Nasty parasitic worm, common in wildlife, now infecting U.S. cats

"First Report of Dracunculus Insignis in Two Naturally Infected Cats from the Northeastern USA," published in the February issue of the Journal of Feline Medicine and Surgery, document the first proof that this raccoon parasite can infect cats.

The worms can grow to almost a foot long and must emerge from its host to lay eggs that hatch into larvae. It forms a blister-like protrusion in an extremity, such as a leg, from which it slowly emerges over the course of days to deposit its young into the water.

Worms in the Dracunculus genus are well known in human medicine. D. insignis' sister worm, the waterborne Guinea worm, infected millions of humans around the world until eradication efforts beginning in the 1980s removed it from all but four countries -- with only 148 cases reported in 2013. Other Dracunculus worms infect a host of other mammals -- but Dranunculus insignis mainly infects raccoons and other wild mammals and, in rare cases, dogs. It does not infect humans.

The cats that contracted the Dranunculus insignis worms likely ingested the parasites by drinking unfiltered water or by hunting frogs," said Araceli Lucio-Forster, a Cornell veterinary researcher and the paper's lead author.

It takes a year from the time a mammal ingests the worm until the females are ready to migrate to an extremity and start the cycle anew.

While the worms do little direct harm beyond creating shallow ulcers in the skin, secondary infections and painful inflammatory responses may result from the worm's emergence from the host. There are no drugs to treat a D. insignis infection -- the worms must be removed surgically.

"Although rare in cats, this worm may be common in wildlife and the only way to protect animals from it is to keep them from drinking unfiltered water and from hunting -- in other words, keep them indoors," said Lucio-Forster.