Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 7 2 2012 06 15 8 14 EN A Heidari Dept. of Pathobiology, School of Medicine, Alborz University of Medical Sciences, Karaj, Iran H Keshavarz Dept. of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran AND Center for Research of Endemic Parasites of Iran (CREPI), Tehran University of Medical Sciences, Tehran, Iran S Shojaee Dept. of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran AND Center for Research of Endemic Parasites of Iran (CREPI), Tehran University of Medical Sciences, Tehran, Iran A Raeisi Dept. of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran S Dittrich Molecular Biology Laboratory Lao Oxford MahosotWelcome Trust Research Unit, Vientaine, LaoPDR 2015 10 03 Background: Plasmodium vivax is the predominant species causes of malaria with about 90% total annual reported malaria in Iran. This study conducted to determine the susceptibility of Plasmodium vivax isolates to chloroquine in Sistan and Balochistan Province, southeastern Iran. Methods: A total 270 subjects with symptomatic malaria and confirmed P. vivax infection completed the designed 28-day in vivo study. The thick and thin film blood smears were screened for malaria parasites by microscopy. The nested PCR was applied using the Plasmodium 18 subunit ribosomal ribonu­cleic (Ssr RNA) genes for detecting mixed infections and diagnosis of parasites in the samples with low parasite on days 0, 5, 6, 7, and 28. Results: P. vivax was cleared in 15%, 50%, 95%, and 100% of patients on days 1, 2, 3, 4 respectively by microscopy assessment. Six patients were exhibited specific P. vivax band in nested PCR on day 5. No recurrence was observed on days 7, 14 and 28. Mean (±standard deviation) parasite clearance time was 2.41 (±0.8) days. Conclusion: P. vivax is still susceptible to chloroquine in Southeatern Iran. This finding is compati­ble with results of neighboring countries Pakistan and Afghanistan. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/230 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/230/229