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Lamb liver fluke antibody test results-September 2020



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. This testing did not commence until August in 2020, due to challenges caused by the COVID pandemic in slaughter plants.

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 (August to November 2020). 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 2020 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 2020 grazing season.

 

Results up to and including September 2020

Results for the country for August and September 2020 are as follows:

Added 09.10.2020

 

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

 

 

Added 09.10.2020

Figure 1: Lamb liver fluke ELISA test results for September 2020. Points have been moved slightly to preserve anonymity of flock owners. Fluke Exposure Sept 2020 (pdf 144Kb)        

 

 

Added 09.10.2020

Figure 2: Non-negative lamb liver fluke ELISA test results up to September 2020. Points have been moved slightly to preserve anonymity of flock owners. Closed points refer to positives for September; open points refer to positive results from the previous month. Non-negative Fluke ELISA results (pdf 133Kb)        

 

Although positive test results have been found in samples associated with flocks from a range of counties, positive results are concentrated in the west and northwest. In September, a few positive cases were also found in flocks based in the midlands. After a wet summer, rainfall levels for September in many areas, especially in the south and east, were lower than the mean value for previous years- see www.met.ie/climate/available-data/monthly-data . This may have reduced the risk of liver fluke in areas other than the north, west and midlands, to some degree. The percentage of positive liver fluke tests for September 2020 is now very similar to that observed in 2019: http://www.animalhealthsurveillance.agriculture.gov.ie/currentnews/title,134255,en.html

Further test results over the next few months will add further information to help farmers, vets and others to assess the risk of fluke for 2020 with additional confidence.

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.

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

Species: Ovine
2:02 PM on Fri, 9 October