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Documenting Three-Year Disease Trends

Influenza continues to make news. Most veterinary diagnostic laboratories are capable of testing for the novel (human) H1N1 Flu Outbreak Virus, but in Iowa, this test is only performed when a veterinarian voluntarily participates in the H1N1 surveillance program

Influenza continues to make news. Most veterinary diagnostic laboratories are capable of testing for the novel (human) H1N1 Flu Outbreak Virus, but in Iowa, this test is only performed when a veterinarian voluntarily participates in the H1N1 surveillance program. To date, no novel (human) H1N1 cases of flu have been detected in U.S. swine.

Veterinary diagnostic laboratories do, however, conduct tests for the common swine influenza viruses (SIV) found in pigs. Data from the Iowa State Veterinary Diagnostic Laboratory suggest the frequency of diagnosis of flu in pigs in 2009 pretty well tracks with the two previous years. (Figure 1).

In contrast, the frequency of diagnosis of the porcine reproductive and respiratory syndrome virus (PRRSV) from tissues appears to have contra-seasonal increase in the first half of 2009 (Figure 2).

The frequency of diagnosis of Mycoplasma-associated pneumonia in 2009 remains similar to that of the two previous years (Figure 3).

The overall impact of disease on production has decreased in recent years, primarily due to the effects of porcine circovirus type 2 (PCV2) vaccination. Vigilance in disease monitoring must be maintained, however, as complacency will inherently lead to distressing surprises.

These three graphs are examples of trends from diagnostic submissions to the Iowa State University Veterinary Diagnostic Laboratory and are not estimates of true incidence or prevalence.

In the three graphs below, the vertical axis represents the number of positive diagnoses of diseases, while the horizontal axis refers to the month of the year.

Changing Roles of Veterinary Diagnostic Laboratories
The vast changes that affect pork production currently and over the past two decades also affect functions of veterinary diagnostic laboratories. Historically, the goal of diagnostic testing has been to put a name to the cause of illness or disease condition. The outcome of this effort has been detection of the extraordinary (new, emerging, or rare) diseases as well as confirming the presence of ordinary (common) diseases.

Diagnostic laboratories continue to provide “diagnostic testing,” but the last decade has seen a rapid growth in what could be called “monitor testing.”The difference between the two is that the latter is usually a routine, proactive testing protocol designed to “monitor” the presence or absence of a disease or agent in a defined population with an acceptable level of confidence. Most of us are familiar with proactive diagnostic testing applied in targeted “diagnostic surveys,” on-farm research, flow comparisons or case series. Some monitoring schemes are used to determine when infections occur to refine or optimize medication and vaccination programs. Larger operations often have the desire to monitor vaccination compliance as well.

As methods of elimination of disease agents from herds improved, the need to monitor for absence of infection has increased. Testing of samples from a population cannot absolutely prove a negative, but we often will have greater confidence if monitor testing is in place and properly executed. A common example of health assurance monitoring is found in monitoring boar studs for PRRSV, but routine testing is also common for seedstock suppliers or herds that have gone to great expense to eliminate pathogens. Monitor testing is and will be directed toward risk abatement and quality assurance, whether it’s applied to seedstock, transportation, production or vaccine compliance. As “production monitors” are tools for producers, “disease monitors” are the tools of swine veterinarians.

Various technologies have allowed diagnostic laboratories to develop extensive arrays of tests, testing strategies and reporting methods. Diagnostic laboratories, veterinarians, and producers are continuing to refine testing protocols to be more cost-effective in agent detection or risk management. Research efforts are being directed at innovative sampling methods and testing methods for high-volume, low-cost monitoring protocols. Oral fluid specimens continue to show promise for detection of agents or antibody, including PRRSV, SIV or PCV2. Samples are more easily obtained and from larger percentages of the population than is usual for nasal swabs or blood. New automated, high-volume testing methods will allow multiple agents and tests to be performed simultaneously. Electronic submission tools provide an easy and less confusing process, leading to faster turn-around and less error.

The Value of Direct Communication
Despite technology, the diagnostic data that is generated, reported, interpreted, captured, stored, graphed, charted and analyzed can be mis-interpreted because of the endless biological variation as well as the mathematical complexities of probabilities, confidence and risk assessments. General information is endlessly available but it does not provide sufficient specific information to help solve a unique problem. As test monitoring protocols are developed, there is greater need to communicate directly with diagnosticians. Web sites are useful but cannot provide the strategic information for unique and specific situations found on some farms. The urgency and focus on one diagnostic question may obscure a potentially more important question. Nuances of tests and test performance may not be discernible from printed material. Likewise, information from cyberspace can be misleading, misinterpreted or simply wrong. Direct communication with the laboratory can be quite rewarding before setting up monitoring protocols or assessing populations by extensive diagnostic testing. Diagnostic laboratories would much rather be a knowledge partner than a scapegoat.


• Diagnostic laboratories not only identify diseases, but have increasing demand of testing for monitoring. The interactions, risk factors and disease agents are inherently complex and must be carefully considered in formulating diagnostic testing strategies.

• The expense of health assurance and disease monitoring can be balanced by decreasing the risk of introduction of infections or optimizing current disease intervention tools.

• Pork production is a team effort. Direct communication between herd veterinarians and veterinary diagnosticians can be a valuable resource in designing cost-effective diagnostic and monitoring protocols. One example of an innovative testing service can be found at:

A list of links to food animal diagnostic laboratories can be found at

Kent Schwartz, DVM
Iowa State University Veterinary Diagnostic Laboratory
[email protected]

Click to view graphs.