Experimental chemotherapy of filariasis

Abstract

This paper offers data obtained from a fairly large project on experimental chemotherapy of several filarial infections. The first work, performed in cotton rats which naturally harbour in filarial parasite known as Litomosoides carinii, showed definitely that this infection in this animal can be eradicated by the intensive administration of any of several antimony-containing drugs, these drugs having their principal action on the adult phase of the parasite. Methods essentially similar to those used in the experimental animals were then applied in infections with three human filarial worms—namely, W. bancrofti, L. loa, and O. volvulus. In the work with W. bancrofti, 114 persons infected with this parasite were treated with any of several antimony-containing drugs, or with an arsenical, and fifteen additional patients were kept untreated as a control group. The results obtained in the treated group varied considerably, depending upon the drug used. The most satisfactory drug, in respect both of the patients' tolerance and of the effect on the parasites, was neostibosan, a pentavalent antimony preparation. Of thirty-five subjects treated with neostibosan, twenty-five appeared entirely to lose their infections with W. bancrofti within 2 years of the end of therapy. All the control patients remained infected for this period of observation, and some of these had substantially more intensive infections at the end of this time than at the beginning. Only three subjects with L. loa infection were available for experimentation. Of these, one had many microfilariae in his day blood; and the other two persons had marked symptoms (Calabar swellings) but no circulating microfilariae prior to therapy. After intensive treatment with neostibosan, the number of embryos fell by over 90 per cent. within 15 months in the blood-positive subject, and all symptoms in the other two individuals disappeared within 8 months after treatment. No control subjects on this part of the work were available. Altogether, forty subjects with O. volvulus were studied but, for reasons states in the text, data on only sixteen can be reported. Of these sixteen, eight were treated intensively with neostibosan and eight were kept untreated as a control group. Ten months after therapy, no essential difference between the treated and control groups could be seen in the numbers of microfilariae in skin biopsies, although during the course of treatment, a marked reduction in the numbers of microfilariae in the skin seemed to occur. It was concluded that neostibosan is without permanent effect on onchocerciasis.