How to Use a Veterinary Diagnostic Laboratory Effectively
By : Dr. Michelle Arnold, UK Veterinary Diagnostic Laboratory
Unusual or unexplained sickness and death loss of farm animals is an unavoidable occurrence for all producers at some point. Whether it is one animal affected suddenly or multiple animals developing symptoms of disease in a short span of time, most producers want to find the cause, the best effective treatment and how to prevent reoccurrence. The local veterinarian is the best resource for this information and should be the first person contacted to examine any affected animals and determine an appropriate treatment. The earlier the veterinarian is contacted in the disease process, the better the chance of instituting an effective therapy. However, in cases of sudden death (found dead) or when disease is spreading or in cases where treatment appears ineffective, veterinarians often turn to a vet diagnostic laboratory for help confirming a diagnosis and assisting in development of a plan for treatment and control based on test results. The UK Veterinary Diagnostic Laboratory in Lexington (Website: vdl.uky.edu ) and the Breathitt Veterinary Center in Hopkinsville (Website: https://breathitt.murraystate.edu/ ) are both full service laboratories serving the veterinarians and producers across the Commonwealth of Kentucky.
Much useful information about an individual animal death and overall health issues in the herd can be gleaned by performing a necropsy (the animal equivalent of a human “autopsy”). During the necropsy, the pathologist will first look for abnormalities they can see with their eyes; this is called “gross necropsy” and often gives an initial indication of the cause of death. Samples are then taken from all the organ systems as well as blood and other bodily fluids and submitted to different laboratory sections for specific testing. In addition, sections of each organ (liver, lung, heart, kidney, brain, etc.) are cut into thin slices, processed and placed on glass slides for examination under the microscope (histopathology). It is under the scope, at the cellular level, that pathologists most often identify the cause of death by recognizing the characteristic patterns of tissue damage caused by a certain disease. It is important to understand that autolysis (rotting) begins immediately after death and progresses rapidly which makes interpretation of tests and other findings very difficult if not impossible. Dead animals should be in the lab within 12-24 hours after death, the sooner the better especially when the weather is hot. If timely submission to a diagnostic laboratory is not possible, the herd veterinarian can open the carcass and take the necessary samples to send to the lab (a “field necropsy”). Once the pieces of the puzzle come together, the pathologist will arrive at a diagnosis and a plan can be formulated with the local veterinarian to control and hopefully prevent the problem in the remainder of the herd.
At the diagnostic laboratory, the tests ordered are based on initial necropsy findings and the history submitted with the animal. The more information available, the easier and faster it is to narrow down the list of possibilities. Try to send a complete “history” which is simply a snapshot of what the situation is on the farm, making sure to note anything out of the ordinary. The answers to the following questions will often yield useful information:
- A description of the herd. How many cattle on the farm, how many in this specific group and how many deaths have occurred over what time period?
- If sick when found, what symptoms were observed? Was treatment attempted? If found dead, when was the last time you saw her/him alive?
- When did this problem first begin? Have you ever had a similar problem on the farm?
- Vaccination history-what was given and when?
- Summarize the diet currently being fed. Include what type of feed (grain) if offered and how much is consumed, forage available (hay/pasture/silage/baleage), and any trace mineral or salt the affected animals are actually consuming daily. It is exceptionally important to note any recent changes to the diet and when the changes were made. For example, have the cattle been without salt or mineral and were just given a new bag? Is water from a pond, creek or stock tank? Is it city water, well water or pond/creek water?
- Note when any new additions joined the herd, including purchased replacement females, bulls, or sale barn animals. Also note if any animals have been on the show circuit and, if so, when they returned to the farm.
- Is there recent history of contact with other animals? Fenceline contact with neighbors’ animals? Are there cats, dogs, rats, and/or wildlife in contact with your herd or their feed?
- Are there any junk piles, burn piles, compost piles, weed trimmings or old barns accessible to the herd? Recent pesticide or herbicide use? Is there a road next to the farm where trash could be thrown over the fence?
Test results come from the lab periodically until a final report is issued. It can take as long as 2 weeks (or longer) to generate the final report if tests were sent to outside laboratories but most are finished quickly. Questions about the report can be addressed by the referring veterinarian or by the faculty and staff at the diagnostic laboratory.
It is important to understand that no veterinary diagnostic laboratory is 100% successful at figuring out every cause of death. To utilize a veterinary diagnostic lab most effectively, come with fresh samples and plenty of information. One of the most important factors is the degree of autolysis (rotting) before submission. Getting the dead animal to the lab as soon as it is found or having a veterinarian euthanize an animal that is close to death and bringing it straight to the lab will increase the effectiveness of testing. In cases of multiple death loss, it is always best to send more than one animal as it increases the odds of finding a cause and to make sure they actually died from the same problem. In cases where a diagnosis is not found, it is not a waste of time and money if there are many diseases ruled out with negative test results. However, rotten animals or those that have been scavenged are much more difficult to work with and often give very few answers.