The periodicity of microfilariae V. Stimuli affecting the periodic migration of the microfilariae of Wuchereria bancrofti and of Loa loa in man

Abstract

1. (1) In patients infected with W. bancrofti, the microfilarial count at night is rapidly diminished by the breathing of oxygen, by muscular exercise and by hyperventilation. 2. (2) In patients infected with L. loa, the count was not affected by any of the stimuli studied, apart from the administration of insulin or a general anaesthetic. The microfilariae of A. perstans were not changed in number by any of the procedures employed. 3. (3) The response of microfilariae to the various stimuli varies greatly, depending on the species of filaria studied. 4. (4) According to our conception, microfilarial periodicity depends on an alternation between a passive phase (when the microfilariae are distributed throughout all the blood and therefore appear numerous in the peripheral circulation) and an active phase (when they accumulate in the capillaries of the lung). This accumulation is due to an active response of the microfilariae to some still unidentified stimulus provided by the 24-hour physiological rhythm of the host.