Human infections with non-typhoidal Salmonella (NTS) serovars are increasingly becoming a threat to human health globally. While all motile Salmonellae have zoonotic potential, Salmonella Enteritidis and Salmonella Typhimurium are most commonly associated with human disease, for which poultry are a major source. Despite the increasing number of human NTS infections, the epidemiology of NTS in poultry in India has not been fully understood. Hence, as a first step, we carried out epidemiological analysis to establish the incidence of NTS in poultry to evaluate the risk to human health. A total of 1215 samples (including poultry meat, tissues, egg and environmental samples) were collected from 154 commercial layer farms from southern India and screened for NTS. Following identification by cultural and biochemical methods, Salmonella isolates were further characterized by multiplex PCR, allele-specific PCR, enterobacterial repetitive intergenic consensus (ERIC) PCR and pulse field gel electrophoresis (PFGE). In the present study, 21/1215 (1.73 %) samples tested positive for NTS. We found 12/392 (3.06 %) of tissue samples, 7/460 (1.52 %) of poultry products, and 2/363 (0.55 %) of environmental samples tested positive for NTS. All the Salmonella isolates were resistant to oxytetracycline, which is routinely used as poultry feed additive. The multiplex PCR results allowed 16/21 isolates to be classified as S. Typhimurium, and five isolates as S. Enteritidis. Of the five S. Enteritidis isolates, four were identified as group D Salmonella by allele-specific PCR. All of the isolates produced different banding patterns in ERIC PCR. Of the thirteen macro restriction profiles (MRPs) obtained by PFGE, MRP 6 was predominant which included 6 (21 %) isolates. In conclusion, the findings of the study revealed higher incidence of contamination of NTS Salmonella in poultry tissue and animal protein sources used for poultry. The results of the study warrants further investigation on different type of animal feed sources, food market chains, processing plants, live bird markets etc., to evaluate the risk factors, transmission and effective control measures of human Salmonella infection from poultry products.

In this study, two isolates of infectious bronchitis virus (IBV) from field outbreaks in 2008 (India/LKW/56/IVRI/08) and 2010 (India/NMK/72/IVRI/10) from broiler chickens in India were isolated and characterized. Reverse transcription polymerase chain reaction-restriction fragment length polymorphism of the entire S1 gene revealed that these isolates belong to two different genotypes, India/LKW/56/IVRI/08 as Mass strain whereas India/NMK/72/IVRI/10 as of different genotype. Nucleotide sequencing analysis showed that India/LKW/56/IVRI/08 shared 99 % homology with THA280252 (Thailand) and India/NMK/72/IVRI/10 shared greater than 99 % homology with 4/91 pathogenic strain (UK), JP/Wakayama/2/2004 (Japan) and TA03 (China), while the two Indian IBV isolates shared 73 % identity between them. Phylogenetic data allowed classification of two Indian isolates, India/LKW/56/IVRI/08 as having unique lineage within Mass genotype and India/NMK/72/IVRI/10 as of 4/91 genotype. Our study confirmed the presence of 4/91 (793/B) IBV nephropathogenic strain for the first time in India by virus isolation and sequencing.

A study was undertaken to assess the virulence of Marek's disease virus (MDV) serotype 1 field isolates obtained from poultry flocks of southern part of India. Five representative MDV serotype 1 strains were isolated from eighty-six blood samples collected from fifteen farms. Three out of five isolates which were free from avian leukosis virus (ALV) and reticuloendotheliosis virus (REV) were adapted in chicken embryo fibroblast (CEF) culture and designated as Ind/TN/11/01, Ind/KA/12/02 and Ind/TN/12/03. Pathotyping assay was conducted in two trials. In the first trial, non-vaccinated chickens were challenged (trial I), while in second trial, two types of vaccinated chickens along with non-vaccinated controls were challenged (trial II). Birds inoculated with field isolate Ind/TN/12/03 had very low body (75.34±3.04 g 15 days post infection (dpi)) and bursa Fabricii weight (1.64±0.06 at 15 dpi) when compared to those inoculated with the other two isolates (Ind/TN/11/01 and Ind/KA/12/02) and uninoculated controls (body weight 111.33±1.30 g and bursa Fabricii weight 4.33±0.11 15 dpi). Incidence of early mortality syndrome (53%) and lymphoma (86%) induced by Ind/ TN/12/03 was comparable with very virulent strains published elsewhere. In protection test, the percentage of Marek's disease (MD) incidence induced by Ind/TN/12/03 was 57.5% and 25% in monovalent and bivalent vaccine inoculated birds respectively compared to uninoculated control (100%). Based on the above findings in pathotyping experimental trials with a supportive evidence of histopathological observations, isolate Ind/ TN/12/03 was considered as very virulent MDV and other two isolates were considered as virulent MDVs.

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Newcastle disease vaccines hitherto in vogue are produced from embryonated chicken eggs. Egg-adapted mesogenic vaccines possess several drawbacks such as paralysis and mortality in 2-week-old chicks and reduced egg production in the egg-laying flock. Owing to these possible drawbacks, we attempted to reduce the vaccine virulence for safe vaccination by adapting the virus in a chicken embryo fibroblast cell culture (CEFCC) system. Eighteen passages were carried out by CEFCC, and the pathogenicity was assessed on the basis of the mean death time, intracerebral pathogenicity index, and intravenous pathogenicity index, at equal passage intervals. Although the reduction in virulence demonstrated with increasing passage levels in CEFCC was encouraging, 20% of the 2-week-old birds showed paralytic symptoms with the virus vaccine from the 18th(final) passage. Thus, a tissue-culture-adapted vaccine would demand a few more passages by CEFCC in order to achieve a complete reduction in virulence for use as a safe and effective vaccine, especially among younger chicks. Moreover, it can be safely administered even to unprimed 8-week-old birds.