Giardia lamblia protozoa. Coloured scanning electron micrograph (SEM) of Giardia lamblia protozoa cysts (green), the cause of the disease giardiasis in humans. Many unidentified bacteria (rod-shaped) are also seen. Giardia protozoa infect the small intestine when the cysts are ingested. The sporozoite stage (not seen) attaches to the intestinal lining using sucking discs. Giardiasis is most common in tropical areas, being spread by direct contact with an infected individual or through contaminated food or water. Symptoms include abdominal cramps, swelling, diarrhoea and vomiting. Severe cases are treated with antibiotic drugs. Magnification unknown.

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