We also found that the C4 photosynthetic carbon assimilation cycle both nicotinamide adenine dinucleotide phosphate–malic enzyme (NADP-ME) type (P < 0.017) and phosphoenolpyruvate carboxykinase (PEPCK) type (P < 0.02) were significantly enriched between infected individuals with asymptomatic and symptomatic giardiasis (Additional file 1: Table S2). The gene discussed is PCK2; the disease is giardiasis.