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.

Sixteen foot-and-mouth disease virus (FMDV) strains of type SAT 1 were compared in complement-fixation tests. With the test used, the range of antigenic variation within a type appeared to be greater than previously described. The concept of a sub-type group within which all strains are more closely related to each other than to any strain outside the group was not supported. Considering the group of strains studied, it is suggested that the classification of strains is best achieved by nominating a reference strain for each sub-type. Others are classified as related strains in one or more sub-type groups according to their relationships with the reference strains.

Inocula of polluted water naturally infected with salmonellas effectively distinguished six brands of selenite and six brands of tetrathionate enrichment media into satisfactory and unsatisfactory categories. Minimal inocula of pure cultures differentiated the tetrathionates, but not the selenites. Inocula of naturally infected chicken giblets suggested that there was a difference between two comparable brands of tetrathionate, but this was not statistically significant. The difference was, however, clearly demonstrated by minimal inocula of pure cultures.

Intensive investigation of two inferior tetrathionates revealed inhomogeneity in the distribution of brilliant green in one bottle of one brand. The importance of the salmonella serotype and even the colonial variant used for the pure culture inoculum was also demonstrated.

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.

Ten mycoplasmas were isolated from 130 nasopharyngeal swabs from thoroughbred horses with acute respiratory disease and three from 198 apparently normal horses. Two mycoplasmas were isolated from 21 tracheal swabs taken at necropsy. These mycoplasmas, together with six isolated from the equine respiratory tract by other workers, were subjected to biochemical and serological tests. Other properties examined in certain representative strains were appearance under the electron microscope, ability to adsorb or agglutinate the erythrocytes of various animal species and the electrophoretic pattern of the cell proteins.

On the basis of these tests, mycoplasmas from the equine respiratory tract were divided into seven species. Three species belonged to the genus Acholeplasma, members of which do not require sterol for growth, and were identified as A. laidlawii, A. oculi (formerly A. oculusi) originally isolated from the eyes of goats, and a recently named species A. equifoetale, previously isolated from aborted equine fetuses.

Of the four sterol-dependent Mycoplasma species, one was identified as M. pulmonis, a common rodent pathogen. Another cross-reacted serologically with M. felis and should probably be classified as that species. The other two species probably represent new species peculiar to the horse. One of these, represented by the strains N3 and N11, ferments glucose and is serologically distinct from 19 recognized species of glucose-utilizing mycoplasmas and from two species which do not metabolize either glucose or arginine. The other species, represented by four strains, hydrolyses arginine and, because it is serologically distinct from all the named arginine-hydrolysing Mycoplasma species, the name M. equirhinis sp.nov. is proposed for it.

Of the seven species, only M. pulmonis and the glucose-utilizing species represented by N3 and N11 were found exclusively in horses with acute respiratory disease. A. oculi was isolated from an apparently normal horse. The other four species were found in normal horses as well as those with respiratory disease, although three out of the four strains of M. equirhinis were from sick horses.

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.

Animal experiments have shown that respiratory administration of pertussis antigen induces a protective immune response. In this study pertussis antibody in human respiratory secretions was measured and the response to aerosol and intramuscular pertussis immunization investigated. Substantial increases in this antibody occurred after aerosol immunization but no changes were found in serum antibody. The reverse was observed after intramuscular immunization. Severe side effects are frequently seen after intramuscular pertussis vaccine in adults but not with aerosol immunization. The latter method may be of value for paediatric medical and nursing personnel exposed to the risk of pertussis infection.

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.

The influence of the Open Air Factor (OAF) and daylight on the survival of foot-and-mouth disease (FMD) virus held as captured aerosols on spider micro-threads has been investigated. Virus inactivation due to OAF was slight. Similarly, the effect of daylight on the survival of virus was not marked. The results are discussed in relation to the airborne spread of FMD virus in nature.

A method for typing ECHO and Coxsackie B viruses using counter-electrophoresis has been developed using stock strains of 15 different ECHO types and 5 Coxsackie B viruses. Work is continuing to see whether the method is a practical one to use for typing of strains from patients infected with ECHO or Coxsackie B viruses.

The virulence of field strains of myxoma virus is increasing in the Mallee region of Victoria where the resistance of the rabbit to myxomatosis is high. This suggests that the climax association will be a moderately severe disease.

After experimental inoculation of Cytoecetes ondiri, the agent of bovine petechial fever (BPF), multiplication occurred in impala, bushbuck, Thomson's gazelles and wildebeest, as shown by infectivity studies and clinical findings. Similar attempts to infect one eland failed.

As a sequel to this, blood and spleen samples were collected from four species of wild ruminants in an area where BPF was endemic. Isolations of C. ondiri were made from three of five bushbuck, but not from any other species.

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.

An attempt was made to correlate serological relationships determined by the pili, the flagella and the O-somatic antigens of Pseudomonas aeruginosa, and to make a preliminary assessment of use of the pilus antigen as an epidemiological marker. A method is described for the preparation of antiserum specific for the ‘normal’ PSA pili of P. aeruginosa. A high titre of pilus antibodies was obtained by immunizing rabbits with mutants whose pili had lost their ability to retract into the cell. The ‘normal’ form of the organism, with retractile pili, was poorly agglutinated by high-titre anti-pilus serum, but suspensions of it that had been treated with osmium tetroxide showed greatly increased agglutinability. Antibody labelling for electron microscopy was used to determine the serological relations of pili and of flagella for P. aeruginosa strains belonging to different serological groups as defined by O-somatic antigens. The distribution of pilar and flagellar antigens among strains was not correlated with the O-somatic serotype. A strain of P. aeruginosa carrying a drug-resistance plasmid had fewer ‘normal’ PSA pili than the background strain.

Pseudomonas aeruginosa normally possesses thin polar pili (fimbriae) which constitute one of the classes of heat-labile antigens of the organism. A previous study of the flagellar antigens (Pitt & Bradley, 1975), which are also heat-labile, was an essential preliminary to the development of a useful typing system based on heat-labile antigens. The present work extends this to the pilus antigens. The principle object is to define serological differences determined by pili, flagella, and heat-stable O-somatic antigens. In order to make this comparison, it has been necessary to develop a method for preparing specific antisera against pili, free from flagellar and O-somatic antibodies.

Many studies have been made of P. aeruginosa pili; two basic types of pili have so far been established: (1) the ‘normal’ polar pili mentioned above (Bradley, 1966), to be called PSA pili for convenience and (2) the non-polar pili determined by the intergeneric P-group drug-resistance plasmid RP1, called RP1 pili (Bradley, 1974a; C. H. To & C. C. Brinton, in preparation). Non-polar pili have also been found in association with the P. aeruginosa-specific drug-resistance plasmid R130 (L. E. Bryan, University of Alberta, Canada, personal communication), but they are still under study and little is known about them. Since the present work is principally aimed at evaluating the usefulness of pilus antigens as serological markers, emphasis has been placed on PSA pili, though obviously the presence of R-factor-determined pili cannot be ignored.

There are two ways of observing the serological relationships of bacterial appendages such as pili: either qualitatively by the direct observation of adsorbed antibodies in the electron microscope (Lawn, 1967), or quantitatively by conventional agglutination tests. In this work we have used the first method to define different serological types of pilus, and the second to study in detail the reactions of antibodies specific to the pilus.

Although the injection into rabbits of formolized suspensions of P. aeruginosa results in the formation of flagellar antibody in high titre, the antibody response to the pili is poor (Pitt & Bradley, 1975). The pilus is in the form of a long thin filament consisting of polymerized pilus protein or pilin. It has been demonstrated (Bradley, 1972a) that under certain influences, such as chemical action or bacteriophage adsorption (see below), the filaments withdraw into the cell, the pilin probably being depolymerized by a mechanism at the base. Certain P. aeruginosa mutants that lack the ability to retract their pili (Bradley, 1972a, 1974b) have many more filaments than do normal strains. We now show that these mutants are valuable in producing high-titre antiserum. Other mutants without pili have been isolated (Bradley, 1972b), and absorption of sera with these organisms removes antibodies to other components of the cell.

Certain bacteriophages use P. aeruginosa pili as receptors (Bradley, 1966, 1973a, b, 1974a; Bradley & Pitt, 1974). One aspect of the present work has been to determine whether the phage-sensitivity pattern varies with pili of different serological types.

A comparison was made of the antibody response and subjective reactions to zonally-purified influenza vaccine in aqueous suspension and in peanut oil adjuvant 65-4. Both preparations contained 700 CCA units of A/Aichi/2/68, and 300 CCA units of B/Mass/1/71.

Subjective reactions were recorded by asking the volunteers to complete a record daily for 5 days. Pain at the injection site was recorded by 64% of the recipients of the oil adjuvant vaccine compared with 35% of the aqueous recipients, but local redness was more frequent after aqueous vaccine. Systemic symptoms were recorded a little more frequently after aqueous than oil adjuvant vaccine.

When measured 7½ weeks after a single dose of vaccine, the HAI geometric mean antibody titre (G.M.T.) to the A/Hong Kong/1/68 antigen (antigenically similar to the A/Aichi/2/68 antigen in the vaccine) increased 2·7-fold after aqueous and 16·4-fold after adjuvant vaccine. Sixty-two weeks after vaccination the antibody titres remained higher in those given adjuvant vaccine. The G.M.T. to B/Mass/1/71 increased 1·9-fold 7½ weeks after aqueous vaccine and 3·7-fold after adjuvant vaccine.

The antibody response to both influenza A and B antigens was broader in the recipients of adjuvant vaccine. The G.M.T. to A/England/42/72 increased 2·8-fold after aqueous and 13-fold after adjuvant vaccine; and to B/England/847/73 it increased 1·3-fold after aqueous and 1·9-fold after adjuvant vaccine.

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.

Most normal bovine whey samples contain a fraction that survives heating at 56° C. for 30 min., passes through a dialysis membrane and kills a maximum of seven out of ten of the different bovine mycoplasma species tested. Some whey samples appear more active than others but not all affect the same strains of mycoplasma indicating some specificity in their action. Absorption of the active factor from whey by heterologous and homologous mycoplasmas and by erythrocytes was observed. Binding of the factor to mycoplasmas appears to be temperature-dependent and non-specific, but subsequent mycoplasmacidal action shows some specificity.

Incidents of non-specific illness associated with the consumption of oysters have highlighted the lack of published information on the bacteriology of shellfish suitable for consumption. Investigations showed that the majority of molluscan shellfish entering English markets conform to the accepted standard of less than 5 Escherichia coli/ml. tissue. The numbers of E. coli were related to the sanitary quality of the growing area but no relation could be established between numbers of E. coli and coliforms, faecal streptococci or Clostridium welchii. The numbers of non-specific bacteria varied considerably but shellfish from sources associated with non-specific illness yielded relatively high counts at 37° C. The results showed that there was no justification for a standard based on total plate counts, which often exceeded 106/g. Such a standard would have to be coupled with spoilage or the incidence of non-specific illness. The relation between the numbers of non-specific bacteria growing at 20 and 37° C. appears to be a useful measure for assessing the likelihood that raw shellfish are a public health risk.

The efficacy of difenacoum as a new anticoagulant rodenticide was evaluated by blood coagulation studies and laboratory feeding tests using warfarin-resistant and non-resistant common rats (Rattus norvegicus), ship rats (R. rattus) and house mice (Mus musculus). Prothrombin assays indicated that the compound had as marked an activity with warfarin-resistant common rats as coumatetralyl had with non-resistant animals. Feeding tests confirmed that 0.005% would be a near-optimal concentration for field use, although there was some evidence of unpalatability.

Results with ship rats and house mice were less favourable. Trials with enclosed colonies of warfarin-resistant mice confirmed the laboratory finding that although difenacoum was more effective than all other currently used anticoagulants, it was unlikely to give complete control.

It is concluded that difenacoum is a valuable new rodenticide, especially for controlling warfarin-resistant common rats.