Tackling The Veterinary Terminology: Suffixes (-iasis)

Remember the Spelling Bee? Big words are easier to tackle when you understand how they're put together. Veterinary terms are composed in the same way. Just like with other words, the main parts of a veterinary term are a prefix, a root, and a suffix. The difference is that they typically come more directly from Greek or Latin.

The suffix is the bit that will tell you about what procedure, condition, disease or disorder you're dealing with.
-iasis [ʌɪəsɪs] from Greek - condition, infection, infestation

This suffix means an abnormal condition, characterized or caused by whatever the root word is. It often stands for an infection, such as parasitic.

Unlike with -itis, the root word here indicates the cause or characteristics of the problem, rather than the affected part of the body.

For example, candidiasis, an infection by candida, a yeast-like parasitic fungus, giardiasis, intestinal infection by a protozoan (single-celled) parasite, or ancylostomiasis, hookworm infection.

Candida albicans is responsible for 80-92% of the Candida infections.
Image Wisconsin State Laboratory of Hygiene.

Though ofter the suffix -osis is used to describe these conditions as well, such as in coccidiosis, a parasitic type of infection, affecting the intestine. Which is interesting, because I came across a paper which calls for consistency in nomenclature for parasitic diseases, as it seems that sometimes things end up being called whatever somebody feels like. 

Seems that -osis and -iasis are often used interchangeably.

Based on that, it would mean that either -osis or -iasis with a parasite name in the root mean infection, while -osis with something else in the root, such as spondylos (vertebra) in spondylosis, then it stands for a non-infectious disease process.

Fun, huh?

I gotta find myself something easier! And asking somebody does not help, trust me. Or don't trust me, try it. If you do, let me know what explanation you got!

For example this was one answer I got from a veterinarian: "-iasis seems to me to means a condition that is happening rather than established. If you google it, it says that the iasis is more in the formation of a medical condition. It seems to be a pretty fine line. For instance erlichiosis is established condition where giardiasis is in the process of? Fun to surmise and try to figure this out. Glad I didn't have to write a dictionary."

Dr. Coates, who did right a dictionary, said, "I ran into similar problems when writing my dictionary. I initially thought, 'hey, I'll just explain what all the prefixes, suffixes, and roots mean and owners can then figure out what everything means.' Turns out it's not quite that straight forward."

So far, either -pathy or -osis are often used for the same thing; -osis and -iasis are used interchangeably ...

No wonder it takes so long to get a degree!

It's like with our door knob, which broke, and we don't seem to be able to find a new one that fits! They're all different and none of them goes into our door. Why not makes doors and door knobs that fit together?


Related articles:
Veterinary Suffixes (-itis)
Veterinary Suffixes (-oma) 
Veterinary Suffixes (-pathy)  
Veterinary Suffixes (-osis)


  1. Hello,

    I happened across this page while writing a paper on Sarcocystis.

    I currently take a graduate class under an esteemed DVM of our veterinary school. He touched upon these distinctions as well, although he insisted that we use -iasis, e.g. coccidiasis, for the presence of the pathogen in the body and -osis, e.g. coccidiosis, for disease caused by the pathogen.

    He noted the common interchange of the two, although made sure we were aware of the difference for the sake of clarity and correctness.

    1. Ah, great. Understanding the basics - biochemistry to understand diseases, and suffixes and prefixes to understand terminology is the way to go.


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