The human tapeworm, Taenia saginata, has a unique lifecycle in that its intermediate host is striated muscle in beef cattle. Sometimes mislabeled the “beef tapeworm”, Jared Taylor, DVMP, MPH, Oklahoma State University, clarifies that it is not a tapeworm of beef, but of humans. Bovine cysticercosis is caused by Cysticercus bovis, the larval stage of the human Taenia saginata. Because of the cyst-like appearance in the bovine muscle, the condition is called “beef measles” (measly beef), but has nothing to do with human measles.
Speaking at the 2010 National Institute for Animal Agriculture annual meeting, Taylor explained that humans are the definitive host for this cestode parasite, a flatworm with a complex lifecycle. Sexual reproduction takes place in the human host, but needs an intermediate host for transmission back to humans. Cattle and to a lesser extent other ruminant are the intermediate hosts.
Cattle pick up eggs from infected humans from some sort of exposure to human waste. The larvae then go through the intestinal wall, circulate through the blood/lymphatic systems, end up in the musculature, and encyst. These can be called “bladder cysts” as they are fluid-filled nodules. If this infective cyst is consumed, a person can then develop a tapeworm infection. While it does not cause disease in cattle, the cysts can calcify and retain an unattractive appearance in the muscle meat.
In humans, Taenia saginata is acquired through beef consumption of the infective cysts if they are present and there is an inadequate cooking process. The tapeworm can segment and viable segments can then be shed by humans. Taenia saginata does not usually cause disease problems in humans, though some may experience vague gastrointestinal disturbances, abdominal pain, nausea, diarrhea and weight loss from competition for nutrients. The human tapeworm does not actively remove nutrients from intestinal walls and the blood supply. Taylor noted that it is not particularly significant in either cattle or humans.
Human tapeworm is readily treatable. Taylor said that the human tapeworm was said to have been advertised as a weight loss agent in early 1900s, but it’s unlikely that the tapeworm or segments could have remained viable for that purpose.
Why should we control it? Because we can.
Human tapeworm and beef measles is not a public health threat, but, Taylor noted, if we can control it, we want to. “If it gives an unappealing characteristic to the beef, we’re not happy about that,” he said.
All cattle carcasses are inspected after slaughter and inspectors look for the cysts in striated muscle. The detection of one cyst in a carcass deems it infected. Once detected, various sites are examined more closely. When one carcass within a lot is found infected, all carcasses within that lot are typically subjected to extensive inspection.
Cattle pick up the proglottid segments containing eggs from exposure to human feces whether it is human sewage used as fertilizer for crop fields or grazing pastures, trucks hauling feed that previously hauled human waste/sewage, as well as direct contamination of feedstuffs by humans (typically employees) through defecation in feedbunks or feed storage areas. Taylor says it’s hypothesized that wildlife can also pick it up from human sewage serve as a mechanical vector, but he’s not sure that has been proven.
Taylor said treating human sewage isn’t necessarily the answer, but if sewage is to be applied to land used to grow crops or graze cattle, a sick week delay between the two should be in place. Toilet facilities should be available and convenient for all employees. Feedlot operations should use designated equipment for handling feed.
Studies by Hancock and Yoder have shown C. bovis associated with feeding potato waste to feedlot cattle in the Pacific Northwest, and it’s assumed that any produce waste can also be contaminated, however various treatments such as pasteurization and ensiling can reduce survival of the parasite.