Carcass disposal is a critical problem after a mass emergency poultry response, whether due to disease or other catastrophy. Carcass disposal needs to be rapid, biosecure, and inactivate any pathogens involved.

Carcass disposal figures promintently in the USDA APHIS AIV guidelines: .“When HPAI outbreaks occur in poultry, the preferred eradication and control methods are quarantine, enforcement of movement restrictions, and depopulation (culling) of all infected, exposed, or potentially infected birds, with proper disposal of carcasses and rigorous cleaning and disinfection of farms and surveillance around affected flocks. ”

In 2004, over 100 million birds were depopulated due to avian influenza. In a high poultry production region, such as the Delmarva penninsula, during a fast moving poultry disease outbreak up to 2.5 million birds every 24 to 48 hours could be depopulated or die to disease. This creates a signficiant logistical challenge.

Carcass disposal raises a host of logitical, legal, economic, and sustainability issues. The disposal method needs to be selected to be compatible with the depopulation procedure, to maximize biosecurity, ensure virus inactivation, and minimize transportation and other logisitcs. To maximize biosecurity, carcasses and contaminated material should remain within the house or on farm. Movement of contaminated carcasses, material, and equipment was implicated in helping to spread virus in the 2002 H7N2 AIV outbreak in Virginia, North Carolina, and West Virginia.

Pit burial is can be used to disposal of carcasses. Pit burial can often be performed on site using common equipment. Pit burial is cheap, but does not inactivate the virus. Avian influenza has been recovered from carcasses buried in pits.

Public landfills in some cases can accept contaminated carcasses. Landfilling has been used in multiple avian influenza responses including Virginia, North Carolina, and West Virginia in 2002, Pennsylvania in 2001-2, and Pennsylvania in 1996-7. Landfilling is expensive and requires transport of material to the landfill. A recent article in Environmental Science and Technology (Graiver et al., 2009) presented results that showed that avian influenza virus could survive in a municipal landfill for 60 to over 600 days. This study, combined with poor biosecurity associated with transport, transport logistics, high costs, and the water table on Delmarva, limit the use of land filling during an emergency poultry disease response.

Incineration, either on site or off site, results in complete inactivation of most pathogens, but can be costly and have air quality implications. Incineration was used in the UK FMD outbreak. Incineration can be performed using open air, air curtain, or fixed facilities. Air curtain and fixed facilities are preferred from an air quality perspective.

Composting can be used to dipose of contaminated carcasses and litter. Composting is the natural decomposition of organic materials by aerobic bacteria and fungi. After construction of a composting windrow, composting goes through a heating stage and a curing stage. During the heating stage, there is a rapid temperature rise, resulting in inactivation of most pathogens. During curing, break down of the carcasses is completed. A sample temperature curve during composting is shown below.

The University of Delaware has been involved in research to improve mass carcass composting. As part of this effort, experiments were performed to evaluate the impact of water based foam (Experiment 1), bulking agents suitable for eastern Europe (Experiment 2), bulking agents suitable for the United States (Experiment 3), compost enhancers (Experiment 4 and 6), and the use of compost covers (Experiment 5). The results from Experiment 1 and 2 were published in Poutlry Science (Benson et a., Poult Sci 2008. 87:627-635. doi:10.3382/ps.2007-00308).

In each of the experiments, a standardized procedure was used. Because of the concerns associated with spread, avian influenza cannot be tested outside of a specialized biosafety facilty (such as the University of Delaware Allen Laboratory). For this reason, a vaccine version of Newcastle Disease virus (NDV) is used for field testing. For each experiment, a composting windrow was created. Each treatment was part of the same windrow, with buffer regions of no treatment between sections. Sample packages were prepared including NDV inoculated chicken breast, tubes of NDV, and identification tags. Temperature recorders were located at two depths at two different locations within each treatment. Two replications of the sample packages we placed in the compost windrow per treatment per day of testing. Most inactivation testing was completed to Day 4. After recovering the sample packages, virus isolation, hemmaglutination activity, and hemmaglutination inhibition was performed on the breast meat and tubes.

In Experiment 1, two types of foam depopulation equipment and two foam concentrates were compared to a control treatment. Experiment 1 showed that fire fighting foam did not adversely impact the use of in-house composting of birds.  The added water from the foam solutions may have contributed to higher temperatures than the no foam control treatment.  The compost windrow went through a rapid temperature rise after creation, with an initial heating period of 2 days.  The compost windrow was turned at day 14, resulting in a spike in windrow temperatures for all treatments.  At shallow treatments (2.5 cm and 30 cm), the foam treatments met or exceeded recommended windrow treatments for virus inactivation (55° C).  At shallow temperatures, the control treatment did not meet the required temperatures.  For all treatments, approximately 95% of the carcass tissue was degraded by the first 2 weeks of composting with no offensive odor any compost material.

In Experiment 2, sawdust, sawdust-straw mixtures and straw bulking agents were used to compost catastrophic mortality. The temperature in sawdust, sawdust-straw, and straw treatments exceeded 60° C for multiple days.  The temperature in all 3 treatments increased after turning of the windrow.  The temperatures for all treatments did not go below 50° C for any treatment until over 20 days had passed.  The temperature in the straw showed the highest peak temperatures, the most variability, and a difference in profile versus other materials.  Straw peaked at over 70° C, which is considered very high for a composting experiment.  In this experiment, the windrow temperatures consistently exceeded the minimum suggested virus isolation temperature of 55° C.  Tissue degradation for all treatments at the 2 week turning was estimated at 97% with odor being characterized as a sweet, non-offensive aroma.  By 4 weeks, all soft tissue was degraded for all treatments.

In Experiment 3, sawdust litter, wood chips, mulch, and processed active compost were compared. Active compost reached a temperature in excess of 55° C within 5 to 10 days, however, temperatures did decline after the initial rise. Early temperature rise is more important for virus inactivation than extended temperatures. Wood chips were able to generate higher sustained temperatures (in excess of 60° C), but were slower to reach those temperatures. In addition, virus inactivation for wood chips was lower than the other treatments tested. In all cases, all soft tissue was degraded for all treatments by week 4.

In Experiment 4, nutrient based and bacteria based compost enhancers were compared. In Experiment 4, two commercially available additives were tested at recommended application levels. Both compost enhancer treatments were indistinguishable from the control treatment with respect to both temperature and virus isolation.

In Experiment 5, a commercially available engineered compost cover, field available cover, and no cover were compared for an on-farm, non-in house compost windrow. Both covers materially improved windrow temperatures, however, there was no material improvement between the engineered cover and the field available cover. Based on the experiment, a cover would be recommended when composting outside of a house. A field available cover, however, would be sufficient for mass emergency composting.

Additional resources on mass emergency depopulation are available through a password protected portion of the Avian Bioscience Center. For access, email Dr. Eric Benson with your creditials and application.

In addition, disposal and composting is included Emergency Poultry Disease Response certification course.