Effects of an H7 highly pathogenic and related low pathogenic avian influenza virus on chicken egg production, viability, and virus contamination of egg contents and surfaces

Authors: Stephens, Christopher; Spackman, Erica; Pantin Jackwood, Mary

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2020
Publication Date: 6/15/2020
Citation: Stephens, C.B., Spackman, E., Pantin Jackwood, M.J. 2020. Effects of an H7 highly pathogenic and related low pathogenic avian influenza virus on chicken egg production, viability, and virus contamination of egg contents and surfaces. Avian Diseases. 64(2):143-148. https://doi.org/10.1637/0005-2086-64.2.143.
DOI: https://doi.org/10.1637/0005-2086-64.2.143

Interpretive Summary: Avian influenza virus (AIV) can occur as either a mild form or a more severe and deadly form in chickens. Very limited information is available on how infection with either form of AIV can affect the fertility and viability of eggs. More information is also needed regarding the potential for the eggs to be externally or internally contaminated with virus. To better characterize these things we have collected eggs from hens infected with mild or severe AIV. The eggs were tested for virus on the surface and internal contents and they were evaluated for fertility and whether they remained viable to 18 days of incubation (we did not attempt to hatch the eggs). Virus could be detected on or in 6.4% eggs laid by hens infected with the mild form and 11.1% of eggs from hens infected with the severe form. Importantly the amount of virus was generally very low. Eggs from hens infected with the severe form did have reduced fertility and 18.4% of their eggs were abnormal. Data presented here will help inform risk assessments for moving and using eggs from hens that have been or are potentially infected with AIV.

Technical Abstract: Both highly pathogenic (HP) and low pathogenic (LP) avian influenza virus (AIV) can cause decreases or even cessation of egg production in chickens and turkeys. Production of abnormal eggs (deformed, thin-shelled, soft-shelled) can also be caused by AIV infection. Additionally, egg surfaces and contents may also be contaminated with virus. Because data quantifying these effects are lacking, white Plymouth Rock hens were inoculated with HP or LP AIV while in production. No decreases in egg production or abnormal eggs were observed with LPAIV-infected hens. No lesions or viral antigen staining in ovary and oviduct were observed in LPAIV-infected hens 3 days postchallenge. LPAIV RNA was detected on eggs collected from 12 hr to 11 days postinoculation (PI) and was on or in 6.4% (15/234) of the eggs. Titer equivalents of LPAIV ranged from 1.3–2.5 log10 50% egg infectious doses (EID50). No virus was detected in embryo tissue from eggs laid by LPAIV-infected hens. In contrast, egg production by HPAIV-inoculated hens decreased at 72 hr PI and 18.4% (16/87) of the eggs were abnormal. However, viability was similar to that of the sham inoculates. HPAIV RNA was detected in or on 11.1% (9/81) of the eggs from 36 hr through 96 hr PI, when the hens were euthanatized. HPAIV RNA was detected on 6.2% of eggshells, in 4.2% of albumin/yolk samples, and in 8.3% of embryo tissue. Forty percent of the abnormal eggs were positive for HPAIV RNA. Titer equivalents on or in HPAIV-contaminated eggs ranges from 1.0–4.0 log10 EID50. Lesions and viral antigen staining were present in the ovary and all sections of the oviduct of infected hens 3 days postchallenge. These data will inform models using production-based triggers for LPAIV monitoring and for risk assessments to determine the disposition of eggs from flocks infected with LPAIV or HPAIV.