Abstract

Antigenic drift of avian influenza viruses (AIVs) has been observed in chickens after extended vaccination program, similar to those observed with human influenza viruses. To evaluate the evolutionary properties of endemic AIV under high vaccination pressure (around 2 billion doses used in the last 12 years), we performed a pilot phylogenic analysis of the hemagglutinin (HA) gene of AIVs isolated from 1994 to 2006. This study demonstrates that Mexican low pathogenicity (LP) H5N2-AIVs are constantly undergoing genetic drifts. Recent AIV isolates (2002–2006) show significant molecular drifts when compared with the H5N2 vaccine-strain or other field isolates (1994–2000). This study also demonstrates that molecular drifts in the HA gene lineages follow a yearly trend, suggesting gradually cumulative sequence mutations. These findings might explain the increasing incidence of LP H5N2 AIV isolated from commercial avian farms. These findings support recent concerns about the challenge of AIV antigenic drift and influenza epidemics.

Salmonella Enteritidis colonizes the intestinal tract of poultry and causes foodborne illness in humans. Reduction of Salmonella Enteritidis colonization in the intestinal tract of poultry reduces potential carcass contamination during slaughter. The purpose of this study was to determine the effect of an avian-specific probiotic combined with Salmonella Enteritidis-, Salmonella Typhimurium-, and Salmonella Heidelberg-specific antibodies on the cecal colonization and organ invasion of Salmonella Enteritidis in broiler as well as on body weights. The treatment group was defined as chicks spray-vaccinated with Avian Pac Plus at the hatchery and given Avian Pac Plus for the first 3 days after placement. An intermediate treatment was given at 10 and 14 days, 2 days prior to vaccination and 2 days postvaccination. All birds were vaccinated with Newcastle disease vaccine, La Sota virus (one drop/eye) at 12 days of age. A final treatment was given 3 days preslaughter. The control group was defined as chicks not given Avian Pac Plus at any time. Six hours after oral administration of the probiotic suspension (treatment group) or water (control group) at placement, the chicks were challenged with Salmonella Enteritidis. All chickens were orally inoculated with 0.25 ml of Salmonella Enteritidis that contained 4 x 10(7) CFU/1.0 ml. Cecal colonization and organ invasion were evaluated for Salmonella Enteritidis on days 0, 1, 3, 7, 10, 17, 24, 31, 38, and 41. The probiotic-treated group had a significantly lower concentration of Salmonella Enteritidis cecal colonization at days 3, 7, 10, 17, 24, 31, 38, and 41 when compared to the nontreated, control group (P < 0.05). Similarly, there was a significant difference (P < 0.05) in the isolation of Salmonella Enteritidis from the internal organs (liver and spleen) when probiotic-treated and nonprobiotic-treated groups were compared. There was no significant difference (P > 0.05) in the mean body weight between the two experimental groups at each collection period. These results indicated that a combination of Lactobacillus acidophilus, Streptococcus faecium, and Salmonella Enteritidis, Salmonella Typhimurium, and Salmonella Heidelberg-Specific antibodies have a beneficial effect in reducing the colonization of Salmonella Enteritidis in market-aged broilers.

To gain insight into the possible origins of the 2009 outbreak of new influenza A(H1N1), we performed two independent analyses of genetic evolution of the new influenza A(H1N1) virus. Firstly, protein homology analyses of more than 400 sequences revealed that this virus most likely evolved from recent swine viruses. Secondly, phylogenetic analyses of 5,214 protein sequences of influenza A(H1N1) viruses (avian, swine and human) circulating in North America for the last two decades (from 1989 to 2009) indicated that the new influenza A(H1N1) virus possesses a distinctive evolutionary trait (genetic distinctness). This appears to be a particular characteristic in pig-human interspecies transmission of influenza A. Thus these analyses contribute to the evidence of the role of pig populations as “mixing vessels” for influenza A(H1N1) viruses.

BackgroundSerologic surveillance of Avian Influenza (AI) viruses is carried out by the hemagglutination inhibition (HI) test using reference reagents. This method is recommended by animal health organizations as a standard test to detect antigenic differences (subtypes) between circulating influenza virus, vaccine- and/or reference- strains. However, significant discrepancies between reference antisera and field isolates have been observed during serosurveillance of influenza A viruses in pig and poultry farms. The objective of this study was to examine the effects of influenza virus genetic and antigenic drift on serologic testing using standard HI assays and reference reagents. Low pathogenic AI H5N2 viruses isolated in Mexico between 1994 and 2008 were used for phylogenetic analysis of AI hemagglutinin genes and for serologic testing using antisera produced with year-specific AI virus isolates.ResultsPhylogenetic analysis revealed significant divergence between early LPAI H5N2 viruses (1994 - 1998) and more recent virus field isolates (2002 - 2008). Results of the HI test were markedly influenced by the selection of the AI H5N2 virus (year of isolation) used as reference antigen for the assay. These analyses indicate that LPAI H5N2 viruses in Mexico are constantly undergoing genetic drift and that serosurveillance of AI viruses is significantly influenced by the antigen or antisera used for the HI test.ConclusionsReference viral antigens and/or antisera need to be replaced constantly during surveillance of AI viruses to keep pace with the AI antigenic drift. This strategy should improve the estimation of antigenic differences between circulating AI viruses and the selection of suitable vaccine strains.

Ten infectious bronchitis virus (IBV) isolates were recovered from broiler chickens in the states of Queretaro and Guanajuato in Mexico. The viruses were isolated from trachea, lung, kidney, and cecal tonsils of birds that showed respiratory signs in spite of vaccination with Massachusetts (Mass) and Connecticut strains of IBV. Each isolate was identified by an accession number from 1 to 10. Six of the isolates were neutralized by Mass monoclonal antibodies, whereas the other four were not. In addition, these four isolates did not produce lesions in embryos in the first five to seven passes. These four isolates were further characterized by the reverse transcriptase-polymerase chain reaction and restriction fragment length polymorphism techniques. The electrophoretic patterns for the four isolates were identical but were different from other known IBV isolates.