was supplied with fresh chicken by a single wholesaler (wholesaler A), who obtained all of the chicken that it distributed from a single farm. This farm and its immediate surroundings were investigated to determine the source(s) of the organisms colonizing the chickens. Evidence was obtained that poultry from the farm caused sporadic human campylobacteriosis in the population served by the farm for at least 18 months after the recognition of the catering college outbreak. A report on this investigation is being prepared for publication elsewhere.

SUMMARYThree populations of small wild British rodents were studied by capture–recapture methods over a period of 3 years, a fourth group was studied for 1 year and a fifth was sampled annually for 4 years. Blood smears were taken from 3 species of rodents: the woodmouseA podemus sylvaticus, the bank voleClethrionomys glareolus(and an island sub-speciesC.g. skomerensis) and the short-tailed voleMicrotus agrestis. The smears were examined microscopically. Four genera of haemoparasitesBabesia, Hepatozoon, TrypanosomaandGrahamellawere detected.Babesiawas absent fromC.g. skomerensis, Hepatozoonwas rarely found inA. sylvaticusandM. agrestisandTrypanosomawas rare inA. sylvaticus. More males were infected than females but the difference was only statistically significant for the infection withHepatozoonin adultC.g. skomerensis. Infections withBabesiaandHepatozoonwere more prevalent in adult animals and infections withTrypanosomawere more prevalent in younger individuals. Only inC.g. skomerensiswas there a significant difference between age classes in the prevalence of infection withGrahamella– there being more adults infected. Concurrent infections were detected,Hepatozoonbeing the parasite most commonly involved. The prevalence of infections was found to be approximately proportional to the number of animals known to be alive, regardless of the season.

Four populations of small wild British rodents were studied by capture--re-capture methods over a period of three years. Samples of blood were taken from these animals and tested for antibodies to nine viruses. Animals were removed from another 11 sites around the UK, and immunosuppressed. Samples of tissue from these animals were tested for the presence of viruses by passage in laboratory mice and serum samples from some of them were tested for antibody to the nine viruses. Indications were found of the possible influence of epizootic outbreaks of certain diseases on animal populations.

A study of Campylobacter jejuni on a broiler chicken farm between 1989 and 1994 gave an estimated isolation rate of 27% (3,304 of 12,233) from a 0.9% sample of 1.44 million broiler chickens from six to eight sheds over 32 consecutive rearing flocks comprising 251 broiler shed flocks. During the study, C. jejuni was found in 35.5% of the 251 shed flocks but only 9.2% (23 of 251) had Campylobacter isolates in successive flocks, with 9 of those 23 sheds having the same serotype between consecutive flocks, indicating a low level of transmission between flocks. Analysis of a systematic sample of 484 of 3,304 (14.6%) C. jejuni isolates showed that 85% were of 10 serotype complexes but 58% were of 3 serotype complexes, indicating a high degree of strain similarity throughout the entire study. The three commonest types were detected in 8 of 32 flocks during the 5-year study period, suggesting an intermittent common external Campylobacter source. This hypothesis was tested by a retrospective cohort analysis of C. jejuni rates and types by reference to hatchery supplier of the 1-day-old chicks. Isolation rates of C. jejuni and frequency distribution of types were determined in 6-week-old broiler chickens identified by the hatchery supplying the original chicks. The isolation rate of C. jejuni in broilers, supplied by hatchery A, was 17.6%, compared to 42.9% (P < 0.0001) for broilers reared from chicks supplied by hatchery B. In two instances, when both hatcheries were used to stock the same farm flock, Campylobacter isolates were found only in those sheds with chicks supplied by hatchery B. Thus, the frequency distribution of Campylobacter types for chickens supplied by the two hatcheries over the 5-year period showed marked dissimilarity. These findings suggest that the isolation rate and type of Campylobacter isolates in broiler chickens was associated with the hatchery supplying chicks. The lack of diversity of types and the intermittent high positivity of sheds is evidence for a common source of C. jejuni introduced by vertical transmission rather than contamination at the hatchery or during transportation.