Faculty of Veterinary Medicine, Urmia University Veterinary Research Forum 2008-8140 7 4 2016 12 01 Age and sex distribution of Dirofilaria immitis among dogs in Meshkin-Shahr, northwest Iran and molecular analysis of the isolates based on COX1 gene 329 334 22165 EN Zabiholah Zarei Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Eshrat Beigom Kia Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Center for Research of Endemic Parasites of Iran, Tehran University of Medical Sciences, Tehran, Iran Zahra Heidari Department of Medical Microbiology, School of Medicine, Ardabil University of Medical Sciences, Ardabil, Iran Fattaneh Mikaeili Department of Medical Parasitology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran Mehdi Mohebali Center for Research of Endemic Parasites of Iran, Tehran University of Medical Sciences, Tehran, Iran Meysam Sharifdini Department of Medical Microbiology, School of Medicine, Guilan University of Medical Sciences, Rasht, Iran Journal Article 2016 10 15 <em>Dirofilaria immitis</em> is an important filarial nematode in dogs. In this study, age and sex distribution of this zoonotic nematode among dogs were investigated in northwest of Iran in Meshkin-Shahr city. Molecular characteristics of the isolates, based on cytochrome oxidase subunit 1 (COX1) gene were compared to the isolates from other areas of the world.Blood samples were collected from 91 dogs which were selected by simple classified accidental sampling. Thin and thick blood smear examinations were used to find out infectivity with <em>D. immitis</em>. DNA extraction was performed from adult <em>D. immitis</em> recovered from heart of infected dogs. The COX1 gene was amplified and sequenced. Phylogenetic analysis was carried out using sequences obtained in this study along with relevant sequences deposited in the GenBank. Phylogenetic analysis and sequence variation was performed using MEGA software in comparison with those COX1 sequences deposited in GenBank. Out of 91 dogs, 19 (20.87%) were found positive for infection with <em>D. immitis</em>. There was no statistically significant difference between males and females of dogs in terms of <em>D. immitis</em> infection. However, the rate of infection in dogs more than 2 years old was significantly higher than those with lower age. Both sequences analyzed in this study showed 100% homology to each other. Intra-species variation of these isolates with those from other areas of the world amounted to 0 to 0.50%. Phylogenetic analysis of the COX1 gene suggested that it is conserved, and can be used for study on genetic diversity and classification of filarial nematodes. https://vrf.iranjournals.ir/article_22165_ec812841d1158ccc7d47278dc75f65cc.pdf