Volume 11, Issue 5
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



Counts of circulating microfilarise and eosinophils were obtained at 90-minute intervals during 24-hour periods from twelve patients infected with , among other parasites.

On the average, both variables showed higher counts at night than during the day. The microfilarial rhythm was the more regular and it showed the greater peak-to-trough difference, when changes were expressed as per cent of series mean.

The microfilarial rhythm, as such, persisted following minor alterations of adrenal function, including ACTH administration and pre-treatment with Δ-9α fluorocortisol acetate (ΔF).

Circadian periodic changes in eosinophil count are demonstrated, apparently for the first time, under standardized conditions in tropical patients infected with , among other parasites. This eosinophil rhythm, however, is more irregular than that recorded for non-infected subjects in the temperate zone. This finding, in turn, obscures the question whether the rhythms in counts of microfilaria and eosinophils in human blood share some of the underlying mechanisms. Therefore, future work, with appropriate sample size, on adrenal mechanisms of microfilarial periodicity should preferably be based on more direct indices such as plasma 17-hydroxycorticosteroids. Such work seems warranted, on the basis of several preliminary and positive findings made during a period of adrenocortical escape from ΔF-suppression. First, correlation coefficients for microfilarial and eosinophil counts in three patients studied, were higher than the corresponding r obtained before treatment and two of these r values were statistically significant. Second, circadian components of the variance in microfilariae and eosinophils were more prominent after ΔF than before. Third, the external timing of microfilariae rhythm in the three subjects studied after ΔF was more closely synchronised than before ΔF.


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