In order to improve the prevention of cases of congenital rubella syndrome in The Netherlands, in 1987 the selective vaccination strategy against rubella infection in girls was replaced by mass vaccination. This decision was supported by mathematical model analyses carried out by Van Druten and De Boo. In order to compare the predicted impact of the rubella vaccination programme with the current available data in more detail, a similar model was built. Although the model predicts elimination of the rubella virus, data show that virus circulation is still present at a higher level than expected by the model. Simulation studies indicate that import of infection and a lower vaccine effectiveness, related to possible asymptomatic reinfection of vaccinated people, could be sources contributing to the present virus circulation. Even though the number of infections is much higher than the number of reported cases of disease, limited serosurveillance data and case notification data show that females of childbearing age are well protected by immunization.

Commercial heat treatment procedures for molluscan shellfish are based on data obtained for the inactivation of hepatitis A virus (HAV) in cockles. However, the most frequently reported illness associated with consumption of bivalve molluscs is gastroenteritis caused by small round structured viruses (SRSVs) of the Norwalk group. Conditions for inactivation of SRSVs are unknown. In this study a feline calicivirus was used as a model for the SRSV group and conditions for its heat inactivation determined. Experiments showed that feline calicivirus is more readily inactivated in shellfish than HAV, and confirmed that current heating recommendations to the UK shellfish industry are adequate. A reverse transcription polymerase chain reaction (RT-PCR) assay for the detection of calicivirus in shellfish was developed and results compared with isolation in cell culture. The RT-PCR detected virus in some samples that failed to yield virus on culture. This has important implications if molecular virology techniques are to be used in the design and monitoring of shellfish treatment procedures and for routine testing of food samples.

This data linkage study examined the extent of hepatitis B transmission and co-infection with HIV among 636 former inmates of Glenochil prison, Scotland, during an outbreak of bloodborne diseases in 1993 which was related to needle sharing. Eleven inmates imprisoned during the first half of 1993 presented with hepatitis B infection, of whom co-infection with HIV was detected in six. Based on dates of test results in relation to time of imprisonment, seven definitely acquired their hepatitis B infection within the prison. Only two infections were reported to Scotland's hepatitis B register and neither could be prison-linked. This outbreak of hepatitis B is the first of its kind to be reported but not the first to have occurred. It not only highlights the urgency for measures to prevent further spread of infection among prisoners but also illustrates the need for comprehensive surveillance of hepatitis B infection, and the need for a protocol on how to manage such outbreaks and on how to establish the extent of transmissions when acute hepatitis B occurs in prison.

Viral haemorrhagic disease of rabbits (VHD), a potential biological control for wild rabbits in Australia and New Zealand, escaped from quarantined field trials on Wardang Island and spread to the mainland of Australia in October 1995. This study looked for any evidence of infection or illness in people occupationally exposed to the virus. Two hundred and sixty-nine people were interviewed and 259 blood samples were collected. Exposures to VHD-infected rabbits ranged from nil to very high. No VHD antibodies were detected in any of the 259 sera when tested by VHD competitive enzyme immunoassay, which had been validated with 1013 VHDV-specific antibody negative sera. A questionnaire designed to elicit symptoms of disease in a range of organ systems found no significant differences between illness in those exposed and those not exposed to VHD, nor could an association be found between exposure and subsequent episodes of illness. The findings are consistent with the view that exposure to VHD is not associated with infection or disease in humans.

The domestic environment was investigated for the presence of viruses and body fluids that may contain viruses. A range of surfaces in 39 homes (17 visited on 2 occasions) were sampled by swabbing and analysed using cell culture, reverse transcription polymerase chain reaction for enteroviral RNA, haemoglobin as a marker for blood, amylase as an indicator of urine, saliva and sweat, and protein as an indicator of general hygiene. Haemoglobin was found on 1·9% of surfaces sampled and of the positive samples 30% were from articles frequently handled. Amylase (>5 U/l) was found in 29·3% of samples tested. Protein was found in 97·8% of samples tested. Enteroviral RNA, indicating the presence of virus, was detected in 3 out of 448 samples tested; they were from a tap handle, telephone handpiece and a toilet bowl. No viruses were isolated in cell culture, however significant problems were encountered with bacterial and fungal contamination. This work demonstrates that only testing environmental samples for bacteria and ATP may not give a total view of the microbiological problem in the home. A range of test methods is useful to gain a broad view of the problems of hygiene in the home and to allow comparative studies of specific areas such as the kitchen and bathroom.

In order to determine whether infection with Schistosoma japonicum is related to a higher rate of infection with hepatitis B virus and/or to a higher probability of HBsAg chronic carriage, a population based survey was carried out in China in which HBV markers were studied in 112 subjects with long-lasting S. japonicum infection, and 93 subjects with no S. japonicum infection 37·5% of the cases and 40·9% of controls showed no markers of HBV infection. The prevalence rate of HBsAg was 12·5% in the cases and 12·9% in the controls. For anti-HBc and anti-HBs the figures were 59·8% and 59·8%, and 27·9% and 35·0%, respectively. These data do not support the hypothesis of an interaction between infection with hepatitis B virus and S. japonicum.

Nymphal Ixodes ricinus ticks collected from woodland areas in South Wales, UK, were tested using the polymerase chain reaction for the presence both of the causative agent of human granulocytic ehrlichiosis (HGE) and Borrelia burgdorferi. Twenty-two of 60 (37%) ticks were found positive in the PCR for B. burgdorferi and 4/60 (7%) for the HGE agent. One tick was found positive both for B. burgdorferi and HGE agent. Our findings imply the presence of the HGE agent in UK ticks and the finding of a tick apparently containing both pathogens underlines the potential for concurrent infection with HGE agent and B. burgdorferi to occur after a single tick-bite. Based on our observations, we conclude that there may be a need to consider a range of pathogens both in laboratory investigation and clinical management of suspected tick-borne disease in the UK, particularly where there is a clinical presentation atypical of Lyme borreliosis alone.

The seasonality and factors associated with Cryptosporidium infection were assessed in a cohort of HIV-infected patients in Los Angeles County to better define the epidemiology of cryptosporidiosis among individuals with HIV. Data were analysed from a cohort of 4247 patients [ges ]13 years of age with HIV infection enrolled from four outpatient facilities in Los Angeles, 1990–6. Cryptosporidiosis was diagnosed in 120 (2·8%) patients. Among the 1296 individuals with complete follow-up until death, cryptosporidiosis occurred in 69 (5·3%). The seasonal rate of cryptosporidiosis showed a modest bimodal trend with the highest rates occurring in March–May and September–October. There was no difference in the rate of cryptosporidiosis for the periods of heaviest rainfall (December–March) and low rainfall (April–November). Infection rates were higher among males (1·59 per 100 person-years) than females (0·92) and lower in blacks (0·98) than other racial/ethnic groups (1·80). A significant trend of decreasing cryptosporidiosis was observed with increasing age, with the highest rate (2·34) in the 13–34 year age group. A strong association between cryptosporidiosis and CD4+ count was noted. These data suggest that cryptosporidiosis among HIV-infected individuals in Los Angeles County exhibits a modest spring and fall seasonality. This pattern of occurrence of cryptosporidiosis appears temporally unrelated to local rainfall patterns. Our findings suggest that HIV-infected men, individuals in younger age groups and those with CD4+ lymphocyte counts <100×106/l are at increased risk of cryptosporidiosis. Blacks with HIV infection appear less likely than other racial/ethnic groups to be diagnosed with Cryptosporidium infection. These results may provide insight into possible routes of transmission and sources of cryptosporidiosis infection in individuals with HIV.

Bank voles (Clethrionomys glareolus) serve as the reservoir for Puumala (PUU) virus, the aetiologic agent of nephropathia epidemica. The animals are believed to be persistently infected and the occurrence of serum antibodies is usually taken as an evidence of active infection. We found serum antibodies to PUU virus in 42 of 299 wild bank voles captured in a PUU virus endemic area. PUU virus RNA was demonstrated in lung specimens of 11 of these 42 animals and in 2 of them antigen was also found. Thus in the lungs of 31 of 42 seropositive animals neither PUU virus RNA nor antigen was detected. In 2 of 257 seronegative animals, lung specimens showed presence of PUU virus antigen and RNA. Isolation of PUU virus from lung tissue was successful in all 4 antigen-positive bank voles but in none of 16 tested antigen-negative animals. In conclusion, only a minority of bank voles with serum antibodies to PUU virus showed evidence of current infection.

A seroprevalence survey was conducted using ELISA and Western blot (WB) assays for antibody to three Cryptosporidium antigens on 380 blood donors in Jackson County, Oregon. The purpose was to determine if either assay could detect serological evidence of an outbreak which occurred in Talent, Oregon 6 months earlier. The ELISA, which tested for combined IgG, IgA and IgM, and the WB, which tested separately for IgG and IgA, detected an almost twofold increase in serological response for persons who consumed Talent drinking water during the previous 11 months. The increases, however, were statistically significant (P<0·05) only for the WB. The identification of serological evidence of infection, using sera collected 6 months after the end of the outbreak in a population not selected because of cryptosporidiosis-like illness, suggests that assays of Cryptosporidium-specific IgG and IgA may assist in estimating the magnitude of asymptomatic infections in the population.

Following the occurrence of an outbreak of Crimean–Congo haemorrhagic fever (CCHF) among workers at an ostrich abattoir in South Africa in 1996, 9 susceptible young ostriches were infected subcutaneously with the virus in order to study the nature of the infection which they undergo. The ostriches developed viraemia which was demonstrable on days 1–4 following infection, with a maximum intensity of 4·0 log10 mouse intracerebral LD50/ml being recorded on day 2 in 1 of the birds. Virus was detectable in visceral organs such as spleen, liver and kidney up to day 5 post-inoculation, 1 day after it could no longer be found in blood. No infective virus was detected in samples of muscle, but viral nucleic acid was detected by reverse transcription-polymerase chain reaction in muscle from a bird sacrificed on day 3 following infection. It was concluded that the occurrence of infection in ostriches at abattoirs could be prevented by keeping the birds free of ticks for 14 days before slaughter.

Leptospirosis has significantly decreased in Korea since 1988, following the leptospiral vaccination programme initiated in 1988. Whether this wholly explains the decreased incidence is uncertain. As an initial step to answer this question, infection rates of Leptospira interrogans in field rodents, Apodemis agrarius, were examined and compared with previous data.

Two hundred and twenty-two A. agrarius were captured during October–December 1996. Spirochaetes were isolated from 22 (9·9%) and leptospiral DNA was detected in an additional 6 rodents (12·6%). Subsequent microscopic agglutination tests (MAT) classified all these isolates as L. interrogans serogroup Icterohaemorrhagiae serovar lai. The above data did not significantly differ from previous surveys in 1984–7. There was no significant change of L. interrogans infection in field rodents following the introduction of the vaccination programme in Korea. Further studies are needed to determine the role of human vaccination in reducing incidence.

The seroprevalence of canine parvovirus (CPV), canine distemper virus (CDV), canine adenovirus (CAV) and canine herpesvirus (CHV) infections in red foxes (Vulpes vulpes) was determined in fox sera collected between 1991 and 1995. A total of 500 sera were selected and the seroprevalences were estimated to be 13% (65 of 500 sera) for CPV, 4·4% (17 of 383 sera) for CDV, 3·5% (17 of 485 sera) for CAV, and 0·4% (2 of 485 sera) for CHV, respectively. No statistically significant differences were observed between the two (rural and suburban) areas under study.

Parvovirus DNA sequences were amplified from tissues of free-ranging foxes and compared to those of prototype viruses from dogs and cats. We report here a parvovirus sequence indicative of a true intermediate between the feline panleukopenia virus-like viruses and the canine parvovirus-like viruses. The red fox parvoviral sequence, therefore, appears to represent a link between those viral groups. The DNA sequence together with a significant seroprevalence of parvovirus infections in foxes supports the hypothesis that the sudden emergence of canine parvovirus in the domestic dog population may have involved the interspecies transmission between wild and domestic carnivores.

To estimate the duration of Cryptosporidium-specific antibody, a Western blot assay measured antibody in paired sera from 124 residents of Jackson County, Oregon collected 0·5 and 2·5 years after the end of an outbreak in Talent, Jackson County. The outcome measure was the intensity of antibody responses, (which may approximate to a titre), to 27-kDa and 15/17-kDa antigens. Intensity of response to the 27-kDa antigen(s) declined to 54% of the 1992 value while responses to a 15/17-kDa antigen(s) remained close to the initial values. Increasing age of the donor predicted higher intensity of antibody to the 15/17-kDa antigen(s) in both the initial (P=0·004) and follow-up (P=0·038) surveys. No relationship was observed between age and antibody intensity for the 27-kDa antigen(s) during either survey (P>0·10). Both the initial and follow-up surveys showed significant elevations in antibody intensity for Talent residents, possibly indicating a high endemic rate of infection/re-infection or high levels of chronic infection.

We report the co-circulation of a new lineage of measles virus (MV) and an Edmonston-like (Ed-like) genotype of MV in China during 1995–7. Sequence analysis of 25 strains was performed on a 282 nucleotides (nt) region of the nucleoprotein (N) gene, a 450-nt region of the haemagglutinin (H) gene and a 152-nt region of the matrix (M) gene by direct sequencing of RT-PCR amplicons obtained from clinical specimens. The entire H gene was sequenced from two strains. The results showed that 24/25 Chinese strains belonged to a new genogroup and were distinct from the vaccine strains used in China and the UK, and also from MV strains previously described in Europe, Africa and the USA. The remaining strain was Ed-like. Two strains of the new genotype (IV) and one of the Ed-like genotype were also detected in the UK in 1996.

Serpulina pilosicoli was isolated from 8 of 43 (19%) faecal specimens obtained from feral waterbirds sampled around a small lake at Perth Zoological Gardens, Western Australia, and from 3 of 7 (43%) samples of the lake water. The organism was only isolated from 1 of 204 (0·5%) samples from captive birds and animals in the zoological collection. Multilocus enzyme electrophoresis analysis of the isolates showed that they were genetically diverse, and none had identical electrophoretic profiles as those previously obtained from human beings, dogs, pigs and other avian species. To determine the survival time of S. pilosicoli in water, cells of strain 1648 were seeded into lake and tap water, and incubated at 4, 25 and 37°C. The organism could be recultured from lake water for up to 66 days at 4°C, and for 4 days at 25°C. A healthy human volunteer who drank water seeded with S. pilosicoli strain Wes B became colonized, and developed abdominal discomfort and headaches. Contamination of water by faeces may represent a source of S. pilosicoli infection for both humans and animals.

The prevalence of antibody to the viruses of bovine virus diarrhoea (BVD), bovine herpes virus type1 (BHV1), rift valley fever (RVF), bovine ephemeral fever (BEF) and bluetongue (BT) and to Leptospira sp. was determined in wildlife populations in Zimbabwe. Evidence of infection with BVD virus was found in 14 of the 16 species examined but was greatest in eland Taurotragus oryx, nyala Tragelaphus angasi and bushbuck Tragelaphus scriptus. Persistent infection with BVD virus was found in 1 of 303 antibody-free eland but not in the smaller sample of 102 antibody-free buffalo Syncerus caffer. Antibody to BHV1 was widespread, being found in 10 of 16 species with the highest prevalence being in buffalo and eland. Antibody to RVF was most prevalent in black rhino Diceros bicornis and white rhino Ceratotherium simum, buffalo and waterbuck Kobus ellipsiprymnus. Both BEF and BT were widespread in all the species examined. Evidence of infection with Leptospira sp. was found in 7 species. Infections were due to up to 3 of 8 different serovars.

In the epidemiology of bovine viral diarrhoea (BVD), immunotolerant – persistently infected animals (IPI) appear to be major sources of contamination. These animals produce large quantities of replicating virus and have therefore been proposed as being responsible for generating antigenic variability. However, limited studies have failed to detect antigenic or genetic changes in viruses isolated at different times from IPI. An hypothesis is that the immunotolerance of IPI against their homologous strain is accompanied by immune elimination of antigenic variants. The presence of an IPI in a herd could therefore limit antigenic variation, eventually leading to the existence of herd specific strains. To verify this hypothesis we characterized, against a panel of monoclonal antibodies, 37 BVD virus strains isolated from IPI of 12 herds in Eastern Belgium. Intra-herd antigenic variation was compared to inter-herd variation. Antigenic variation within herds was found to be surprisingly high but, nevertheless, significantly lower than variation between herds.