Case #472 – July, 2018
A 22 year old man diagnosed with gastroenteritis underwent subsequent gastrointestinal endoscopic examination. The gastroenterologist observed a worm which he extracted from the duodenum and sent to the laboratory for identification. Stool samples were also processed for ova and parasites (O&P) examination. Images of the worm and objects seen in a wet mount preparation from a formalin-ethyl acetate (FEA) concentration of the stool samples were captured by the laboratory technologist and sent to DPDx for identification. Travel history was not provided. The objects in Figures C – E measured 130 µm in length by 65 µm in width on average. The adult worm measured approximately 70 mm by 18 mm. What is your diagnosis? Based on what criteria?
This case and images were kindly provided by The Institute of Medicine, Tribhuvan University and Teaching Hospital, Nepal.
This was a case of fasciolopsiasis caused by the intestinal trematode Fasciolopsis buski. F. buski is one the largest parasites that infect humans. The eggs are very similar in size and appearance and difficult to distinguish morphologically from eggs of Fasciola hepatica and Gastrodiscoides hominis. Diagnostic features were:
- morphology and location of the worm.
- size and morphology of the eggs were consistent with the size range of F. buski: (130-150 µm in length by 60-90 µm) but as noted, F. hepatica eggs fall within this size range as well. G. hominis may be slightly larger (130-160 µm).
- presence of an indistinct operculum (Figure C, blue arrow).
Eggs of F. buski are sometimes broader at the end with the operculum, as the egg in the image shows. Eggs of F. hepatica often have a roughening or irregularity at the abopercular end.
For more information about F. buski, please visit: https://www.cdc.gov/dpdx/fasciolopsiasis/index.html
Images presented in the dpdx case studies are from specimens submitted for diagnosis or archiving. On rare occasions, clinical histories given may be partly fictitious.
DPDx is an educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.cdc.gov/parasites/.