Nasty parasite causes summer lamb deaths

Nasty parasite causes summer lamb deaths


Sheep
INCREASING ISSUE: Sheep producers are urged to be on the lookout for weak or lethargic sheep - a sign of barber's pole worm infestation.

INCREASING ISSUE: Sheep producers are urged to be on the lookout for weak or lethargic sheep - a sign of barber's pole worm infestation.

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SHEEP producers are well experienced in recognising and treating signs of worm infestations in their sheep, but one particular parasite is becoming more common - barber's pole worm.

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SHEEP producers are well experienced in recognising and treating signs of worm infestations in their sheep, but one particular parasite is becoming more common.

Barber’s pole worm – Haemonchus contortus – does not behave like other worms. The most common sign of a problem with BPW is when lambs in good condition start dying in mid-summer, with no signs of scours, usually about two to three weeks after summer rain.

Deaths in ewes, rams or wethers can occur, but these are rare in my experience in SA. Unfortunately, it is usually the best lambs that are affected, especially if they have been in a confinement feeding situation during summer, as will be the case for many sheep this season in semi-arid regions such as the Mallee, Yorke Peninsula and West Coast.

Once BPW has been diagnosed, drench all affected mobs immediately.

Although deaths may seem to begin suddenly, lambs may have appeared to be weaker or lacking energy prior to this. This is because the parasite sucks blood from the sheep and causes profound anaemia (blood loss).

If the membranes in the eyelids of sick lambs or ewes is inspected they will look white, rather than the usual pink colour. Another sign, more visible in ewes, is the development of ‘bottle jaw’ – fluid swelling under the throat – again caused by blood loss.  

This parasite is one of the most prolific egg layers known, with a single adult worm able to produce 10,000 eggs a day. Total worm egg counts in affected mobs of sheep can be 20,000 to 30,000 eggs a gram. Beware though – immature worms can kill sheep and the worm egg count could still be lower at that time.

This parasite also lives in the fourth stomach (abomasum) of the sheep, so it will not be visible in the intestines. Adult worms are about one to two centimetres long and have a red and white striped appearance. Immature worms are shorter and red coloured.

What to do?

If you suspect BPW in your flock, immediately get a worm egg count done on a manure sample from that mob. If any recently deceased sheep are available an autopsy is highly recommended. You can even do a basic autopsy yourself and send photos to your vet or PIRSA veterinary officer.

Once BPW has been diagnosed, drench all affected mobs immediately. Fortunately, worm drench resistance has not been reported in the semi-arid parts of SA very often, although some drenches are more specific and will have longer duration for this parasite than others. Contact your livestock consultant, vet or PIRSA district veterinary officer for further advice.

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