Institution: University of Delaware
Principal Investigator:
E.R. Benson, Ph.D.
University of Delaware
Department of Animal and Food Sciences
042 Townsend Hall
531 South College Avenue
Newark, DE 19716
Management and control of fast-moving poultry diseases such as highly pathogenic avian influenza (HPAI) requires a combination of steps including biosecurity, surveillance, quarantine, depopulation, disposal, and cleaning and disinfection. Because of the difficulties associated with cleaning and disinfection, an alternative heat treatment program was used during the spring-summer 2015 HPAI outbreak. In this response, facilities were dry cleaned to remove gross organic matter. High risk areas were cleaned to less than 6 mm (0.25 inch) of organic material and low risk areas were allowed up to 12 mm (0.5 inch) of organic matter. Facilities were then heated for seven days, with the temperature reaching to 37 to 48° C (100 to 120° F) for three continuous days. This heat treatment process needed to be evaluated to determine how effective the method is at inactivating virus and bacteria within various depths of organic material. The depth profiles used in this study were: surface, 6 mm (0.25 inch), 2.5 cm (1 inch) and 10 cm (4 inches) of litter to more accurately reflect depths of litter left after the initial dry cleaning.
This project involved evaluation and comparison of heat treatment versus wet cleaning with chemical disinfection under field conditions. For biosecurity reasons, a LaSota vaccine strain of Newcastle Disease Virus (NDV) and a mixture of Salmonella serovars were used as surrogates for HPAI virus and other bacteria. Screened and dried used poultry litter was used as a source of consistent organic matter. The project was split into three objectives. For objective A the most appropriate temperature, time and humidity profiles along with the maximum depth of organic matter that can be effectively heat treated were determined. In objective B, NDV and Salmonella were inoculated onto steel sample platforms and treated in the laboratory with the levels of organic matter and heat profiles determined in objective A. In objective C, the procedures evaluated in objectives A and B were evaluated under field conditions.
Maintaining the required temperature profile throughout the poultry house was found to be critical. In testing during colder months, samples at 10 cm (4 inches) did not reach the required temperature of 100° F. This observation further supports the recommendation that houses must be well sealed and adequate heat sources utilized when heat treating during cold weather.
However, the temperature results do validate that thinner layers (2.5 cm or less) of organic matter are acceptable. If heat treatment is performed after carcass and litter disposal, litter depth should not be a concern since a large portion of the organic matter will have been removed. If heat treatment is performed prior to carcass and litter disposal, litter should be treated as contaminated during disposal since pathogens in the litter will likely not be inactivated.
Based on the results of this study, the heat treatment protocol developed by USDA is effective for the reduction of microorganisms in litter; specifically, NDV and Salmonella. Caution should be used to ensure that almost all organic material is removed from the facility before heat treatment since it was found that, under field conditions in cold weather, as little as four inches of litter could harbor viable pathogens after heat treatment.
