Rising temperatures cause shift in parasites picture

Liver fluke

The season for disease due to liver fluke in cattle and sheep continues to shift, as winters get milder and wetter, and this year there were reports of acute disease in early spring, which could catch some producers out, said Moredun’s Philip Skuce. 

There has also been evidence of immature liver fluke at post mortem, said APHA’s Rebecca Mearns, speaking in April. Farmers outwintering livestock on pastures at risk of carrying liver fluke need to keep up their guard.

Given the later onset of the liver fluke challenge, treatments given too early leave livestock vulnerable to infection and disease in late winter and spring.

Experts stressed the importance of testing and risk assessment. Faecal egg counts are the most appropriate test in spring, with a positive result indicating there are adult fluke burdens present. However, egg counts may not be as useful in animals at risk from acute disease caused by juvenile flukes.

Previously, the use of an adulticide in spring would have covered most situations, said Rebecca.

If livestock had been housed or kept away from infected pastures for 10 weeks or more then any fluke they carried would be old enough to be laying eggs – but the shift to later fluke activity means farmers must now ask if animals could have been infected or reinfected much more recently, as the fluke they are carrying may not be mature enough to lay eggs, so a negative FEC should be repeated.

To avoid putting unnecessary pressure on some actives, farmers are advised to choose a product based on the maturity of the stage of liver fluke to be targeted. Talk to your vet or SQP about the options and do not use a product in combination with a wormer unless you know that a worming treatment is required, SCOPS and COWS said.

Blowfly warning

There have been early season strikes in lowland areas in southern England, with red warnings in place on the Blowfly Watch risk alert. In more northerly or upland regions, strikes are more likely to start from mid to late May, but on-farm conditions can pose higher or lower risks.

As well as applying an insect growth regulator, Elanco’s Matt Colston stressed that product must be applied to clean sheep – aided by effective worm control and actions such as dagging and timely shearing.

Nematodirus

The rise in temperatures this spring has been early, relatively gradual, and sustained, meaning the nematodirus threat to lambs so far has been relatively low, which is borne out by few, if any, reports of disease, said Lesley Stubbings, SCOPS, in mid-April.

Upland flocks and cooler coastal areas that have not yet reached temperatures to trigger hatching should keep monitoring and risk assessing when lambs start grazing. They could be at high risk if we have a return to cold weather followed by a sudden warming.

However, there are reports of high counts of strongyle species in hoggets and some older sheep, and these could be leading to high levels of contamination on pastures this spring.

Once we get rain, there could be a rapid rise in these worm species, and the concern is that those who have treated for nematodirus will get a false sense of security and may get caught out. Again, FECs are recommended to monitor the situation.

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