The effects of diethylcarbamazine on the ultrastructure of microfilariae of Wuchereria bancrofti in vivo and in vitro.

An ultrastructural study of microfilariae of Wuchereria bancrofti was performed after treatment in vitro and in vivo with diethylcarbamazine citrate (DEC). The morphological alterations produced by treatment in vitro with 5 micro g/ml of DEC were the loss of microfilarial sheaths and lysis of the cytoplasm, with the destruction of all organelles and the formation of several vacuoles, the contents of which presented various degrees of electron-density, or showed an empty appearance. Some of these vacuoles seemed to be extruding from the cytoplasm as apoptotic bodies and others presented organelles inside. Similar alterations were observed after in vivo treatment. At 40 min after treatment of a microfilaremic individual with DEC, almost all microfilariae observed had lost their sheaths; and, in some of them, remains of the microfilarial sheath on the larval surface could be detected. Numerous vacuoles were observed, mainly in the hypodermis and somatic cells, showing organelles inside or an empty appearance. Condensed chromatin was also observed in some somatic cells. At 1 h after treatment of a microfilemic individual with DEC, microfilariae presented drastic morphological alterations, with large vacuoles within somatic cell cytoplasm and complete lysis of all cellular organelles. Therefore, both treatments with DEC in vitro and in vivo had a direct mechanism of action on the microfilariae of W. bancrofti, including organelle damage and apoptosis.