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.

Weaner pigs (n = 72) were fed 1 of 4 diets. These were based on either cooked rice and animal protein, cooked rice and lupin, wheat and lupin, or wheat and animal protein. Twenty-six of the pigs were slaughtered after 1 month. Those fed the highly digestible cooked rice and animal protein diet had drier colonic contents and faeces, lighter large intestines, and the contents of their large intestines had increased pH values and decreased total VFA concentrations. The other 46 pigs were orally challenged with broth cultures of Serpulina hyodysenteriae, and were monitored for faecal excretion of the spirochaetes, and for the development of swine dysentery (SD). None of 18 pigs fed the cooked rice and animal protein diet developed colonic changes or disease, whereas most pigs on the other diets developed mucohaemorrhagic colitis and dysentery. The reduced fermentation that occurred in the large intestines of pigs fed cooked rice and animal protein was associated with a subsequent failure of colonization by S. hyodysenteriae, and resultant protection against SD.

No animals tested were positive for feline leukaemia virus antigen and Chlamydia psittaci antibodies, but all were positive for antibodies to feline calicivirus (FCV), feline herpesvirus 1 (FHV1) and rotavirus. They had antibodies to feline parvovirus (96%), feline coronavirus (84%) and cowpox virus (2%). Antibody to feline immunodeficiency virus (FIV) was found in 53% of animals, which were less likely to be infected with Haemobartonella felis, and had higher FHV antibody titres than cats without FIV. FCV was isolated from 51% cats and FHV1 and feline reovirus each from 4%. H. felis was present in 42% of animals, and antibody to Toxoplasma gondii in 62%. Clinical abnormality had a significant association with FIV and feline calicivirus infections, but sex, age, social status and feeding group had no significant association with prevalence of any parasites. Toxocara cati and Toxascaris leonina eggs were found, respectively, in 91% and 82% of animals tested.

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.

A multidrug resistant (MDR) variety of Salmonella typhi emerged as the cause of epidemic typhoid fever in some Asian countries including India, during the late 1980s. We faced the epidemic from April 1990 to the first quarter of 1993. However, during this period we continued to isolate chloramphenicol sensitive (CS) S. typhi also. The relative prevalences showed that the frequency of CS variety was unaffected by the epidemic of MDR variety. This is an unusual epidemiological pattern, which indicates that there may have been factors which favoured the epidemic of the MDR variety but not the CS one.

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).

Epidemiol. Infect. 115 (1995), 387–97

K.Cartwright, M.Logan, C.McNulty, S.Harrison, R. George, A.Efstratiou, M.McEvoy and N.Begg

A cluster of cases of streptococcal necrotising fasciitis in Gloucestershire

Page 389,final paragraph should read:

Patient B

Three days later (7 February), patient B underwent a routine sapheno-femoral disconnection for varicose veins in the same operating theatre. In the evening she developed diarrhoea which persisted overnight; gastroenteritis was suspected. Early the next morning she was re-examined by her surgeon and was transferred to the district general hospital at about midday. NF was suspected, broad-spectrum intravenous antibiotics were commenced and surgery arranged. The diagnosis was confirmed at operation. The affected tissues were excised and specimens sent for culture and histology. Chains of Gram-positive cocci were seen in tissue sections and later, S. pyogenes was isolated.