Microfilaraemia, filarial antibody, antigen and immune complex levels in human filariasis before, during and after DEC therapy. A two-year follow-up.

A study on the effect of DEC therapy on microfilaraemia and the immune status in 27 patients with W. bancrofti infection was carried out for two years. Persistence of microfilaraemia was observed in 4 out of 27 cases after one course of DEC therapy and were treated again for one week. On further follow-up, none was microfilaraemic upto Day 60. The mean filarial antibody titres of IgM and IgG showed a gradual decrease as assessed by enzyme linked immunosorbent assay (ELISA). The mean titres of circulating microfilarial excretory-secretory (ES) antigens and immune complexes (ICs) showed an initial increase during therapy, followed by a gradual fall upto Day 60. Filarial antigen was detected in urine of all the carriers during therapy. Excretion pattern of antigen in urine showed correlation with DEC dose. Reappearance of microfilariae (mf) in circulation in 12 patients after a year showed that DEC had temporary attenuating effect on adult worms or no effect on developing larvae, suggesting further treatment and follow-up of patients. Parasitological and immunoscreening at the end of 2 years showed that the presence of mf ES antigen in blood correlated with the appearance of microfilariae in blood.