Cryptosporidiosis at the human–ruminant interface in Aswan, Egypt: a one health epidemiological study using microscopy, immunofluorescence, and PCR

BACKGROUND: Cryptosporidiosis is a significant zoonotic enteric infection at the human-livestock interface. In Egypt, Cryptosporidium spp. has been widely reported in both humans and domestic animals, with prevalence varying across regions and host species, highlighting its importance as a public health and veterinary concern. This study investigated the prevalence and epidemiological correlates of Cryptosporidium spp. infection among domestic ruminants and closely exposed humans in Aswan Governorate, Egypt, using parasitological and molecular approaches. METHODS: A total of 870 fecal samples were collected, including 684 from domestic ruminants (cattle calves n = 238, buffalo calves n = 186, lambs n = 127, and goat kids n = 133) and 186 from humans (1-65 years) in close contact with the examined animals. Samples were initially examined using microscopy and an immunofluorescence assay (IFA). PCR was subsequently performed on IFA-positive samples to confirm the presence of Cryptosporidium DNA. Associations between infection and potential risk factors were assessed using logistic regression analysis, and results were expressed as odds ratios (OR) with 95% confidence intervals (CI). RESULTS: The prevalence of Cryptosporidium spp. infection in ruminants was 34.5% (236/684; 95% CI: 30.9-38.2) and 31.6% (216/684; 95% CI: 28.1-35.2) as determined by microscopic and immunofluorescence examination, respectively. Among humans in close contact with the examined ruminants, the prevalence was 25.3% (47/186; 95% CI: 19.4-32.0) and 18.8% (35/186; 95% CI: 13.5-25.2), respectively. Nested PCR analysis of immunofluorescence-positive samples confirmed infection in 89.8% (194/216; 95% CI: 85.0-93.4) of ruminant samples and 91.4% (32/35; 95% CI: 76.9-98.2) of human samples. In ruminants, univariable analysis showed that infection was significantly associated with sex (OR = 1.76; 95% CI: 1.28-2.42; p < 0.05), age (highest in 1-3 months: OR = 4.58; 95% CI: 2.66-7.88; p < 0.001), season (spring: OR = 2.64; 95% CI: 1.59-4.38; p < 0.001), and fecal consistency (liquid feces: OR = 8.32; 95% CI: 3.75-18.47; p < 0.001). Multivariable analysis identified age and fecal consistency as independent predictors. In humans, age was the only significant factor, with higher odds in children aged 1-10 years (OR = 6.44; 95% CI: 1.75-23.77; p = 0.0412), remaining significant after adjustment. CONCLUSION: Cryptosporidiosis is highly prevalent in Aswan, particularly among young ruminants, with prevalent infection observed among closely exposed humans-especially children. These findings highlight the importance of improving hygiene in young livestock, managing diarrheic animals, and reducing environmental contamination of manure and water sources. Species-level identification was not performed; therefore, zoonotic transmission could not be confirmed. Further molecular characterization studies are needed to determine circulating Cryptosporidium spp. and better understand transmission dynamics within a One Health framework.