To improve both safety and stability of the oral vaccines used in the field to vaccinate foxes against rabies, a recombinant vaccinia virus, which expresses the immunizing G protein of rabies virus has been developed by inserting the cDNA which codes for the immunogenic glycoprotein of rabies virus into the thymidine kinase (TK) gene of the Copenhagen strain of vaccinia virus. The efficacy of this vaccine was tested by the oral route, primarily in foxes. The immunity conferred, a minimum of 12 months in cubs and 18 months in adult animals, corresponds to the duration of the protection required for vaccination of foxes in the field. Innocuity was tested in foxes, domestic animals, and in numerous European wild animal species that could compete with the red fox for the vaccine bait. No clinical signs or lesions were observed in any of the vaccinated animals during a minimum of 28 days post vaccination. Moreover, no transmission of immunizing doses of the recombinant occurred between foxes or other species tested. To study the stability of the vaccine strain, baits containing the vaccine were placed in the field. Despite considerable variations of environmental temperatures, the vaccine remained stable for at least one month. Because bait is taken within one month, it can be assumed that most animals taking the baits are effectively vaccinated. To test the field efficacy of the recombinant vaccine, large-scale campaigns of fox vaccination were set up in a 2200 km2 region of southern Belgium, were rabies was prevalent. A dramatic decrease in the incidence of rabies was noted after the campaigns. The recombinant is presently used to control wildlife rabies in the field both in several European countries and in the United States.

This review presents experimental, preclinical and clinical data illustrating the multiple uses of recombinant non-replicating virus vectors in the fields of immunoprophylaxis and gene therapy.

This report summarizes studies on 1699 foodborne outbreaks, in Italy, reported to the Istituto Superiore di Sanità (ISS) (the National Institute of Health of Italy, Rome) during the period 1991–4. The most frequently reported foodborne outbreaks were caused by salmonellae (81%), in particular by Salmonella enteritidis and non-serotyped group D salmonella (34% and 33% of the total salmonella outbreaks, respectively). A vehicle was implicated in 69% of the salmonella outbreaks; eggs were implicated in 77% of the outbreaks for which a vehicle was identified or suspected. Salmonella strains isolated in 54 outbreaks were studied for phenotypic and genotypic characteristics. The isolates belonged to S. enteritidis (50 outbreaks), S. typhimurium (three outbreaks) and S. hadar (one outbreak). In the S. enteritidis outbreaks, phage type 4 was most frequently isolated (64·8%), followed by phage type 1 (14·8%). The virulence plasmid of 38 megadaltons was found in many different phage types of S. enteritidis.

Strains of Salmonella enterica serotype Berta, collected over a period of 6 years from a well documented natural outbreak in Denmark, have been characterized in order to assess the stability of chromosomal typing systems and virulence properties. Outbreak strains were identical in Pvu II and Pst I IS200 profiles, all but two strains showed the same Sma I ribotype, and all but one strain showed the same Not I pulsed field gel electrophoretic pattern, indicating that these molecular markers remained almost constant during the outbreak. In general, strains of S. Berta were found to be of moderate to low virulence; log VC10 values were found to vary between 3·0 and 4·4 after i.p. challenge of mice, and maximum CFU in internal organs of day-old chicks varied between 2 and 4 log10 units following oral challenge. The minor differences observed between strains in vivo did not correlate with differences in in vitro invasion into cultured MDCK cells, nor with in vitro growth characteristics. A succession of different plasmid profile types was observed during the outbreak but a hierarchical selection of clones based on differences in virulence was unlikely to have caused the succession of types of S. Berta during this outbreak.

At the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR, B) Dhaka we studied the trends in cholera for the period January 1992 to May 1995. Vibrio cholerae O139 Bengal emerged as a second aetiologic agent of cholera in Dhaka in January 1993. In 1993, the majority of cholera cases was due to V. cholerae O139, with V. cholerae O1 accounting for a small proportion of cases. During the latter part of the study period (Jan 1994–May 1995), V. cholerae O1 re-emerged as the predominant cholera strain. The predominant age group affected in endemic cholera due to V. cholerae O1 was children 2–9 years old, and the organism was isolated from more females than from males at all ages. In contrast, cholera due to V. cholerae O139 caused disease mostly in adults 15 years and older, which indicated that this organism was new in this population. As with V. cholerae O1, V. cholerae O139 was isolated from more females than males. The initial rapid emergence and predominance of V. cholerae O139 was considered possibly to herald the start of the eighth pandemic of cholera. However, just after a year, the prevalence of V. cholerae O139 decreased dramatically with V. cholerae O1 resuming the role of the dominant cholera strain. The factor(s) contributing to the dramatic decline in prevalence of V. cholerae O139 is not well understood.

A 3-year study of Escherichia coli infections in Grampian Region was conducted to ascertain the incidence, document clinical sequelae and identify at-risk groups. Approximately 30000 stools from patients with acute diarrhoea were screened for E. coli O157, and an epidemiological questionnaire filled in for each patient whose stool was positive. Eighty-three patients were studied. The annual incidence was 6 per 100000. Proportionately more infections occurred in people involved in agriculture. Evidence was seen of case-to-case transmission, and contamination of a water supply. Eight cases developed haemolytic uraemic syndrome (HUS). There were 2 deaths due to HUS and 2 due to haemorrhagic colitis (HC). Symptomatic E. coli infection is relatively common in the Grampian Region, more common in the agricultural community, and is the main cause of HUS in this Region.

In this paper, the results of a pilot study of willingness to pay (WTP) to avoid poultry-borne illness are reported. Through this, the problems of devising an economic measure of the ‘intangible’ benefits of prevention of food-borne risk are explored. The study is the first to allow those against a prevention policy (irradiation of poultry-meat) to register their WTP not to have the policy implemented. The study demonstrates that it is feasible to obtain answers to WTP questions from a self-selected sample. Future studies should ensure greater representativeness of respondents, that better information about benefits is provided to respondents and that an appropriate method of aggregation of benefits is used.

Phage typing of Shigella sonnei has been used to examine isolates from the 1991–2 sonnei dysentery outbreak in England and Wales and compare them with strains isolated during and following a widespread foodborne outbreak in 1994 which was associated with consumption of imported lettuce. The distribution of phage types was different in the three periods studied with PT 3 predominating during 1991–2, PT 2 during the ‘lettuce’ outbreak in the summer months and PT 6 during the subsequent months. PT 6 was frequently associated with travel outside the UK. Variation was also seen in the distribution of drug resistance patterns.

In an outbreak of gastroenteritis affecting 43 people, cryptosporidium and campylobacter were isolated from stool specimens and in two cases dual infection was found. All the cases had drunk unboiled water from a private untreated water supply.

Investigations revealed the carcasses of three lambs in a collection chamber connected with the water supply, and these, or run-off of slurry from surrounding fields, were the presumed source of contamination. Issues relating to the maintenance and monitoring of private water supplies are discussed. Problems with such supplies include old piping, proximity of livestock, inadequate knowledge of the layout and limited resources for monitoring and maintenance.

In 1994 we investigated a large outbreak of Burkholderia (formerly Pseudomonas) cepacia respiratory tract acquisition. A case patient was defined as any patient with at least one sputum culture from which B. cepacia was isolated from 1 January to 31 December 1994. Seventy cases were identified. Most (40 [61 %]) occurred between 1 February and 31 March 1994; of these, 35 (86%) were mechanically ventilated patients, 30 of whom were in an intensive-care unit (ICU) when B. cepacia was first isolated. Compared with control patients who were mechanically ventilated in an ICU, these 30 case-patients were significantly more likely to have been ventilated for 2 or more days (30/30 v. 15/30; P < 0·001) or to have been intubated more than once (12/30 v. 2/30; OR = 9·3, 95% CI 1·6–68·8; P = 0·002) before the first isolation of B. cepacia. By multivariate analysis, the 35 mechanically ventilated case-patients were significantly more likely to have received a nebulized medication (OR = 11·9, 95% CI = 1·6–553·1; P < 0·001) and a cephalosporin antimicrobial (OR = 11·9, 95% CI = 1·6–553·1) in the 10 days before the first isolation of B. cepacia, compared with B. cepacia-negative control-patients matched by date and duration of most recent mechanical ventilation. Although B. cepacia was not cultured from medications or the hospital environment, all outbreak strains tested had an identical DNA restriction endonuclease digestion pattern by pulsed-field gel electrophoresis. Review of respiratory therapy procedures revealed opportunities for contamination of nebulizer reservoirs. This investigation suggests that careful adherence to standard procedures for administration of nebulized medications is essential to prevent nosocomial respiratory infections.

Enterotoxin-producing Staphylococcus aureus is a common cause of staphylococcal food poisoning. To determine the incidence of carriage of enterotoxin-producing S. aureus in a sample of the healthy population in Kuwait city, restaurant workers in the city were screened for nasal carriage of S. aureus. 26·6% of 500 workers studied carried S. aureus and 86·6% of the S. aureus produced staphylococcal enterotoxins. 28 % produced enterotoxin A, 28·5 % produced enterotoxin B, 16·4% produced enterotoxin C and 3·5% produced enterotoxin D. Ten isolates produced both enterotoxins A and B or A and C. 73 % of the isolates were untypeable with standard phages. However, 17·1%, 3% and 6% belonged to phage groups I, II and III respectively. The results demonstrated a high level of enterotoxigenic S. aureus carriage among restaurant workers which although lower than that reported for the general population and hospital workers may be important in the restaurant industry.

In view of the known cross-reactivity of sera from patients with intestinal parasites to some Schistosoma mansoni antigens, field work was conducted in an area of Venezuela non-endemic for schistosomiasis using the routine immunoenzymatic assay (ELISA) with soluble egg antigen (SEA). False positive reactions represented 15·3% of the total population as determined by SEA–ELISA. SEA-immunoblotting of the false positive sera indicated that protein fractions of 91 and 80 kDa appear to be responsible for cross-reactivity. Sera from hookworm infected individuals produced a higher frequency and intensity of cross-reaction than other sera. SEA-fractions of 105, 54, 46, 42, 32, 25 and 15 kDa were the most specific.

An outbreak of parvovirus B19 infection at a primary school was investigated using saliva samples. Antibody capture immunoassays for salivary B19 IgG and IgM were developed using a recombinant B19 antigen and monoclonal antibody to B19 virus. Evaluation of the salivary IgG assay using paired serum and saliva samples from 43 staff at St Thomas' Hospital showed that it had a sensitivity of 100% and a specificity of 95%. Evaluation of the salivary B19 IgM assay using 87 paired blood and saliva samples from a study of general practitioner rubella notifications showed it had a sensitivity of 60% and a specificity of 98%. Using the salivary assay the level of B19 IgG within 2 weeks of the start of the outbreak ranged from 5–33% in children and 29% in staff. By detecting salivary B19 IgM and/or B19 IgG seroconversions, attack rates of 8–50 % in children in different classes and 47 % in staff were observed. Household transmission was also studied and an attack rate of 45 % was recorded in 11 susceptibles. After the outbreak, the level of B19 IgG in children with the highest attack rates was 60–70%, similar to that seen in adults in the UK. This study highlights the risk of B19 infection in an institutional setting and shows that saliva samples are a useful alternative to blood.

We determined the nucleotide sequences of Norwalk-like viruses in 10 PCR products from stool or oyster specimens obtained from four outbreaks of gastroenteritis in which shellfish was suspected as the cause in Shizuoka prefecture in Japan between 1987–94. The sequences were determined from nucleotide positions 4561–852 (292 bp) in the polymerase region. Two types of sequences were detected. One (genotype 1) had 87% sequence homology with the prototype Norwalk virus, and the other (genotype 2) had 59 % sequence homology. The sequences from isolates belonging to the same genotype were almost the same regardless of the year of isolation. Because sequences of 2 genotypes were detected in 2 of the 4 outbreaks, nested PCR was performed with genotype-specific primers to detect the presence of 2 genotypes in the same specimen. In 5 of 10 specimens, PCR bands were detected with both genotype-specific primers, indicating the coexistence of 2 genotypes in 1 specimen. We also detected two genotypes of Norwalk-like virus in an oyster from a sample implicated in one of the outbreaks which may provide direct evidence of oysters as the cause of the gastroenteritis.

Effective primary prevention of congenital toxoplasmosis requires up to date information on locally relevant risk factors for infection in pregnant women. In Naples, risk factors for toxoplasma infection were compared in recently infected women (as assessed by detection of specific IgM in serum) and susceptible, IgG negative women. Recent infection was strongly associated with frequency of consumption of cured pork and raw meat. Eating cured pork or raw meat at least once a month increased the risk of toxoplasma infection threefold.

This simple study design for determining locally relevant sources of toxoplasma infection is the first report of cured pork as a risk factor for infection. Further research is required to determine cyst viability in cured pork products. Our findings suggest that in southern Italy, cured pork and raw meat should be avoided by susceptible pregnant women.

In the course of investigating suspected cases of viral haemorrhagic fever in South Africa patients were encountered who had been bitten by ticks, but who lacked evidence of infection with Crimean–Congo haemorrhagic fever (CCHF) virus or non-viral tick-borne agents. Cattle sera were tested by enzyme-linked immunoassay to determine whether tick-borne viruses other than CCHF occur in the country. The prevalence of antibody in cattle sera was 905/2116 (42·8%) for CCHF virus, 70/1358 (5·2%) for Dugbe, 21/1358 (1·5%) for louping ill, 6/450 (1·3%) for West Nile, 7/1358 (0·5%) for Nairobi sheep disease, 3/625 (0·5%) for Kadam and 2/450 (0·4%) for Chenuda. No reactions were recorded with Hazara, Bahig, Bhanja, Thogoto and Dhori viruses. The CCHF findings confirmed previous observations that the virus is widely prevalent within the distribution range of ticks of the genus Hyalomma, while antibody activity to Dugbe antigen was detected only within the distribution range of the tick Amblyomma hebraeum. Cross-reactivity for the nairoviruses, Hazara, Nairobi sheep disease and Dugbe, was detected in serum samples from 3/72 human patients with confirmed CCHF infection, and serum from 1/162 other patients reacted monospecifically with Dugbe antigen. The latter patient suffered from febrile illness with prolonged thrombocytopenia.

Outbreaks of foot-and-mouth disease persist in dairy cattle herds in Saudi Arabia despite revaccination at intervals of 4–6 months. Vaccine trials provide data on antibody responses following vaccination. Using this information we developed a mathematical model of the decay of protective antibodies with which we estimated the fraction of susceptible animals at a given time after vaccination. The model describes the data well, suggesting over 95% take with an antibody half-life of 43 days. Farm records provided data on the time course of five outbreaks. We applied a ‘SLIR’ epidemiological model to these data, fitting a single parameter representing disease transmission rate. The analysis provides estimates of the basic reproduction number, R0, which may exceed 70 in some cases. We conclude that the critical intervaccination interval which would provide herd immunity against FMDV is unrealistically short, especially for heterologous challenge. We suggest that it may not be possible to prevent foot-and-mouth disease outbreaks on these farms using currently available vaccines.

The prevalance of subclinical Johne's disease was estimated in adult cattle slaughtered at three major abattoirs in south west England. A polymerase chain reaction (PCR) based on IS900 was used to detect Mycobacterium paratuberculosis in intestinal lymph nodes of 1553 cattle. Culture was also carried out on all PCR positive and inconclusive samples. The prevalence of subclinical disease in adult cattle was 3·5% (95% confidence intervals (CI) 2·6–4·7) by PCR and 2·6% (CI 1·8–3·6) by culture. The proportion of the disease in each month ranged from 1·6% (CI 0·2–5·5) in April to 4·6% (CI 2·8–6·9) in November, but the difference was not significant (P > 0·05). The proportion of PCR positive lymph nodes in each abattoir ranged from 2·8% (CI 1·6–4·6) to 4·9% (CI 2·9–7·6), this difference was not significant either (P > 0·05). The prevalence in young cattle was 2·0% (CI 0·6–4·5). The difference between age groups was not statistically significant (P > 0·05).