Do I really need to worm my horse?

or ELISA enzymelinked immunosorbent assay blood tests can be used for tapeworms but are more expensive. Furthermore an ELISA detects the antigen the immune response to a parasite level thus the burden may appear high as antibodies are still circulating against the old burden even if the worms are now dead.
However there are means of interval dosing that do not require administration of a wormer regardless of whether the horse needs it. We must focus on what burdens are of concern and when
SPRING Performing a faecal egg count FEC for strongyles ivermectin or single dose pyrantel can be utilised if there are over 200 eggs per gram. Stronglyes were previously a huge concern for causing colic but thanks to ivermectin they have become less of a menace hence the need to protect the efficacy of this wormer by responsible use. Additionally treatment for tapeworms in the form of praziquantel or double dose pyrantel may be used in spring.
SUMMER FEC for Strongyles and treatment when the FEC indicates again with ivermectin or pyrantel.
AUTUMN we must treat for any encysted cyathostomes. Remember the larval cyathostomosis? Commonly these larvae will encyst and emergence can occur in late winterearly spring. Treatment of a heavy burden is advisable a five day course of fenbendazole or a single dose of moxidectin are licensed for encysted cyathostomes. However a large amount of dead worms and a huge inflammatory reaction can spell out a disaster in the form of colic so if theres a heavy burden your vet may recommend using the older and less potent but gentler course of fenbendazole first and then following up with moxidectin 46 weeks later to mop up any survivors.
Tapeworms can be treated with praziquantel or double dose pyrantel again at this time of year.
WINTER The same treatment or not! for strongyles when indicated if bot flies were a problem over the summer ivermectin or moxidectin will kill the larvae in the stomach.
From all of us here from VetHelpDirect we hope your horses have a wonderfully wormfree year ahead!