Histological Demonstration of the Organisms Causing Human Tungiasis in Eastern Uganda

Background: Tungiasis, a neglected tropical ecto-parasitic disease, has resurged in Sub-Saharan Africa, causing public concern and at times confusing diagnosis. In October 2010, following widespread human disease within the Busoga sub-region of Eastern Uganda the Ministry of Health sought to verify the cause. Tungal extraction was therefore performed to provide specimens for diagnosis. Aim: To identify the organisms enucleated from the feet of residents in two affected districts. Method: The formalin-preserved enucleate was macroscopically described, processed and embedded in paraffin wax. Sections four micrometers thick were then stained with haematoxylin and eosin and microscopically examined. Results: Histology showed cystic bodies with internal structures. At the periphery a multi-layered cuticle overlay a stratum of hypodermal cells. At the centre, distended globular sections lined by columnar cells characteristic of digestive epithelia had speckled content representing ingested human blood. Eccentric bipolar sections had convoluted microvillous epithelia typical of filtration-excretory surfaces. Eosinophilic rings formed sub-cuticular chains and central clusters, describing tracheal routes. Numerous eosinophilic anisocytic spheres were enclosed in circular sections lined by cuboid cells characteristic of ovarian epithelia. Fat globules and striated muscle were noted; the head, thorax and terminal abdomen were not seen. Conclusion: The structures described were distinct from those observed in cutaneous helminthiasis, cutaneous myiasis and acariasis. The organisms were thus reported as tissue-embedding haematophagous oviparous arthropods of the genus Tunga. Tungiasis has since been listed among the thirteen neglected tropical diseases of highest public health importance in Uganda.