For a look inside the offerings, operations, and objectives of diagnostic laboratories, AVMA News spoke with representatives of state laboratories as well as commercial laboratories. This is the second article in our four-part series.
State diagnostic laboratories protect all creatures, great and small
The caseload at the Oklahoma Animal Disease Diagnostic Laboratory has more than doubled since the 1990s, but the personnel has dropped by about half with the use of new technologies.
Yet, staffing continues to be a big challenge at the OADDL to meet the ever-increasing number of cases—with the main caseload coming from swine, cattle, chickens, and horses, in that order.
The type of cases varies among state veterinary diagnostic laboratories, with a mixture of large and small domestic animals and some wildlife. Diagnostic work even has extended to humans recently with the COVID-19 pandemic. The state laboratories have a broad mission to protect animal and public health.
“This testing work on the animals—whether it be livestock or pets or horses—all this work combined across the country represents the herd health status for that particular species,” said Dr. David H. Zeman, executive director of the American Association of Veterinary Laboratory Diagnosticians. He said the two federal laboratories act as a reference center.
Dr. Zeman said the AAVLD’s big avenue for advancing the discipline of veterinary diagnostics is the association’s program to accredit the state laboratories, about three-quarters of which are based at universities. The AAVLD also offers a journal, an annual meeting, and other benefits for about 1,000 members mostly employed by state or federal veterinary diagnostic laboratories.
The veterinarians employed at the state laboratories are generally specialists in a variety of fields, particularly pathology. The other employees are bench scientists and technical support people. Some state laboratories have extension veterinarians, so if there is an outbreak of fowl cholera in chickens, the extension veterinarian can consult with animal owners. Diagnostic reports usually go back to the referring veterinarians, however, for the actual management of cases.
Dr. Zeman said diagnostic work at state laboratories steadily grows because there is always disease, plus the human population grows, so there are more food animals and companion animals.
“The business is changing, though, and in a good way,” he said. “When I started out in this business in the early 1980s, we did a lot of what I call reactive diagnostic veterinary medicine.”
The farmer would open the barn door and find 20 dead turkeys, and then the laboratory tried to figure out what happened. Things like that still happen, Dr. Zeman said, but now people do a lot more monitoring and surveillance with more and better tests.
He said, “We can check animals beforehand and ask the question, ‘Are they healthy?’ and ‘Do we have this in the barn or that in the flock?’ Veterinarians secure samples from live animals for diagnostics to support preventive care.
Most food animal practitioners have a good relationship with their state diagnostic laboratory because they handle a lot of animals and don’t have time to run a laboratory on their own, Dr. Zeman said.
If a new disease comes along, state laboratories will partner with companies to develop a new test. State laboratories are the go-to for necropsies, rabies testing, and testing for foreign animal diseases.
Dr. Jerry Saliki, OADDL director and 2021-22 AAVLD president, said the two major changes that he has seen at state veterinary diagnostic laboratories are continual improvement in quality control and the establishment of the National Animal Health Laboratory Network.
The NAHLN, implemented in 2002, is a partnership between the state laboratories and the federal reference laboratories to detect biological threats to the nation’s food animals. The OADDL is among the state laboratories that have been testing for highly pathogenic avian influenza as part of the network.
Dr. Saliki said another trend over the past 20 years is the growth of molecular diagnostics based on testing for DNA or RNA. In the old days, diagnostic laboratories relied mostly on actually culturing and identifying infectious agents. Now, laboratories can simply find the presence of RNA or DNA from an agent.
The OADDL also is using more robotics in handling and processing samples. The testing throughputs have increased tremendously in the past two decades, Dr. Saliki said.
State veterinary diagnostic laboratories historically have helped protect human health, too, Dr. Saliki said. The laboratories detect zoonotic diseases in animals, for example. When the COVID-19 pandemic began, the OADDL was the first veterinary diagnostic laboratory in the United States to help test for the SARS-CoV-2 virus in humans.
“We play a key role in one health and are looking forward to increasing that role based on lessons learned from the COVID pandemic,” Dr. Saliki said.
When to seek a second laboratory opinion
A mysterious parvolike illness seen in several dogs in northern Michigan was identified as actually being canine parvovirus in late August by the Michigan State University Veterinary Diagnostic Laboratory.
The dogs displayed clinical signs suggestive of parvovirus, but they consistently tested negative on point-of-care tests performed in clinics and shelters.
Sometimes it helps for veterinarians to get a second laboratory opinion, while reportable diseases need to be confirmed by state and often federal laboratories, said Dr. Michael Murphy, director of the AVMA Division of Animal and Public Health.
While canine parvovirus does not need to be reported, state veterinary diagnostic laboratories routinely do regulatory work and are set up to communicate with state and federal authorities regarding those diseases that are reportable. Commercial veterinary laboratories have been reporting back to veterinarians on positive test results for SARS-CoV-2 in animals—and now monkeypox in animals—but the results are not official until confirmed by the appropriate authorities.
Confirmation is necessary because these reportable diseases have important implications for animal and public health and for international trade. Highly pathogenic avian influenza is another current example of a reportable disease that needs to be confirmed by the appropriate authorities.
In some situations, veterinarians may want to ask their commercial laboratory whether it will consider sending a sample to a state laboratory for a second opinion. The state laboratory may use a different technique to determine whether a false-negative or false-positive test result was obtained.