Case #196 – January, 2007

A missionary traveled to various countries in sub-Saharan Africa for one year. He went to his physician complaining of abdominal pain and occasional diarrhea which he experienced since his return to the U.S. He reported he swam in various lakes while he was abroad. An ova and parasite (O & P) stool examination revealed objects, measuring 135 µm, like the one shown in Figures A and B (200×). The images show the same area of the slide but two separate focal planes. What is your diagnosis? Based on what criteria?

Figure A

Figure B

This was a case of schistosomiasis caused by Schistosoma mansoni. Diagnostic features were:

a miracidium is visible in the egg (Figure A, bracket).
an unoperculated egg within the size range for S. mansoni (118-180 µm in length).
presence of the typically prominent lateral spine, which was visible in a different focal plane (Figure B). Suspicious objects should be observed in different focal planes or key diagnostic features could be overlooked.

Figure A

Figure B