Sand fleas, likely, haven’t found paradise
Virginia, a reader from New Mexico, recently sent me this e-mail: "I've been enjoying Hawaii's beaches since 1968 and have never experienced a sand flea.
"I'm planning a trip to Panama and the resort area of Boca del Toros. The travel doctor and various guide books have warned about sand fleas. Are there no sand fleas in Hawaii? Hawaii is paradise, and maybe that's the reason for no sand fleas."
I've never received bites on a Hawaii beach, either, but I know several people who after North Shore beach camp-outs got itchy red bites on their feet and legs. The victims blamed sand fleas, but I didn't know what they meant by that. Virginia's good question prompted me to look into it.
At least four diverse creatures share the common name of sand flea. The most medically dangerous of these is the one Virginia was warned about in Panama. This creature is a skin-burrowing, tropical American flea called a chigoe. The chigoe is a true flea, but smaller than our common cat and dog fleas.
Chigoe fleas live in sand and soil and burrow into human and animal skin, especially feet. There the fleas engorge themselves with blood and soon become a painful, pea-size ulcer that can get infected. Tungiasis, as the infection is called, is a serious health problem in some African, Caribbean and South and Central American nations where medical care is limited.
Other creatures people sometimes mistake for sand fleas are chiggers, common in the southern United States. Chiggers, also called redbugs and harvest lice, are the larvae of several species of mites. These larvae hang onto plant stems in woods and dunes and latch onto people or animals brushing past. Chigger bites itch like mad but aren't medically dangerous.
Another possible beach biter is the common flea that plagues our cats and dogs. After several blood meals, the female flea lays hundreds of eggs that fall off pets onto carpets, lawns, soil or sand.
After several molts, flea hatchlings enclose themselves in cocoons that can live for years. The vibrations of a nearby person or animal trigger the adult fleas to emerge. When this happens on a beach, and the fleas bite human feet and legs, people call them sand fleas.
The most harmless so-called sand fleas are amphipod crustaceans, also known as beach fleas or beach hoppers. One species, about half an inch long, is abundant on sandy beaches of the Atlantic, from Canada to Argentina and Europe. A closely related species is about 1 inch long and lives on Pacific beaches, from Canada to Southern California.
Both species are called fleas because they jump like fleas.
Hawaii has some version of these beach hoppers, because I've seen them and felt them hit my legs while walking through clumps of seaweed on Kailua Beach.
I've never been bitten by these scavengers, though, because they don't bite. These amphipods eat decaying plant and animal material and often graze, as well as hide from the sun and seabird predators, in lines of seaweed high on the beach.
Since Hawaii hosts no chiggers or chigoe fleas, and amphipods don't bite, it's my guess that the occasional "sand flea" bites people get here come from the flea offspring of beach-going dogs.
Bottom line about sand fleas: Hawaii is paradise.