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Sri Venkateswara Veterinary University, Tirupati


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  • ThesisItemOpen Access
    ABSTRACT : Respiratory diseases have emerged as a great challenge to our poultry industry. A group of respiratory diseases, often called as Respiratory Disease Complex which produces closely resembling symptoms, mixed infections of respiratory system with multiple etiologies are contributing to the complexity in the proper diagnosis and differentiation of respiratory diseases. Infectious coryza is a respiratory disease of chickens caused by the bacterium, Avibacterium paragallinarum primarily affecting upper respiratory tract including the involvement of nasal passages, infra orbital sinus and paranasal sinuses. This disease is recognised as the cause of significant loss to the poultry industry all over the world including India. During the present study, we came across with six outbreaks of infectious coryza; three of them were in commercial chicken, two from native Azeel chicken and one from emu. The birds were showing signs of acute upper respiratory tract infections like coughing, sneezing, nasal discharge, facial oedema, oedema of wattle and comb, lacrimation and conjunctivitis. Anorexia and prominent infra orbital sinus swelling were observed. Post mortem examination revealed inflammation of upper respiratory tract and sinuses, copious amount of mucus in infra orbital and paranasal sinuses. Infra orbital sinus swabs were collected from acutely infected birds and nasal swabs were collected from birds at chronic stage of disease. Infra orbital sinus swabs collected from acutely infected birds were used for the cultural examination on blood agar which gave typical dew drop, mucoid or rough colony morphology of Avibacterium paragallinarum. Out of total 74 infra orbital sinus swabs inoculated, 27 (36.4%) gave isolates of Avibacterium paragallinarum but it was found very difficult to isolate the bacterium due to lack of special media with costly ingredients. All the 27 isolates obtained in the cultural examination were tested for antibiotic sensitivity with 14 different antibiotics which is commonly used in poultry industry. The isolates showed varying sensitivity to antibiotics used in the test with maximum sensitivity towards Doxycycline (92.5%), Chloramphenicol (85.1%) and Gentamicin (81.4%). For preventing the economic losses associated with the disease, an early, accurate and rapid diagnosis is essential. The conventional method of diagnosis of infectious coryza is based on clinical signs, cultural examination and demonstration of satellitic colonies and further biochemical characterisation. This method is difficult and demanding for laboratories operating with limited resources in developing countries like India. Many factors like simultaneous occurrence of combined infections, occurrence of NAD- independent strains, overgrowth of vigorously growing bacteria, etc make this conventional method of diagnosis unattractive. Polymerase Chain Reaction is a rapid and highly sensitive diagnostic technique which can substitute conventional cultural examination. The PCR was standardised for the diagnosis of infectious coryza by using Infectious Coryza Killed Vaccine, Ventri Biologicals, Pune as source of DNA of Avibacterium paragallinarum. The results of PCR analysis showed 71 positives (69.6%) for infectious coryza out of total 102 samples tested. Out of 74 infra orbital sinus swabs tested, 60 were positive (81.1%) and 11 nasal swabs (39.2%) out of 28 tested had given positive results for infectious coryza. Samples collected from birds at acute stage of disease and samples collected before treatment with antibiotics were given better results on PCR. PCR was found to be more sensitive than cultural examination for the diagnosis of infectious coryza. The epidemiological data regarding infectious coryza was collected for the last five years (from January, 2008 to September, 2012) from Regional Disease Diagnostic Laboratories of Srinivasa Hatcheries Private Limited operating at coastal districts of Andhra Pradesh. In the past five years, 848 infectious coryza outbreaks were recorded from south coastal districts of Andhra Pradesh. The disease was found to be highly endemic in Guntur district when compared to other districts and most frequently reported from farms operating on a small scale with an average flock size of 20,000 where no proper biosecurity, cleanliness, disinfection and vaccination were followed. Maximum numbers of cases were reported in the year 2012 including an epidemic in Guntur district. There was no seasonal variation observed in the occurrence of infectious coryza in south coastal districts of Andhra Pradesh. The poultry industry in Andhra Pradesh must adopt strict biosecurity measures and vaccination to prevent the disease which produces huge losses.