Lamb Fluke ELISA November 23

Using abattoir blood samples from slaughtered lambs to detect the timing & spread of fluke infection.

Since 2015, from June to December, DAFM has taken lamb blood samples in factories from a proportion of flocks at the time of slaughter. These have been tested for liver fluke antibodies to determine the timing and geographical spread of liver fluke challenge to grazing lambs. 

The number of flocks selected for sampling from each county is intended to be proportionate to the sheep population of that county over the entire sampling period (July to November 2023). A number of samples are taken from each selected flock, and these are pooled at laboratory level. The presence of liver fluke antibodies reflects the level of challenge the lambs have experienced during the most recent grazing season. The presence of liver fluke antibodies in 2023 born lambs is therefore a sentinel for exposure to liver fluke in the wider sheep population in the region, as by definition these lambs must have been exposed during the 2023 grazing season.

Results for July - November 2023

Results for the country for July – November 2023 are as follows:

Please see maps below (figures 1 and 2) for more detail on the distribution of positive and negative results. 

Fluke Distribution November 2023

Figure 1: Lamb liver fluke ELISA test results for November 2023. Points have been moved slightly to preserve anonymity of flock owners. (Numbers in the circles indicate more than one sample within this area)

              Up to November ’23                                                                         November ‘23

Figures 2: Non-negative results from July to November on left compared to non-negative results from November 2023 on the right.  Points have been moved slightly to preserve anonymity of flock owners. (Numbers in the circles indicate more than one sample within this area)

In the November testing, 54 flocks were seen to be positive, again this was scattered across the country from the west coast towards the central midlands and again in the mid-east coastal counties. The highest number of positive cases were recorded in Donegal 23 positive results out of 32 flocks tested, with multiple cases also seen in Carlow, Galway, Kildare, Mayo, Roscommon, Sligo, Westmeath and Wicklow.  In addition to this there were 18 inconclusive results recorded country wide.  The percentage of negative flocks throughout the country in October was 60%. Counties Cork, Kerry, Kilkenny and Meath recorded negative fluke results only for this month.  It is important to note that this month samples were not obtained from the counties Clare, Dublin, Laois, Leitrim, Limerick, Louth and Tipperary so fluke levels in these counties cannot be assessed.

As the sample size for some counties is small, farmers in these particular counties need to be cautious when interpreting the results of the survey as they relate to their areas. Additionally, the county associated with a batch of lambs is that where the flock of submission is registered. In a minority of cases, where the lambs had been purchased shortly before slaughter, the county associated with a batch will not reflect accurately where the batch of lambs spent its life.  Absence of inconclusive or positive test results for a particular county should not be taken as conclusive evidence that liver fluke is absent from that county.

In recent months the Regional veterinary Laboratories have had numerous submissions in both sheep and cattle where the cause of death has been liver fluke.

Image of Fluke from a postmortem – with thanks to Denise Murphy, Athlone RVL

If you have any concerns about fluke in your flock please contact your private veterinary practitioner for further advice.

Thanks to Kate O’Keeffe, DAFM blood testing laboratory in Cork, Michael Horan of RAH and Seamus Fagan of Athlone Regional Veterinary Laboratory for the information provided.

Species: Ovine