Taenia Solium and Cysticercosis: Symptoms and Prevention
General Characteristics of Cestodes
Cestodes are organisms with a body flattened dorsoventrally. They are variable in size and have no body cavity or digestive system; their nutrition is effected by osmosis. They are hermaphrodites and reproduce by eggs. They are commonly known by the name of Tapeworms.
Morphology
- Scolex: Features 4 suction cups and 2 botri.
- Rostellum: A fixed or retractable crown of hooks used for attachment.
- Strobile: The generation of proglottids (immature, mature, and gravid), which function in reproduction.
Human Taeniosis and Swine Cysticercosis
Taenia solium and Cysticercus cellulosae represent a serious public health problem, especially in Latin American countries. Their presence is associated with traditional practices of pig husbandry, poor sanitation, hygiene, poverty, and ignorance. Mexico and Brazil record the highest frequencies. In Chile, the frequency is low and primarily associated with the rural sector.
Taeniosis
A human infection produced by Taenia solium. Transmission requires the consumption of pork containing the Cysticercus cellulosae larva.
Cysticercosis
An infection in pigs produced by the consumption of Taenia solium eggs. Accidental infection can also affect human beings.
Life Cycle of Taenia Solium
Eggs: Round with a double radiated membrane containing a hexacanth embryo inside. The eggs are removed from gravid proglottids and eliminated outdoors through feces, resulting in immediate infectivity. Because the pig is coprophagous, it eats the feces and swallows the proglottids eliminated in the stool of the infected definitive host massively.
In the duodenum, the eggs remain until gastric juices act on the corona radiata, freeing the hexacanth embryo. It penetrates the intestinal villi to reach the blood circulation and eventually reaches the muscles. After 2 months, it develops into larvae. The larva is inserted outside the muscle fiber and becomes a small vesicle, resembling a small grain of rice. This larval development is known as Cysticercus cellulosae.
After a human eats undercooked pork sausages containing these vesicles, the digestive juices dissolve the capsule. The scolex is freed, which involves the winding and rostellum with a double crown of hooks adhering firmly to the mucosa of the small bowel. After 2-3 months, the complete worm will have formed and egg elimination starts. In 25% of cases, eggs are emptied from the gravid proglottids into the intestinal lumen; in the remaining 75%, they are removed within the gravid proglottids arising from the strobile and dragged outside the infected individual with the bowel movement.
Neurocysticercosis
Morphology and Location
- Cystic and Nodular: Solitary or multiple; located in the corticomeningeal, parenchymal, and ventricular areas.
- Racemosa: Located in the subarachnoid space, cerebral cisterns, and brain base; characterized by expansive growth.
Clinical Manifestations
Symptoms depend on the number, location, and toxic action:
- Convulsive: Seizures occurring in patients over 20 years old.
- Hypertensive: Intracranial hypertension, severe headache, and vomiting.
- Insanity: Mental confusion, dementia, and hallucinations.
- Pseudotumoral: Symptoms mimicking a tumor.
Diagnosis
- Lumbar puncture: Presence of eosinophils.
- ELISA: Performed on serum and cerebrospinal fluid (CSF).
- Complementary Imaging: X-ray of the skull, CT, and MRI.
Treatment
Includes corticosteroids, anticonvulsants, antiparasitics, and surgery.
Prophylaxis of Human Cysticercosis
- Proper disposal of human excreta to avoid open defecation.
- Hand washing before and after using the bathroom.
- Avoid exposure to food delivery risks and use insecticides.
- Wash fruits and vegetables under running water.
- Improve water supply, sewerage, and sanitation.
- Foster closed pigsties and ensure veterinary supervision of meat in slaughterhouses.
Human Taeniosis: Symptoms and Diagnosis
Acquired by humans through the consumption of pork containing the Cysticercus cellulosae larva.
General Symptoms
- Headaches, listlessness, emaciation, and changes in appetite.
- Nervous Symptoms: Alteration of character.
- Allergic Symptoms: Nasal itching and urticarial reactions.
- Gastrointestinal Symptoms: Nausea, vomiting, and colicky abdominal pain.
Treatment and Diagnosis
Treatment: Praziquantel and Niclosamide.
Diagnosis: Telemann (PSD) method to search for eggs and gravid proglottids.
Diagnostic Certainty: Finding a gravid proglottid with fewer than 12 branches or identifying a scolex morphology corresponding to T. solium.
Mechanisms of Cysticercosis Infection
Human infection is caused by the accidental consumption of T. solium eggs through three mechanisms:
- External Consumption: If the human is not parasitized by T. solium, infection occurs via eggs in food or water, often involving vectors.
- Exogenous Autoinfection: If the human is parasitized, the cycle is hand-to-mouth (fecal-oral).
- Endogenous Autoinfection: Occurs via antiperistalsis.
Other Locations and Symptoms
- Subcutaneous Tissue: Lymph nodes appear upraised, uninflamed, soft, and painless.
- Eyeballs: Preferably in the retina (can cause uniocular blindness or retinal detachment) and vitreous (inflammatory reaction and temporary loss of vision).
- CNS (Neurocysticercosis): Intense headache.