Life Cycle of <i>O. volvulus</i>

<p>Mean dimensions of parasite stages are: Adult females, 35–70 cm × 400 µm; adult males, 2–4 cm × 150–200 µm; microfilariae, 250–360 × 5–9 µm; L1 larvae, 200 µm × 12 µm (front) and 20 µm (rear); L3, 440–700 × 20 µm. L1 larvae molt into L2, pre-infective larvae, and L2 into L3, infective larvae [<a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0030371#pmed-0030371-b005" target="_blank">5</a>]. (Illustration: Giovanni Maki, derived from a CDC image at <a href="http://www.dpd.cdc.gov/dpdx/HTML/Filariasis.htm" target="_blank">http://www.dpd.cdc.gov/dpdx/HTML/Filariasis.htm</a>)</p

The Incidence of Blindness and Excess Mortality Rate, by Sex, Plotted against <i>O. volvulus</i> Microfilarial Load

<p>Arithmetic mean of microfilarial counts from two skin snips, taken from the right and left ileac crests, using a 2-millimeter Holth corneoscleral punch. (A) Blindness; (B) excess mortality rate. Error bars denote 95 percent confidence intervals [<a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0030371#pmed-0030371-b010" target="_blank">10</a>,<a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0030371#pmed-0030371-b022" target="_blank">22</a>].</p