Case #185 – August, 2006

A worm measuring approximately 11 mm in length was sent to CDC for identification by a laboratory in the Southeastern United States. The following images were obtained by placing the worm on a 1″ × 3″ glass slide and gently “floating” a 24 × 30 mm glass coverslip on top of it with water. Figure A shows the anterior end of the worm. Figures B and C (a digital zoom of B) show the posterior end of the worm. All images were captured at 100× magnification. Based on the images, identification at the genus level, as well as determination of whether the worm is male or female, is possible. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

The worm shown in this case was an adult female Ancylostoma sp. Diagnostic features were:

the presence of teeth in a large buccal capsule. Necator americanus has cutting plates. Ancylostoma caninum has three pairs of teeth and A. duodenale has two pairs. It was difficult to determine exactly how many pairs were present in this specimen.
a small spine can be seen at the posterior end in Figure B, and more clearly in Figure C. This feature is seen in female A. caninum.