You get a tapeworm by swallowing its larvae or eggs, almost always through food, water, or accidental contact with contaminated feces. The most common route is eating undercooked or raw meat or fish that contains tapeworm larvae. Less commonly, you can pick up tapeworm eggs from contaminated water, unwashed produce, or contact with infected animals.
There are several species of tapeworm that infect humans, and each has its own pathway into your body. Understanding those pathways is the key to avoiding infection.
Undercooked Meat: The Most Common Source
Beef and pork are the two foods most frequently linked to tapeworm infections worldwide. When cattle graze on pasture contaminated with tapeworm eggs, larvae develop inside the animal’s muscle tissue. If that beef is later eaten raw or undercooked, the larvae survive and grow into an adult tapeworm inside your intestine. The same process happens with pork, though pork tapeworm carries more serious health risks (more on that below).
Killing larvae in meat requires proper cooking temperatures. Whole cuts of beef or pork need to reach an internal temperature of 145°F (63°C), while ground meat needs to hit 160°F (71°C). Freezing meat at sufficiently low temperatures for an extended period can also kill larvae, but cooking to the right temperature is the most reliable safeguard. Dishes like steak tartare, rare burgers, and undercooked pork carry the highest risk.
Raw Fish and the Fish Tapeworm
A different species of tapeworm lives in freshwater and certain farmed fish. You can pick it up by eating raw or undercooked fish that harbors larvae in its flesh. Salmon, trout, perch, and pike are among the species most commonly involved. Traditionally, infections in Europe and North America occurred among people who tasted bits of raw freshwater fish while preparing dishes like gefilte fish.
More recently, the expansion of salmon farming in regions like southern Chile has broadened the risk. Research published in Emerging Infectious Diseases found that farmed rainbow trout and other aquacultured salmon species in that region carried tapeworm larvae, meaning the parasite had jumped into fish species that weren’t historically affected. Sushi and sashimi made from freshwater or anadromous fish (fish that move between fresh and saltwater) pose the greatest concern. Most commercial sushi-grade fish is flash-frozen to kill parasites, but fish prepared at home or sourced from less regulated suppliers may not have gone through that step.
Swallowing Tapeworm Eggs: A Different, More Dangerous Route
Eating larvae from undercooked meat gives you an adult tapeworm in your gut. Swallowing tapeworm eggs is a completely different type of infection and potentially far more dangerous. This distinction matters most for the pork tapeworm.
When someone already carrying an adult pork tapeworm has poor hygiene, they shed microscopic eggs in their stool. Those eggs can contaminate hands, surfaces, food, or water. If another person (or even the same person) accidentally ingests those eggs, the eggs hatch into larvae that burrow through the intestinal wall and travel to other tissues, including the brain, muscles, and eyes. This condition is called cysticercosis, and when it reaches the brain, it can cause seizures, headaches, and serious neurological problems.
The World Health Organization identifies the pork tapeworm as the only tapeworm species that causes major health problems in humans. The beef tapeworm and Asian tapeworm, by contrast, cause intestinal infections that are generally mild. Pork tapeworm eggs spread through the fecal-oral route: contaminated water, unwashed fruits and vegetables, or simply not washing hands after using the bathroom. In areas with poor sanitation, where open defecation contaminates soil and water, this cycle is especially hard to break.
Dog and Cat Tapeworm From Fleas
A lesser-known route involves accidentally swallowing a flea. Dogs and cats commonly carry a tapeworm species that uses fleas as an intermediate host. If an infected flea ends up in your mouth, you can develop an intestinal tapeworm. This sounds unlikely, but it happens, and most reported cases are in young children who play on the floor, put their hands in their mouths, and have close contact with pets.
The risk goes up when a pet has a flea infestation. Keeping your pets on regular flea prevention and treating any infestations promptly reduces the chance of this type of transmission significantly.
Contact With Dogs and Livestock
A particularly dangerous tapeworm species cycles between canines (dogs, wolves, coyotes) and livestock like sheep and cattle. Humans are accidental hosts. You become infected by swallowing microscopic eggs shed in dog feces, either through direct contact with an infected dog or by eating unwashed fruits and vegetables contaminated with eggs from the environment. Dogs can carry eggs on their paws and fur, not just in their stool, so petting or being licked by an infected dog is a plausible route.
Once ingested, these eggs form slow-growing cysts in internal organs, most often the liver and lungs. This condition, called hydatid disease, can take years to produce symptoms and often requires surgical treatment. Risk factors include sheepherding, allowing dogs to eat raw animal organs, home slaughter of sheep, and close contact with dogs, sheep, and swine.
How to Tell You Have a Tapeworm
Most intestinal tapeworm infections cause few or no symptoms, which is why prevalence stays below 1 to 2 percent even in regions where the parasite is common. When symptoms do appear, they tend to be mild: vague abdominal discomfort, nausea, changes in appetite, or diarrhea.
The most recognizable sign is finding tapeworm segments in your stool. Adult tapeworms continuously produce small, flat, rice-grain-sized segments that break off and pass out of the body, roughly six per day. These segments are sometimes visible in the toilet or on underwear and may still be moving when freshly passed. A mature beef tapeworm can contain 1,000 to 2,000 of these segments, while a pork tapeworm averages around 1,000. If you see anything matching this description, bring a sample to your doctor for identification.
Practical Steps to Prevent Infection
The core prevention strategies map directly to the transmission routes above:
- Cook meat thoroughly. Use a meat thermometer. Whole cuts to 145°F (63°C), ground meat to 160°F (71°C). Avoid tasting meat before it’s fully cooked.
- Be cautious with raw fish. If you eat sushi or ceviche, choose sources that properly freeze fish to kill parasites. Avoid raw freshwater fish prepared at home unless it has been frozen at parasite-killing temperatures first.
- Wash hands after using the bathroom, before preparing food, and after touching animals. Soap and running water for at least 20 seconds is the standard. Alcohol-based hand sanitizers are a backup but less effective against certain parasites, especially if your hands are visibly dirty.
- Wash fruits and vegetables thoroughly, particularly if you live in or are traveling through areas with poor sanitation infrastructure.
- Keep pets on flea prevention and avoid letting dogs eat raw organs from livestock.
- Avoid drinking untreated water in regions where open defecation may contaminate water sources.
Tapeworm infections are treatable with antiparasitic medication, and most intestinal cases resolve quickly once diagnosed. The greater concern is the tissue-invading forms, particularly cysticercosis from pork tapeworm eggs, which can cause lasting damage before anyone realizes the infection is there. Prevention is straightforward: cook your food, wash your hands, and manage your pets’ parasites.