Pathobiological and molecular studies on infectious Laryngotracheitis virus (ILTV) infection in commercial chicken flocks in India Munuswamy Palanivelu1*, Singh Karampal2*, Mariappan Asok Kumar1, Kaore Megha3, Latheef Shyma K.1, Anbazhagan Karthikeyan4, Singh Vidya1, Reddy Maddula Ramakoti5, Dhama Kuldeep1 1Division of Pathology 2CADRAD, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, India 3Department of Veterinary Pathology, College of Veterinary and Animal Sciences, Nagpur, Maharashtra, India 4Department of Animal Genetic and Breeding, College of Veterinary and Animal Sciences, Salem, Tamil Nadu, India 5ICAR-Directorate of Poultry Research, Rajendranagar, Hyderabad, Telangana, India Dr. Palanivelu Munuswamy, Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly -243122, India, E-mail: drpalvet@gmail.com
Dr. Karampal Singh, CADRAD, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly - 243122, India, E-mail: karamcadrad62@gmail.com
Abstract Infectious laryngotracheitis (ILT) is one of the highly infectious and contagious diseases of chickens caused by Gallid Herpesvirus 1, a member of the genus Iltovirus. It is an economically important disease in major poultry producing countries, including India. Despite India having large population of poultry birds, very limited information is available on the disease magnitude and molecular epidemiology. We screened 560 tissue samples collected from necropsied cases of tracheitis and conjunctivitis to diagnose ILT by histopathology, immunohistochemistry and polymerase chain reaction. Out of 560 samples, ILT was diagnosed in 90 (16.07%) cases by histopathology; however, polymerase chain reaction detected ILT virus (ILTV) in 128 (22.85%). Immu-nohistochemistry of representative PCR positive tissues (n=30) from trachea, lungs and conjunctiva detected viral antigen in the lining or denuded epithelial cells in 76.66% (23/30) cases. Analysis of age wise occurrence of ILT cases in our study revealed 47.65% in adult birds over 18 weeks of age, 35.15% in grower birds aged between 7 and18 weeks of age, 17.18% in chicks aged less than 6 weeks. Nucleotide sequence of gene encoding viral thymidine kinase revealed involvement of vaccine and virulent strains of ILTV in the investigated cases. Based on our findings and recent publications, we conclude that there is resurgence or re-emergence of ILT in the chicken flocks in different parts of India, indicating a possible biosecurity breach. Further genetic characterization of virus by whole genome sequencing technologies would decipher the genotype circulating in India, and help to design suitable native vaccine candidate(s). Top Keywords Chicken, Infectious laryngotracheitis, Pathology, Molecular epidemiology. Top |