U.S. Response to Outbreaks of Avian Influenza

Although avian influenza outbreaks occur periodically in poultry flocks, only recently has avian influenza been considered a significant threat to human health and the global economy. The 1997 emergence of H5N1 first brought attention to avian influenza’s ability to cause disease in humans. However, human infection with influenza from avian sources is not a new phenomenon.

Using lung tissue from 1918 influenza victims, researchers have conducted a genetic analysis of the 1918 virus and have linked the virus to avian origins. This 1918 influenza, also known as the Spanish flu, infected up to one-third of the worldwide population and resulted in the death of up to 50 million people.

In her 2016 book, “Pandemic: Tracking Contagions, From Cholera to Ebola and Beyond,” science journalist Sonia Shah cites a study in which 90 percent of epidemiologists say they believe a global pandemic will sicken one billion and kill up to 165 million within the next two generations. Though not all scientists agree with the validity of this study, clearly the control of emerging infectious diseases such as avian influenza is a crucial part of any nation’s health agenda.

The 2014-2015 outbreak of Highly Pathogenic Avian Influenza (HPAI) in the United States illustrates the economic impact of an avian influenza outbreak. Between 19 December 2014 and 17 June 2015, 219 detections of HPAI were reported across the country, resulting in the death – either directly from the virus or in an effort to prevent the spread of the disease – of nearly 50 million birds. The total cost of the outbreak extends well beyond the cost of destroying and disposing of the birds and includes lost market opportunities from trade restrictions. Eighteen countries banned U.S. poultry products, including Russia, China, South Korea, and Thailand. Thirty-eight countries instituted regional restrictions including Canada, Mexico, Japan, Singapore, and the European Union. Estimates put the total economic impact of the 2015 outbreak at over US$3.3 billion.

On 15 January 2016, a highly pathogenic strain of avian influenza (H7N8) was detected in a commercial turkey operation in Dubois County, Indiana. Subsequent surveillance effortsentified eight cases of low pathogenic avian influenza at nearby turkey operations. Lessons learned from the 2015 outbreak of HPAI in the Midwestern United States guided the response in Indiana and included the importance of having strong carcass and manure management plans.

Role of Carcass Management  An effective disease management strategy includes a number of components including biosecurity, surveillance, quarantine and movement control, mass depopulation, carcass disposal, and cleaning and disinfection. Outbreaks of foot-and-mouth disease (FMD) in the United Kingdom in 2001, and Japan and South Korea in 2010 are clear reminders that carcass disposal plays a critical role in an effective disease response strategy. Dramatic photos of cattle burning in open pyres during the 2001 outbreak in the United Kingdom resulted in widespread public opposition to open burning.

In Japan, the lack of acceptable burial sites resulted in delays in disease eradication efforts and required the Japanese government to implement a vaccinate-to-kill strategy. This strategy, although helpful in limiting the spread of the disease, required the expenditure of already limited resources. In addition to increasing resource demands, delaying eradication efforts may result in increased case detections and total economic impact. A recent study of a simulated FMD outbreak in California concluded that delaying the response from 7 to 22 days increased the mean number of herds under quarantine from 680 to 6,200. The economic impact of this simulated FMD outbreak in California increased from $2.3 billion to $69 billion when the delay increased from 7 to 22 days.

In South Korea, disease eradication efforts resulted in the destruction of 20 percent of the country’s livestock and the creation of over 4,000 burial sites. This widespread carcass burial resulted in concerns about massive environmental impacts associated with this activity. Although investigations to characterize the actual effects of this activity are in their early phases, many worry that the environmental impacts, including those to drinking water supplies, will last for decades. One unconfirmed report from rural South Korea described drinking water wells flowing red following the burial of livestock at a nearby burial site.

Despite this history of costly and ineffective carcass disposal efforts, disposal methods have advanced little in the decade since the 2001 FMD outbreak in the United Kingdom. A disease outbreak today should not be managed with the same techniques used in previous decades, which would result in the same economic, health, and environmental impacts. Now, more than ever, first responders need better options for disposing of animal carcasses.

Poultry Carcass Management As described at the joint annual meeting of the U.S. Animal Health Association and the American Association of Veterinary Laboratory Diagnosticians, poultry carcasses have been disposed of with a variety of methods including burial, incineration, landfilling, and composting:

• Burial – The burial of poultry carcasses in pits and trenches has been a common practice for decades and is still widely accepted. Millions of birds have been buried in the response to the H5N1 and H7N9 strains of avian influenza circulating around the globe. Though burial can be fast and cheap, concerns about the environmental impact of the practice are increasing.

• Incineration – During the avian influenza outbreak in Virginia in 2002, more than 600,000 birds were burned in air curtain destructors (see Figure 1). During the 2015 HPAI outbreak in the Midwest, several types of incineration units were used with varying degrees of success.

• Landfilling – Poultry carcasses have been disposed of at landfills since the emergence of the modern poultry production industry (see Figure 2). The two greatest challenges of the method are managing the biosecurity implications of transporting infected carcasses to the landfill sites and gaining approval from the owners of the landfills. In 2015, it took 42 days to gain approval to dispose of infected poultry carcasses at landfill facilities. These delays can have significant logistical implications.

• Composting – The poultry industry in Delaware was the first to implement a composting strategy during a 2004 outbreak in broiler chickens. Later that same year, Virginia researchers demonstrated the ability to compost market aged turkeys. This technique was used during low pathogenic avian influenza outbreaks in West Virginia and Virginia in 2007 (see Figure 3). Based on the success of these experiences, composting was the primary carcass disposal method used during 2015 and 2016 HPAI outbreaks. 

  Composting on a large scale, like during an animal disease outbreak, requires technical expertise and familiarity with agricultural operations. Early in the 2015 outbreak, the U.S. Department of Agriculture (USDA) and poultry industry representatives were concerned about consistency in implementing the composting process. Small variations in design can significantly increase the cost of the composting process or, even worse, decrease the processes’ effectiveness in inactivating the influenza virus. To address this concern, USDA established the Composting Technical Committee made up of subject matter experts from around the country with experience composting animal mortality.

In May 2015, the committee began meeting weekly to discuss technical issues and to develop USDA’s composting protocol, entitled Mortality Composting Protocol for Avian Influenza Infected Flocks. In addition to developing the composting protocol, subject matter experts traveled to each infected farm to oversee composting operations. With their guidance, farmers and emergency response contractors were able to successfully compost each farm’s poultry carcasses, bedding material, feed, and eggs. The compost created by the process was deemed free of active virus and suitable for application to agricultural lands as a soil amendment.

The Future of Animal Mortality Management Animal carcass disposal remains a significant weakness in many nations’ comprehensive national strategies for biodefense. Although incidents of high-consequence foreign animal diseases like African swine fever, avian influenza, and foot-and-mouth disease are increasing, response plans often lack comprehensive carcass disposal considerations. The next outbreak is likely just around the corner. Now is the time to revisit and update foreign animal disease response plans.