Histopathological changes in experimental infestation of Paederus fuscipes in rats

The genus Paederus consists of approximately 621 species associated with outbreaks of dermatitis. Our aim was to determine gross and microscopic changes induced by Paederus fuscipes. Adult P. fuscipes beetles were collected from infested house and then sent to laboratory. In the first group beetles were placed on the shaved parts over the shoulders of each rat. In the second group smashed insect materials were rubbed over the ear of examined animals. Gross changes after 12 hr were noticed as erythematous papules and in 72 hr the red elevated area became bigger and swollen. Microscopic examination revealed edema and mild infiltration of inflammatory cells (lymphocytes and eosinophils) after 12 hr, cell swelling and vacuolar degeneration in basal and squamous cells after 24 hr, but by 72 hr the epidermal cells were necrotic with intense accumulation of fluid and vesicles formation. Gross and microscopic changes were compared between rats exposed with squeezed beetle materials and rats exposed to live beetles. The typical gross changes were maculopapuls on the skin that histologically showed dermal edema and infiltration of lymphocytes and eosinophils.