This suggestion, contained in a new study from the University of Aberdeen, will certainly do little to bolster the creature's reputation.
Because far from being simply a pesky muncher of leaves, the study suggests that they could be agents of spreading a dangerous bacterial strain.
Escherichia coli O157, an emerging zoonoses in many countries including the UK, has a 3 to 5 per cent mortality rate in humans. In 1996, an outbreak of Escherichia coli O157:H7 in Japan affected over 6,300 school children and resulted in two deaths.
WHO claims that this is the largest outbreak ever recorded for this pathogen. It has emerged rapidly as a major cause of bloody diarrhoea and acute renal failure since it was first identified in 1982, and is a major cause for concern for the food industry.
Farm animals such as cattle and sheep have been previously identified as major reservoirs of this strain of E. coli by passing it through manure, which is then used to fertilize crops.
The slug, a widespread agricultural pest as any gardener will know, continuously ingests bacteria from the soil and their environment. According to the Aberdeen scientists, their tendency to contaminate leafy vegetables often targeted for human consumption identifies them as likely source for E. coli transmission.
Laboratory testing found E. coli O157 in 0.21 per cent of field slugs on a sheep farm in the UK. Further studies revealed that the slug species, Deroceras reticulatum, could maintain viable E. coli on its external surface for 14 days.
Slugs that were fed E. coli shed viable bacteria in their faeces persisting for up to 3 weeks.
"This study provides evidence that slugs can act as vectors of E. coli O157 from an environmental source to fruit or vegetables," said the researchers. "The research demonstrates that E. coli in D. reticulatum has a relatively long external and internal survival time."
The findings should be of interest to food makers who handle salad ingredients.
The Aberdeen University scientists reported their findings in the January 2006 issue of the journal Applied and Environmental Microbiology.