Widespread health concerns about food-borne illness, zoonotic disease, bioterrorism and antibiotic resistance have brought together experts in both animal and human health to work to protect both animal and human populations. Developing new disease testing and surveillance methods is the mission of a select group of researchers in Minnesota.
Protecting animal and human heath and ensuring a safe food supply is the three-prong approach of the University of Minnesota's (UMN) Veterinary Diagnostic Laboratory (VDL). The state-of-the-art laboratory is unique in many ways — from its working relationship with state and federal agencies to its across-university projects — as it strives to create a unique exchange of information and ideas.
“We're located in an area where we're part of a major university. We're also in what's called the academic health center, so we're one of only two vet colleges in the country affiliated with a medical school and a school of public health,” says VDL director James Collins. He's referring to UMN's Medical School and School of Public Health. The VDL is also the official Minnesota Board of Animal Health laboratory and works closely with USDA.
“We have a real interface of animal and human health, and public health and food safety,” he adds.
Collins says VDL's mission is to provide rapid animal testing services to identify emerging diseases as quickly as possible and to develop new methods for quicker and more economical disease diagnoses.
The facility performs surveillance on such foreign animal diseases as foot-and-mouth-disease and vesicular stomatitis in cattle, avian influenza in poultry and hog cholera in swine.
“We do passive surveillance for these diseases, meaning the animals coming through here that would normally not be tested for these diseases will be tested at no cost to the producer,” Collins says.
He adds, “Increased surveillance can mitigate a disease's economic damage if you find it quickly.”
How the VDL operates
A few of the bovine diseases VDL monitors include brucellosis, Johne's disease (see sidebar) and bovine viral diarrhea.
Jeremy Schefers, a VDL pathologist and diagnostician, works to identify diseases from samples forwarded by veterinarians around Minnesota. He says a large part of his job is communicating with veterinarians and producers in the field to accurately diagnose diseases.
“There are a lot of things the vet knows at the herd level that we'll never know. We receive a sample from the farm and a brief history of what's wrong, but that's really it,” Schefers says. “So, we form a good triangle — the veterinarian, pathologist and producer. If everyone does his job correctly, we can decide the proper approach to solve whatever disease process is going on.”
Schefers says he works with 25-30 cases daily, four days a week. He examines the tissues and determines which tests to run before sending the tissue to the lab.
Because of the number of people working in the diagnostic lab, he says it can be hard to disseminate information in a timely fashion. This problem was solved three years ago when test results were put on a secure, password-protected Internet site as soon as they were completed.
“It makes transfer of information much faster and easier, while ensuring confidentiality,” he adds. “Sometimes, the veterinarian knows the test results before I do if he looks on the Web first.”
Another of Schefers' responsibilities is supervising the transmissible spongiform encephalopathy (TSE) lab. TSEs are found in Minnesota's sheep and deer populations, and the VDL monitors incidence in both species. Each fall, the lab tests 6,000 deer for chronic wasting disease (CWD) and regularly tests sheep for scrapies.
“It's a rapid test and all testing equipment is made by BioRad, the same testing equipment used for BSE testing; the process is almost identical,” Schefers says. “We can do 500-600 samples/day using a crew of four technicians.”
On March 15, 2004, USDA announced an enhanced BSE surveillance program designed to test an additional 268,000 high-risk animals. Thirteen laboratories were selected to conduct the quick tests for surveillance; Minnesota's VDL was one of them. Due to USDA's indecision on which test to certify for use, the Minnesota VDL has yet to run a single BSE surveillance test, however.
“USDA is still planning to send us some samples of BSE for testing, but since the surveillance plan has been scaled back, it will probably be a very low number of samples,” Collins says.
New waste disposal methods
VDL performs another aspect in disease surveillance — necropsies to determine cause of death. For years, Collins says carcasses were dispatched to a rendering company for disposal. Eventually, however, the rendering company stopped accepting the waste due to high disease risk concerns.
“That left us with the problem of how to keep our necropsy facility open without proper animal waste disposal,” he adds.
Few options were available. One was packing the waste into biohazard barrels and entering them into the biomedical waste stream. That's expensive and requires long-distance trucking for disposal.
“We decided to dispose of our own materials,” Collins says. “In the interest of destroying prions like CWD or scrapie, or in the event of a BSE case, we needed a waste disposal system to deal with hard-to-destroy prions.”
The solution was a huge, stainless-steel vat called the Digester, which employs alkaline hydrolysis to destroy the waste. It can handle up to 7,000 lbs. at one time, is the largest unit made and is one of only seven operating in the U.S.
The waste is placed in the unit then heated and pressurized. Potassium hydroxide is added to raise the pH above 12, which is very alkaline.
“This breaks down everything in a matter of hours and renders it non-infectious,” Collins says. It essentially liquefies the carcass. The only residue is lime from the bones.
“All the liquid goes into the sanitary sewer system, and the lime is used as fertilizer,” he says, adding that the apparatus is available to anyone in the state who needs access to it.
Collins encourages producers to use the lab, and those similar to it in other states, for animal testing to ensure herd health.
“The real purpose of VDL is to find emerging diseases quickly and protect animal agriculture,” Collins says. “I call it inexpensive insurance.”
For more on the program and the tests performed, visit www.vdl.umn.edu or call 800/605-8787.
Jumping on Johne's
The disease can sneak into your herd virtually undetected and go unidentified for years. Still, Johne's disease can wreak havoc on economic performance and your bottom line, while taking years to control.
It's only during the last few years that Johne's has come to the forefront in disease control. In Minnesota about 12% of beef and dairy cattle have tested positive for Johne's.
“Johne's is intensive, meaning the closer you have animals, the more likely they'll become infected if there's a positive animal in the herd,” says Scott Wells, head of the Veterinary Public Health Division of the University of Minnesota (UMN) College of Veterinary Medicine. He also leads the university's Johne's disease control program.
Wells says UMN has received funding from USDA Animal and Plant Health Inspection Service for the last five years to research methods for controlling the disease on farms through testing, risk assessment and herd management.
“We have a demonstration herd control program that we started in 2000,” Wells says. “Within the program we have three beef cow-calf herds and eight dairy herds.”
The herds all have known problems with Johne's disease infection and were willing volunteers to be example herds — in exchange for free testing and management consultations.
“The goal is to control Johne's in these herds through herd management — using whatever strategies they can to control the disease over time,” Wells says.
Methods used to manage the disease include reducing calving-pen density of cows, as calves are the most susceptible to contract Johne's, he says.
“The highest risk situation is a clinically infected cow with diarrhea and a newborn calf nursing her,” Wells says. “The most common mode of transmission is through fecal material.”
Wells also recommends keeping animals in cleaner areas — out of mud and manure — and buying replacement heifers and bulls from tested negative herds.