Mode of Transmission of Neurocysticercosis
The mode of transmission is faecal-oral route through ingestion of Taenia solium eggs, NOT through consumption of undercooked pork. 1
Clinical Reasoning
This patient presents with the classic triad of neurocysticercosis (NCC):
- Progressive headaches and seizures in a young adult from a rural endemic area 1
- CT findings of intraparenchymal cysts with central hyperdensity (representing the scolex) 1
- CSF eosinophilic pleocytosis (present in 20% of NCC cases) with lymphocytosis and elevated protein 1
Critical Distinction: Transmission vs. Acquisition
The key misconception to avoid: Undercooked pork consumption causes intestinal tapeworm infection (taeniasis), NOT neurocysticercosis. 2, 3
Correct Transmission Pathway:
- Neurocysticercosis occurs via faecal-oral transmission of T. solium eggs from human feces 1
- Eggs can be transmitted through contaminated food, water, or direct contact with a tapeworm carrier 1, 2
- Autoinfection can occur when individuals with intestinal tapeworms contaminate themselves through poor hand hygiene or reverse peristalsis 2
Why Not Undercooked Pork:
- Eating undercooked pork containing cysticerci causes intestinal tapeworm infection, where the person becomes the definitive host 2, 3
- The person then sheds eggs in their stool, which can infect others (or themselves) to cause cysticercosis 2
Geographic and Epidemiologic Context
- Endemic regions include: South and Southeast Asia, Central and South America, and Africa 1
- Incubation period: Average 3.5 years (range: months to >10 years) from egg ingestion to symptom onset 1
- In endemic villages, 10-20% of individuals show CT evidence of NCC 1
Eliminating Other Options
- Cat litter exposure: Associated with Toxoplasma gondii, which causes ring-enhancing lesions, not cysts with scoleces [@general knowledge@]
- Misfolded prion proteins: Cause spongiform encephalopathies without cystic lesions [@general knowledge@]
- Inhalation of arthroconidia: Associated with fungal infections like Coccidioides, not parasitic cysts [@general knowledge@]
- Mosquito bite: Transmits arboviruses and malaria, not cestode infections [@general knowledge@]
Clinical Management Implications
Immediate diagnostic steps:
- Serology with enzyme-linked immunotransfer blot (EITB) for confirmation 1
- MRI brain with contrast (more sensitive than CT for scolex visualization and subarachnoid involvement) 1, 4
- Stool microscopy of patient and household contacts to identify tapeworm carriers 1
Treatment approach: