Parasitic infestations: Tapeworms in the gastrointestinal tract

Noninvasive Tapeworms

Some of us may not be that particular when it comes to cooking meat. However, at the end of reading this article, you might as well try to reconsider.

Among the consequences of not eating properly cooked food is the ingestion of parasites, among of which are the cestodes, commonly known as tapeworms. These organisms are classified as to whether they cause invasive disease or not, and are also divided according to the animal serving as mediator for transmission from human to human.

There are four major tapeworms that can cause noninvasive infections in humans. Let us tackle this one after the other.

Beef tapeworm - Taenia saginata

First, we have the most popular. The beef tapeworm, or Taenia saginata, is most common in cattle breeding areas. Though humans are identified as the definitive host, contaminated human feces containing gravid segments of T. saginata are usually ingested in part by cattle grazing on the soil. Upon ingestion, these eggs hatch and lodge themselves onto the muscles of the cattle (wherein they are called cystecerci), and when humans ingest raw or poorly cooked beef, these are consequently passed on to them. Most often, those who are infected remain asymptomatic, except in some wherein there is abdominal pain as well as other gastrointestinal symptoms. The worms lodge themselves at the duodenum, and adult worms are usually visible within three months from initial infection. Passage of proglottids (or the segments of the tapeworm) is an evidence of infection.

Pork tapeworm - Taenia solium

The pork tapeworm, or Taenia solium, is transmitted from humans to pigs through ingestion of feces containing T. solium eggs. Alike that of the beef tapeworm, infection can present without symptoms, although a few gastrointestinal symptoms may take place. Proglottids can also be seen upon stool examination of infected individuals. Ingestion of cystecerci found in pigs can lead to cerebral infection. This tapeworm has the potential to produce infection that can progress into the invasive type, according to the location it lodges itself in.

Fish tapeworm - Diphyllobothrium latum

The fish tapeworm, otherwise known as Diphyllobothrium latum, is transmitted through intake of undercooked freshwater fishes. This is typical in temperate regions, and the infection process proceeds from ingestion of infected human feces by crustaceans, followed by ingestion of these crustaceans by larger fishes, and afterwards ingestion of improperly cooked freshwater fish by humans. This can occur over years, and multiple worms can infect a single individual due to repeated ingestion of infected fishes. Like the previous two tapeworms, the patient is usually asymptomatic, but other gastrointestinal symptoms such as abdominal pain and diarrhea can also take place. Diagnosis is established upon discovery of proglottids in the stools. Contrary to the first two tapeworms, the fish tapeworm has worse effects, wherein chronic heavy infection can result to megaloblastic anemia as well as neuropathy due to Vitamin B12 deficiency (the worm uses up the vitamin for its own consumption, and the infection causes dissociation of the vitamin from its intrinsic factor).

Dwarf tapeworm - Hymenolepsis nana

The last major tapeworm that can infect humans is the dwarf tapeworm or the Hymenolepsis nana – it is the only tapeworm that can be transmitted from human to human! Infection is usually dominant among warm areas, and areas with poor hygiene and sanitation. Alike the previous three, infection is also through ingestion of eggs in contaminated human feces. After a period of four days, the ingested eggs hatch into adult worms, but the worms are only dwarf in size compared to the previous three. Children are mostly the recipients of the disease, and clinical manifestations include abdominal discomfort characterized by stomach pain, diarrhea, as well as anorexia. Therefore, keep your children from playing in areas wherein they are susceptible to contamination.

The usual treatment employed by physicians for these noninvasive tapeworm infections is Praziquantel, adjusted according to the weight of the patient. It is administered in much higher doses for H. nana infections. Adverse effects of the drug may include dizziness, headache, nausea, malaise, and abdominal pain.

The only preventive measure against these worms is through cooking meat properly, and avoiding ingestion of masses that are sometimes visible within the muscle of either beef or pork meat. These masses may be cystecerci – encystments that the worms do upon entry into the human body. They usually insert themselves onto the striae of skeletal muscles. Do not take the risk of eating raw food in the thinking that these tapeworms are nevertheless non-invasive, for they can also progress into the invasive type (tapeworms of this type will be discussed separately). So take extra care, and ensure good health and prevent disease by eating properly cooked food!