Co-infection of Newcastle disease virus genotype XIII with low pathogenic avian influenza exacerbates clinical outcome of Newcastle disease in vaccinated layer poultry flocks

Newcastle disease (ND) and avian influenza (AI) are economically important infectious diseases of poultry. Sometime, concomitant secondary viral/or bacterial infections significantly alters the pathobiology of ND and AI in poultry. As of now, the disease patterns and dynamics of co-infections caused by ND virus (NDV, genotype XIII) and Low Pathogenic AI viruses (LPAI, H9N2) are explicitly elusive. Thus, we examined the clinicopathological disease conditions due to these two economically important viruses to understand the complex disease outcomes by virus-virus interactions in vaccinated flocks. The findings of clinicopathological and molecular investigations carried on 37 commercial ND vaccinated poultry flocks revealed simultaneous circulation of NDV and AIV in same flock/bird. Further, molecular characterization of hemagglutinin (HA) and neuraminidase (NA) genes confirmed that all the identified AIVs were of low pathogenicity H9N2 subtype and fusion (F) gene analysis of detected NDVs belong to NDV class II, genotype XIII, a virulent type. The NDV and H9N2 alone or co-infected flocks (NDV + LPAI) exhibit clinical signs and lesions similar to that of virulent NDV except the degree of severity, which was higher in H9N2-NDV co-infected flocks. Additionally, avian pathogenic E. coli and mycoplasma infections were detected in majority of the ailing/dead birds from the co-infected flocks during progression of the clinical disease. Overall, the findings highlight the multi-factorial disease complexity in commercial poultry and suggest the importance of NDV genotype XIII in intensifying the clinical disease in vaccinated birds.

Pathology of a H5N1, highly pathogenic avian influenza virus, in two Indian native chicken breeds and a synthetic broiler line

In this study, susceptibility to H5N1 virus infection was studied in two Indian native chicken breeds viz. Kadaknath and Aseel (Peela) and an Indian synthetic broiler strain (Synthetic dam line (SDL-IC). Fifty birds from each genetic group were infected intra-nasally with 1000 EID50 of a highly pathogenic avian influenza virus (HPAIV) strain A/chicken/Navapur/India/7972/ 06 (H5N1) and observed for a period of 10 days. Significant differences in severity of clinical signs, gross lesions and time for onset of symptoms were observed. The overall severity of clinical signs and gross lesions was less in SDL-IC broilers as compared to the other two genetic groups. The mortality percentages were 100, 98 and 92% with Mean Death Time (MDT) of 3.12, 5.92 and 6.96 days, respectively for the two native breeds Kadaknath and Aseel (Peela), the and SDL-IC broiler strain. Comparison of histological lesions revealed differences in disease progression among the genetic groups. Vascular lesions such as disseminated intravascular coagulopathy (DIC) were predominant on 3 days post infection (dpi) in Kadaknath, and on 5 and 6 dpi in Aseel (Peela) and SDL-IC broiler. The mean log2 HA titres of the re-isolated virus from various organs of H5N1 AIV infected birds of the three genetic groups ranged from 2.32 (lung, trachea and bursa) to 5.04 (spleen) in Kadaknath; 2.32 (lung) to 6.68 (brain) in Aseel (Peela); and 2.06 (liver) to 7.01 (lungs and kidney) in SDL-IC broiler. These results suggest that the susceptibility to H5N1 highly pathogenic avian influenza virus infection differed among the three breeds; Kadaknath being highest followed by Aseel (Peela) and synthetic SDL-IC broiler. This is possibly the first report on the differences in the susceptibility of the India native breeds to H5N1 virus infection and its severity.

Molecular detection and epidemiology of chicken infectious anaemia virus in India

Chicken infectious anemia (CIA) is an economically important disease affecting poultry, especially young chicks, characterized by poor weight gain, anemia, immunosuppression and production losses. Recent reports indicate that the virus is emerging and re-emerging worldwide.  Also, scarce reports regarding the molecular detection and epidemiology of virus from India are available. The aim of this study was to determine the prevalence of the virus in the commercial poultry farms of the country employing polymerase chain reaction (PCR). Out of the suspected 424 field samples tested from 12 different states of the country during the last five years (2007-2012), 311 (73.3%) samples were found positive for CIAV-DNA indicating the wide prevalence of the virus in India. The age wise prevalence of the virus indicated high prevalence in young chicks of up to three weeks (80.3%) of age compared to 3-7 (66.6%) and 7-12 (25%) week age groups. Being an immunosuppressive emerging pathogen circulating among the poultry flocks of the country, suitable prevention and control measures need to be adopted timely. This is a first elaborative report on the molecular epidemiology of CIAV in poultry flocks of the country. Extensive epidemiological studies are suggested to know the magnitude of the virus affecting poultry industry of the country, and design and formulate effective disease prevention and control strategies to reduce economic losses being caused by emerging virus.

Fowl adenovirus (FAdV) in India: evidence for emerging role as primary respiratory pathogen in chickens

Adenoviruses have been isolated from both clinically healthy and diseased birds worldwide. The pathogenic role of most of the FAdVs is still questionable. They can quickly take on the role of opportunistic pathogens when additional factors, particularly concurrent infections, adversely affect the health of the avian host. Immnosuppressing agents especially chicken infectious anemia and infectious bursal disease viruses are known to enhance the pathogenicity of FAdVs upon coinfection. The aim of the present study was to screen for the involvement of FAdV in poultry flocks affected with respiratory disease complex by RT-PCR. The samples were also screened by RT-PCR/PCR for other respiratory pathogens. Thirty two commercial poultry flocks with the history of respiratory disease complex from various parts of India. FAdV nucleic acid could be detected in tissue samples of 13 out of 34 farms investigated. Out of 13 FAdV positive farms, FAdV and CIAV were alone detected in 4/13 (31%) whereas, in other farms more than two respiratory pathogens were detected together. CIAV was detected in all the farms (34/34) investigated. Eosinophilic intranuclear inclusion bodies were noticed in FAdV infected laryngeal and tracheal epithelium under light microscopy. The findings of the study assert that FAdV can play the role of primary respiratory pathogen in immunocompromised birds and also in the presence of other respiratory pathogens.