A 10-YEAR OBSERVATION ON EXPERIMENTAL-INFECTION OF PERIODIC BRUGIA-MALAYI IN MAN

This paper reports the results of 10 years of observations on the clin ical manifestations, pathology and immunity to filariasis and aetiolog ical biology of filariae in three volunteers (first author and his fam ily members) who were inoculated experimentally with infective larvae of periodic Brugia malayi in 1981. The changes in clinical symptoms an d signs were recorded systematically. Microfilariae were first detecte d at 41 and 46 weeks after inoculation in two subjects and remained de tectable in small numbers until 8-8.5 years after infection. The micro filarial density fluctuated at 1-2 mf 120 mu l(-1). Thereafter no micr ofilariae were detected in 12 blood sample examinations, suggesting th at the adult reproductive period of periodic B. malayi could last up t o 8-9 years in the human body. Eosinophilia occurred mainly before and at the initial stage of microfilaraemia. An increase in the lymphocyt es was observed to some extent at 2-156 weeks after infection. Biopsy at the inoculation site 6 weeks after inoculation showed infiltration of the lymph node by inflammatory cells, mainly eosinocytes, lymphocyt es and monocytes. Lymphangiectasis and lymphostasis were observed in b oth limbs and pelvic regions by lymphangiogram taken 11 weeks after in oculation. Antibodies against B. malayi first appeared at 2-5 weeks af ter infection, peaked at 12-56 weeks and thereafter declined gradually . Subjects A and C became antibody free but subject B remained positiv e to antibody against B. malayi 10 years after infection. E-rosette fo rming lymphocytes became lower than normal at 11 weeks and recovered t o normal within 10 years after infection.