Swine Surveillance Quarterly Updates

May 11, 2011 — 

The USDA's National Animal Health Laboratory Network (NAHLN) conducts a number of routine surveillance projects involving swine diseases including classical swine fever, influenza, and PRV. Following is an update on each of these surveillance projects as reported in the 2011 May edition of the NAHLN Quarterly Newsletter.

Classical Swine Fever
The United States Department of Agriculture (USDA), Animal and Plant Health Inspection Service (APHIS), Veterinary Services' (VS) 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 with high risk of exposure (including waste feeding operations) in Florida, Texas, and Puerto Rico
• Swine foreign animal disease investigations as suspicious for CSF submitted to the USDA, APHIS, VS, National Veterinary Services Laboratories' Foreign Animal Disease Diagnostic Laboratory (FADDL) in Plum Island, New York.

NAHLN laboratories conduct CSF surveillance testing for the first two surveillance streams listed above; samples from the remaining three surveillance streams are tested at FADDL. In FY2010, 22 NAHLN laboratories provided diagnostic testing for the VS CSF surveillance program.

Below are the number of animals tested for CSF by NAHLN laboratories in each surveillance target population in Federal FY2008 (October 2007 - September 2008) through Federal FY2010 and the first quarter of FY2011.

• Sick pigs submitted to VDLs
  • FY2008 = 3,166
  • FY2009 = 4,309
  • FY2010 = 3,431
  • FY2011 (Qtrs 1 and 2) = 1,715
• High-risk slaughter swine
• FY2008 = 1,497
• FY2009 = 2,086
• FY2010 = 2,753
• FY2011 (Qtrs 1 and 2) = 1,089

Swine Influenza Virus
The goals of the USDA, APHIS, VS' 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 veterinary diagnostic laboratories
• Swine exhibiting influenza-like illness at first points of concentration or commingling events such as markets and fairs
• Swine populations that are epidemiologically linked to confirmed human cases involving swine influenza virus

NAHLN laboratories provide testing for all of the SIV surveillance streams. In FY2010 and the first quarter of FY2011, 26 NAHLN laboratories provided diagnostic testing results data for SIV surveillance.

SIV testing results reported by NAHLN laboratories, FY2011 (year to date) Number of herds (accessions) tested, number of influenza-positive herds, and number of herds with virus sub-typing results reported in FY2011.

Since the surveillance program was instituted in the fall of 2010, there have been 1003 accessions submitted. Of those, 487 were determined to be SIV positive and 121 were sub-typed. Of the 131 accessions with sub-typing results reported, one herd in October 2010 and another herd in March 2011 reported mixed sub-typing results (multiple sub-types present).

Pseudorabies Surveillance
The USDA, APHIS, VS' pseudorabies (PRV) surveillance program was initiated in FY2009 as an extension of VS' successful PRV eradication efforts. The goals of the PRV surveillance program are to detect PRV entry and infection in commercial swine, demonstrate PRV-free status, and monitor domestic sources of PRV (e.g., via feral swine). Surveillance data are captured from eight target populations; the target populations and associated objectives are:

Objective 1: Rapid detection of PRV entry and infection into U.S. commercial swine

• Sick pig submissions to veterinary diagnostic laboratories (VDLs)
• Routine serology and herd profiling
• Swine populations with high risk of exposure to feral swine
• Pigs with known feral swine exposure
• Swine cases reported to State and Federal officials as suspicious for PRV

Objective 2: Demonstrate freedom from PRV in commercial herds

• Cull sow-boars at slaughter
• Market swine at slaughter

Objective 3: Monitoring domestic sources of PRV

• 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 FY2010 and the Quarters 1 and 2 of FY2011, 13 NAHLN laboratories provided diagnostic testing results data for PRV surveillance.

NAHLN laboratories tested 16,305 swine for PRV surveillance in FY2010 and 14,337 swine in the Quarters 1 and 2 of FY2011 (October 2010 through March 2011; these figures do not include testing for PRV in feral swine).