Thermal Inactivation of Avian Virus Surrogates in Aged Chicken Litter

Introduction: The epizootic viral diseases, linked to highly pathogenic avian virus, have been increasing in poultry production system. The raw or under-treated poultry waste appears to be a reservoir for the spread of the pathogen. In order to establish the sanitization guideline, the uses of bacteriophage as a virus surrogates need to be investigated. 

Purpose: The objective of this study was to determine the inactivation of bacteriophages FO, MS2 and ø6 as avian virus surrogates during thermal treatment of chicken litter. 

Methods: Aged chicken litter with 30% moisture content was inoculated with Salmonella phage FO, Escherichia coli phage MS2 and Pseudomonas phage ø6, separately. Afterwards, samples containing bacteriophages were distributed inside a glass tube and placed into hotplate at 75°C and 85°C up to 3 h. The subsamples were taken at the selected time intervals, and the titers were determined by 10-fold serial dilution and enumerated according to the double-layer agar method using the host strain for each phage.

Results: The come-up times for heating chicken litter with 30% moisture contents at 75°C and 85°C ranged from 6-9.5 min. The bacteriophage ø6 was undetectable after come-up time by direct enumeration at both temperatures. A non-liner thermal inactivation curve was observed for both FO and MS2. For the liner part of the curve, the D-values of bacteriophages FO and MS2 were calculated as11.90 and 5.49 min at 75°C, respectively, and 11.07 and 4.72 min at 85°C, respectively. Clearly, both FO and MS2 are more heat resistant than avian virus based on the published D-values.

Significance: Our results demonstrated that using bacteriophages FO and MS2 as surrogates for avian virus can guarantee a large safety margin for thermal processing of chicken litter.