Ticks are small, blood sucking parasites of mammals. This can include horses, dogs, cats and humans. They are increasingly common in the UK. The three most common species of tick are: Ixodes ricinus (sheep or deer tick); Ixodes hexagonus (hedgehog tick); Dermacentor reticulatus (marsh tick). Ticks vary in colour from red-brown to black. Before feeding they are small (<0.5mm) but once engorged, they have a larger, rounded shape.
Ticks cannot jump or fly, but crawl onboard to take a blood meal when a host passes by. Once they have fed, they detach from the host and drop to the ground to lay eggs or moult. Ticks are most prevalent in rural areas of woodland, grassland and moorland, such as, the Highlands of Scotland, Exmoor, the Lake District and the New Forest. The highest number of ticks can be found in areas with high livestock density, including water troughs, feeding areas and around trees.
Ticks are more active from April to November but they can remain active in temperatures as low as 3.5 degrees celsius. Therefore, although tick bites are most common from Spring to Autumn, it is important to take a precautionary preventative approach all year round.
Tick bites themselves rarely cause a problem. In very large numbers they may cause anaemia or challenge the immune system, but this is very unlikely in horses. However, ticks can transmit a variety of potentially dangerous diseases, including Lyme Disease, Babesiosis, Anaplasmosis, Bartonellosis, Q-fever and Louping ill virus.
Lyme Disease is a tick-borne infection caused by the bacterium Borrelia burgdorferi. It is a serious chronic inflammatory disease that affects many body systems. Humans and other animals, including horses, can be affected by Lyme Disease. The vast majority of ticks will not transmit the disease. However, it cannot pass from one infected animal to another without the help of ticks. Lyme Disease is a growing concern and owners should be aware of the dangers that ticks can pose and remove them quickly to minimise the risks. Infection typically occurs after the tick has been attached to the horse for around 24 hours.
Diagnosis in horses is difficult because lameness, caused by other musculoskeletal injuries, is common. In addition, subclinical exposure is common, so a positive blood test result only indicates exposure to Borrelia burgdorferi, and does not confirm an active infection.
If your horse is bitten by a tick, or a tick is dislodged by accident and the mouth parts remain in the skin, the area should be monitored closely for signs of infection. A localised skin reaction may occur, which can take several weeks to fully resolve.
As a bacterial infection, the treatment for Lyme Disease is an intensive and prolonged course of antibiotics. Kidney function is closely monitored before, during and after treatment. Sometimes, despite the appropriate tests being performed, a definitive diagnosis of Lyme Disease cannot be made and your vet may recommend treating your horse presumptively. Unfortunately, despite apparently successful treatment, clinical signs may recur.
Please note that any human health concerns should be addressed by your GP.
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