Page 75 - The Veterinary Care of the Horse

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Figure 2.23 Strongyle egg as seen under the microscope

The worm eggs are not uniformly distributed throughout the droppings so correct

sampling is essential for an accurate result. The sample should be collected from five
different faecal balls within a single dropping and within 4 hours of being passed. The

sample should be placed in a leak-proof container or bag in a cool place (below 6°C/43°F)
with the air squeezed out and examined as soon as possible to prevent the eggs from
hatching. Avoid posting samples on a Friday or at the weekend.

A negative worm egg count does not exclude the presence of worms. For example, if the

horse has just been treated with an anthelmintic, there may be very few adults left to produce
eggs. However, the horse may still be infected with large numbers of larvae unless a
larvicidal drug was used. A low positive worm egg count (less than 200 epg) does not justify

treatment, since a few worms will help to boost the horse’s immunity to infection.

BLOOD TESTS

When large numbers of worms or larvae are present, the following results may be seen on

blood tests:
• anaemia due to blood loss

• raised neutrophils and eosinophils as a response to the parasites

• low plasma albumin