Scanning electron microscope study on larvae of Wuchereria bancrofti from the vector and from experimental rodent...

The surface structures of larvae of Wuchereria bancrofti from Liberia were examined by scanning electron microscopy. For this study microfilariae from man, first-stage, second-stage, and third-stage larvae from the vector Aedes aegypti, and fourth-stage larvae from the experimental rodent hosts Mastomys natalensis and Meriones unguiculatus were available. From these larvae the structure of the anterior ends, the cuticle in the midbody regions, and the posterior ends are presented. As an obvious structure at the anterior end of the microfilaria and the first-stage larva there is a cephalic cap with a hook on its left side. Three spines are found on the right side close behind the border of the cap. The amphidial openings are found immediately beside the cephalic cap. A simply formed oval mouth is found in the second-stage larva. A small elevation is situated on each side of the mouth. On the anterior end of the third-stage larva there are eight papillae. The four outer papillae are round, the four inner papillae are cone-shaped. The caudal extremity of this larva carries three characteristic bubble like papillae. The mouth of the fourth-stage larva from the experimental rodent host is surrounded by an oral field. The cephalic papillae are indented and the amphidial openings are associated with papillary protuberances. The cuticle of these larvae is regularly annulated. On the caudal extremity, the dorsal papilla is reduced.