Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 20 2 2025 06 08 299 306 Fariba Berenji Department of Parasitology and Mycology School of Medicine, Mashhad University of Medical Sciences, Iran Hossein Zarrinfar Department of Parasitology and Mycology School of Medicine, Mashhad University of Medical Sciences, Iran Ali Gholizadeh Department of Allied Medicine, Gonabad University of Medical Sciences, Iran Fatemeh Sargazi Doctor of Medicine (M.D.), Mashhad University of Medical Sciences, Iran Jamshid Jamali Department of Biostatistics, School of Health, Mashhad University of medical Sciences, Mashhad, Iran Mahmoud Parian Noghabi Department of Parasitology and Mycology, Imam Reza Hospital, Mashhad University of Medical Sciences, Iran Ghodratollah Salehi Sangani 1. Department of Parasitology and Mycology School of Medicine, Mashhad University of Medical Sciences, Iran 2. Cutaneous Leishmania Research Center, Mashhad University of Medical Sciences, Iran Bibi Razieh Hosseini Farash 1. Department of Parasitology and Mycology School of Medicine, Mashhad University of Medical Sciences, Iran 2. Cutaneous Leishmania Research Center, Mashhad University of Medical Sciences, Iran 2024 09 09 2025 04 21 Background: Respiratory infections caused by Lophomonas blattarum and Pneumocystis jirovecii are significant threats, especially to immunocompromised patients. Both pathogens are associated with severe pneumonia and are often underdiagnosed due to the challenges in identifying them accurately, particularly in co-infections. We aimed to evaluate the prevalence and clinical impact of co-infections with L. blattarum and P. jirovecii in patients with respiratory symptoms. Methods: This cross-sectional study involved 111 patients admitted to the Pulmonary Ward of Imam Reza Hospital in Mashhad, Iran in 2023. Bronchoalveolar lavage (BAL) samples were collected from all patients and analyzed microscopically and molecularly. PCR amplification targeting L. blattarum and P. jirovecii was performed, with subsequent sequencing for molecular identification. The presence of Pneumocystis was identified using a 346-bp PCR band. Results: Of the 111 patients, Lophomonas was detected in 48 patients (43.2%), and Pneumocystis in 47 patients (42.3%). Co-infections were identified in 26 patients (23.6%). Both infections were more common in males, though the difference between genders was not statistically significant. The highest prevalence was observed in patients over 60 years, with 18% and 19.8% infection rates for Lophomonas and Pneumocystis, respectively. Co-infection rates were significantly higher in older patients and in males (P= 0.028). Conclusion: The study demonstrates a significant prevalence of co-infections with L. blattarum and P. jirovecii in patients with respiratory conditions, particularly in the elderly. The findings underscore the need for comprehensive diagnostic strategies, including molecular and microscopic approaches, to accurately diagnose and manage these co-infections in high-risk populations. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/4360 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/4360/1434