NAHLN Update on CSF and Influenza Surveillance Testing

December 9, 2011 — 

The National Animal Health Laboratory Network (NAHLN) is tasked with conduct testing for swine surveillance programs including classical swine fever, swine influenza and pseudorabies. Following is an update on the numbers of samples tested through the third quarter of Fiscal Year 2011.

Classical Swine Fever Surveillance

The classical swine fever (CSF) surveillance program was initiated in 2006 to rapidly detect CSF virus and monitor the risk of introduction of the virus in the U.S. swine herd. The surveillance program targets five specific swine populations for testing:

• Sick pig submissions to veterinary diagnostic laboratories (VDLs)
• Slaughter swine with high risk of CSF exposure
• Feral swine
• Swine populations (including waste feeding operations)with high risk of CSF exposure in Florida, Texas, and Puerto Rico
• Swine highly suspicious for CSF and entered into a Foreign Animal Disease Investigation

NAHLN laboratories conduct CSF surveillance testing for the first two surveillance streams listed above; samples from the remaining three surveillance streams are tested at NVSL's Foreign Animal Disease Diagnostic Laboratory (FADDL), the CSF confirmatory laboratory. In FY 2010 and Quarters 1-3 of FY 2011, 22 NAHLN laboratories provided diagnostic testing for the CSF surveillance program.

Data collected through the 3rd quarter of FY 2011 indicate that 1,948 sick pig samples submitted to veterinary diagnostic labs and 1,704 samples from high risk slaughter swine have been tested as part of the ongoing surveillance program. The number of animals tested for CSF by NAHLN laboratories in each surveillance target population in FY 2008 through FY 2010 is available in the NAHLN Quarterly Newsletter.

Swine Influenza Virus Surveillance

The goals of the swine influenza virus (SIV) surveillance program are (1) to monitor the genetic evolution of endemic SIVs to better understand endemic and emerging influenza virus ecology, (2) make SIV isolates and associated epidemiologic data available for research and analysis, and (3) select proper isolates for the development of relevant diagnostic reagents, updating diagnostic assays, and vaccine seed stock products. The program was initiated in May 2009 with a focus on monitoring the pandemic H1N1 2009 [pH1N1 (2009)] virus in swine. As the human health threat of pH1N1 (2009) declined in 2010, SIV surveillance efforts were re-focused on monitoring all current circulating SIVs.

Also in 2010, an anonymous submission protocol was adopted to encourage more industry participation and increase the number of samples available for monitoring SIV in the U.S. swine herd. SIV surveillance efforts are targeted towards these three swine populations:

• Case-compatible sick pig submissions to VDLs
• Swine exhibiting influenza-like illness at first points of concentration or commingling events i.e., markets, fairs
• Swine populations that are epidemiologically linked to confirmed human cases involving SIV NAHLN laboratories conduct SIV surveillance for the above-mentioned streams.

The NVSL Diagnostic Virology Laboratory in Ames, Iowa is the SIV confirmatory laboratory. In FY 2010 and Quarters 1-3 of FY 2011, 26 NAHLN laboratories provided diagnostic testing results data for SIV surveillance.

Data collected thus far for FY 2011 show that 1,426 total herds have been sampled. Of those, 633 accessions were influenza positive. 222 accessions had sub-typing results reported October - June in FY 2011. The testing breakdown by month and the distribution of the various subtypes detected can be viewed in the NAHLN Quarterly Newsletter.

Swine Pseudorabies Surveillance

The pseudorabies (PRV) surveillance program was initiated in 2009 as an extension of USDA's successful PRV eradication efforts. The program gathers surveillance data to support three specific objectives: (1) rapidly detect PRV entry and infection in U.S. commercial swine, (2) demonstrate freedom from PRV in commercial herds, and (3) monitor domestic sources of PRV.

Targeted Populations (surveillance streams)

• Investigation and diagnosis of suspicious PRV cases
• Sick pig submissions to veterinary diagnostic laboratories (VDLs)
• Herds participating in routine serology and herd profiling
• Herds classified as high risk
• Herds with reported exposure to feral swine
• Cull sow-boars at slaughter
• Market swine at slaughter
• Feral swine

PRV-approved NAHLN laboratories provide the diagnostic testing for sick pig submissions, routine serology and herd profiling, high risk swine populations, swine with known feral swine exposure, and feral swine. In FY 2010 and Quarters 1-3 of FY 2011, 13 NAHLN laboratories provided diagnostic testing results data for PRV surveillance. The NVSL Diagnostic Virology Laboratory performs confirmatory testing for suspect and positive submissions for PRV.

NAHLN laboratories tested 16,825 swine for PRV surveillance in FY 2010 and 16,556 swine in the Quarters 1-3 of FY 2011 (this figure does not include testing for PRV in feral swine).

Additional information is available online: NAHLN Quarterly Newsletter, December, 2011