Study on Soil Contamination with Toxoplasma gondii Oocysts in Eastern Iran

Mahmoodi, Akram; Mousavi, Seyed Mohammad; Tavakoli Kareshk, Amir; Behravan, Mahmoodreza

doi:10.22092/ari.2025.369928.3721

Study on Soil Contamination with Toxoplasma gondii Oocysts in Eastern Iran

Articles in Press

Document Type : Original Articles

Authors

¹ Infectious Diseases Research Center, Birjand University of Medical Sciences, Birjand, Iran.

² Research Center for Hydatid Disease in Iran, Kerman University of Medical Sciences, Kerman, 7616914115, Iran. mosavi.mohammad110@gmail.com

³ Infectious Diseases Research Center Birjand University of Medical Sciences

10.22092/ari.2025.369928.3721

Abstract

Toxoplasma gondii is one of the most common zoonotic protozoan parasites worldwide, with felids serving as definitive hosts that shed environmentally-resistant oocysts. Soil contamination represents a significant transmission pathway for human infection. This study aimed to determine the frequency of T. gondii oocysts in soil samples from Birjand city, Eastern Iran, using both concentration and molecular methods, and to evaluate potential seasonal and geographical variations in contamination.In this descriptive cross-sectional study, 254 soil samples (500g each from 3-5cm depth) were collected from parks, playgrounds, garden beds, and public squares across Birjand city during all four seasons (2024-2025). Samples were processed using sodium nitrate flotation technique followed by microscopic examination for oocyst identification. All samples were subsequently analyzed by PCR targeting the B1 gene of T. gondii. Statistical analyses were conducted to evaluate associations between contamination rates and geographical locations or seasonal variations.Of the 254 soil samples examined, 23 (9.0%) were positive for T. gondii oocysts by both microscopic examination and PCR confirmation. No statistically significant differences in contamination rates were observed between different geographical areas within the city (p>0.05). While the highest positivity rate was detected during summer months, seasonal variations were not statistically significant (p=0.1).This study revealed a considerable prevalence (9%) of T. gondii oocyst contamination in soil samples from Birjand city. The findings highlight the potential risk of soil as an important source of T. gondii infection for humans and animals in Eastern Iran. Public health interventions targeting soil-borne transmission should be considered, particularly educational campaigns about proper handwashing after soil contact and safe gardening practices

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