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Lamb liver fluke antibody test results - August 2019



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 (June to November 2019). 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 2019 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 2019 grazing season.

 

Results up to and including July 2019


Results for the country, for July and for the year up to and including July 2019, are as follows:

Please see maps in Figure 1 and Figure 2 below for more detail on the distribution of positive and negative results. 

Figure 1: Lamb liver fluke ELISA test results for July 2019

Figure 2: Non-negative lamb liver fluke results for the year up to and including July 2019. July results are represented by closed (filled) points; previous results are represented by open points

 

Given the moderate fluke forecast provided by DAFM for last winter and the early stage in the grazing season at which samples were taken, it is unsurprising that so many of the samples tested negative. The positive samples seen in the North and West serve to remind us of the need for caution when assessing the liver fluke status of Irish sheep flocks, and of the need to consider information from a range of sources when deciding whether or not to dose. The substantial number of non-negative results in counties where only negative results had previously been seen in 2019, such as Galway and Sligo, suggests a gradual expansion of the area where liver fluke is active as the year goes by.  Please see maps below.

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. 

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

Species: Multi-Species
10:26 AM on Wed, 14 August