Last Updated on November 12, 2019

The Truth About the Candiru

Though the fish most frequently blamed for human attacks is the catfish species Vandellia cirrhosa, the term candiru (alternatively pencil catfish, vampire catfish, or carnero) actually refers to a group of parasitic catfishes that have not been well studied.

Claims that they are attracted by urine, suck blood, and survive inside a human host are based on supposition and embellishment of anecdote over the centuries. This is what we do know:

Vandellia spp. normally ingest the blood of fish hosts. The catfish attack by entering the gill opening and anchoring near a major blood vessel. Jansen Zuanon and Ivan Sazima studied the feeding habits of several species of vampire catfish including V. cirrhosa, and report their findings in a 2004 paper in the Journal of Ichthyology and Aquatic Biology (“Vampire Catfishes Seek the Aorta, not the Jugular: Candirus of the Genus Vandellia Feed on Major Gill Arteries of Host Fishes”). The researchers observed that the fish do appear to use spines on their gill openings to anchor themselves in the gills of the host fish, but rather than actually sucking blood, they lacerate the host’s artery and feed on blood that pumps out through the wound. Feeding takes less than two and half minutes, and then the candiru leaves the host.

Entering a human urethra would be as devastating for the fish as it would for the human. This is a vastly different environment from a fish’s gill and, as Dr. Bauer states in her paper, “with no oxygen available and no room to ‘swim’ up the urethra it is unlikely that the fish survives even a few minutes.”