height of 2 metres.

Bacillus globigii spores from contaminated blood leaked in small numbers into the dialysing fluid through apparently intact coils. T3 phage, with a particle size of the same order as hepatitis B virus, passed in small quantities through the membrane of a Kiil dialyser from blood to dialysing fluid and also in the reverse direction when added to the header tank. A number of other dialysers were also permeable to phage.

Visual assessment of the appropriate moment for inserting the venous line into the ‘patient’ at the onset of dialysis was shown to be unreliable, as the displaced fluid from the end of the venous line was already contaminated before it contained visible red blood cells.

Considerable contamination of exposed surfaces and of the buttons on the proportionating unit cabinet occurred. Minor visible splashing of blood was a commonplace of the laboratory experiments and was shown to be also a common event during routine haemodialysis in two of the dialysis units taking part in the studies.