BLOOD AND TISSUE NEMATODES
This family consists of members which have a unique stage in their life cycle
called the microfilaria. This stage is equivalent to the rhabditiform larva of other
nematodes. This is the stage which is infective to the vectors and, therefore, it must
reach either the circulatory or lymphatic system. The microfilariae of some species
retain the elongated egg membrane which shows as a characteristic sheath. In other
species, the membrane is discarded and these are referred to as being unsheathed.
Figure 4-29. Typical microfilaria.