249 Iranian Journal of Veterinary Medicine Iran J Vet Med., Vol 11, No 3 (Summer 2017), A survey of pathogenic avian mycoplasma involvement in mul- ticausal respiratory disease in broiler focks Rahmani, E. 1 , Hosseini, H. 2* 1 Graduated from the Faculty of Veterinary Medicine, Karaj Branch, Islamic Azad University, Karaj, Iran 2 Department of Clinical Sciences, Faculty of Veterinary Medicine, Karaj Branch, Islamic Azad University, Karaj, Iran Abstract: BACKGROUND: Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) are the most important and pathogenic mycoplasma in chicken production. The tenden- cy of avian mycoplasma for interaction with other pathogens is well-known. Interaction within several disease-produc- ing factors in respiratory tract exacerbate the disease and is known as multicausal respiratory disease. OBJECTIVES: In recent years, high prevalence of multicausal respiratory disease in broiler focks cause economic loss in Iran. The aim of the current study was to fnd the role of avian myco- plasma in recent outbreaks of respiratory diseases in broiler focks. METHODS: Four hundred ffty tracheal or choanal cleft swabs were collected from 30 broiler farms with sev- er respiratory disease. The samples subjected to polymerase chain reaction (PCR) using specifc primers for MG and MS. RESULTS: One fock (3.3%) and three focks (10%) of broil- er were found to be positive for MG and MS, respectively. CONCLUSIONS: The results show that mycoplasma (MG and MS) are not the major part of recent respiratory diseases and anti-mycoplasma drugs administration needs precise test to evaluated mycoplasma statues. Key words: broiler, molecular detection, multicausal respiratory disease, Mycoplasma gallisepticum, Mycoplasma synoviae Correspondence Hosseini, H. Department of Clinical Sci- ences, Faculty of Veterinary Medicine, Karaj Branch, Islamic Azad University, Karaj, Iran Tel: +98(21) 66434643 Fax: +98(21) 66121546 Email: hosseini.ho@gmail.com Received: 10 January 2017 Accepted: 10 April 2017 Introduction Avian mycoplasma consist of more than 23 Mycoplasma species. Mycoplasma gal- lisepticum (MG) and Mycoplasma syno- viae (MS) are the major avian pathogenic mycoplasmas and economically important pathogen in chicken focks. M. gallisepti- cum known as chronic respiratory disease (CRD) and M. synoviae may cause respi- ratory disease or synovitis (Ferguson-Noel & Noormohammadi, 2013; Raviv & Ley, 2013). The tendency of avian mycoplasma for interaction with other pathogens is well- known. Interactions within several dis- ease-producing factors in respiratory tract exacerbate the disease and are known as multicausal respiratory disease. Multicausal respiratory disease is a condition that mul- tiple etiologies include a combination of in- fectious agents plus environmental factors may be involved. In this situation, harmless microbes which cause no disease in healthy bird imperil the bird’s life (Glisson, 2013). Recently, the high prevalence of multi- causal respiratory disease in broiler focks causes huge economic losses in Iran. While viral pathogens include Newcastle disease 249-253