WVC parasite Q&A: Fecals and centrifugation
Holly Morss, CVT, answered these attendee questions during her Western Veterinary Conference presentation about ova identification.
Q. We're using sugar solution in a centrifuge with a positive meniscus and cover slip. The slide frequently flies off the swing arm, making a big mess. What can we do?
It's likely that your meniscus is too high, so there's too much surface tension pushing it up. Try positioning your cover slip slightly to the inside so there's a little room. This will let your swing arm move a bit so it doesn't fly off.
Q. Do you recommend using a centrifuge with a cover slip or a sterile fecal loop for egg recovery?
I prefer the cover slip. Letting it stand for five minutes offers more time for the eggs to collect and it's more consistent. The fecal loop allows for too much differentiation among people because the results depend on how far you dip it in, how long you leave it in, and so on.
Q. We recently saw coccidia on a fecal exam. Many were normal size, but some were larger. How do we tell which type of coccidia is present?
Noninfective coccidia feature a single-celled center. Infective coccidia feature a double-celled center. These infective organisms are sporulated and can be larger. Also, different species of coccidia can be larger. So I recommend just keeping the test general to coccidia.