Pulse - November 2024 - 19
INDUSTRY INSIGHTS
A Parasite by Any Other Name,
Places Dots on RBCs Just the Same
Christopher A. Lee, DVM, MPH, DACVPM
T
he proverb " Fool me once, shame on you; fool
me twice, shame on me " fails when it comes to
being a doctor. If a pathogen fools us once, we have
let down our patient - our greatest fear. Yet still
this happens to the best of us. Pathogens are ever
tricky and, on occasion, fail to read the textbooks.
Darn pathogens.
In bygone years, Feline Hemotropic Mycoplasmosis (FHM) has
also born the monikers of Feline Infectious Anemia (FIA) and hemobartonellosis.
Renaming of genera occurs as we better understand the
organisms and still, we have much to learn about this one. No wonder
it has fooled doctors over the years. While flea bites are suspected to be
a mode of transmission, the complete cycle of infection remains unclear.
Even the genus name of this causative bacteria originates from late 19th
Century confusion. The Greekμύκης, mykes (fungus) andπλάσμα, plasma
(formed), described a fungus-like pathogen of plants. Three species are
implicated with FHM: M. haemofelis, Candidatus M. haemominutum, and
Candidatus M. turicensis. As an aside, the term " Candidatus " is assigned to
bacteria that cannot be cultured. Could these bacteria be more frustrating?
The clinical signs are unhelpfully vague: depression, lethargy, anorexia,
pallor, weakness, weight loss, and lymphadenopathy. As the older name
of FIA implies, anemia can help alert clinicians to this pathogen's possible
presence. Other changes in white blood cells and platelets do occur.
In a recent article, we discussed the importance of using blood smears
with rattlesnake envenomation. Once again, this column provides a
similar call to action - run blood smears! They are cheap, easy, and fast.
What could be better?
During an overnight shift, I took over a mystery cat case with fever of
unknown origin and mild anemia. The pet was scheduled to be turfed
to specialty in the morning. At a 2 am lull, I asked an assistant to run a
blood smear. She came over and asked if she made the slide wrong, " The
red blood cells look speckled. "
After congratulating the
assistant on a great smear, the
next step was pulling a sample
for a comprehensive fever of
unknown origin panel, instituting
appropriate antibiotics, and
client communication when it
wasn't 3 am.
As it turned out, the client
Figure 1
PULSE
NOVEMBER 2024
was planning on declining to
go to specialty due to financial
concerns and was considering
euthanasia. Confirmation
with a comprehensive fever
of unknown origin test was similarly declined, but with a presumption
diagnosis and appropriate antibiotics, the pet made a full recovery.
Unfortunately, with today's high costs of pet medical care, working with
limited diagnostics is a familiar story.
Returning to the original mid-17th Century proverb, being fooled by
a pathogen is never fun. I recall many years ago when I missed a diagnosis
of FHM in a patient. Luckily, another doctor was there who did not.
I confessed to her that I was not highly proficient at looking under the
microscope and tended to send everything out to the laboratory. Again,
the owner of this pet declined additional testing.
She responded, " Can you tell if a red blood cell has measles? "
My blank stare led to her further explanation.
" Just look for spots on the red blood cells. Here, let me show you. "
Since then, I have been heralded as a " microscope master, " but the
truth is my skills have only marginally improved. When things look
" odd, " I request submitting additional slides be sent to an external laboratory.
I am not, and never will be, a pathologist. Still, I love listening
to pathologists describe histopathology slides. It is reminiscent of an
art critic detailing the meaning behind each of a painter's strokes. I find
both explanations wonderful and mysterious in their origin.
Blood smears, ear cytology, and gross anatomy of parasites, always seem
to yield a wealth of knowledge for a patient, even if only ruling out a disease.
If lack of experience is preventing you from running blood smears,
then fear not. Perhaps, ask a co-worker. Shortly after the FHM incident,
a wise technician walked me through blood smears and taught me most
of my current knowledge. Additionally, there are many helpful websites
providing seemingly endless comparison pictures and descriptions.
What should be more fearful than a lack of microscope expertise, is
the possibility of missing a simple diagnosis. Then there may proverbially
be " shame on you. " Therefore, run those smears!
With that said, an absence of evidence is not evidence of absence. A
negative blood smear for Mycoplasma spp does not rule out the bacteria's
presence. Luckily, the PCR tests for FHM are highly sensitive and
usually include a whole list of other infectious agents which could be
causing similar clinical signs. P
References:
1 Brooks, DVM, DABVP, W. (2022). Infectious anemia in cats. VIN. https://veterinarypartner.vin.
com/default.aspx?pid=19239&id=4952073
2 Krass, C. J., & Gardner, M. W. (1973, January 1). Etymology of the term mycoplasma. microbiologyresearch.org.
https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/00207713-23-1-62
3 KY Phrase. (2022, June 7). Fool me once, shame on you - saying - its meaning and origin. Know
Your Phrase. https://knowyourphrase.com/fool-me-once
4 Hemotropic Mycoplasma infections in animals - hemotropic mycoplasma infections in animals.
Merck Veterinary Manual. (n.d.). https://www.merckvetmanual.com/circulatory-system/
blood-parasites/hemotropic-mycoplasma-infections-in-animals
5 Hunter, DVM, T. (n.d.). Feline hemotrophic mycoplasmosis: VCA Canada Animal Hospitals.
VcaCanada. https://vcahospitals.com/know-your-pet/feline-hemotrophic-mycoplasmosis
6 Wei W, Zhao Y. Phytoplasma Taxonomy: Nomenclature, Classification, and Identification. Biology
(Basel). 2022 Jul 26;11(8):1119. doi: 10.3390/biology11081119. PMID: 35892975; PMCID: PMC9394401.
19
https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4952073
https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4952073
https://www.microbiologyresearch.org/
https://www.microbiologyresearch.org/
https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/00207713-23-1-62
https://www.knowyourphrase.com/fool-me-once
https://www.merckvetmanual.com/circulatory-system/blood-parasites/hemotropic-mycoplasma-infections-in-animals
https://www.merckvetmanual.com/circulatory-system/blood-parasites/hemotropic-mycoplasma-infections-in-animals
https://www.vcahospitals.com/know-your-pet/feline-hemotrophic-mycoplasmosis
Pulse - November 2024
Table of Contents for the Digital Edition of Pulse - November 2024
Chapter Meetings & Calendar
President’s Perspective
Pulsepoints
SCVMA Profile
FEATURE STORY
Practical Pathology
UC Davis Update
Updates
Tools for Success
Industry Insights
Angel Fund
AVMA Diplomates
Resources
Disease Table
From the SCVMA Office
Pulse - November 2024 - Cover1
Pulse - November 2024 - Cover2
Pulse - November 2024 - Chapter Meetings & Calendar
Pulse - November 2024 - 2
Pulse - November 2024 - President’s Perspective
Pulse - November 2024 - Pulsepoints
Pulse - November 2024 - 5
Pulse - November 2024 - 6
Pulse - November 2024 - 7
Pulse - November 2024 - SCVMA Profile
Pulse - November 2024 - 9
Pulse - November 2024 - FEATURE STORY
Pulse - November 2024 - 11
Pulse - November 2024 - 12
Pulse - November 2024 - 13
Pulse - November 2024 - Practical Pathology
Pulse - November 2024 - UC Davis Update
Pulse - November 2024 - Updates
Pulse - November 2024 - 17
Pulse - November 2024 - Tools for Success
Pulse - November 2024 - Industry Insights
Pulse - November 2024 - Angel Fund
Pulse - November 2024 - AVMA Diplomates
Pulse - November 2024 - Resources
Pulse - November 2024 - 23
Pulse - November 2024 - Disease Table
Pulse - November 2024 - 25
Pulse - November 2024 - 26
Pulse - November 2024 - 27
Pulse - November 2024 - 28
Pulse - November 2024 - 29
Pulse - November 2024 - 30
Pulse - November 2024 - 31
Pulse - November 2024 - 32
Pulse - November 2024 - 33
Pulse - November 2024 - 34
Pulse - November 2024 - 35
Pulse - November 2024 - 36
Pulse - November 2024 - 37
Pulse - November 2024 - 38
Pulse - November 2024 - 39
Pulse - November 2024 - From the SCVMA Office
Pulse - November 2024 - Cover3
Pulse - November 2024 - Cover4
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