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A histological study of the skin and nodule during the course of diethylcarbamazine treatment in onchocerciasis

Abstract:

Histological observations of the skin and nodules of 29 Guatemalan patients with onchocerciasis were performed semi-quantitatively during the administration of diethylcarbamazine (DEC). In the affected area of the skin, microfilariae appear to migrate immediately from the dermis to the epidermis where they are found encapsulated in micro-abscesses 24 hours later. An increase of mast cell degranulation was observed 3 hours after the first dose of DEC; thereafter eosinophils were seen to accumulate in the dermis. Thus the involvement of a type I hypersensitivity mechanism in the killing of microfilariae was suggested. An increase of histiocytes, loosening and degeneration of connective tissue, and dilatation of blood capillaries also occurred in the dermis. In contrast, these changes were much weaker in the unaffected skin areas of the same patients. Following DEC treatment the density of degenerated microfilariae increased in nodules containing fertile females. In such nodules, the degranulation of mast cells and accumulation of eosinophils and foreign body giant cells in the connective tissue were more marked than those in the nodules containing nongravid or degenerated adult worms. Adult morphology and the fecundity of females were apparently not affected by DEC treatment.