Soft-shelled turtles may spread cholera

Seafood lovers, take note! Consuming soft-shelled turtles may spread cholera – a life- threatening diarrhoeal disease, a new Chinese study warns.

A pathogen called Vibrio cholerae can colonise the surfaces, as well as the intestines of soft shelled-turtles, researchers said. Researchers from Chinese Centre for Disease Control and Prevention inserted the genes producing bio-luminescent proteins into V cholerae that enabled them to directly observe the pathogens colonising the turtles.

The team infected turtles, by dipping them in a phosphate buffered saline solution containing the now bio-luminescent bacteria, serogroup 0139. Over the next four days, the researchers checked the turtles at 24 hour intervals. They first detected light signals at 24 hours. At 96 hours, the entire dorsal side of the turtles’ shells was emitting bio-luminescence. The latter was also easily detected on the dorsal side of the turtles’ limbs and necks, and in the calipash, the gelatinous protoplasm, regarded as a delicacy, that lies directly beneath the shells’ surface.

Determining intestinal colonisation was more difficult. The turtles were inoculated intragastrically with the bio luminescent V cholerae. Knowing that digestion takes roughly 34 to 56 hours in 150 gramme turtles, the investigators euthanised and dissected the turtles at 72 hours, and checked all their internal organs. Bioluminscence could be detected only in the intestines, researchers said.

The team also identified the different colonisation factors – molecular machinery on the surface of V cholerae – that enabled the bacteria to stick to the turtles’ dorsal surfaces and intestines. “Cholera is a life-threatening diarrhoeal disease,” said Biao Kan, professor at the Chinese Centre for Disease Control and Prevention.

Besides soft shelled turtles, aquatic hosts of V cholerae include zooplankton, fish, shellfish, egg masses of midges, waterfowl and crustaceans. Fish and shellfish are also proven to spread this disease. The study was published in the journal Applied and Environmental Microbiology.