You are driving home from work and are hungry. Naturally, you decide to stop at your local burger joint because you know you won't have the energy to cook when you get back. When you get there you see there is a long line and the restaurant workers seem to be scrambling around trying to cope with all the customers. You put in an order for a scrumptious sounding beef burger. The burger arrives much quicker than you anticipated and looks a little too pink but you gobble it up. Eh, you like your meat cooked rare anyway. This can't hurt you. A few weeks later you have a stomachache and a persistently itchy bum. You don't understand why this is happening. You go to your primary care provider and after taking a brief history and running some tests, they tell you there is a parasite inside your body. Yikes! You swear never to eat undercooked meat again.
Well, that was the story of Taenia saginata, more commonly known as the beef tapeworm. It is from a group of parasites called Platyhelminthes aka flatworms and is called a cestode in the world of microbiology. Although not very common in the United states( almost all cases are imported from overseas), it is native to Africa and some parts of Europe and Asia. Let's "unravel" (pun not intended) some information about this sneaky tapeworm.
Anatomy and lifecycle of Taenia saginata:
As can be told from the name, Taenia saginata is a flat and beige colored worm. The biggest one ever reported was 59 feet in a Thai man. The head of the tapeworm is called scolex and the body consists of segments called proglottids. The scolex attaches to the intestinal wall with the help of grooves. These proglottids are responsible for egg production and are then termed gravid when they contain eggs. The eggs produce embryos called oncospheres. Below is the life cycle of the tapeworm.
The human is the definitive host meaning the reproductive part of the parasite's life occurs inside the body of the human while cattle are intermediate hosts and are responsible for the non reproductive part of the life cycle. Humans excrete gravid proglottids which are ingested by cattle if feces are not disposed of properly. The eggs form oncospheres which hatch from the egg and travel via blood vessels to the muscle of the cows and are stored there. Inside the muscle they form cysticerci which are larvae. Humans then ingest infected cow meat which has the tapeworm larvae. The larvae grows to become an adult worm inside the intestines. This takes roughly three months. The worms are hermaphrodites which means they contain both male and female counterparts within the same body and self fertilize to produce more eggs which are stored inside proglottids and shed through feces thereby completing and repeating the cycle. Humans may actually reinfect themselves by ingesting the eggs they pass through fecal-oral contact.
Clinical findings:
Patients will experience mild abdominal pain, nausea, changes in appetite, weight loss, and diarrhea. The expulsion of the proglottids from the anus can also cause anal pruritus aka itching. Most people do not have severe symptoms as the worm has limited contact with the mucosa of the gut. Occasionally tapeworms may cause obstruction which leads to issues like cholecystitis and pancreatitis.
Diagnosis:
This parasite is diagnosed by observing gravid proglottids in the stool. The proglottids from beef tapeworm will have 15 to 20 uterine branches inside them, which is more than other kinds of tapeworms. Anal swabs may be recommended.
ELISA( enzyme-linked immunosorbent assay) can be done on stool samples but is not able to differentiate between this and other tapeworms.
Treatment:
Praziquantel is prescribed to patients with beef tapeworm. It has mild side effects which are temporary.
Prevention:
We must cook beef to an internal temperature of 131 degrees Fahrenheit or freeze it at -10 for at least 5 days. Meat can also be pickled in 25% brine for 5 days to kill any parasites within it. There needs to be proper waste disposal systems in place so that the water carried to the vegetation consumed by animals is free of pathogens.
By emphasizing hygiene and proper food preparation techniques, communities can shield themselves from this silent invader, ensuring a healthier, safer future for all.
Sources:
Review of Medical Microbiology and Immunology by Warren Levinson, MD, PhD
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