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Tick Talk

Rebecca McCloy BVMS MRCVS

Rebecca qualified from Glasgow in 2014 and works in farm animal practice in the south-west of Scotland.

 

 

Although turnout is always a time of year we look forward to, it brings it own unique set of challenges – like the parasites in the grass that weren’t an issue in the house. As spring turns to (Scottish) summer, our creepy-crawly concerns switch from lice and mites to flies and ticks.

Ticks themselves are not a serious problem unless a large number feed on a small or sick animal. Their usual blood serving size is around half a millilitre, which most healthy cattle and sheep will barely notice, having roughly 60 and six pints of blood respectively (depending on their age and body size).

However, ticks can spread disease from one animal to another in much the same way as a dirty needle: when they pierce the skin to suck blood, they can end up injecting bacteria, viruses or parasites which make the cow or sheep much sicker than the tick itself does. Tick feeding season kicks off in spring and lasts until autumn. Often, if a tick-borne disease is permanently resident in one region, livestock will be exposed and develop some natural immunity. This means caution is required when buying and selling: purchased animals can be extra vulnerable to an unfamiliar infection, or they could expose your existing stock to new diseases.

Like any disease, it is very hard to conduct a realistic cost-benefit analysis for your farm without measuring the impact, so get a diagnosis where possible and keep a tally of cases each year.

The most common infections spread by ticks in Scotland are:

Tick-borne fever: affects cattle and sheep and causes a high temperature, poor appetite, milk drop, and occasionally abortion – making it hard to distinguish from many other diseases. It can also damage the animal’s own immune defences, making it susceptible to further infections, especially pneumonia. Diagnosis by blood test or post-mortem.

Tick pyaemia is a bacterial infection which can get into the bloodstream and joints. It is mainly seen in lambs pre-weaning, making them lame or just under-the-weather. It can resemble joint-ill and may respond to antibiotics if caught very early.

Louping ill: a brain virus, with a name that used to confuse me, because I thought ‘louping’ always meant pain. The second meaning, ‘leaping,’ makes more sense, as affected sheep stagger about. I suppose their heids may also be louping, but they can’t tell us. To diagnose, we need a post-mortem brain sample, best collected at the lab, sheep skulls being fairly solid - as anyone who has ever had one collide with their shins will testify. Blood tests can also be useful.

Redwater is a parasite which bursts red blood cells, resulting in the pigmented urine which gives the disease its name. It can be diagnosed with a blood sample. Remember antibiotics do nothing for parasites or viruses.

When it comes to reducing tick-borne diseases, we basically have two strategies: grazing management and treatments applied to skin (in the form of spot-ons, pour-ons or dips).

In terms of pasture choices, ideally, we avoid high-risk stock on high-risk pasture during peak tick season – for example, young lambs or bought-in stores on the hilliest parts of the farm or on pasture with a history of disease issues. Rougher ground does tend to be worse for ticks, but it is not so clear cut – you can find ticks on lowland grazing and the wee blighters are also highly mobile, travelling at speeds of up to 35mph if they are hitching a ride on a deer, with no respect for fences.

For skin treatments, look for a word ending in ‘methrin’ on the pack and carefully check what the product claims to do – many of the pour-ons will kill or repel different parasites on cattle vs sheep and some are only suitable for one species or the other. Take care also with the pattern of application – some products need to go on a different part of the animal for flies vs ticks. As always with parasite treatments, use them responsibly by following the instructions carefully, and dose precisely to avoid wasting your time and money.

For sheep, dipping is a great tick control option, with the added bonus of scab prevention. Mobile dippers mean you don’t even have to have the facilities yourself. Since tick pyaemia is mainly a disease of lambs, some farms choose to dip the ewes pre-lambing. Although obviously not so close to lambing that you end up with water births in the plunge dip.

As with most things in farming, there is not a one size-fits-all approach to controlling these diseases. Your own vet and local SRUC lab are great sources of information if you want to know which tick-borne (and other) diseases are present in your area.