In a high-school biology class, we had to dissect planaria, or flatworms, mostly to witness their miraculous regeneration into two completely different organisms. Well, I say, “we.” From worms on up to frogs, I was loathe to take a blade to anything in that class, so my friend Katherine did all that sort of thing. The point is, there are a wide variety of flatworms, some of which, including feline tapeworms, enact their platyhelminthine revenge by living and breeding in our cats’ intestines.
Our focus today: Are tapeworms in cats contagious? Can humans contract these intestinal parasites from their feline friends? The short and simple answer is yes. There’s no need to panic, though. The tapeworm life cycle is such that your chances of hosting a parasite colony in your own intestines are remote and, better yet, it’s easily preventable.
First, let’s get our flatworms straight. According to the Centers for Disease Control and Prevention, the specific tapeworm species that afflicts domestic cats is the flea tapeworm. Also called Dipylidium caninum — the dog tapeworm — or colloquially known as the cucumber tapeworm, this parasite’s main mode of transmission is by way of larval fleas. Fleas, you know, nourish themselves on blood. Baby fleas, on the other hand, eat whatever organic matter is ready to hand, including tapeworm eggs. As the flea, the intermediate host, grows and matures, so too, do tapeworm larvae.
Once a flea is mature and ready to feast on sweeter foods, it finds a cat or dog on which to slake its eternal bloodthirst. During the normal course of self-grooming, a cat starts scratching at its fleas. Then the cat starts biting at the fleas. While gnawing or licking at a particular itch, the cat ingests and swallows an infected flea. Digestive fluids liberate the larval tapeworm from the body of the flea, leaving the tapeworm free to grow to maturity in the cat’s intestines.
Upon reaching a cat’s small intestine, the young tapeworm latches its toothy little scolex to an intestinal wall and grows to adulthood. This process takes anywhere from 3-4 weeks. When it is mature, the tapeworm begins to slough off segments of its body, all filled with new and fresh eggs. These emerge in cat poop, waiting to burst and be eaten by larval fleas. At this point, the cycle begins again.
“Contagious” isn’t the most precise word; tapeworm zoonosis is more about parasite transmission, not necessarily communicable disease. The point is, yes, tapeworms in cats can become parasites in humans. People can become definitive hosts in the same way your cat got tapeworms in the first place. You have to ingest a mature flea that is carrying a tapeworm larva.
Unlike some other parasites or health problems related to cats, fleas, and poop, you cannot develop a tapeworm infestation from simple contact with cat poop. Even the fecal-oral route, popular a mode of disease and parasite transmission though it is, cannot lead to intestinal parasites in humans. Ingesting a tapeworm egg will not yield an adult tapeworm. The feline tapeworm life cycle has a determined structure; it must develop inside the flea before it can reach maturity in a human or cat intestine.
Now, the chances of this happening are remote indeed, but it is not beyond the realm of possibility that fully-grown, well-meaning, generally clean-living humans might satisfy the conditions necessary for tapeworm zoonosis. How, you ask? Well, let’s say your cat is carrying even one flea containing a tapeworm egg. That cat probably has free reign of your house, perhaps even your bed. You start snoring, your mouth agape, and a flea hops in your mouth. I admit, that’s an unlikely train of events, but one which is entirely plausible.
Symptoms of tapeworms in cats are notoriously difficult to pin down. At the start of an intestinal parasite infestation — when there are only one or two mature tapeworms — there really aren’t any obvious physical reactions that you would notice. The first signs of worms in cats are to be found in their poop, or in the area immediately surrounding the cat’s anus. These are the proglottids, those egg-filled segments of the tapeworm that it releases as it grows in size and length.
The fresher and more recently the proglottid has broken from the mature tapeworm, the more mobile it is on its own. You may be able to see very small, dull-white to cream-colored segments, resembling nothing quite so much as grains of rice, or cucumber seeds, in the area right around the anus, or they may be visible in recently-excreted cat dung. A cat would have to have quite a large number of mature tapeworms living inside it to exhibit pronounced symptoms. A cat with a substantial tapeworm infestation may start losing weight or tend to vomit more than normal.
It is extremely rare for humans to nuture or develop mature cat tapeworms. How rare? According to the precis for this 2014 research article on tapeworm transmission in the Asian Pacific Journal of Tropical Biomedicine:
In the past 20 years only 16 cases have been reported in Europe, China, Japan, India, Sudan, Latin America, and the United States.
16 cases in the last 20 years, and most of them were young children, who enjoy putting strange things, like fleas, in their mouths.
You’re in luck, if, in the next 20 years, you or a small child you know are among the next 16 people to develop an intestinal parasite thanks to a wayward cat. The most effective and common treatment option is a medication called praziquantel. A single dose may be sufficient to eradicate tapeworms from a human.
There are a few simple things you can do to reduce the chances of hosting a flatworm party in your or your cat’s intestines. First is to establish a good flea control plan with your cat. That can mean anti-flea medications, baths for indoor-outdoor cats, and a flea collar. You could also monitor your cat’s poop or put a hind-quarters inspection on your monthly cat calendar. It is easy enough to keep your cat flea-free. Where there are no fleas, there can be no risk of tapeworms!
About the author: Melvin Peña trained as a scholar and teacher of 18th-century British literature before turning his research and writing skills to puppies and kittens. He enjoys making art, hiking, and concert-going, as well as dazzling crowds with operatic karaoke performances. His 17-year-old cat, Quacko, passed away the day before Thanksgiving, and his online life is conveniently encapsulated here.