Consumption of infected and inadequately heated beef can lead to infection with bovine tapeworm (Taenia saginata). It is a parasitosis with a benign course. In Central Europe, due to well-established drugs, the disease has now become rare.
What is bovine tapeworm?
Tapeworms live as parasites in the intestines of humans or other vertebrates. There are many different types of tapeworms. Each species can cause different symptoms, although only a few species could become a danger to humans. In the picture, the head of a tapeworm. Click to enlarge. The bovine tapeworm belongs to the family of so-called flatworms and, like all pathological parasites, undergoes a certain developmental cycle, i.e. it requires an intermediate host as well as a final host for complete development and maturation. The intermediate host of the bovine tapeworm is cattle, and the final host is humans. Although the infectious disease is rare in Germany, it is nevertheless the most common tapeworm disease in humans. The cattle tapeworm consists of a head and many tapeworm segments, the so-called proglottids. These segments are shed via the anus when the tapeworm reaches a certain size. However, the head of the parasite has bored into the fine mucosal layers of the intestinal wall, from where it also absorbs the nutrients for its further growth. Since the bovine tapeworm is a hermaphrodite, fertilization occurs independently. After self-fertilization, the proglottids contain tapeworm eggs that are excreted in the feces. A new tapeworm can only mature if its eggs are ingested by the intermediate host, in this case a cow.
Occurrence, distribution, and characteristics
The bovine fin tapeworm lives and reproduces in the intestine of humans as the definitive host. When newly infected, the worm is only a few millimeters in size and is barely visible. However, adult bovine tapeworms can reach a length of up to several meters. The infection rate has fallen sharply, especially in Germany, due to government meat inspection. This is because the encapsulated fins can be seen quite easily in the raw beef. Infection with the bovine fin tapeworm is still a mass affliction in East Africa. Although the parasite can reach a considerable length, its presence often remains asymptomatic, so the infected patients do not necessarily experience symptoms. The most noticeable disease symptom is the discovery of tapeworm segments, proglottids, on the stool. Each proglottid has the ability to move on its own, meaning it can contract and move on its own through muscular contraction. Under a light microscope, the head of the bovine fin tapeworm can be seen quite clearly. The four suction buttons with which the parasite attaches itself to the inner wall of the intestinal mucosa are considered the most reliable diagnostic feature. This does not pose a vital danger, because the tapeworm is not able to penetrate the intestinal mucosa, which would result in a life-threatening condition. In direct comparison with other human pathogenic tapeworms, the bovine tapeworm also remains in the intestine for life and does not spread to other organs. In order for the worm to reach full development, the eggs must be ingested by cattle as an intermediate host. This occurs as a result of human feces entering the wild as untreated sewage. Tapeworm eggs are considered very robust and survive adverse environmental conditions unscathed. The chain of infection is completed when the infected feces are spread as manure on pastures and fields and consumed by grazing cattle. Rain is also known to wash tapeworm eggs from contaminated soil and transfer them to adjacent pastures. Once ingested by cattle, the eggs enter the ruminant’s intestine unharmed. Once there, the larvae of the bovine tapeworm hatch from the eggs after several days. However, these eggs are able to penetrate the intestinal wall and spread throughout the body via the bloodstream. The target organ of the tapeworm eggs in cattle is the well-supplied muscles, where they attach themselves and encapsulate in the form of a so-called fin. This meat can then be used to infect humans as the final host. The parasite then grows from the fin-containing meat into the sexually mature form in the human intestine. The development cycle of the bovine fin tapeworm is then considered closed.
Diseases and ailments
Symptoms rarely occur in association with infection by bovine tapeworm. The leading symptom at an advanced stage of infection with Taenia saginata is weight loss, because an adult bovine tapeworm consumes enormous amounts of nutrients. In addition, a feeling of general weakness, indigestion, loss of appetite or nausea may occur. Causal therapy can be given at any stage of the disease. Even a single administration of a high-dose anthelmintic ensures that the tapeworm, including the head, dies off safely. In severe cases, appendicitis or intestinal obstruction can also occur, but these clinical pictures are the absolute exception in connection with the infection. Due to the unspecific or non-existent symptoms, the diagnosis can only be made via a stool sample. Infection with the bovine tapeworm can be effectively prevented by avoiding eating raw or insufficiently heated beef. In Germany, the greatest risk of infection comes from so-called scraped meat or tartar. If beef is heated to over 70 °C for only a few minutes, the tapeworm’s fins reliably die. There is then no longer any risk of infection. Freezing the meat at at least -18 °C for a period of ten days also has the same effect.
