Case #339 – January, 2013

The CDC conducted a survey with the Ministry of Health in Uganda to evaluate the prevalence of filariasis among the local population. Skin snips and blood specimens were collected and sent to a regional laboratory for preparation. Thick blood films were made and stained with Giemsa, and then forwarded to the CDC in Atlanta for evaluation. The objects seen in Figures A–D were seen in low numbers on several of the patients’ smears. The object in Figure A measured 325 micrometers in length; Figure B shows a close-up of one of its ends. The object in Figure C measured 237 micrometers in length. The object in Figure D measured 225 micrometers in length. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

The objects shown in the images were fungal elements (artifacts) and a diagnosis of No Parasites Found (NPF) was made. Contamination of drying slides, stains, and buffers with airborne fungal conidia is not uncommon. Often these conidia (most notably with the genus Helicosporium) are long and coiled, resembling microfilariae and possibly causing diagnostic problems. In this case, the structures have defined demarcations between the cells, a feature not seen in true microfilaria. Also, in this case, the structures are all very long and slender, with a longer length-to-width ratio than seen in the microfilariae.