Periodicity in microfilaraemia is, as I am sure you can imagine, quite
complicated. There have been any numbers of hypothesis as to why it
happens including the one mentioned by Mark that is oxygen tension. All
of these hypothesis, although theoretically plausible, lack scientific
evidence to prove any one of them. The classical one mentioned by Mark is
that when a person retires to bed the oxygen concentration goes down and
the carbon dioxide levels go up and the microfilaria are triggered back
in the peripheral blood circulation. This sounds OK but why then do
people kept awake and moving around by scientists waiting to take blood
to detect Microfilaria still get the microfilaria in their blood.
I am sure like most parasites life is not as compartmentalised as we
would like and the truth is a combination of a number of factors. Like
most circadian rhythms the periodicity of microfilaria will change with
shift work or travel.
On Mon, 18 Sep 1995, Mark Siddall wrote:
> In article <43hv12$dm2$1 at mhafm.production.compuserve.com> Eberhard Kniehl <100674.1442 at CompuServe.COM> writes:
> >conc.: microfilariasis
> >My question:
> >What happens when the patient is transferred by plane, lets say
> >from Asia to Europe. Do microfilaria have a strict 24h
> >periodicity, that means: in Europe Wuchereria bancrofti will
> >appear in peripheral blood in the afternoon, or do they have a
> >day-light triggered cycle?
>> My understanding is that microfilariae do not carry pocket watches and that in
> fact, this has more to do with the worms' responding to human diurnal
> physiological changes. I seem to recall something about oxygen
> tension in the capillary beds of the lungs... but I'm sure someone else out
> there has more insight.
> Mark E. Siddall "I don't mind a parasite...
>mes at vims.edu I object to a cut-rate one"
> Virginia Inst. Marine Sci. - Rick
> Gloucester Point, VA, 23062