en انگل شناسی Parasitology تحقيقي Original Paper <div style="text-align: justify;"><span style="font-size:12px;"><span style="font-family:Times New Roman;"><b>Background:</b> <i>Cryptosporidium</i> is one of the most important protozoan parasites causing waterborne diseases worldwide. The parasite&rsquo;s oocysts are resistant to conventional water treatment, making molecular detection crucial for identifying contamination sources.<br> <b>Methods:</b> A total of water samples were collected from different sites in Zabol and Zahedan, southeastern Iran. Microscopic screening was performed after concentration and staining with modified Ziehl-Neelsen and Trichrome methods under 1000&times; oil-immersion magnification. DNA was extracted from positive samples, and the SSU rRNA gene (~800-900 bp) was amplified by PCR. The resulting products were subjected to enzymatic digestion using AluI and RsaI restriction enzymes, and representative amplicons were sequenced.<br> <b>Results:</b> Microscopic examination confirmed the presence of <i>Cryptosporidium</i> oocysts in several water samples. PCR amplification successfully produced fragments of the expected size without nonspecific bands. AluI digestion revealed distinct fragment patterns consistent with <i>Cryptosporidium</i> spp., while RsaI showed no cutting sites. Sequence analysis through BLAST showed high identity (&ge;99%) with <i>C. parvum</i> isolates. The phylogenetic tree constructed using the BLAST distance-tree method grouped the sequence closely with <i>C. parvum</i>, confirming its identity.<br> <b>Conclusion</b>: Molecular characterization of <i>Cryptosporidium</i> from water samples in southeastern Iran indicated contamination primarily with <i>C. parvum</i>. These findings emphasize the necessity of continuous molecular surveillance to ensure the safety of drinking and recreational waters in the region.</span></span></div> Cryptosporidium, DNA Sequencing, Polymerase Chain Reaction, Water Pollution, Zabol, Zahedan 31 35 http://mlj.goums.ac.ir/browse.php?a_code=A-10-1853-1&slc_lang=en&sid=1 Mansour Dabirzadeh mdabirzadeh20002000@gmail.com 100319475328460032799 100319475328460032799 Yes Department of Parasitology and Mycology, Faculty of Medicine, Zabol University of Medical Sciences, Sistan-Baluchistan Province, Zabol, Iran Reza Shahraki predator4tear@gmail.com 100319475328460032800 0009-0004-7828-2631 No Department of Parasitology, Medical School, Zabol University of Medical Sciences, Sistan-Baluchistan Province, Zabol, Iran Mohammadreza Beheshtizadeh dmrbz@hotmail.com 100319475328460032801 100319475328460032801 No Department of Parasitology, Medical School, Zabol University of Medical Sciences, Sistan-Baluchistan Province, Zabol, Iran Mahdi Khoshsima Shahraki mail.khoshsima6144@vet.uk.ac.ir 100319475328460032802 0009-0007-7239-8125 No Zabol Medical Plants Research Center, Zabol University of Medical Sciences, Zabol, Iran