Before proceeding to describe the imago of Anopheles, we wish to record some observations regarding the hibernation of the larvae of various Culicidae. Grassi (1900, p. 47)1 considered that A. bifurcatus hibernated chiefly in the larval form, for he found the larvae of this species in midwinter in Southern and Central Italy, the imagines being rarely encountered. It was quite different with A. maculipennis. In this case the imagines congregated in houses, huts, caverns, etc., whereas no larvae could be found during the winter. Though he assumed that it was so, his finding the larvae in midwinter in the first instance did not prove that they hibernated, for they might well have been derived from late-laid eggs.

In the absence of perfect reference standard, classical techniques result in biased diagnostic accuracy and prevalence estimates. By statistically defining the true disease status, latent class models (LCM) constitute a promising alternative. However, LCM is a complex method which relies on parametric assumptions, including usually a conditional independence between tests and might suffer from data sparseness. We carefully applied LCMs to assess new campylobacter infection detection tests for which bacteriological culture is an imperfect reference standard. Five diagnostic tests (culture, polymerase chain reaction and three immunoenzymatic tests) of campylobacter infection were collected in 623 patients from Bordeaux and Lyon Hospitals, France. Their diagnostic accuracy were estimated with standard and extended LCMs with a thorough examination of models goodness-of-fit. The model including a residual dependence specific to the immunoenzymatic tests best complied with LCM assumptions. Asymptotic results of goodness-of-fit statistics were substantially impaired by data sparseness and empirical distributions were preferred. Results confirmed moderate sensitivity of the culture and high performances of immunoenzymatic tests. LCMs can be used to estimate diagnostic tests accuracy in the absence of perfect reference standard. However, their implementation and assessment require specific attention due to data sparseness and limitations of existing software.

We conducted a prospective birth cohort study in rural Sudan to assess measles virus (MV)-specific antibody levels at different time points in infancy. Dried blood spots were collected on filter paper at birth (cord blood) and at ages 6, 12 and 24 months (heel-prick). Maternally derived MV-specific antibody levels were high in cord blood samples, but at the age of 6 months had dropped below cut-off values in half of the infants. By extrapolation it was concluded that the current Expanded Programme of Immunization (EPI) target age for measles vaccination of 9 months was an appropriate choice for this area. At the age of 24 months acquired MV-specific antibodies were detected in 65–85% of the cohort, which corresponded well with the 79% of infants reported to be vaccinated by this age. This study demonstrates the usefulness of filter paper blood samples for seroepidemiological studies in developing countries.

The susceptibility to antimicrobial agents of 569 salmonella isolates collected in 1977–8 from patients in hospitals in Rome was tested. Fifty-nine per cent of all isolates were resistant to one or more antimicrobials. Resistance was most common to sulphathiazole, tetracycline, streptomycin, whereas colistin, gentamicin, tobramycin, trimethoprim-sulphamethoxazole and nalidixic acid were the most active in vitro.

Multiple resistance was most frequently found in strains of Salmonella wien and S. typhimurium (94% and 38% respectively).

A significant change in the resistance pattern of S. wien was observed between 1977 and 1978, with a significant increase of susceptibility to some antimicrobials in 1978.

Twenty-one R-plasmids transmissible to E. coli K12 were derived from 46 resistant strains of S. typhimurum.

This study investigated the extent to which proximity to cattle and weather events in Alberta predispose human populations to E. coli O157 disease. Cases of human E. coli O157 infection in Alberta between 2004 and 2011 were obtained from the province's Communicable Disease Reporting System and Discharge Abstract Database. Regression models based on spatial area incorporated human infection data with livestock and weather covariates. A variety of regression models were applied (i.e. least squares, spatial lag/error, Poisson, negative binomial) to test the most appropriate approach. Ratios for the total number of calves, bulls and beef cows to human population were highlighted as significant cattle density variables in all final best-fitting models. Weather variables were not significant in final regression models averaged over the full study period. Our results provide evidence of a significant association between measures of cattle density and human E. coli O157 disease in Alberta.

Foodborne disease outbreaks (FBDOs) occur frequently in Europe. Employing analytical epidemiological study designs increases the likelihood of identifying the suspected vehicle(s), but these studies are rarely applied in FBDO investigations. We used multivariable binary logistic regression analysis to identify characteristics of investigated FBDOs reported to the European Food Safety Authority (2007–2011) that were associated with analytical epidemiological evidence (compared to evidence from microbiological investigations/descriptive epidemiology only). The analysis was restricted to FBDO investigations, where the evidence for the suspected vehicle was considered ‘strong’, i.e. convincing. The presence of analytical epidemiological evidence was reported in 2012 (50%) of these 4038 outbreaks. In multivariable analysis, increasing outbreak size, number of hospitalizations, causative (i.e. aetiological) agent (whether identified and, if so, which one), and the setting in which these outbreaks occurred (e.g. geographically dispersed outbreaks) were independently associated with presence of analytical evidence. The number of investigations with reported analytical epidemiological evidence was unexpectedly high, likely indicating the need for quality assurance within the European Union foodborne outbreak reporting system, and warranting cautious interpretation of our findings. This first analysis of evidence implicating a food vehicle in FBDOs may help to inform public health authorities on when to use analytical epidemiological study designs.

Contamination of a laboratory environment with pathogenic or non-pathogenic micro-organisms may be relevant to safety of technicians and quality of technical performance. Two widely separated incidents in 1968 and 1974 initiated a study of aspects of the laboratory environment. Water-baths, water of syneresis and portions of salmonella cultures spurting out of the sterilizing flame were examined. The water of water-baths was shown to be contaminated from the fluid cultures incubated in them. This raised questions of potential cross-contamination and reporting of false positives. Water of syneresis was sometimes contaminated with salmonellas. A few quantitative counts were made. The range of counts varied between 16 salmonellas per ml. and 13,000,000 salmonellas per ml. Five hundred portions of salmonella cultures and 571 portions of Shigella sonnei cultures which had spurted from the sterilizing flame were examined. All these samples failed to grow salmonellas or shigellas.

Precautions necessary to avoid environmental contamination are briefly discussed.

A dipthericin typing scheme has been constructed using 441 strains of Corynebacterium diptheriae isolated in eastern Australia from 1962 to 1971. Ten types have been distinguished using seven strains of C. diphtheriae and two strains of C. belfanti as indicators of the diphthericins produced by the newly isolated strains. Strains grouped into types L2, L3 and L3a were found only in Melbourne and types L1 and L4 were predominant in Sydney. Type L5 strains were isolated intermittently throughout the period of study and were found in all eastern states. Numerical analysis of the characteristics of the strains suggests that associations exist between, on the one hand, diphthericin type and, on the other hand, bacteriophage type, serotype and biochemical activity.

Cryptosporidiosis and giardiasis have been recognized by the WHO as ‘Neglected Diseases’. Minimal attention has been paid to the spatial and temporal distribution of disease incidence patterns. Using disease notification data, we detected spatio-temporal clusters of cryptosporidiosis and giardiasis across three time periods: (i) 1997–2000, (ii) 2001–2004, (iii) 2005–2008. There was substantial variation in the geographical location and timing of recurrent cryptosporidiosis and giardiasis clusters. Statistically significant (P < 0·05) giardiasis clusters tended to occur in predominantly urban areas with little apparent seasonal influence, while statistically significant cryptosporidiosis clusters were detected in spring, in areas with high livestock land use. The location and timing of cryptosporidiosis clusters suggest an influence of livestock production practices, while urban exposures and host behaviour are likely to influence giardiasis clusters. This approach provides a resource-efficient method for public health authorities to prioritize future research needs and areas for intervention.

Between 1961 and 1972, 4547 independent strains of Staphylococcus aureus isolated from one hospital were examined for phage type. After 1967 there was a decline in the number of strains received, which we consider reflects a decline in the number of infections in the hospital, and which was largely accounted for by a great reduction in the number of strains in four ‘epidemic’ types. Overall, the number of multiple-resistant staphylococci received also declined; this was in part due to the decline in the epidemic types and in part to a reduction in the proportion of multiple-resistant strains of all types.

If a medium containing either 1 per cent. ammonium succinate or 1 per cent. ammonium fumarate together with certain inorganic salts be inoculated with B. pyocyaneus and incubated aerobically at 37° C. a vigorous growth of the organism will ensue, the rates of growth in both cases not being markedly different from each other. If the growth be allowed to proceed for a fortnight, analysis of the media shows that essentially similar products (mixtures of the lower fatty acids) have been produced in both cases. If the growth be allowed to proceed for not longer than three days, analysis shows that in the succinate medium over 80 per cent. of the succinic acid has not been utilised, whilst in the other medium the entire fumaric acid has disappeared, giving rise in its stead to pyruvic acid which is further utilised as growth proceeds(1). Quantitative data support the view that the breakdown of succinic acid occurs through the intermediate production of fumaric acid, the rate of fermentation of fumaric acid being greater than that of succinic acid, so that fumaric acid is not detected among the products of fermentation of succinic acid. If this view is true, it should be possible to show that B. pyocyaneus has the power of oxidising succinic acid to fumaric acid. It is clear that the proliferating organism cannot be used to demonstrate this experimentally, for the fumaric acid is utilised as quickly as it is formed. Hence it is necessary to use the organism in such a condition that proliferation is completely (or almost completely) eliminated. Under such circumstances the fumaric acid will accumulate and its detection will be made possible.

The performance of the rodenticide 5-p-chlorophenyl silatrane at 0.5% in a wholemeal flour/pinhead oatmeal/corn oil bait was compared with that of zinc phosphide at 3% in the same base in poison treatments carried out against urban infestations of the house mouse (Mus musculus L.). Each poison treatment was conducted for 1 day and after 3 days' pre-baiting. The success of the treatments was assessed from census baitings conducted before and after treatment. Treatment success varied considerably with both poisons used but in general 5-p-chlorophenyl silatrane proved to be at least as effective as zinc phosphide, a commonly used acute rodenticide for the control of mice.

The air of loose-boxes holding pigs affected with swine vesicular disease was sampled for virus. In the multistage impinger virus to a titre of 102·6 TCID50 was associated with particles greater than 6 μm., 101·6 with particles 3–6 μm. and 101·4 or less with particles less than 3 μm. In the noses of workers in contact with the pigs for periods not less than 5 min., virus to a titre of 102·4 TCID50 was found. Virus was recovered from the air for 2–3 days during the disease and maximum titre in pigs infected by injection or by contact occurred on the second to third day after generalization of the lesions. The amounts of virus were about 160-fold less than those recovered from pigs affected with foot-and-mouth disease, and the quantity and time of excretion suggest that the source of swine vesicular disease virus in the aerosol may be from the lesions and skin rather than from the respiratory tract.

The stool samples of 75 patients with gastroenteritis and/or loose and watery faeces at three hospitals and one clinic in Zaria were examined for Cryptosporidium. The stool samples were concentrated by the formol–ether method and stained with safranin–methylene blue. Sixteen (21%) samples were positive. The rate of detection was higher among females (27%) than males (17%) and among adults (29%) than children (8%). The study confirmed the presence and possible significance of Cryptosporidium, which is a known zoonotic protozoan, in the aetiology of human gastroenteritis in Zaria, Nigeria.

Samples of blended mutton tissue in small polyvinyl chloride sachets were incubated in water baths for different times and at varying temperatures. The temperature of each bath was recorded accurately throughout each experiment. Using equations previously derived for the lag and generation times of coliform organisms in blended mutton tissue, the expected increases of these bacteria were calculated from the time/temperature recordings. These were compared with the data obtained from plate counts made on the tissue samples in the sachets before and after incubation. The studies were done with a strain of Escherichia coli, one of Salmonella lyphimurium and the coliform organisms naturally present on sheep carcasses processed in a commercial abattoir. The calculated growth agreed closely with that measured. Therefore, if mutton, after overnight chilling, is warmed again to temperatures within the growth range of these bacteria, the possible increases in the numbers of cells present can be calculated directly from time and temperature measurements.

The implications for the present codes of practice in abattoirs are discussed.

The pattern of phage types of 2553 strains of Salmonella typhi isolated over the 10-year period 1970–9 was studied. During the period 29 different phage types were encountered, not including the categories of ‘untypable strains’, ‘degraded Vi-strains’ and Vi negative strains. For the period as a whole, the commonest phage types encountered were A (20·9%), E1 (14·8%), D1 (10·3%), degraded Vi positive strains (10·3%), untypable Vi strains (7·3%), C4 (7·1%), D2 (4·4%), E2 (3·9%) and type 25 (2·6%). There were phage types which appeared in the early years of the period and then disappeared (types B2, D9 and D1-N). Others only made their appearance in recent years (K1 and 53). Notable differences were also seen in the predilection of some phage types for certain geographical areas.

1. A study has been made of different types of coliform bacteria with particular reference to (a) their ability to ferment lactose in MacConkey broth at different temperatures, and (b) the effect of using different temperatures of incubation for the indol, methyl-red, V.P., and citrate tests.

2. It was found that 97% of the cultures of Bact. coli (indol positive, methyl-red positive, V.P. negative, citrate negative) examined could ferment lactose with production of acid and gas between 40 and 44° C. The number was not appreciably reduced at 45° C. but was markedly reduced at 46° C. 28% of the cultures of Bact. coli (indol negative, methyl-red positive, V.P. negative, citrate negative) and 15% of Bact. aerogenes (indol negative, methyl-red negative, V.P. positive, citrate positive) were found to be positive at 44° C.

3. The adoption of a temperature of incubation of 30°C. for the V.P. test as advocated by Levine (1941) and the use of O'Meara's test showed that many cultures previously regarded as unable to produce acetylmethylcarbinol were in fact able to do so. Employing a temperature of 30°C. for 5, or in some cases 7, days for the methyl-red test, it was found that with nearly all the cultures tested there was an inverse correlation between the results of the methyl-red test and those of the V.P. test. With these modifications in technique some cultures originally designated as Intermediate type I were found to have reactions corresponding with those of Bact. aerogenes type I. Similarly, many cultures originally classified as Intermediate type II should have been typed as Bact. aerogenes type II.

4. It was found that all cultures of Intermediate type I classified as such by the new technique were incapable of using the nitrogen of uric acid for growth, but that the majority produced hydrogen sulphide. Cultures of Bact. aerogenes type II, on the other hand, grew well in uric acid medium, but produced no hydrogen sulphide.

The investigation described in this paper was carried out by the Freshwater Biological Association, as part of the programme of the Water Pollution Research Board of the Department of Scientific and Industrial Research. The paper is published by permission of the Department.

A field survey conducted amongst children in a semi-rural area of Ceylon has revealed a high rate of Schick negative conversion early in life. A high carrier rate of C. diphtheriae in cutaneous ulcers which probably accounts for this early Schick conversion has been detected. The role of cutaneous diphtheria and that of non-toxigenic organisms in the acquisition of natural immunity to the disease is discussed.

During a recent epidemic of poliomyelitis three viruses isolated (one Type 1 and two Type 2) elicited both Type 1 and Type 2 CF and precipitating antibodies in the patients whilst only the homotypic neutralizing antibodies were present. These viruses inoculated into animals produced specific CF and neutralizing antibodies, but precipitating antibodies to both types were present in a significant number of animals. These findings suggest that certain polioviruses have complement-fixing and precipitating antigens common to both Type 1 and Type 2 viruses.

We would like to thank our colleagues in the Virus Research Unit for their helpful advice and criticism and Dr J. Hampton (Poliomyelitis Inst., Johannesburg) for the concentrated Type 1 poliovirus vaccine.