It’s not Fluke it’s Worms

Significant worm burdens can cause ill thrift and death in lambs.


Diagnoses that we make in the post mortem room can sometimes give us a skewed picture of livestock health locally and are often assumed to be the tip of the iceberg. A run of similar cases might therefore suggest quite a big iceberg!

At the moment we are being presented with ill thriven lambs by farmers who are concerned that liver fluke is the problem. So far, we have not found any evidence of fluke, but their worm burdens have been high enough to cause both ill thrift and death.
Trace element deficiency is common in autumn and in some areas lambs are most often short of cobalt. However, since the start of September low selenium levels have been found in 83% of liver samples tested. This included tissue from both ill thriven lambs and ewes.

The histories provided suggest that group of lambs had been failing to gain weight or losing weight for several weeks before being investigated. On this basis we would recommend that:

  • Worm egg counts of ewe lamb replacements and store/fattening lambs are checked as soon as possible and then monthly.
  • Trace element status is assessed especially if concentrates are not being fed. Blood samples could also be used to check for exposure to liver fluke using the fluke antibody ELISA test, giving the earliest indication that exposure has occurred.
  • Ill thriven lambs should continue to be submitted for post mortem examination.

Large numbers of worm eggs being deposited on pasture in late autumn/winter could lead to higher than expected larval challenge in these fields in late spring/early summer 2023.

Posted by SRUC Veterinary Services on 10/11/2022

Tags: Parasitology, Livestock Parasites
Categories: Sheep