Gastroenteritis (GE) is among the most common illnesses of humans but the burden of disease, its epidemiology, and the distribution of pathogens in adults have not been fully examined. This information is needed to plan prevention strategies particularly for high-risk groups. This study is a retrospective analysis of data from the National Hospital Discharge Survey for the years 1979 through 1995 which describes the disease burden and epidemiology of hospitalizations associated with GE among adults in the United States. Diarrhoea was listed as a diagnosis on an average of 452000 hospital discharges per year representing 1·5% of all hospitalizations among adults. The annual number of GE hospitalizations has decreased by 20% from approximately 500000 in 1979 to 400000 in 1995. The aetiology of 78% of cases coded as GE was undetermined. Until the aetiology of disease can be better established, specific strategies for prevention cannot be developed.

Because enterotoxigenic Escherichia coli (ETEC) is not identified by routine stool culture methods, ETEC outbreaks may go unrecognized, and opportunities for treatment and prevention may be missed. To improve recognition of adult ETEC outbreaks, we compared them with reported outbreaks of viral gastroenteritis. During 1975–95, we identified 14 ETEC outbreaks in the United States and 7 on cruise ships, caused by 17 different serotypes and affecting 5683 persons. Median symptom prevalences were: diarrhoea 99%, abdominal cramps 82%, nausea 49%, fever 22%, vomiting 14%. The median incubation period was 42 h, and for 8 of 10 outbreaks, the mean or median duration of illness was >72 h (range 24–264). For 17 (81%) ETEC outbreaks, but for only 2 (8%) viral outbreaks, the prevalence of diarrhoea was [ges ]2·5 times the prevalence of vomiting. ETEC outbreaks may be differentiated from viral gastroenteritis outbreaks by a diarrhoea-to-vomiting prevalence ratio of [ges ]2·5 and a longer duration of illness.

The utility of phage typing, pulsed-field gel electrophoresis (PFGE), and plasmid profile analysis was compared, to differentiate between Canadian Escherichia coli O157[ratio ]H7 strains of human (n = 27) and cattle (n = 24) origin. The diversity indices for phage typing, plasmid analysis and PFGE were 0·85, 0·69 and 0·93, respectively. PFGE and phage typing were also applied to study the role of direct transmission of E. coli O157[ratio ]H7 from cattle to humans on isolates collected from two separate farm outbreaks. PFGE showed that more than one E. coli O157[ratio ]H7 strain with varying PFGE DNA subtype profiles, may be responsible for an outbreak, and that more than one E. coli O157[ratio ]H7 subtype may be circulating on a particular farm at any one time. To our knowledge, this is one of the first reports where PFGE typing was used to verify the direct transmission of E. coli O157[ratio ]H7 from cattle to humans.

Restriction patterns obtained with EcoRI and Southern hybridization were used for the differentiation of tetracycline-resistant (Tetr) R plasmids in enterobaemorrhagic Escherichia coli (EHEC) O157[ratio ]H7 isolates from a mass outbreak at a kindergarten in Obihiro-City, Hokkaido, Japan, 1996. Two kinds of Tetr R plasmids of 50 and 95 kb were detected. The 50-kb plasmids were identical to each other, while the 93-kb plasmids were of three types that were very similar to each other. The tet genes of both 50- and 95-kb R plasmids were 100% identical to the tet gene of pSC101 and all plasmids hybridized to a probe for tet. Because food-origin O157 strains were sensitive to tetracycline, we concluded that such Tetr R-plasmids might transfer to drug-sensitive O157 strains in the infected individuals.

We investigated an outbreak of Salmonella enteritidis involving at least 19 British tourists returning from one hotel in another European country. A retrospective cohort study of 47 hotel guests identified lasagne as the most likely vehicle of transmission (RR 11·5; 95% CI 3·0–44·1; P<0·0001). However, difficulties in information exchange and lack of formal mechanisms to agree on the aims of the cross-national investigation hampered efficient management of the outbreak. The factors leading to contamination of the food vehicle were not identified and therefore specific action to prevent reoccurrence could not be taken. There is need to develop protocols for cross-national investigations of outbreaks in Europe which should include specifying objectives, roles and responsibilities of investigators and control agencies, with formal reporting of the outcome of the investigation.

Sixty-seven strains of the five described Salmonella serotypes having antigens 6,7[ratio ]c[ratio ]1,5, that is S. enterica serotype Choleraesuis sensu stricto, Choleraesuis var. Kunzendorf, Choleraesuis var. Decatur, Paratyphi C, and Typhisuis, were examined for 16S rrn profile ribotype, presence of IS200 and phenotypic characters, including rate of change of flagellar-antigen phase and nutritional character. Choleraesuis sensu stricto and its Kunzendorf variant had related but distinct ribotypes. Therefore, ribotyping appears to be a suitable method for differentiating Choleraesuis non-Kunzendorf from Choleraesuis var. Kunzendorf. Some strains of Paratyphi C had 16S profiles that resembled that of Choleraesuis non-Kunzendorf, while others resembled that of Choleraesuis var. Kunzendorf. The Typhisuis profiles were like those of Choleraesuis non-Kunzendorf, while the Choleraesuis var. Decatur profiles were unlike those of any of the other four groups. Furthermore, IS200 fingerprinting discriminated between Choleraesuis var. Decatur and the other strains with antigenic formula O6,7[ratio ]c[ratio ]1,5, and comparison of IS200 patterns showed a high degree of genetic divergence within Choleraesuis var. Decatur. Our findings show that ribotyping and IS200 fingerprinting, combined with classical microbiological methods, distinguish the groups Choleraesuis non-Kunzendorf, Choleraesuis var. Kunzendorf, Choleraesuis var. Decatur, Paratyphi C and Typhisuis.

Campylobacter is the most commonly reported cause of gastro-intestinal infection in England and Wales, with over 50000 reported cases in 1997. The majority of human campylobacter isolates in England and Wales are C. jejuni (c. 90%) with most of the remainder being C. coli. We describe the use of phage typing as an extension to serotyping for more detailed characterization within these two species. The scheme was piloted during a study of 2407 C. jejuni and 182 C. coli strains isolated in Wales between April 1996 and March 1997. Fifty- seven C. jejuni phage types were identified, with the ten most prevalent phage types accounting for 60% of isolates tested; 16% of isolates were untypable. The most common phage type was PT 1 which represented c. 20% of isolates. A further 7% of isolates reacted with the phages but did not conform to a designated type (RDNC). Only 12 phage types were identified among C. coli, with the two most common types, PT 2 and PT 7 accounting for 75·2% of isolates. When used in conjunction with serotyping, the ability of phage typing to identify between 6 and 29 subtypes within each of the predominant HS types has enabled a further level of discrimination to be achieved that enhances the epidemiological typing of C. jejuni and C. coli.

There have been no previous longitudinal studies of otitis media conducted in non-Aboriginal Australian children. This paper describes the rate and risk factors for middle ear effusion (MEE) in children attending day care in Darwin, Australia. A prospective cohort study of 252 children under 4 years was conducted in 9 day care centres over 12 fortnights between 24 March and 15 September 1997. Tympanometry was conducted fortnightly and multivariate analysis used to determine risk factors predicting MEE. The outcome of interest was the rate of type B tympanograms per child detected in either ear at fortnightly examinations. After adjusting for clustering by child, MEE was detected on average 4·4 times in 12 fortnights (37% of all examinations conducted). Risk factors associated with presence of effusion were younger age, a family history of ear infection, previous grommets (tympanostomy tubes), ethnicity and the day care centre attended. A history of wheeze appeared protective. These effects were modest (RR 0·57–1·70). Middle ear effusion is very common in children attending day care in Darwin. This has clinical importance, since MEE during early childhood may affect optimal hearing, learning and speech development. There is little scope for modification for many of the risk factors for MEE predicted by this model. Further study of the day care environment is warranted.

One question of particular importance in phase III HIV vaccine trials is the choice of efficacy measure (EM) to validly and precisely estimate the true vaccinal efficacy. Traditional EMs, based on hazard rate ratio (HRR) or cumulative incidence ratio (CIR) are time-sensitive to mode of vaccine action and population heterogeneities. Through Monte-Carlo simulation, the performance of HRR and CIR based EMs are examined across different trial designs and vaccine and population characteristics. A new EM based on log-spline hazard regression (HARE) is proposed. Given that vaccinal properties (mode of action, time-lag, waning) are unknown a priori, appropriate selection of EM is problematic, and HRR and CIR can be unreliable to estimate the true maximum efficacy of candidate products. Non-random sexual mixing can exacerbate biases in HRR and CIR. HARE can offer valid estimation across different modes of vaccine action and in presence of frailty effects, contrary to its traditional counterparts. Our simulation studies highlight the weaknesses of widely used EMs while offering guidelines for trial design and suggesting new avenues for statistical analysis.

In 1997, prevalence of and risk factors for hepatitis A virus (HAV) infection were evaluated in 146 homosexual and 286 heterosexual men attending a Sexually Transmitted Disease (STD) Clinic in Rome, Italy. Total HAV antibody (anti-HAV) was detected in 60·3% of homosexuals and 62·2% of heterosexuals. After adjustment for the confounding effects of age, years of schooling, number of sexual partners, use of condoms, and history of STD, homosexuals were not found to be at increased risk of previous HAV exposure than heterosexuals (OR 1·1; 95% CI 0·7–1·9). Independent predictors of the likelihood of anti-HAV seropositivity among homosexuals and heterosexuals were: age older than 35 years and positive syphilis serology which is likely a proxy of lifestyles that increase the risk of faecal–oral infections.

These findings do not support a higher risk in homosexual men but could suggest a role for the vaccination of susceptible patients attending STD clinics.

A cross-sectional study was conducted in prisons of Cantabria (northern Spain) from June 1992 to December 1994. Inmates were asked to participate in a survey on prevalence and risk factors for monoinfections and coinfections with HIV, HBV and HCV. Crude and multiple odds ratios of risk factors were calculated (by polychotomous logistic regression). Prevalence of coinfections was higher than that of monoinfections. IDU risk factors were the main independent variables associated with monoinfections and coinfections with these agents. The strength of association increased with the degree of coinfection for IDU risk factors and penal status, e.g. duration of injecting drug use for more than 5 years yielded an adjusted OR ranging from 1·3 (95% CI: 0·4–5·1) for HBV monoinfection to 180 (95% CI: 61·0–540·0) for HIV–HBV–HCV coinfection. In comparison, sexual behaviours were less important than IDU risk factors.

In a prospective study of community-dwelling people 60–90 years of age, we examined the coverage of influenza vaccine during 1992–3 and 1993–4, the efficacy of vaccination in reducing serologically-confirmed clinical episodes of influenza A during 1993, and the effect of cigarette smoking. During 1992 and 1993, influenza vaccine was given to 106/215 (49%) and 120/204 (59%) people with risk conditions, and 84/225 (37%) and 103/235 (44%) without risk conditions. Influenza vaccination and general practitioner consultations during 1992 were independent predictors of vaccination in 1993, but current smoking was a negative predictor. Of 209 unimmunized people, 8/35 (23%) smokers had clinical influenza as compared with 11/174 (6 %) non-smokers (OR 4·4, 95% CI 1·6 to 11·9). Of 371 non-smokers, 1/197 (0·5%) vaccinees had influenza as compared with 11/174 (6 %) non-vaccinees (OR 0·075, 95% CI 0·587 to 0·009). No cases of influenza occurred among 21 current smokers who were vaccinated.

To investigate the feasibility of using information about the health and management of lambs on farms to predict the risk of gross abnormalities at post-mortem meat inspection, 6732 lambs from 30 different farms in Great Britain were followed through to slaughter in 1995/6. The farm-level data were collected during farm visits at the beginning of the study. Routine meat inspection findings for the lambs were obtained from the 10 participating abattoirs. The most common abnormalities found during post-mortem inspection were pneumonia/pleurisy (53% of cohorts), lungworm (40%), abscesses (30%), liver fluke (27%) and nephritis/nephrosis (27%). The farm-level risk factors associated with abnormalities at slaughter varied with the type of lesion. The most significant risk factor was the age of the lambs at slaughter. Lambs slaughtered at an older age were more likely to have an abnormality, especially pneumonia, abscesses and liver fluke. After age, environmental factors appeared to be better predictors of those cohorts that would have lesions at slaughter than health and disease control variables. However, a much larger study would be required to identify a set of farm-level factors that adequately discriminated between lambs with high and low risks of lesion at slaughter. At the end of the study, the farmers were informed of the meat inspection findings for their lambs and a third indicated that they would improve their animal husbandry as a result of the information.

Experimental infections of different salmonella serotypes were established in a commercial line of ducks to provide baseline information on which control measures might be based. The ducks were very resistant to systemic infection with Salmonella typhimurium, S. enteritidis and S. gallinarum within 36 h of hatching. This was associated with an inherent inability of the strains to multiply in the reticulo-endothelial system. The resistance was not associated with poor invasiveness or serum sensitivity. Individual strains of S. typhimurium, S. enteritidis, S. heidelberg and S. orion colonized the gut well and were excreted in the faeces for at least 6 weeks by ducks when they were infected orally within 2 days of hatching. The main sites of colonization were the caeca and, to a lesser extent, the crop. Viable counts of each inoculated strain in the caeca remained in excess of 106 c.f.u. 3 weeks after infection although the organisms had been cleared from the spleen by this time. Much less excretion occurred when the birds were infected at 3 weeks of age. When infected ducks, which had cleared themselves of infection, were challenged orally with the homologous strain expressing a different genetic marker, very low levels of excretion of the challenge strain were detected when compared with a control group. After infection low titres of circulating lipopolysaccharide-specific IgG antibodies were detected by an ELISA. Intestinal colonization of newly hatched ducks with an aroA strain of S. enteritidis resulted in extensive colonization which exerted an exclusion effect on the parent strain inoculated 24 h later.

Pulsed-field gel electrophoresis (PFGE) was applied as a molecular typing tool for the spirochaete Serpulina hyodysenteriae, the agent of swine dysentery. Analysis of a collection of 40 mainly Australian isolates, previously characterized by other methods, divided these into 23 PFGE types. This confirmed that there are many strains of the spirochaete in Australia. PFGE was more discriminatory for strain typing than both multilocus enzyme electrophoresis and serotyping. It had similar discriminatory power to restriction endonuclease analysis, but the results of PFGE were easier to interpret. When applied to 29 isolates collected from 4 farms over periods of up to 8 years, 2 PFGE patterns were found on 3 farms, and a single pattern on the other. In each case a new strain had apparently emerged as a variant of an original parent strain. PFGE was found to be a powerful technique for investigating the molecular epidemiology of swine dysentery outbreaks.

In a cross-sectional study conducted between March 1993 and February 1995, 7103 indiscriminately collected foxes were examined for Trichinella larvae. A total of 3295 serum samples were serologically investigated with an ELISA based on excretory-secretory antigen. The proportion of serologically positive animals ranged between 3·3% and 17·6% in random samples from individual counties or towns and resulted in an estimated overall prevalence of 7·7% (95% CI: 6·9–8·7%). Trichinella larvae were detected in the muscles of five foxes, corresponding to an estimated prevalence of 0·07% in the total sample (95% CI: 0·02–0·16%). The analysis of DNA of the Trichinella isolates by random amplification of polymorphic DNA (RAPD) lead to the identification of the isolates as Trichinella spiralis. The differences between serological and parasitological findings are discussed.

Two Ag-ELISAs, an IgG-specific antibody detection ELISA (IgG ELISA) and a card agglutination test (CATT) for the detection of Trypanasoma evansi infections in buffaloes in Indonesia, were compared. Diagnostic sensitivity estimates were obtained by testing sera from 139 Indonesian buffaloes which had been found to be infected by parasitological tests. Diagnostic specificity was estimated by testing sera from 263 buffaloes living in Australia. Response-operating characteristic curves were constructed, and optimal ELISA cut-off values, which minimized the number of false–negative and false–positive results, were chosen. The IgG ELISA had the highest sensitivity (89%) and the CATT had the highest specificity (100%). There was a significant difference between the sensitivities (71 and 81%), but not between the specificities (75 and 78%), of the two Ag-ELISAs. The four tests were further compared by calculation of post-test probabilities of infection for positive and negative test results using a range of prevalence values, and likelihood ratios. The results suggested that the CATT was the best test to ‘rule-in’ infection (i.e. the highest probability of infection in test-positive animals) and the IgG ELISA was the best test to ‘rule-out’ infection (i.e. the lowest probability of infection in test-negative animals).

During a serosurvey of domestic dogs in Tanzania, a rapid fluorescent focus inhibition test (RFFIT) and a liquid-phase blocking ELISA (LPBE) were used to measure rabies antibodies in vaccinated and unvaccinated dogs. Post-vaccination titres measured by LPBE correlated closely with those found by RFFIT. Of 567 unvaccinated dogs tested using the LPBE, 42 (7·4%) were seropositive, with titres exceeding 32. Of this group, 233 dogs were tested using the RFFIT and 115 (49·4%) were seropositive, with titres exceeding 0·5 IU/ml. Two lines of evidence pointed to the greater specificity of the LPBE when measuring rabies antibodies induced by natural infections: (a) no seropositive dogs were detected among the 162 unvaccinated dogs from the rabies-free island of Pemba, Tanzania, when using LPBE, whereas 15/145 (10·3%) dogs of the same group were seropositive using RFFIT; (b) among Tanzanian dogs there was a close association between the location of rabies cases and location of seropositive dogs when using LPBE, but not when using RFFIT. These results suggest that LPBE may be of value in rabies seroepidemiological studies and could be developed as a reference technique for the detection of rabies antibody in domestic dogs.

SAD B19 is an attenuated vaccine virus for oral vaccination of carnivores against rabies. The safety of SAD B19 was investigated in 16 animal species by different routes of administration. During the observation period all animals given the vaccine virus, irrespective of the route of administration, did not show any clinical signs of rabies, with the exception of certain rodent species. In these animals a low residual pathogenicity was observed, however transmission of the vaccine virus to control animals was not demonstrable. No vaccine virus could be detected in the saliva of the six mammal species examined. Furthermore, the genetical stability was shown for SAD B19 through passaging in neural tissue of dogs, foxes and mice. From the results presented here on innocuity and stability, it can be concluded that SAD B19 rabies vaccine is suitable for oral vaccination campaigns for carnivores against rabies.

After PCR amplification with conservative cytomegalovirus primers, a 520 nucleotide putative partial sequence of the DNA polymerase gene of porcine cytomegalovirus (PCMV) was determined. Sequence comparison revealed homology to DNA polymerase genes from various beta herpes viruses and a dendrogram was constructed depicting the relationship of PCMV to other members of the Herpesviridae family. The dendrogram indicates that PCMV is indeed a beta herpes virus that is more closely related to human herpes virus types 6 and 7 than to type 5.

To address the difficulties encountered during conventional PCMV detection and characterization a set of nested PCR primers were constructed which generated DNA fragments of 415 and 257 bp from the DNA polymerase gene. The nested PCR system proved specific for PCMV and provided a novel means for the detection of this poorly characterized herpes virus in pig populations, vaccines and in organs used in xenotransplantation.