African Journal of Microbiology Research Vol. 6(21), pp. 4614-4619, 9 June, 2012 Available online at http://www.academicjournals.org/AJMR DOI: 10.5897/AJMR12.585 ISSN 1996-0808 ©2012 Academic Journals Full Length Research Paper Quantification of antibodies against poultry haemagglutinating viruses by haemagglutination inhibition test in Lahore Shahzad Munir 1 , Mubashir Hussain 1 , Umar Farooq 1 , ZabidUllah 1 , Qaiser Jamal 1 , Mehwesh Afreen 1 , Kalsoom Bano 1 , Jafar Khan 1 , Sultan Ayaz 2 , Kil Yong Kim 3 and Muhammad Anees 1 * 1 Department of Microbiology Kohat University of Science and Technology Kohat, Pakistan. 2 Department of Zoology Kohat University of Science and Technology Kohat, Pakistan. 3 Department of Biological Chemistry, Environment-Friendly Agriculture Research Center, Chonnam National University, Gwangju 500-757, South Korea. Accepted 25 April, 2012 A study was conducted for quantification of antibodies to haemagglutinating viruses such as AIV (H9N2 and H7N3), NDV and IBV in vaccinated poultry flocks. A total of 198 serum samples from different commercial broiler and layer farms in Lahore, Pakistan, were checked for their serological statuses. Haemagglutination inhibition (HI) test was performed to determine the titer of serum antibodies against the above mentioned viruses. It was observed that 25 and 44% samples were positive for H7N3 and H9N2 in broilers, respectively. The seropositivity of H7N3 and H9N2 in serum samples of commercial layers were 66 and 94%, respectively. It was recorded that 96% of the samples in broilers and 100% of those in layers, were found seropositive for antibodies against NDV. Moreover, 69 and 86% were seropositive for IBV in broilers and layers, respectively. Calculated geometric mean titers for groups of 0-2, 2-4 and 4-6 weeks of age were found to be 36.8, 78.8, and 111.4 for H9N2; 48.5, 157.6, 222.9 for NDV; and 97, 84.4, 111.4 for IBV, respectively. It was concluded that the samples were not having protective antibody titers indicating unsuccessful vaccination practiced in these poultry farms which may lead to significant economic losses. Key words: Avian influenza virus, Newcastle disease, bronchitis virus, haemagglutinating. INTRODUCTION Livestock sector plays an important role in the agricultural economy of Pakistan. It accounts for almost 50% of agricultural value added and about 11.4% of the gross domestic product (GDP) (Economic Survey, 2003-04). In Pakistan, the investment in poultry sector is about 1 billion US $. The importance of poultry industry can be judged from the fact that every family in rural and every fifth family in urban areas are directly or indirectly associated with poultry production (Sadiq, 2004). In Pakistan, poultry industry is facing various diseases such as Newcastle disease (ND), infectious bronchitis (IB), infectious bursal disease (IBD), egg drop syndrome (EDS), hydropericardium syndrome (HPS) and avian *Corresponding author. E-mail: muhamadanees@yahoo.com. Tel: +923365291519. influenza (AI). These diseases are causing high economic losses in terms of high mortality, morbidity, stress, decreased egg production and hatchability all over the world including Pakistan (Alexander, 2000). Several viruses have the ability to agglutinate chicken red blood cells and cause ND, EDS, AI and, after special enzyme treatment, IB. The test is serotype-specific for these viruses and different antigenic viral strains of AI, IB occur. Avian influenza viruses are classified in the family Orthomyxoviridae, genus Influenza virus A. The surface is covered by two types of glycoprotein projections, that is, rodshaped trimers of haemagglutinin (HA) and mushroom shaped tetramers of neuraminidase (NA). The HA is the major antigen that elicits antibodies protecting against death and clinical signs. These antibodies are HA subtype specific and can last for periods greater than 35 weeks (Brugh and Stone, 1987). Protection by maternal antibodies to homologous HA last probably for the first