Thermophilic campylobacters in surface waters around Lancaster, UK: negative correlation with Campylobacter infections in the community.

The incidence of campylobacter enteritis in Lancaster City Health Authority is three times the UK average for similar sizes of population and has marked seasonal peaks in May and June. Environmental monitoring of surface waters around Lancaster showed that thermophilic campylobacters were absent from drinking water from the fells and from the clean upper reaches of the River Conder but were present in the main rivers entering Morecambe Bay, the lower reaches of the River Conder, the Lancaster canal, and seawater from the Lune estuary and Morecambe Bay. All the surface waters tested showed the same seasonality, namely, higher numbers in the winter months and low numbers or none in May, June and July. The absence of thermophilic campylobacters in the summer months may be due to high sunshine levels because experiments on the effects of light showed that campylobacters in sewage effluent and seawater were eliminated within 60 and 30 min of daylight respectively but survived for 24 h in darkness. As the concentrations of campylobacters in surface waters were at their lowest precisely at the time of peak infections in the community it is unlikely that surface waters form Lancaster's reservoir of campylobacter infection for the community.

Seasonal variation of thermophilic campylobacters in sewage sludge.

The seasonal variation of thermophilic campylobacters in Lancaster's sewage sludge was studied over a 21 month period. The numbers in fresh sludge (from primary sedimentation) vary between approximately 200 and 5000/100 ml for most of the year but there was a large increase in May and June (in May 1988 there were 42,100 campylobacters/100 ml which is 17 times more than in the preceding April). In 1989 there was a similar May/June peak but with lower numbers. This seasonal variation, measured by environmental monitoring, reflects the incidence of infections in the community. The same pattern was found in 2-d old sludge but the numbers were substantially lower (40% lower over the experimental period). Thermophilic campylobacters were virtually absent from digested sludge and sludge prior to land distribution. Survival experiments confirm that campylobacters survive for only a few hours in both sterile and unsterile digested and undigested sludge. These results suggest that it is safe to dispose of Lancaster's digested sludge on land but there is still uncertainty about the ability of campylobacters to survive in sludge in the viable but non-culturable form.

Correlation between environmental monitoring of thermophilic campylobacters in sewage effluent and the incidence of Campylobacter infection in the community.

Environmental monitoring of thermophilic campylobacters in liquid sewage effluent (primary settlement only) during 1988 and 1989 showed a prominent seasonality with distinct peaks in May and June (the average number of bacteria per 100 ml of effluent in months other than May and June was 2244 and the average for the peak months was 50,778). Apart from September 1989, this seasonality coincided precisely with the seasonal variation of campylobacter enteritis in the community with similar distinct peaks in May and June (the incidence of infection in May and June was twice or three times that in the other months). Sampling of sewers showed that the campylobacters in the sewage effluent came mainly from abbatoir and animal processing plants with only a minor input from the community. Therefore, the seasonal peaks in the sewage effluent and in the community may not be dependent on human infections but on zoonotic infections which may also peak in May and June.