with Phil Rennie
The Barber’s Pole worm (Haemonchus contortus) season will soon be upon us…
As a sub tropically-adapted parasite it prefers the type of warm, humid conditions found as we move into summer and autumn. It sucks blood from the stomach lining of naive small ruminants; large burdens can extract enough blood to kill lambs/kids/cria and even adults in some cases.
This gut infestation often strikes without warning; mostly in late summer and autumn, though the odd cases can occur prior to the New Year. Most outbreaks occur after a spell of hot, dry weather followed by some moisture. Typically 25mm (one inch in old school terms) of rain is enough, however a few heavy dews can also be enough to set up a challenge.
With the right environmental conditions, and in the absence of effective management/control, ‘outbreak’ situations occur where larval numbers on pasture rise rapidly. Their ingestion by grazing stock results in the sudden appearance of ill-thrift, lethargy and at times apparent ‘sudden’ death - without any obvious sign of diarrhoea.
One of the problems with Barber’s Pole is in predicting the seasonal onset of challenge. Unfortunately, studies have found no correlation between farms for the timing and severity of Barber’s Pole challenge. Even though a particular farm has high levels, doesn’t mean nearby farms will be similar. And even on the same farm, the relationship between Barbers Pole levels in ewes and lambs may not be consistent.
Testing by way of an early faecal egg count (FEC) of lambs, even while still on mum, can be a guide. Bearing in mind egg counts of unweaned lambs do vary a lot; with very high FECs indicating Barbers Pole is likely to be present.
A further step to consider is a larval culture on that same faecal sample. The eggs are hatched and grow into larvae; then examined by microscope and a composition of the species present made.
On-farm clues need to be monitored also entering into summer. When handling lambs/other young ruminants, look for paleness of the eye membranes. Normal eye membranes (the pink tissue under the lower lid is commonly used) are a pink colour. Gums are less easy to assess; as they may look pale, even in healthy lambs.
General flock/group control measures include keeping drench intervals for lambs grazing contaminated pasture to no more than four weeks to be on the safe side. Monitor ewes, two tooths and lambs separately. It may be necessary to treat two tooths for Barbers Pole without all MA ewes requiring a treatment.
In terms of further diagnostic options to track progress, more faecal egg counts of lambs just prior to when they require their next drench can be enlightening. As mentioned, if high counts are still running high/yet to develop, tactics for controlling Barbers Pole can be modified.
In terms of specific drench options in clinic, feel free to ask your local vet for advice on which product is best for your flock/group of small ruminants.