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NAHLN Network marks 20 years protecting U.S. livestock

Laboratories critical for HPAI testing; prepared for diagnostic lab submissions for the presence/absence of African swine fever, classical swine fever via PCR.

January 2, 2023

6 Min Read
NAHLN Network marks 20 years protecting U.S. livestock

The U.S. livestock and food sectors, which account for more than $150 billion in annual cash receipts, are under continual threat from outbreaks of foreign and emerging animal diseases. Since 2002, these agricultural assets have been protected in part by the National Animal Health Laboratory Network, created through the cooperation of the USDA-APHIS Veterinary Service, USDA's National Institute of Food and Agriculture and the American Association of Veterinary Laboratory Diagnosticians.

NAHLN is a network of federal, state and university-associated veterinary diagnostic laboratories that provides ongoing disease surveillance; responds quickly to disease events; communicates diagnostic outcomes to decision makers; and has the capability and capacity to meet diagnostic needs during animal disease outbreaks.

Originally composed of 12 AAVLD laboratories, NAHLN has grown to include 60 laboratories distributed throughout the United States that are capable of testing large numbers of samples for specific disease agents.

The University of Arkansas System Division of Agriculture's Tollett Veterinary Diagnostic Lab is the latest lab to join the network. The Tollett Lab has been operated by the Arkansas Agricultural Experiment Station for 14 years, offering diagnostics for poultry and mammals.

"Being certified by NAHLN is a complex and rigorous process," say Nathan Slaton, assistant director of the experiment station. "The lab must maintain a required amount of instrumentation and staff must pass certification to do the testing."

The Tollett Lab's NAHLN certification comes as the poultry industry in Arkansas is dealing with highly pathogenic avian influenza, known as HPAI. In 2020, the poultry industry was the state's top commodity in terms of cash receipts at more than $2.6 billion.

Americans eat more poultry than any other type of meat protein, and that means poultry production is big business in the United States. In 2020, the total production value of all poultry products topped $35.5 billion, according to USDA's National Agricultural Statistics Service.

As of Dec. 12, HPAI has been found in more than 5,000 wild birds and more than 690 domestic flocks. Fifty-two NAHLN laboratories have been activated within 39 states and performed more than 170,000 polymerase chain reaction tests for HPAI.

The largest outbreak of HPAI in U.S. history began in January 2015 when HPAI was diagnosed in a commercial poultry flock in California. Over the next six months, infected premises were identified in 14 additional states, with Iowa and Minnesota hit the hardest. In total, 232 commercial and backyard premises were infected, and approximately 50 million birds were lost to the outbreak. Numerous infections in wild birds were also detected.

The cost of the outbreak was $850 million and NAHLN laboratories completed approximately 80,000 PCR tests for HPAI. This outbreak was devastating for U.S. poultry producers with the loss of their birds and long-lasting trade implications. The labs applied many lessons learned from the 2015 outbreak to the current HPAI outbreak. 

"Because a large portion of our poultry production occurs in northwest Arkansas, adding the Fayetteville lab to the department's NAHLN certification for HPAI testing will greatly enhance our state's animal disease response capabilities," says Wes Ward, Arkansas Secretary of Agriculture.

In response to the global pandemic of SARS-CoV-2, or COVID-19, the NAHLN network entered uncharted territory by heeding a call for help from human diagnostic laboratories to increase human testing capacity within the United States. Many NAHLN labs utilize high-throughput PCR testing for various animal pathogens, which is not a common practice among their human counterparts.

To make this happen, each laboratory independently obtained Clinical Laboratory Improvement Amendments approval, and many took on all human testing for their states. Some also performed next generation sequencing, aiding in the identification and tracking of viral mutations, including detection of the Delta variant as it spread across the country.

By October 2021, 33 NAHLN laboratories were conducting SARS-CoV-2 testing; 22 of those for human samples, and 26 testing for the virus in animals. The National Veterinary Services Laboratories in Ames, Iowa, also served as the reference laboratory for animal testing. More than 5.6 million human samples were tested in veterinary diagnostic labs across the NAHLN.

Antimicrobial resistance
Antimicrobial resistance of bacterial pathogens is an emerging public health threat to people and animals because it compromises the ability to treat infections. Traditionally, antimicrobial resistance surveillance programs in the United States, such as the National Antimicrobial Resistance Monitoring System, have focused on collecting data from healthy food animals, retail foods and people.

In March 2015, the Executive Office of the President released the National Action Plan for Combating Antibiotic-Resistant Bacteria, with the primary purpose to guide activities and actions by the government, public heath, healthcare and veterinary partners to address the AMR threat. The National Action Plan laid out five main goals and charged all federal agencies to work together to identify emerging resistance with the goal of increasing antimicrobial stewardship.

As a result, NAHLN initiated the NAHLN AMR pilot project in January 2018, which is on track to be converted to a permanent program early in 2023. The project monitors data from four livestock species (cattle, swine, poultry and horses) and two companion animal species (dogs and cats).

Establishing a surveillance program within NAHLN to monitor AMR profiles in animal pathogens will enhance the nation's early detection of, response to, and recovery from animal health emergencies. It will also help identify new or emerging AMR profiles and help monitor continued usefulness of antimicrobials over time.

African swine fever
African swine fever is a devastating, highly infectious animal disease that, if found in the United States, threatens the multibillion-dollar pork industry. While ASF poses no threat to human health, its impact on U.S. pig populations — and the domestic and foreign markets that depend on them — would be severe. Preliminary estimates suggest that losses to the pork industry can be as high as $50 billion if we are unable to contain and eliminate ASF in a 10-year scenario.

Since the first known outbreak in 1907, ASF has infected swine in Africa, Europe and Asia. The virus was recently discovered on the Caribbean Island of Hispaniola— first in the Dominican Republic and in Haiti in September. Previous outbreaks in other countries have resulted in devastating swine losses for pork producers through both high mortality and significant culling to control the spread of the disease. On June 1, 2019, APHIS implemented an active ASF Surveillance Program within NAHLN that supplemented an already existing CSF surveillance program. This program tests diagnostic lab submissions for the presence/absence of ASF and CSF via a real-time polymerase chain reaction.

With support from NIFA, APHIS Wildlife Services is seeking to develop a disease spread model focused on populations of feral swine. Led by Kim Pepin, a quantitative research biologist with the National Wildlife Research Center, the project will provide responders across the nation with a toolbox to rapidly eliminate the ASF virus if an introduction were to occur.

Source: USDA National Institute of Food and Agriculture

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