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Parasite Matters Summer 2020

Following on from a very wet February, late spring/ early summer has been warm and very dry. The charts (below) show temperatures up to 2C above the 30 year average, and rainfall below 50% of average for large parts of the country. What does this mean for parasite challenges through the summer?

Blowfly Leaflet


  • Some areas have already seen high levels of blowfly challenge (see the Blowfly Tracker here to see where cases of strike have been reported or to report a case of strike). Any increase in humidity/moisture levels (rain) with continued warm weather is likely to increase the blowfly risk considerably.


  • The Nematodirus challenge looks to have largely passed for the southern half of the country, with risk levels falling. However, northern England and Scotland are still showing high to very high risk at the beginning of June. Check the SCOPS Nematodirus forecast for daily updates on local risk levels here. The dry weather will minimise challenge from summer worms. However, any rainfall is likely to bring a flush of worms along with the flush of grass. Checking worm egg counts from lambs will let you know when the time is right to treat, and avoid wasted treatments when there are no worms present.


  • There have been reports of high levels of tick challenge this spring. Using insecticidal pour on products can help to reduce the number of tick bites and so reduce the risk to livestock of tick borne diseases. For more information on managing tick numbers and tick borne diseases click here.
Liver Fluke

Liver Fluke

  • A warm dry May and June means that overall mud snail populations will be low, and any fluke eggs hatching will find it difficult to infect a snail. This usually gives a low risk autumn, provided that the weather remains warm and not too wet through the summer. Remember that 'Low Risk' does not mean 'No Risk', and that in a dry summer, the only available grazing may be in normally wet areas where there is a large snail population and a correspondingly high liver fluke challenge. Look out for updates from SCOPS and COWS as the summer progresses.

Parasite Matters Archive

Spring Parasite Alert - Blowflies (published May 2020)
Spring Parasite Alert - Ticks (published April 2020)
Parasite Matters Spring (published March 2020)
Parasite Matters Winter (published December 2019)
Parasite Matters Autumn (published September 2019)
Parasite Matters Summer (published May 2019)
Parasite Matters Spring (published March 2019)


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