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4. Parasitology 169
7. Remove the syringe from the filter holder and draw up
approximately 5ml of air.
8. Reconnect the syringe to the filter holder and push the air
through the filter over the dish containing disinfectant,
to remove excess water from the filter. Discard the disinfectant
solution into a sink.
9. Remove the syringe from the filter holder. Dismantle
the filter holder and remove the membrane filter using
forceps.
10. Place the membrane filter, top side facing up, on a slide.
Add a drop of sodium chloride solution and cover with a
coverslip.
11. Examine the entire membrane for motile microfilariae,
using the ¥ 10 objective. (Microfilariae will still be motile
in a “night blood” specimen examined the following
morning.
12. Count the number of microfilariae in the preparation and
divide by 10 to give the approximate number of
microfilariae per ml of blood.
Considerable experience is required to identify unstained
microfilariae. It is recommended that identification be performed
on stained preparations (see below). To prepare a
stained preparation, follow the method described above, with
the following modifications:
Fig. 4.125 Drawing up citrated blood into a syringe
Fig. 4.126 Filtering the blood sample
Fig. 4.127 Rinsing the filter