Cryptosporidium is a globally important enteric parasite that causes diarrhoea in humans and animals. The molecular epidemiology of Cryptosporidium infection among adults in Zambia has been poorly described. This study aimed to determine the prevalence, identify risk factors and provide molecular characterization of Cryptosporidium infections in Zambian adults aged 18–50 years.
A total of 566 stool samples were collected from adults between 18 and 50 years of age. Initial screening for Cryptosporidium oocysts employed light microscopy after modified Ziehl–Neelsen staining. Samples that were microscopy-positive underwent molecular analysis targeting genes commonly used for genotyping: the 60-kDa glycoprotein (gp60) and the 70-kDa heat shock protein (HSP70). Demographic data and potential risk factors were collected using semi-structured closed questionnaires administered to participants.
The study population comprised 566 adults aged 18–50 years. Demographic and clinical information—including HIV status, antiretroviral therapy (ART) use, water source, income level, and stool characteristics—were obtained for analysis of associations with infection.
The overall prevalence of Cryptosporidium infection detected by modified Ziehl–Neelsen microscopy was 3.0% (17 of 566 participants). Prevalence differed by HIV status and treatment exposure, with infection more common among people living with HIV. The highest prevalence was observed among people living with HIV who were not receiving ART, a difference that reached statistical significance (p = 0.001).
Several factors were significantly associated with Cryptosporidium infection in this cohort. These included:
These associations indicate both clinical and socio-environmental correlates of infection in the adult population studied.
Molecular genotyping of microscopy-positive samples identified both Cryptosporidium parvum and Cryptosporidium hominis species. Subtyping at the gp60 locus showed that all C. parvum subtypes detected were associated with anthroponotic transmission patterns. The reported C. parvum subtype distribution was:
For C. hominis, the subtypes identified were IeA11G3T3 (n = 2), IaA26R3 (n = 1) and IdA13 (n = 1). These subtype findings suggest human-to-human transmission was an important route among the cases characterized.
Clinical features linked with Cryptosporidium infection in this adult cohort included watery stool and frequent diarrhoea. Laboratory correlates included lower haemoglobin levels (<10 g/dl) among infected individuals. The higher prevalence among people living with HIV, and specifically those not on ART, underscores the interaction between immunosuppression and susceptibility to symptomatic cryptosporidiosis.
In this Zambian adult population, Cryptosporidium infection had a prevalence of 3.0% and was concentrated among people living with HIV, especially those not receiving ART. Molecular typing revealed both C. parvum and C. hominis, with C. parvum subtypes consistent with anthroponotic transmission. Associated factors included municipal water use, moderate income, diarrhoeal symptoms and anaemia.
The authors conclude that Cryptosporidium remains a significant concern among individuals living with HIV in this setting. They recommend prioritizing health education that targets reduction of anthroponotic transmission routes. The study used gp60 and HSP70 molecular targets for subtype identification, and further details on laboratory procedures, recruitment, and full statistical analyses are reported in the primary article.
(Note: This summary reflects only the data and conclusions reported in the source abstract.)