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CHAPTER 9 The Filariae
Nuclei not continuous; two at tip of tail
Sheath
Size range: 200-280 m long
FIGURE 9-4 Brugia malayi microfilaria.
Adults. The adult worms of B. malayi resemble
those of W. bancrofti in that members of both
species are white in color and threadlike in
appearance. The typical adult female worm measures
53 mm in length, whereas the adult male
measures 24 mm in length.
FIGURE 9-5 Brugia malayi microfilaria. Note the sheath
and characteristic nuclei in the tip of the tail (Giemsa stain,
×400).
TABLE 9-2
Parameter
Size range
Sheath
Arrangement of nuclei in
tail
Brugia malayi Microfilaria:
Typical Characteristics at
a Glance
Description
200-280 µm long
Present
Presence of two distinct
nuclei in the tip of
the tail; the
organism tissue
tends to bulge
around each of the
two nuclei
Laboratory Diagnosis
Although a limited number of documented B.
malayi microfilariae have been recovered, examination
of stained blood films serves as the best
method for diagnosis. Because B. malayi generally
exhibits nocturnal periodicity, specimens collected
during the nighttime hours are most likely
to yield large numbers of circulating microfilariae.
Subperiodic organisms may appear and this
possibility should be considered when determining
specimen collection protocol. The Knott
technique may also be used. Serologic methods
have also been developed and are now
available.
Life Cycle Notes
B. malayi may be transmitted by the mosquito
genera Aedes, Anopheles or Mansonia depending
on the location and animal reservoirs present.
The Anopheles mosquito can also transmit W.
bancrofti so co-infection can theoretically be
possible. All other aspects of the life cycle of B.
malayi are similar to that of W. bancrofti.
Epidemiology
Areas of the world in which the mosquitoes
breed are the primary locations in which B.
malayi may be found. These include the