Nematode chemosensory behaviors underlie fundamental processes and activities in development, reproduction, tropisms and taxes. For parasitic species, chemosensation is essential for host seeking and host and tissue invasion behaviors. Such fundamental biology presents an attractive target for developing behavior-blocking anthelminthic drugs, but the anatomy and functional relevance of parasitic nematode chemosensory machinery are poorly understood. The goals of this study were to better understand the chemosensory apparatus and behaviors of infectious stage Brugia malayi (Spirurida: Onchocercidae), a mosquito-borne nematode and etiological agent of Lymphatic Filariasis. Scanning electron microscopy revealed that amphids, the major chemosensory organs, are present on adult B. malayi and arranged in a conserved manner. Internal sensory neuroanatomy display structural differences between life stages, and a simpler chemosensory architecture as compared to free-living nematodes. Positive and negative chemotactic behaviors were identified for a repertoire of chemicals with known chemostimulatory activity for the mosquito host that may facilitate host-selectivity and invasion. This is the first description of chemosensory anatomy and chemotactic behaviors in B. malayi that reveal the involvement of chemosensation in parasite transmission and host invasion
