Sheep being dipped©FLPA/Wayne Hutchinson/Rex

Farmers are being advised to keep a look out for tick infestations and treat animals promptly, following abnormally high numbers of sheep ticks being blamed for lamb deaths in parts of the UK.

It is unusual for ticks to be a problem before May, but dry and sunny weather conditions this spring appear to have accelerated infestations.

Sally Harmer, animal health specialist at Clynderwen and Cardiganshire Farmers, says several farms in north and mid Wales are reporting an unusually high level of sheep tick infestations.

“Some lamb deaths have been reported due to the large numbers of ticks causing severe anaemia,’’ she says. “Lambs are more at risk than older sheep, because the older animals do develop some immunity, but anything can get bitten and infected.’’

See also: Mild winter sees more tick diseases

One farmer whose flock has been badly hit is Jeff Rees, of Bwlchyddwyallt, Tregaron. Ten days after turning out a group of New Zealand Romney hoggets on to the hill their health deteriorated. “Their condition nose-dived, they were very weak,’’ says Mr Rees, whose land rises to 300m (1,000ft).

“We brought them in and found they have large numbers of ticks around their jaws and necks. It really knocked them for six.’’

Mr Rees quickly treated the group, but it was too late to save one of the animals.

As part of its lifecycle, the sheep tick needs a blood meal from a host animal. Adult females are most likely to be found attached to the head, legs or other areas of skin not covered by wool. Their feeding can also cause abscesses in the joints, spine and internal organs of lambs, leading to a condition known as tick pyaemia.
Tick-borne fever, an illness characterised by a sudden high fever for between four and 22 days, can be a problem in some areas.

See also: Tick and blowfly products launched

Ticks also transmit louping ill – a viral disease of the nervous system, which can cause high mortality. The disease affects the brain and symptoms include poor co-ordination, paralysis and convulsions.

Mr Rees believes his New Zealand Romneys, which had been bought in, could have been affected because they hadn’t previously been exposed to ticks. “There were some of my neighbour’s sheep mixed in with them – hardy, small Welsh ewes – and they didn’t have a tick on them,’’ he says.

Although he experienced problems with ticks a few years ago, he recalls that infestation was later in the year. “I wouldn’t expect to see ticks this early in the season,’’ he admits.

Ticks are inactive in the winter and only start seeking a host when the mean maximum weekly temperature exceeds 7C.

Treatment advice

Ms Harmer advises farmers to treat their flocks promptly to prevent losses, especially in flocks on rough and unimproved pastures where the natural increase in numbers coincides with the turnout of ewes and young lambs.

“Cypermetherin and alphacypermethrin can be used to treat and prevent ticks in flocks,’’ she says. “Both prevent and treat blowfly but should not be used in lambs under one week of age.’’

Deltamethrin can also be used, but has no blowfly recommendation.

“Organophosphate sheep dips are also effective in preventing and controlling ticks; however these are not licenced for use in showers or jetters,’’ says Ms Harmer.