Parasitology

• Cyst is the infective stage to human
• Cysts detected in faecal specimens of infected human

Diagnostic Features

• Shape: Spherical
• Size: 15 – 25 mm (range 10 to 35 µm) – larger than histolytica
• Nuclei: Contains up to 8 nuclei (usually >4 visible; need to change fine focus to see nuclei in different planes)
• Large, eccentric karyosome in nucleus; Regular, coarse chromatin dots on nuclear membrane
• Chromatoid bars visible occasionally – splinter-like with pointed ends
• Diffused glycogen mass seen in immature and mature cysts