High prevalence of Enterocytozoon bieneusi (microsporidia) in asymptomatic schoolchildren, Zambia.

Microsporidia are single-celled, fungi-related eukaryotic intracellular parasites able to infect a wide diversity of invertebrate and vertebrate hosts. Among them, Enterocytozoon bieneusi and Encephalitozoon spp. (including Enc. cuniculi, Enc. hellem, and Enc. intestinalis) are known causative agents of infectious diseases in immunocompromised individuals, including HIV/AIDS patients and organ transplant recipients. Additionally, asymptomatic microsporidial infections seem more frequent than initially anticipated and might represent an overlooked public health threat. Here, we provide novel data on the occurrence and genetic diversity of microsporidial infections in individual stool samples (n = 247) collected from apparently healthy schoolchildren (age range: 5-18 years; male/female ratio: 1.1) in Lusaka, Zambia. Stool DNA samples were analysed by PCR and Sanger sequencing methods. A basic epidemiological questionnaire was used to retrieve data on variables potentially linked with higher odds of harbouring E. bieneusi infections. A high prevalence rate was found for E. bieneusi (9.3%, 23/247; 95% CI: 6.0-13.6), whereas Enc. intestinalis was much less frequent (0.4%, 1/247; 95% CI: 0.01-2.2). Four known (D, S2, S6, and Type IV) and three novel (HhZbEb1, HhZbEb2, and HhZbEb3) genotypes were identified within E. bieneusi. Genotype D was the predominant genotype found (30.8%, 4/13), followed by genotypes Type IV, HhZbEb2, and HhZbEb3 (15.4%, 2/13 each), and genotypes S2, S6, and HhZbEb1 (7.7%, 1/13 each). The only Encephalitozoon-positive sample was identified as Enc. intestinalis. Subclinical infections by E. bieneusi were common in the investigated paediatric population. Infected children could act as disregarded spreaders of microsporidial pathogens at the community level, thus representing a potential public health concern.