Taeniasis is helminthiasis caused by parasitism in the small intestine of pork tapeworm and characterized by signs of digestive disorders and astheno–neurotic manifestations. The course is accompanied by a decrease in appetite, abdominal pain, nausea, vomiting, stool disorders, dizziness and headaches, sleep disorders, fainting states. A dangerous complication of taeniasis can be cysticercosis of the eyes and brain. The diagnosis is made on the basis of the detection of segments of pork tapeworm in feces or perianal scraping. Niclosamide, praziquantel, etc. are used as specific anthelmintic drugs.
ICD 10
B68 Taeniasis
General information
Taeniasis is an intestinal parasitic disease from the group of cestodoses caused by a tapeworm – pig, or armed tapeworm. There are three global foci endemic to taeniasis in the world: Asian (India, Northern China, Philippines, Laos, South Korea), Latin American (Mexico, Colombia, Nicaragua, El Salvador, Honduras) and African (Zaire, Nigeria, Cameroon), but the true geography of helminthiasis is much wider. In hyperendemic zones, the infestation of pigs reaches 25-35%, and the infection of people with taeniasis is hundreds of thousands of people.
Causes
Taeniasis, like teniarynchosis, is caused by a ribbon parasite from the family Taeniidae (Teniidae), so both diseases belong to human teniidosis. Taenia solium (porcine, or armed tapeworm) is a large helminth, the length of an adult individual of which reaches 2-4 meters. The body of the helminth consists of a head with suckers and hooks, a neck and numerous (up to 1000 pieces) segments of a quadrangular shape, each of which contains 30-50 thousand eggs. Inside each egg of a pork tapeworm contains a six-pointed embryo (oncosphere), which is invasive. Mature segments rejected from the body of the helminth are released with human feces into the external environment, where the eggs are dispersed over the soil.
For the full cycle of development of the pork tapeworm, a change of two owners is necessary. Domestic pigs or wild boars serve as an intermediate host for the pathogen of taeniasis, in which invasive eggs enter the body together with feed or land. In the digestive tract of pigs, oncospheres are released from eggs, which penetrate into the bloodstream, spread throughout the body and settle in muscle tissue. Here, after 2-2.5 months, the embryos turn into cysticerci, or finns – larval vesicles, inside of which there is a head (scolex) armed with hooks. In the pig’s body, cysticerci can be up to 3-6 years old; later they calcify and die. In some cases, the intermediate host of pork tapeworm may be a person whose helminth larvae cause a dangerous disease – cysticercosis.
The subsequent stages of development and the final parasitization of pork tapeworm are associated with humans. Infection with taeniasis occurs when eating pork or wild boar meat infested with cysticerci. In the human small intestine, the head of the helminth comes out of the larval vesicle, which is fixed to the intestinal wall with the help of suckers and hooks and after 2-2.5 months, as the segments grow, turns into a sexually mature helminth.
Thus, the leading factors of infection with taeniasis are pig meat, poorly heat-treated, not passed veterinary control, sometimes – hands contaminated with cysticerci or water. The mechanism of infection is alimentary, the ways of infection are food or water. A person with taeniasis poses an epidemiological danger, since he can infect himself and others with the larval stage of cysticercosis of skeletal muscles, brain, and eyes. The basis of pathological reactions in intestinal taeniasis is mechanical injury of the mucous membrane of the small intestine with suckers and hooks, toxic-allergic reactions, absorption of nutrients by helminth. Parasitization of adult helminths in the human intestine can last for decades.
Symptoms
Taeniasis can occur with mild nonspecific symptoms or with their almost complete absence. In clinically pronounced cases, dyspeptic, abdominal and astheno-neurotic syndromes develop. Symptoms occur approximately 6-8 weeks after ingestion of cysticerci. Early complaints of patients with taeniasis include nausea, vomiting, upset stools (diarrhea or constipation), lack of appetite, weight loss. Abdominal pain can be mild, aching or intense, cramping. Often, patients suffering from taeniasis are concerned about anal itching. Signs of astheno-neurotic syndrome are represented by dizziness, headache, irritability, sleep disorders, fainting. Changes in peripheral blood are characterized by eosinophilia and iron deficiency anemia. Complications of taeniasis occur rarely, but may include such serious pathological conditions as acute appendicitis, intestinal obstruction, pancreatitis, cholangitis.
During vomiting, segments of pork tapeworm containing invasive eggs can be thrown into the stomach of a patient with taeniasis. The oncospheres released from the eggs migrate through the body with blood flow, settling in the muscles and internal organs. This is how endogenous infection with cysticercosis occurs – an extra-intestinal form of taeniasis caused by cysticerci – larvae of pork tapeworm. At the place of parasitization of cysticerci, cysticercosis of the brain, eyes, skin, heart, lungs is isolated.
Cysticercosis of the brain accounts for 60% of cases of extra-intestinal taeniasis. The defeat of the large hemispheres is accompanied by hydrocephalus and cerebral hypertension. Patients experience attacks of taeniasis and headaches, suffer from sensitivity disorders, speech disorders, epileptic seizures. In endemic areas, cysticercosis is the most common cause of epilepsy among the local population. With cysticercosis of the brain, mental disorders may be noted – excitement, depression, hallucinatory delusions. If cysticerci enter the ventricular system (more often the IV ventricle) of the brain, Bruns syndrome develops (intense attacks of headache and vomiting caused by a change in the position of the head), disorders of cardiac activity and consciousness. With cysticercosis of the base of the brain, a clinical picture of basal meningitis develops, accompanied by vomiting, headache, bradycardia, damage to cranial nerves.
The next most common form of extra-intestinal taeniasis is cysticercosis of the eyes. Larvae can penetrate into the conjunctiva, vitreous, anterior chamber, retina, causing inflammatory and dystrophic changes. Cysticercosis of the eyes can be manifested by persistent conjunctivitis, uveitis, retinitis, often leading to atrophy of the eyeball, retinal detachment and blindness. Lung cysticercosis is asymptomatic and is diagnosed on the basis of radiological findings. Parasitic heart disease is characterized by a violation of the heart rhythm. The most favorable course among all forms of extra-intestinal taeniasis has cysticercosis of the skin. In this case, tumor-like subcutaneous formations are formed in the places where the larvae settle.
Diagnosis and treatment
The main criteria for recognizing taeniasis are clinical data (removal of helminth segments with feces), epidemiological information (eating poorly processed pork) and laboratory confirmation of the diagnosis. In order to detect the oncospheres of pork tapeworm, repeated examination of feces and perianal scraping is carried out. The oncospheres of porcine and bovine tapeworm are morphologically identical. Macroscopic examination of mature helminth segments, which have a different number of lateral branches of the uterus (pork tapeworm 8-12, bovine tapeworm 18-32), helps to distinguish taeniasis from teniarinchosis. Careful differential diagnosis involves the exclusion of gastrointestinal diseases of non–parasitic etiology – gastroenteritis, cholecystitis, Crohn’s disease, as well as other intestinal helminthiasis.
Patients with suspected cysticercosis need a more in-depth examination with the involvement of neurologists, ophthalmologists, pulmonologists, cardiologists, dermatologists. Along with helminthological examination, according to the indications of patients, brain CT, craniography, cerebrospinal fluid examination, biomicroscopy, ophthalmoscopy, lung x-ray, ECG, histological examination of skin biopsies and other studies are performed. Of the methods of specific diagnosis in cysticercosis, serological reactions (IFT, RPH, ELISA) are used to detect antibodies to pig tapeworm antigens. Cysticercosis must be differentiated, first of all, from brain tumors, echinococcosis.
Deworming of patients with taeniasis is carried out in stationary conditions. For this purpose, drugs praziquantel, niclosamide, male fern extract, pumpkin seed are prescribed; the second stage (after 1-2 hours) is given a saline laxative to remove segments with helminth eggs. To exclude antiperistalsis and endogenous autoinvasion, vomiting should be avoided. After a course of anthelmintic treatment of taeniasis, a 4-fold control study of feces is carried out with an interval of one month. Treatment of cysticercosis of the brain and eyes (in the presence of single cysticerci) is surgical with simultaneous etiotropic therapy.
Prognosis and prevention
With intestinal invasion, the course of taeniasis is benign, but after healing, re-infection is not excluded. Cysticercosis of the skin has a favorable prognosis; in case of eye and CNS lesions, the outcome depends on the massiveness of invasion and localization of cysticerci. Dispensary monitoring of a patient who has undergone taeniasis is carried out for 2 years.
Prevention of taeniasis dictates the need to purchase pork only in stores or markets where veterinary and sanitary examination of meat products is carried out. Only well-fried (boiled, baked) meat can be eaten; tasting of raw minced pork should be excluded. According to epidemic indications, a survey of persons engaged in caring for pigs is carried out. Prevention of cysticercosis requires compliance with personal hygiene standards (washing hands after going to the toilet, contact with the ground, before eating, etc.).