Of 26 subjects from one community examined at different hours of the day, on one, two or three days, 24 exhibited greater mean numbers of microfilariae in late afternoon or evening than in the morning. The difference between morning and afternoon levels was highly significant. Maximum numbers of microfilariae appeared in the afternoon with a possible peak around 7 p.m., but there was no evidence of a definite period when minimum numbers were present. Of 2 persons examined at different hours on two days and of 5 persons examined on three days, all except one exhibited a fairly consistent microfilarial fluctuation at each examination.
A study of the microfilarial fluctuation among 13 to 26 persons in each of four widely separated communities revealed that the periodic tendency was common around the island.
Children, aged 6 to 14 years, whose bloods were examined both morning and evening, 4 on six days during the year and one on four days, with one exception, revealed more microfilariae in evening than morning smears.
Microfilarial counts of 10 positive subjects examined once a month during one year and of 6 subjects examined 11 times during one year revealed that December to January was the peak period for microfilariae and April was the low month.
Laboratory of Tropical Diseases, National Institutes of Health, Bethesda, Maryland.
Field Director, Filariasis Foundation, School of Medicine, University of Southern California.
Director, Institut de Recherches Médicales, Papeete, Tahiti.
Technician, Institut de Recherches Médicales, Papeete, Tahiti.