News from the National Pork Board

Oral fluids as an alternative to blood sampling for surveillance of PCV2 and other pathogens

Effective disease surveillance, control, and prevention can be expensive, but can result in the overall reduction of herd health and veterinary costs in swine farms. One of the tools used for disease surveillance is herd health profiling; that is, determining the health (or immune) status of animals in a herd at a given time, or profiling the health of animals as they move through production. Profiling historically has involved blood sampling of animals, and although useful, systematic disease profiling using blood samples is labor-intensive and cost-prohibitive, and, as a result, rarely done. Sampling oral fluids appears to be a simple and cost-effective alternative to blood sampling for the health profiling of large swine herds.

In humans, oral fluids (saliva and other fluids found in the mouth) collected using swabs have been used as samples for the detection of viruses and other signs of infection, including antibodies. In pigs sampled experimentally, oral fluids have been shown to contain detectable levels of porcine reproductive and respiratory syndrome virus (PRRSV) RNA, anti-PRRSV antibodies, and porcine circovirus type 2 (PCV2) DNA.

With this in mind, Prickett et al¹ designed a study to find a cost-effective, fast, and simple way to obtain oral-fluid samples, conserve them, and use them for pathogen surveillance in large swine herds.

As part of their study, Prickett et al¹ collected oral fluid from 12-week-old pigs, contaminated the fluid with PRRSV and anti-PRRSV antibodies, and divided the resulting sample stock of oral fluid into three parts. One part was left intact and an antimicrobial agent was added to the other two. The samples were divided and stored at different temperatures (-20, 4, 10, 20, and 30°C). Samples were periodically tested for PRRSV RNA, antibodies (IgG, IgM, and IgA), PRRSV ELISA-detected antibody, and total bacteria.

The results showed that oral fluids stored in the same manner as serum samples (frozen or chilled for same-day laboratory testing) are suitable for antibody detection. Higher storage temperatures appear to affect detection of antibodies.

Prickett and his team² took the experiment to the field and evaluated the feasibility of collecting oral fluids from a large herd for disease surveillance. In their experiment, oral-fluid samples were collected from 10 wean-to-finish production sites across the Midwest. At each site, oral-fluid samples from six pens (25 to 30 animals per pen) were collected at 2-week intervals from load-in to load-out.

Farm staff at each site was trained to collect oral-fluid samples using a length of cotton rope suspended at the pigs’ shoulder-height, in a clean area of each pen, far from feeders and drinkers. The rope was left in the pens for 20 to 30 minutes. As pigs chewed on the rope they left oral fluids on it. Once extracted, these fluids were processed and shipped to the diagnostic laboratory for testing.

Upon completion of the study, oral-fluid samples were tested for the presence of PRRSV, PCV2, and the swine influenza virus (SIV). All of the viruses were detectable in oral fluids using polymerase chain reaction (PCR) throughout the 18-week observation period. Mycoplasma hyopneumoniae PCR testing is currently underway.

On-farm use of oral-fluid samples was found to be feasible. Samples were easily collected and processed by the farm staff and viruses including PCV2, PRRSV, and SIV were readily detectable and stable when samples were held at refrigerator temperature or lower. The preliminary data presented by Prickett et al^1,2 shows that oral fluids have good promise as diagnostic samples and as part of a cost-effective herd-health profiling program.

This information is posted online at www.pork.org.

Detailed steps for the collection, handling, and submission of oral-fluid samples are available from Iowa State University’s Veterinary Diagnostic and Production Animal Medicine Web site at http://www.vetmed.iastate.edu/diagnostic-lab/diagnostic-services/disease-topics/oral-fluids.

References

1. Prickett JR, Cutler S, Kinyon J, Naberhaus N, Stensland WR, Yoon K-J, Zimmerman JJ. PRRSV surveillance – Stability of diagnostic targets in oral fluid: sample storage and critical techniques for testing. Proc Am Assoc Vet Lab Diagn 51st Ann Conf. 2008;140.

2. Prickett JR, Hoffmann P, Stensland W, Yoon K-J, Zimmerman JJ. Practical disease surveillance in growing pig populations. Proc Am Assoc Vet Lab Diagn 51st Ann Conf. 2008;139.

PQA Plus^™ update

Over 870 veterinarians, animal scientists, Ag Extension specialists, and Ag Educators make up the network of adult PQA Plus^™ advisors and trainers. Without them, PQA Plus^™ training and assessment of production sites would not be possible.

As of December 2008, more than 20,000 pork producers had received certification in the program. Youth PQA Plus^™ certified producers totaled approximately 20,000.

MRSA update

A factsheet developed for customers (packers, retailers, and restaurants) on methicillin-resistant Staphylococcus aureus is now available from the Pork Checkoff. The factsheet details what the industry knows about MRSA in pigs and pork. The factsheet also is available online at www.pork.org.

“Euthanasia of Swine” brochure updated

The Pork Checkoff’s animal welfare committee and the American Association of Swine Veterinarians have updated the brochure, “On-Farm Euthanasia of Swine: Recommendations for the Producer.” The updated brochure is available from the Pork Checkoff in hard copy or online at www.pork.org or www.aasv.org.

“Alternative Feed Ingredients in Swine Diets II: Use, Advantages and Disadvantages of Common Alternative Feedstuffs”

This second booklet in a series discusses 11 ingredients that can be used to replace a portion of the corn and soybean meal common in swine diets. The goal of this publication is to offer producers alternatives that can reduce the cost of swine feed, and list benefits and precautions on the use of these ingredients.

Feed costs represent up to 75% of the variable costs of production. Increased costs in the price of corn and other feed grains have increased variable costs recently. Adopting lower-cost alternatives to traditional ingredients may be a way producers can reduce costs. Alternatives may not be economical or may not complement the goals of every production system. Many factors besides lower ingredient costs should be considered before a change in diet formulation is decided upon.

The booklet is available online at www.pork.org.