Electron microscopic studies on microfilariae of Dipetalonema viteae and Litomosoides carinii: the occurrence of intracellular parasites after treatment with metrifonate or diethylcarbamazine.

Microfilariae of Dipetalonema viteae and Litomosoides carinii were studied by means of electron microscopy after oral treatment of their hosts with metrifonate (3 x 100 mg/kg) or diethylcarbamazine (3 x 250 mg/kg). These dosages led to the disappearance of microfilariae from the peripheral venous blood. However, in numerous organs blood capillaries or interstitial spaces contained degenerating microfilariae. In these cases the cytoplasm of the microfilarian cells was completely lysed, whereas the cuticle seemed to be unaffected, at least initially. Microfilariae of both species were also often found intracellularly especially in liver and muscle cells after application of both drugs. The intracellular microfilariae, however, had fewer or even no lesions, suggesting that they might escape the activity of the drug.