Worm egg counts

Perfoming faecal worm egg counts with a microscope is a simple and quite inexpensive procedure that is used for the detection of anthelmintic resistance and parasite surveillance. The worm egg count (WEC) identifies the individuals that require worming if a targeted approach to parasite control is being used.

If the pretreatment WEC is compared with a post treatment count the method can be used to perform a ‘faecal egg count reduction test’. If the count has been reduced by >95% the treatment is deemed as being successful and no drug resistance problems identified.

The standard method is to use the McMaster flotation technique to count the worm eggs. This technique is good for quantifying strongyle eggs but not so good at quantifying tapeworm infestation. It does not account for the presence of migrating large strongyles or the encysted small strongyles. Ideally the WEC is performed on fresh faeces i.e. <12 hours old and if 24 hours old should have been refridgerated. Results are given in eggs per gram (EPG).

A general guide to results:

<200 EPG LOW 200-1000 EPG MEDIUM >1000 EPG HIGH

The equipment needed is a GX Microscopes Worm Egg Count microscope, a McMaster slide with some dilution flasks and a dropper.