Soil and groundwater contamination with Cryptosporidium spp. oocysts: An environmental epidemiological study of pollution hotspots in rural areas of Diyala Province

This study aimed to assess the extent of soil and groundwater contamination by Cryptosporidium spp. egg cysts in rural areas of Diyala Governorate, and to identify environmental pollution hotspots and associated risk factors using microscopic examination combined with qualitative staining and morphometric analysis. Three hundred (300) environmental samples were collected, including 150 surface soil samples and 150 groundwater/well samples, from various agricultural and pastoral rural areas in the governorate between October 2025 and February 2026.
The soil samples were treated using the modified zinc sulfate flotation method, while the water samples were concentrated using (0.45 µm) and backwash centrifugation. All prepared smears were examined microscopically using modified acid-fast staining and modified saffron and methylene blue staining, with precise morphometric measurements of bag diameters performed using a graduated eyepiece. The results showed that the overall percentage of parasite contamination was %22.30 300/65)). Soil samples showed a higher contamination rate of 150/42) %26.55) compared to groundwater samples, which showed 150/23) %15.00). Analysis of contamination hotspots revealed that areas adjacent to dense livestock farms had the highest environmental contamination rate, accounting for 63% of all positive samples, followed by areas near cesspools and informal sewage treatment facilities, with rates ranging from 26.5% to 30%. This study confirms that relying on morphometric microscopy combined with double staining is a crucial, low-cost, and highly efficient epidemiological tool for monitoring environmental parasitic pollutants in rural Diyala, supporting One Health strategies.