How to eliminate the solitary worm

The passion for carpaccio and tartare of meat and fish, molluscs and raw crustaceans that has invaded Italy in recent years exposes to a fair number of food risks related to possible contamination by bacteria, viruses and parasites capable of causing more or less important disorders, mainly (but not only) at the gastrointestinal level.

It is not only hepatitis A or the now famous Anisakis infestation (fearsome intestinal worm transmitted above all by raw or undercooked tuna not properly “killed”), but also an old acquaintance such as tapeworm, better known as “solitary worm”, of which we often worry too little.

The species that can infect humans through food are above all the Taenia solium (pork tapeworm), the Taenia saginata (cattle tapeworm), the Diphyllobothrium latum (fish tapeworm) and the Taenia asiatica, a variety very similar to the saginata, whose transmission (which occurs through pork) affects especially Asia. Let’s see what are the symptoms they cause.

Symptoms not only gastrointestinal

Tapeworms are a group of parasites of animals and humans belonging to the type of flatworms and the class of cestodes, characterized by a fairly complex life cycle that can differ from species to species.

Like all their fellows, these flat-bodied, segmented parasites go through three vital stages: the egg stage, the larval stage, and finally the adult stage.

The adult worm dwells in the small intestine of the final host, from which it absorbs the nutrients necessary for its development. In particular, the species that infest the human being have a head equipped with hooks or suckers (the “scolex”), with which they anchor to the intestinal mucosa to feed, and a germinative neck from which, as they grow, new segments are generated (called “proglottids”).

It is the proglottids furthest from the neck that produce the eggs: these, once ripe, detach from the rest of the body and are expelled through the faeces of the host.

The eggs will then be ingested by an intermediate host, in which they will hatch into larvae.

Humans can be infected either by ingestion of eggs, released into the environment with the feces of animals (or people) that host tapeworms in the intestine, or by ingestion of larvae (cysts or cysticercus) present in the muscles of contaminated animals.

In the first case, after entering the digestive system, the eggs arrive in the intestine, and larvae develop, which become mobile and can spread to other organs and tissues, such as the liver, lungs, nervous system, producing large lesions. In these locations, cysts multiply, interfering with the functioning of infected organs and, in severe cases, causing serious and life-threatening disorders.

For example, if they get to the brain they can cause headache, seizures, confusion or neurological symptoms, such as seizures; in the eyes can cause blindness; In the spinal cord, they can result in muscle weakness or paralysis. This form of invasive infestation, called cysticercosis, is almost absent in countries with good hygiene standards.

More frequent, although uncommon, is instead the ingestion of cysts through raw or undercooked meat and fish. In this case, once in the intestine, the larvae develop into the adult form of the worm, which can grow to a length of several meters.

How to notice its presence

In most people, teniasis is asymptomatic. Although it may seem surprising, the presence of the adult tapeworm in the intestine does not cause symptoms of any kind, because this allows the worm to grow undisturbed and gradually release the eggs through the feces.

In some cases, however, the digestive system does not tolerate the presence of the unwanted guest and symptoms such as nausea, loss of appetite, gastrointestinal discomfort, itching, diarrhea and weight loss may appear. The tapeworm transmitted by fish can also cause anemia because it subtracts vitamin B12, a substance necessary for the formation of red blood cells.

Beyond the symptoms mentioned and the possible weight loss (not very specific), generally the first suspicion of having contracted the tapeworm is linked to the finding of small pieces of the worm in the feces (the aforementioned proglottids), often recognizable to the naked eye as mobile whitish fragments. To confirm the diagnosis, stool examination is required, which can detect both smaller proglottids and tapeworm eggs.

Reporting to the doctor your eating habits and, in particular, the fact of having eaten raw or undercooked meat or fish in the days / weeks before the onset of symptoms, also specifying in which contexts, helps to direct the diagnosis.

Tips to stay away from tapeworms

Once it is established that an intestinal tapeworm has been contracted, the therapy involves taking only one dose of an antiparasitic drug called praziquantel. If the parasite has given rise to cysticercosis, however, treatment is only provided if the cysts have contaminated the brain. In this case, antiparasitic drugs (albendazole or praziquantel) and corticosteroids can be administered, resorting to surgical intervention in the event that an increase in intracranial pressure has occurred or intraventricular cysticercus has formed.

In addition to the more or less serious disorders it can cause, hosting a tapeworm in the intestine also puts at risk of infection all the people with whom you share meals and toilets (starting with family members). The best strategy to avoid problems for yourself and others is to take some simple preventive measures.

Among the main recommendations to follow, it should be remembered above all to cook well the meat (in particular, pork) and fish (especially freshwater meat), keeping the temperature high enough (over 60 ° C) for sufficient time to heat even the innermost parts, since the whole portion of muscle is at risk.

Preventive freezing for at least 24-48 hours at a temperature below -20°C offers additional protection against tapeworms and other parasites and should always be provided for all fish that are eaten raw (carpaccio, tartare, sushi, sashimi etc.). Freshwater fish, particularly at risk of tapeworm contamination, should always be brought to the table cooked at the right point. It should also be considered that marinating, smoking and drying do not eliminate cysts and therefore are not effective methods in preventing this parasitosis.

If you eat away from home, in addition to choosing the right foods, you have to pay attention to the reliability of the restaurant, the hygienic state of the rooms, the dishes and the staff, the proximity between the kitchen and toilets and how the dishes are managed during the service: if something does not convince, it is better to change the room. This will help to avoid not only tapeworms, but a wide range of food-borne diseases.

Similar warnings apply when shopping: for the purchase of meat and fish it is better to contact trusted shops, which are supplied by certified producers, regularly subjected to careful health checks and with complete traceability of the supply chain.