Ask the Expert: What Can I Learn From a Diagnostic Report? – Dr. Edie Brandt, De Pere Veterinary Service

Question:  Once in a while, we will take in samples collected from a deceased calf for analysis.  Can you please help me to better understand the findings and how to use this information?

A:  First of all, the best person to help answer your questions is your veterinarian.  I can’t emphasize enough the value of a good working relationship with your vet.

The amount of information presented in a diagnostic lab report can be overwhelming.    A complete lab workup from tissues submitted will include:

• Bacteriology (culturing for bacteria like Salmonella and Pasteurella)
• Direct microscopic exam and stains (coccidia, Giardia and Cryptosporidia)
• Virology (BVD, rota and coronavirus are examples)
• Histology (tissues are fixed in formalin and then examined under a microscope)

You will often receive “preliminary results” because some of the lab procedures are quicker to set up and run, such as the stain for Cryptosporidia.  Additional detail comes with a bit more time as the virology is completed and the bacteria cultured can be speciated.  For example, is it Salmonella newport or Salmonella dublin?  The pathogenicity can vary greatly between these two.  If significant bacteria are isolated, antibiotic sensitivities are performed to aid in the treatment of other sick animals you may have.

Usually the histology exam of the tissues takes longer because of the extra prep time get the tissues ready for the pathologist to examine under the microscope.  That pathologist has to use their trained eyes to identify microscopic changes in the tissues that may help make a diagnosis or confirm the disease process occurring.

When finalized, the report should contain a summary of all the lab tests and the pathologist’s comments at the end.  With a good history and appropriately submitted samples, the pathologist can help diagnose the cause of that calf death.

For this lab analysis to be of most value, it must be pieced together with the rest of the picture.  Below are a few questions you should discuss with your veterinarian before calf tissue samples are submitted.

1.  What is the primary complaint/problem?  Is it diarrhea, pneumonia or sudden deaths?

2.  What is the typical age of calf at the time of disease onset?  Are we identifying sick calves early?  The time of disease onset can help determine the source of infection.  If the problem is occurring within the first five days of life, we need to look to a problem with the dam or the calving area.  If the onset occurs after seven days of life, we need to look for a problem in the calf’s environment.

3.  Are the submission samples from a calf that was chronically or acutely ill?  Usually we obtain more valuable information from the earlier identified sick calf.  For example, a chronic pneumonia calf when sampled may only yield Pasteurella when, in fact, the underlying cause was an earlier BRSV infection.  Pasteurella causes the formation of much scarring and abscesses that can mask any viral agents present.

4. Was the calf treated with antibiotics?  Antibiotic treatment can interfere with culturing of bacteria such as Salmonella.

5. What was seen grossly during the necropsy of the calf?  What did the inside of the calf look like?  Did the calf illness present as a diarrhea issue and then the necropsy revealed that the lungs appeared to have a severe pneumonia?  That may be valuable information leading to the diagnosis of a pathogen like Salmonella that can infect multiple organ systems.

Lab analysis of calf tissues is a valuable tool to help you and your veterinarian determine the cause of a calf health issue and work on a preventative plan to raise healthy heifers.