“I just found two worms on the floor by Savoy’s food bowl,” the woman on the phone said, clearly upset. We’re used to that. I have had people page me late at night because their kitten vomited a puddle of roundworms or, worse yet, a tiny tapeworm segment wiggled out of their cat’s you-know-what. “They are small and blackish,” she added. Hmmm. None of the typical parasites of cats would fit that description. “I wonder if they’re maggots,” I said. If a dish of canned cat food sits out too long, flies sometimes come and lay their eggs, which eventually hatch out into maggots. Not usually “blackish,” but they can have a brown or gray tint. But flies and maggots are more a summertime thing. Besides, Savoy’s mom wasn’t the type to leave spoiled cat food festering in her kitchen.
“Or maybe flea larvae?” I speculated. Many folks don’t know that fleas have a wormlike larval stage in their life cycle. But flea larvae are not really “blackish.” Besides, they are very active, quickly squirming away to places dark and hidden. It would be highly unusual to find them lounging in plain sight by Savoy’s bowl. So were the worms on the kitchen floor coming from the cat? And, if so, what should we do about it? Let’s learn a little parasitology by discussing three common intestinal worms that infect cats: roundworms, hookworms, and tapeworms.
Roundworms. We start with the first “host” — an adult cat we will call Napa. Napa has adult roundworms living in her intestines. These worms lay eggs that pass in her feces. When Napa poops outside in the flowerbed, the eggs disperse into the soil, where they can hibernate for a long, long time. (I recently heard a parasitologist call roundworm eggs “virtually indestructible.”) Eventually a tiny baby worm forms inside that egg, just waiting for a new home. One possible home is a mouse or other rodenty creature. Mr. Mouse is busy cleaning the dirt off his little mousy paws, inadvertently eating roundworm eggs. The baby worms happily emerge from their eggs in Mr. Mouse’s intestines. They burrow through the gut wall, then form cysts in his muscles, where the baby worms essentially just go back to sleep. For now.
In cats, things go differently. Our first host cat, Napa, has left roundworm eggs in the flowerbed. Savoy can ingest roundworm eggs the same way Mr. Mouse did — by grooming contaminated soil off her paws. But Savoy can also ingest roundworms by, well, ingesting Mr. Mouse. Remember those encysted baby worms in Mr. Mouse’s muscles? They get released when Savoy digests Mr. Mouse. (Isn’t Mother Nature wonderful?)
Whichever way Savoy gets infected, either directly by eating soil, or indirectly by eating Mr. Mouse, roundworm larvae hatch inside her intestine. They then burrow through the gut wall, and migrate around her body until eventually getting to her lungs. Savoy coughs up the larvae, then swallows them back down into her intestines, where they become mature worms and set up housekeeping. Amazing.
Adult cats rarely show any outward signs of roundworm infection. Kittens are more susceptible, and can get infected through the mother’s milk when they nurse. Serious infections can cause vomiting, diarrhea, weight loss, potbellied appearance, and general “unthriftiness” — lack of vigor, strength, or health — because the parasites compete for nutrients. Rarely, roundworms can cause intestinal blockages, and even death. Roundworms live inside the cat, so are generally not visible to owners. Occasionally a cat may vomit them up. They look a bit like spaghetti. White, long, thin.
Hookworms. Much smaller than roundworms, but much nastier. Rather than passively soaking up nutrients, hookworms latch onto the intestinal wall and suck their hosts’ blood, leaving a trail of bleeding ulcers. The life cycle is fairly similar to that of the roundworm, but includes intermediate hosts such as birds, and insects like cockroaches, as well as rodents. Napa can get infected directly through ingestion of contaminated soil, or by eating any of these intermediate host species. Clinical signs may be absent or similar to roundworm, but signs related to blood loss may also occur, especially in kittens. Anemia, pale gums, tarry stools, trouble breathing. The adult worms are quite small, less than half an inch, and can look “blackish” due to the blood they have eaten. But it is very uncommon for adult hookworms to be seen outside the cat’s body.
Tapeworms. There are many kinds, but the one we see most frequently is carried by fleas. Let’s call this cat Kimchi. Kimchi has a tapeworm — a big, long, flat, segmented worm — in her intestines. It anchors itself to the gut wall with its mouth, but does not suck blood. Like roundworms, tapeworms passively absorb nutrients. Periodically, the tapeworm sheds little egg sacs called proglottids from the tail end of her body. These are shed in Kimchi’s feces, or simply crawl out her the anus. This really freaks cat owners — finding writhing proglottids under Kimchi’s tail.
The proglottids dry up. They look like grains of rice. Then they break down in the environment, releasing the eggs. But wait. There’s more. These eggs are not infective to mammals. First they need fleas. More specifically, flea larvae — those wiggly worms I mentioned earlier. Flea larvae eat tapeworm eggs. Flea larvae then turn into cocoons, which later hatch into adult fleas that hop onto Kimchi and bite her. Kimchi bites back, eating the adult flea. The flea is inside Kimchi. The tapeworm egg is inside the flea. Kimchi digests that flea, liberating the tapeworm egg, which then hatches out, and we start all over again.
Intestinal worms. Rarely an emergency, but certainly in need of treatment, but proper treatment requires proper identification. Savoy’s owner brought us the specimens in a tiny glass jar labelled WORMS with Sharpie on the lid. Inside were two small purplish and white linear objects. Not intestinal parasites. Purple cabbage. That’s right. Cabbage. We all had a good laugh with Savoy’s owner, with assurances that cruciferous vegetables posed no danger to her cat.
