Specialized Diagnostics: Total Worm Count

This is used, most often on ruminants, to quantify and identify the helminth parasite burden in the lumen, and sometimes the mucosa (larval stages of nematodes), in part or all of the gastro-intestinal tract. The technique is most often applied to the abomasum.

Careful recovery of all the contents of part or all of the gastro-intestinal tract allows quantification of the nematodes and cestodes present. In addition, all or part of the mucosa of a section of the tract can be examined for nematode larvae, usually following incubation (fresh material) or digestion (previously frozen material). If parasite numbers are large, only measured sub-samples of the contents or mucosa are examined. The technique involves recovery and sieving of the tract contents, fixation of the parasites and quantification and identification of the helminths. There are a number of variations to the basic technique in the literature, but the basic principle for all is the same.

For accurate counts it is best to have the gastro-intestinal tract from a freshly-killed animal or from one that was well frozen immediately after death. Parasites from tracts that have undergone any decomposition may disintegrate before or during recovery. Also, for accurate quantification, it is very important that no contents are lost from the section of the tract being examined. This is sometimes difficult when material is also being collected for pathological, bacteriological or other purposes. A total worm count, even on a single part of the gastro-intestinal tract, is a time-consuming and labour-intensive procedure.