01/21/2026
The Barber Pole worm (Haemonchus) in sheep, goats and alpacas, small strongles (Cyanthostomes) in horses and donkeys, and the Brown Stomach (Ostertagia) in cattle all undergo an inhibited phase in the gut wall. When parasite worm burdens build to high levels while grazing parasite contaminated summer pastures, newly acquired parasites often stop development in the gut wall as a protective mechanism for both the parasites and their host animals (it is not in the best interest for these parasites to kill their host animals because they die with their host). These inhibited larvae are embedded in the gut tissues and can remain in this state for months plus they are refractory to normal deworming practices. As temperatures decline when winter approaches and the old worm parasites die off, the conditions in the gut begin to improve triggering the inhibited larvae to start redevelopment, growing into egg-laying adult parasites attached to the gut wall ready to seed the spring pastures. F***l worm egg counts conducted in midwinter will determine whether these inhibited larvae have emerged and are shedding eggs. These emerging larvae can also cause clinical disease in the host animals while ensuring immediate recontamination of the spring pastures. We often find equine and small ruminant samples with counts over 1000 worm eggs/sample during this late winter period. Monitoring your animals’ f***l worm egg counts will alert you to this problem and determine whether treatment is necessary! Go to www.midamericaagresearch.net for complete instructions.
