Photo by Rick Geary

Eat all the flea eggs you like.

Matmail: Okay, now don 't give me any trouble about this. I kiss my cat. Not on the mouth (yuck!), on the head. She's a very loving affectionate cat. Bumps heads (the cat way of saying “Hi, we’re pals"), nuzzles, always next to me on the couch. Anyone who has this kind of cat will understand. Anyway, I am positive that every now and then I get a flea egg in my mouth. Gross, huh? Ingesting flea eggs is apparently how cats and dogs get worms. Please, please tell me this can't happen to a human. Lie if you have to. — TEESEEBEE, the Net

Well, Tee, I have some good news and some bad news. The good news is, except for a detail or two, you’re smarter about fleas and worms than most people are. Of course, that’s also the bad news. I’ll turn down your generous offer to believe whatever lie I might sling your way. But at least I’ll warn you before things turn really ugly. Then you can go back to kissing the cat while the rest of us hang around to face life on life’s terms.

First, the flaw in your scenario: Flea eggs have nothing to do with it. Eat all you like, Tee. So much for the lighter side of the news. Now you’d better grab kitty and take a hike. Bye-bye.

For the rest of us, the ugly truth: The flea itself is the guilty party. The common household cat/dog flea (Ctenocephalidesfelis) is a vital participant in the life cycle of one common type of tapeworm (Dipylidium caninum). The flea cycle works like this. Flea lays dry, unsticky egg on Tee’s cat; egg rolls around in fur, falls into carpet, bedding; egg hatches to larva; larva scavenges meals of skin flakes, flea droppings, other carpet crud; larva spins cocoon, becomes pupa, becomes mature flea; cocooned flea whittles, reads, watches TV for weeks, months, waiting for passing host Tee's cat happens by, flea stimulated to bust out of cocoon, jumps onto cat, lays eggs. The eternal entomological mandala.

In the meantime, Dipy, the adult tapeworm, is living in cats’/dogs'/people’s intestines. Worm sheds egg sac; sac expelled by host lands in carpet, bedding; eggs eaten by flea larva; eggs hatch inside mature flea; Tee consumes flea while kissing cat (or cat consumes flea while grooming); tapeworm lodges in intestines, matures, sheds egg sacs.

According to medical reports, kids are the more common sufferers, probably because they’re closer to the floor and stick things in their mouths a lot. The Dipylidium tapeworm isn’t a medical emergency since it mostly lounges around in your gut and eats part of your dinner. It’s easy to treat, once it’s diagnosed, On the other hand, there’s a rarer tapeworm (Echinococcus) that’s transmitted by cats and dogs that eat rodents. If a human consumes an Echino egg sac shed in cat or dog feces, the worm enters the bloodstream through the intestines and forms a cyst in the liver, lungs, brain, or other organ. In humans it can be fatal. Fleas are innocent of any involvement in this ugliness, though.

Beyond being itchy annoyances, fleas can transmit parasites and diseases to humans. So if you’re a habitual cat (or dog) kisser, take pet to vet for some anti-flea pills. And if any of you happen to run into Tee, please pass along the suggestion.