Who Put Salmonella in my Sand
August 15, 1999 2 minutes read
Who Put Salmonella in my Sand?
Source:Epidemiol Infect 1999;122:7-13.
Gastrointestinal symptoms are more frequent in swimmers who bathe or swim in fecally contaminated coastal waters, but simply sunbathing on the beach has not been considered a big risk factor for enteric disease. Could sand act as a sieve for nasty bacterial organisms that end up in coastal waters?
To examine this question, a total of 182 samples of sand were collected over a four-week period from four different beaches in England and examined for the presence of thermophilic Campylobacter and Salmonella. Two of the beaches were in compliance with British water directives, but two were located within 1-3 miles of sewage pipes and/or fecally contaminated agricultural run off. Separate samples of dry sand found just below the high water mark as well as wet sand from the water’s edge at low tide were collected from each beach.
Overall, 45% of the samples contained Campylobacter spp. and 6% contained Salmonella. Salmonella were isolated from 9% of specimens obtained from noncompliant beaches vs. 2% of the compliant beaches, but S. enteritidis and S. typhimurius were isolated from both. The major human pathogens, C. jejuni and C. coli, were more frequently isolated from the noncompliant beaches, but other Campylobacter spp. commonly associated with seagulls and migratory birds were more prevalent in sand from the compliant beaches. Wet sand was more frequently contaminated with Campylobacter (24-77%), but about one-third of the dry sand samples were also contaminated (10-54% of specimens). These data suggest that even dry sand may function as an effective reservoir for Campylobacter despite its minimal water content.
While the risk to public health is difficult to assess from this information, it is reasonable to stick to beaches distant from fecally contaminated run off, to avoid foods and beverages contaminated with sand, and to shower once you get home from the beach. On a similar note, a municipality in the San Francisco East Bay recently banned children in diapers from visiting public waterways, including lakes, streams, and beaches. This seems like an overly extreme response to a complex issue, especially given the numerous other potential sources for public waterway contamination.
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