Earlier today, Dr. Veronica Matawaran said something that caught my attention.
“Ehrlichia is a bacterium. So is Anaplasma.”
My immediate reaction?
Since when did Ehrlichia become a bacterium?
For years, many veterinarians, including myself, casually grouped Ehrlichia and Anaplasma with the “blood parasites.”
After all, they are tick-borne.
They affect blood cells.
They cause thrombocytopenia.
They are often discussed in the same breath as Babesia and Hepatozoon.
But the truth is this:
Ehrlichia and Anaplasma did not become bacteria. They have always been bacteria.
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Who Are Ehrlichia and Anaplasma?
Ehrlichia and Anaplasma belong to the family Anaplasmataceae.
They are:
- Gram-negative bacteria
- Obligate intracellular organisms
- Tick-borne pathogens
- Organisms that survive and multiply inside host cells
Ehrlichia canis primarily infects monocytes.
Anaplasma platys infects platelets.
Anaplasma phagocytophilum infects neutrophils.
These are not protozoa.
They are not parasites in the taxonomic sense.
They are bacteria.
Then Why Do We Call Them Blood Parasites?
Because veterinary medicine is full of practical language.
When a veterinarian says “blood parasite screening,” everyone immediately thinks about Ehrlichia, Anaplasma, Babesia, and Hepatozoon.
The terminology became part of clinical culture.
It was useful.
It was familiar.
But familiarity does not always equal scientific accuracy.
Why Does It Matter?
Because understanding the organism helps us understand treatment.
Doxycycline works against Ehrlichia and Anaplasma because they are bacteria.
Babesia, on the other hand, is a protozoan parasite.
Different organism.
Different biology.
Different treatment.
Different outcome.
The more accurately we understand disease, the better clinicians we become.
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The Bigger Lesson
One of the most dangerous phrases in medicine is:
“That’s how we’ve always called it.”
Veterinary medicine evolves.
Our understanding evolves.
The organisms themselves do not change just because we describe them differently.
Ehrlichia was a bacterium when it infected the first dog diagnosed with ehrlichiosis.
It remains a bacterium today.
The same is true for Anaplasma.
Perhaps what changed was not the organism.
Perhaps what changed was our willingness to look deeper into what it really is.
And that is what good veterinarians do.
They never stop learning.
References
Merck Veterinary Manual. Ehrlichiosis and Related Infections in Dogs.
Merck Veterinary Manual. Anaplasmosis in Dogs.
Iowa State University Center for Food Security and Public Health. Ehrlichiosis and Anaplasmosis in Mammals.
Atif FA. 2016. Alpha-proteobacteria of genus Anaplasma: Epidemiology and characteristics of Anaplasma species related to veterinary and public health importance. Parasitology.
Dr. Geoff Carullo is a Fellow and the current President of the Philippine College of Canine Practitioners.
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