J Vet Sci.  2013 Dec;14(4):487-490. 10.4142/jvs.2013.14.4.487.

Prolonged excretion of a low-pathogenicity H5N2 avian influenza virus strain in the Pekin duck

• Carranza-Flores JM
• Padilla-Noriega L
• Loza-Rubio E
• Garcia-Espinosa G

• KMID: 1712317
• DOI: http://doi.org/10.4142/jvs.2013.14.4.487

Abstract

H5N2 strains of low-pathogenicity avian influenza virus (LPAIV) have been circulating for at least 17 years in some Mexican chicken farms. We measured the rate and duration of viral excretion from Pekin ducks that were experimentally inoculated with an H5N2 LPAIV that causes death in embryonated chicken eggs (A/chicken/Mexico/2007). Leghorn chickens were used as susceptible host controls. The degree of viral excretion was evaluated with real-time reverse transcriptase-polymerase chain reaction (RRT-PCR) using samples from oropharyngeal and cloacal swabs. We observed prolonged excretion from both species of birds lasting for at least 21 days. Prolonged excretion of LPAIV A/chicken/Mexico/2007 is atypical.

Keyword

ducks; H5N2 subtype; influenza A virus; pathogenicity; poultry

MeSH Terms

Animals
Chickens
Cloaca/virology
*Ducks
Influenza A Virus, H5N2 Subtype/*physiology
Influenza in Birds/*physiopathology/virology
Oropharynx/virology
Poultry Diseases/physiopathology/virology
Real-Time Polymerase Chain Reaction/veterinary
Reverse Transcriptase Polymerase Chain Reaction/veterinary
Time Factors
*Virus Shedding

Figure

• 

  Fig. 1 Cloacal excretion of LPAIV A/chicken/Mexico/2007 from experimentally infected chickens and ducks. Cloacal swabs obtained from eight Pekin ducks (○) and four leghorn chickens (●) that were infected with 107 EID50 LPAIV A/chicken/Mexico/2007 (H5N2) via nasal, oropharyngeal, and ocular routes were analyzed by RRT-PCR using matrix gene primers. RRT-PCR was performed on pooled samples (two birds per group). Ct values for viral RNA extracted from the swabs were converted into EID50/mL by interpolation. Data for both groups are shown. The solid lines represent the average EID50/mL values detected at each time point tested. EID50: egg infectious doses, DPI: days post-inoculation.

• 

  Fig. 2 Oropharyngeal excretion of LPAIV A/chicken/Mexico/2007 from experimentally infected chickens and ducks. Oropharyngeal swabs obtained from eight ducks (○) and four chickens (●) that were infected with 107 EID50 LPAIV A/chicken/Mexico/2007 (H5N2) via nasal, oropharyngeal, and ocular routes were analyzed by RRT-PCR using matrix gene primers. RRT-PCR was performed on pooled samples (two birds per group). Ct values for viral RNA extracted from the swabs were converted into EID50/mL values by interpolation. Data for both groups are shown. The solid lines represent average EID50/mL values measured at each time point shown.

• 

  Fig. 3 Mean AIV hemagglutination inhibition (HI) geometric titers in sera from chickens and ducks that were experimentally infected with LPAIV A/chicken/Mexico/2007. HI titers were measured using A/chicken/Mexico/2007 antigen in the sera of eight Pekin ducks (○) and four leghorn chickens (●) infected with 107 EID50 LPAIV A/chicken/Mexico/2007 (H5N2). Data from both groups are shown. Solid lines represent the average GMT values calculated at each time point shown. GMT: geometric mean titer.

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