The assessment of nematodes as they generate and die is not a simple thing to do due in part to the complexity of the organism, and the fact that still relatively little is known about their physiology and internal biology. Indeed, the pathological changes in the internal organs of the worms are still only recognized in general terms. Obviously dead worms are easily recognized (when fractured, or calcified, etc.) but the lesser obvious changes can be difficult to detect and interpret. The point at which a worm can be defined as dead is not a simple matter; cessation of motility is currently the most commonly used parameter for this but it is not always a robust indicator and better indicators are needed. Various methods can be used to assess the presence, viability, and functionality of nematodes but these must be used with an understanding of the situation at hand and the specific questions being addressed. Careful use of appropriate statistics is essential given the complex nature of the target organism and the variability in the changes that can be seen within even one anatomical component of these worms. Histological assessment of the parasites present in both parasitized host tissues and isolated worms used in in vitro experiments can provide information that gives a more detailed understanding of the changes in nematodes as they degenerate and die. Understanding of the pathways nematodes follows as they degenerate naturally or under various external pressures, such as chemotherapy, remains a fascinating and potentially productive goal for investigation. Likewise, a complete understanding and definition of specific indicators that reflect parasite load, parasite viability, and damage, or reduced fecundity, will greatly help the fight against those nematode infections that currently cause significant burdens of disease in humans and animals.
Part of the book: Nematology
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.
Part of the book: Roundworms