Case #409 – December 2015

A 42-year-old dairy farmer sought medical attention for watery diarrhea, fever, and nausea that he had been experiencing for about one week. A stool specimen was collected for ova-and-parasite (O&P) work-up that included a formalin ethyl-acetate concentration. A fecal smear was prepared from the concentrate and stained with Kinyoun’s modified acid-fast stain. Figures A–E show what was observed at 1000x magnification with oil in moderately high numbers on the acid-fast stained fecal smear. The stained objects measured 5 micrometers in diameter on average. What is your diagnosis? Based on what criteria? What, if any, other tests would you recommend?

Figure A

Figure B

Figure C

Figure D

Figure E

This was a case of cryptosporidiosis caused by Cryptosporidium sp. Diagnostic morphologic features shown in the figures were:

acid-fast stained objects within the size range of Cryptosporidium sp.
presence of sporozoites within some of the oocysts (best seen in Figures B and C)

Kinyoun’s modified acid-fast stain may not be part of a standard ova-and-parasite (O&P) examination so laboratorians and health care providers should be aware that direct fluorescent antibody (DFA) assays and enzyme immunoassays (EIA) are also available for diagnosing Cryptosporidium. Molecular methods such as PCR are necessary to determine the species of Cryptosporidium which may be useful in determining the source of infection such as during an outbreak investigations.