... is sig-nificant lymphadenitis with clinical manifesta-tions such as headache, low-grade fever, and sin-gle or multiple lymph node enlargement, particu-larly in the neck. Involvement of the ... Important Causative Organisms of Tropical DiseasesVIIFig. 195 a – d. Filariasisa Microfilaria of Mansonella perstans, seealso Fig. 1 96 b High-power view of a Loa loa micro-filaria with granules ... dif-ferential diagnosis of the various microfilariaethat occur in the blood (see method on p 19).M. perstans microfilariae are 165 – 2 16 lm long(shorter than the others), slender, and un-sheathed....