Deterioration of eggshell quality in laying hens experimentally infected with H9N2 avian influenza virus.

Xuefeng Qi,Chengqi Wu,Ruiqiao Li,Jingyu Wang,Tao Li,Caihong Liu,Chao Tang,Xueying Han,Dan Tan,Jing Wang

doi:10.1186/s13567-016-0322-4

Xuefeng Qi, Chengqi Wu + Show 8 more

Open Access

https://doi.org/10.1186/s13567-016-0322-4

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Abstract

This study aimed to determine the mechanism by which H9N2 avian influenza virus (AIV) affects eggshell quality. Thirty-week-old specific pathogen free egg-laying hens were inoculated with the chicken-origin H9N2 AIV strain (A/Chicken/shaanxi/01/2011) or with inoculating media without virus by combined intraocular and intranasal routes. The time course for the appearance of viral antigen and tissue lesions in the oviduct was coincident with the adverse changes in egg production in the infected hens. The viral loads of AIV have a close correlation with the changes in the uterus CaBP-D28k mRNA expression as well as the Ca concentrations in the eggshells in the infected hens from 1 to 7 days post inoculation (dpi). Ultrastructural examination of eggshells showed significantly decreased shell thickness in the infected hens from 1 to 5 dpi (P < 0.05). Furthermore, obvious changes in the structure of the external shell surface and shell membrane were detected in the infected hens from 1 to 5 dpi as compared with the control hens. In conclusion, this study confirmed that H9N2 AIV strain (A/Chicken/shaanxi/01/2011) infection is associated with severe lesions of the uterus and abnormal expression of CaBP-D28k mRNA in the uteri of the infected hens. The change of CaBP-D28k mRNA expression may contribute to the deterioration of the eggshell quality of the laying hens infected with AIV. It is noteworthy that the pathogenicity of H9N2 AIV strains may vary depending on the virus strain and host preference.

Highlights

H9N2 subtype avian influenza virus (AIV) has been widespread in domestic poultry in Asian countries since the mid-1990s with AIV infections causing mortality ranging from 5 to 30%
Viral loads in oviduct Absolute quantitative detection of virus load by real time quantitative PCR demonstrated that different AIV DNA loads were observed in five parts of the oviducts in inoculated hens at 1 dpi
It is important to note that the viral loads of AIV measured in magnum and uterus was significantly higher as compared with that measured in infundibulum, isthmus, and vagina tissues at 1, 3, and 5 dpi

Summary

Introduction

H9N2 subtype avian influenza virus (AIV) has been widespread in domestic poultry in Asian countries since the mid-1990s with AIV infections causing mortality ranging from 5 to 30%. The organic and mineral precursors required for eggshell mineralization are secreted daily by the uterus over a period of approximately 20 h into a cell-free medium (uterine fluid), which bathes the egg during the three phases of shell mineralization (initiation, growth and arrest). This fluid contains all the elements (mineral and organic) necessary for shell formation [9]. Calcium ion for shell formation is secreted from the tubular gland cells of the uterus, and calbindin (CaBP)-D28k plays a primary role in Ca2+ transportation [11]. Whereas a considerable number of studies have addressed the ways in which eggshell characteristics are influenced by factors such as genetics, the time the eggs spend in the uterus, female characteristics, and the diet of the female [16,17,18,19], the role of calbindin in determining eggshell quality during infection has received limited attention

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