​November 2018

Flotation solution matters

A 3-month-old dog presented to Riverside Animal Hospital in Miami, FL with a three-day history of watery diarrhea. The dog is indoor/outdoor and has a 1 year old canine housemate. A centrifugal fecal flotation with Sheather's sugar solution (specific gravity 1.25) was performed and revealed numerous half-moon shaped objects. 

A centrifugal fecal flotation with Sheather's sugar solution revealed numerous half-moon shaped objects in the entire slide. Original magnification, 400x.

​A centrifugal fecal flotation was repeated using a 33% zinc sulfate solution (specific gravity, 1.18).  

A Centrifugal fecal flotation with a 33% zinc sulfate solution. Now more Giardia cysts were observed on the slide and most cysts showed details. Original, 400x.

What's your diagnosis?

Many thanks for a great case with nice photos to Dr. Kamilyah R. Miller, Tuskegee University, College of Veterinary Medicine & Dr. Yoko Nagamori, Center for Veterinary Health Sciences, Oklahoma State University.  

Answer

They are Giardia spp. cysts. 

Since this fecal sample was taken from a dog it could either be Giardia duodenalis Assemblage C and/or D (G. canis).
 
There has been suspicions of Giardia being zoonotic, but current research is now questioning that theory -- Giardia may be more species specific, and may not be zoonotic.
 
It is important to note the difficulties of identifying Giardia cyst on centrifugal fecal flotation. When performing a fecal flotation, it is important to use a zinc sulfate solution (specific gravity of 1.18) allowing the cyst to float showing with more details of internal structures. The slide must be prepared and read immediately following the centrifugal flotation so not allow the cyst to collapse. The cyst will have a green hue to them when using a zinc sulfate solution, you must fine focus in and out to identify the distinguishing features that make up the Giardia cyst.