We confirmed that filarial larvae established intralymphatic infections by imaging motile, fluorescently labeled BmL3 within GFP-tagged Prox-1+ collecting vessels (lymphangions) of the infected hind limb (Figure 1B and Supplemental Video 1; supplemental material available online with this article; https://doi.org/10.1172/JCI140853DS1). The gene discussed is PROX1; the disease is infection.