Science puts high price on the flea

WHEN next you see your domestic moggie scratching itself vigorously behind the ears, pause before you reach for the flea-spray.

To American science, fleas are worth more than their weight in gold. Living fleas sell for about 10 cents each, while the freeze-dried variety will reach dollars 40 per gram. Gold bullion fetches only about dollars 11 per gram.

Inevitably perhaps in the land of free enterprise, researchers at Cornell University in New York State have patented an 'Artificial Dog' capable of breeding 12,000 fleas a day.

The device replaces laboratory animals which were once used as the source of fleas, and will produce the equivalent of about 25 severely infected animals' worth of fleas, while occupying the space of one sleeping dog.

According to Dr Jay Georgi, co-inventor of the artificial dog, the dead insects are used in allergy testing among humans and domestic pets, whose allergic reaction to flea bites is thought to result from flea saliva. Live fleas are used to test the effectiveness of new insecticides and in studies of the insect's physiology.

While living fleas might be valuable to American scientists, their compatriots spend about dollars 400m a year buying insecticides trying to control flea infestations. Some estimates put the cost much higher - as much as dollars 1bn a year.

Before Dr Georgi and his colleague Dr Susan Wade invented the artificial dog, fleas had to be collected from the fur of dogs or cats and flea-eggs winnowed from the debris at the bottom of animal cages.

In contrast, the artificial dog is a transparent acrylic box containing 25 circular cages each capable of feeding 300 fleas. The internal cages, shaped like pill boxes, have a nylon mesh screen at top and bottom to prevent the fleas from escaping.

On the top of each cage is an aluminium cylinder filled with cow's blood collected fresh from the local slaughterhouse. The cylinders have a plastic membrane stretched across the bottom which mimics the role of skin for the fleas to pierce with their mouthparts and drink the blood.

However, there are refinements even in flea husbandry. The fleas need support to perch on if the insects are to drink in tranquility.

In lieu of fur, they have had to provide a second nylon mesh close to the one stretched across the top of the cage. With this double mesh the fleas happily drink and breed.