Parasites, Laboratory Practices…. and a Case Study!

 Over the past week or so we have been covering material on protozoan parasites which included the standard procedures used in diagnosis as well as some specialized techniques.  As stated in my post from last week, these life forms can present difficulty in the processing, detecting, and diagnosis of disease compared to other organisms such as bacteria.

The standard techniques for the detection of intestinal parasites include a direct wet prep, a concentrated method, and a permanent stain.  The wet prep allows a technologist to look for motility of living, mobile forms of protozoan parasites known as trophozoites, while the concentrated prep increases the likelihood of observing a parasite, thus increasing the overall sensitivity. The permanent stain, usually a trichrome stain, aids in the ability of viewing cysts, eggs, etc by adding color to morphology which would normally not be easily observed. 

Some organisms may need special staining in order to be detected.  These include Cryptosporidium, Cyclospora, and Isospora which require an Acid-Fast staining technique to be utilized for their oocysts to be observed.

Here is a case study I came across on the CDC website which gives an example of laboratory methods in the detection of protozoan parasites.

“A 34-year-old missionary worker sought medical attention for abdominal pain, nausea, and watery diarrhea after returning from visiting friends in Central America. A stool specimen was collected for laboratory testing and a modified Kinyoun’s acid-fast stained smear was prepared.  The objects of interest measured 8-9 micrometers in diameter on average.”¹

 



Centers for Disease Control and Prevention-

DPDx Case #374-June,2014 (Figure A)¹

 

Based off the information provided in the case study along with the picture, it can be concluded that the causative pathogen was Cyclospora cayetanensis.  One of the clues which could aid in determining this is the fact that an acid-fast technique had to be used to view the oocyst.  Also, from our lectures I have learned that this organism causes traveler’s diarrhea and is endemic to Central America.

Here is the link to the case study I referenced in this post if you would like to see additional pictures.  There are also many other informative case studies available on their website which you might enjoy. 

http://www.cdc.gov/dpdx/monthlyCaseStudies/2014/case374.html

Works Cited

1. "Case #374 - June, 2014." DPDx - Laboratory Identification of Parasitic Diseases of Public Health Concern. CDC, June 2014. Web. 10 July 2014.