Question
A 21-year-old female presented with recurrent episodes of seizures, headache and vomiting and vertigo. MRI of the brain showed multiple ring enhancing lesions in the brain parenchyma. The causative agent was thought to be a cestode. (
- (a) What is the probable causative agent. (
- (b) Which is the infective stage of the parasite responsible for the above-mentioned condition. (
- (c) What is the mode of transmission. (
- (d) Name other four cestodes with their definitive hosts. (e) Name two stool concentration methods. (f) How do you treat the patient. (g) How to prevent this infection. (1+1+2+4+2+2+3) (PTO)
Answer
(a) Probable causative agent: Taenia solium (larval/cysticercus stage) — causing neurocysticercosis, the classical cause of multiple ring-enhancing lesions in the brain parenchyma presenting with seizures.
(b) Infective stage responsible for this condition: the egg of Taenia solium — when a human ingests T. solium eggs (acting as an accidental intermediate host, via faeco-oral transmission/autoinfection), the released oncospheres penetrate the intestinal wall and disseminate haematogenously to tissues including the brain, developing into cysticerci (causing neurocysticercosis). (Note: this differs from the infective stage for intestinal taeniasis, which is the cysticercus in undercooked pork — ingestion of the larval cyst causes intestinal tapeworm infection, whereas ingestion of the eggs, shed by a tapeworm carrier, causes the tissue-invasive cysticercosis seen in this patient.)
(c) Mode of transmission: faeco-oral route — ingestion of T. solium eggs in food/water contaminated with human faeces from a tapeworm carrier, or via autoinfection (a patient who is themselves an intestinal tapeworm carrier ingesting their own eggs, e.g., via faeco-oral contamination or reverse peristalsis).
(d) Four other cestodes with their definitive hosts:
- Taenia saginata — definitive host: human (adult tapeworm stage; cattle is the intermediate host).
- Echinococcus granulosus — definitive host: dog.
- Hymenolepis nana — definitive host: human (can complete its entire life cycle in a single human host).
- Diphyllobothrium latum — definitive host: human (and fish-eating mammals).
(e) Two stool concentration methods: Formol-ether (formalin-ether) sedimentation technique and Zinc sulphate flotation technique.
(f) Treatment: Albendazole (or Praziquantel), typically combined with corticosteroids (e.g., dexamethasone) to reduce the inflammatory response and cerebral oedema resulting from dying cysticerci, and anticonvulsants to control seizures; surgical intervention may be needed for large or strategically located cysts causing mass effect/hydrocephalus.
(g) Prevention: improved sanitation and safe disposal of human faeces (to prevent environmental contamination with eggs); proper cooking of pork (to prevent the separate, though related, risk of acquiring intestinal taeniasis, which can subsequently lead to autoinfection); health education and hand hygiene (to prevent faeco-oral transmission/autoinfection); identification and treatment of intestinal tapeworm carriers in the community, and meat inspection of pork for cysticerci.