Understanding the Pathogenesis of the Major Human Filarial Nematode Infections

Abstract

Filarial infections are very common across the animal kingdom despite their tendency to be host specific. Although often being silent infections with relatively little clinical consequence, three filarial infections can cause significant morbidity: onchocerciasis (OV) (caused by Onchocerca volvulus) and lymphatic filariasis (LF) (caused by Wuchereria bancrofti or Brugia sp), and in the veterinary world, the common canine condition of dirofilariasis. Successful elimination programs for these have been developed in the endemic countries based on extensive chemotherapy distribution, and these have catalysed a much greater understanding of the treatment and epidemiology of these infections. In contrast, the pathogenesis and clinical presentation of the two human filarial diseases, and a third, loiasis—which can complicate chemotherapy distribution in OV and LF co-endemic areas—are still not well understood. This present discussion addresses recent knowledge concerning the pathogenesis and presentation of the two major human filariases and makes suggestions as to approaches that could be taken to better understand their pathobiology and clinical forms. Better understanding and improved monitoring of the clinical condition are both likely to augment the already successful progress to global elimination.