Ticks
Ticks on Horses-
Ticks are endemic in the UK with approximately twenty (20) species present. They are not considered species-specific so will happily infect most animals including horses, dogs and humans. Quick recap- ticks are small (0.5mm – 3mm), blood-sucking parasites that attach to their host, puncture the skin, and then feed from the host’s blood before falling off.
In all species, including horses, ticks can cause:
- local skin and tissue irritation ranging from very mild to severe
- anemia due to blood loss in heavy infections and,
- some dangerous microbial diseases including Lyme Disease (Borreliosis), Babesiosis, Anaplasmosis/ Ehrlichiosis, Bartonellosis, Q-fever and the Louping ill virus
Want further information on prevention and how to treat ticks? Read on…
Ask us what treatment we recommend for your horse
The Parasite:
About the Tick
Ticks are arachnids- they belong to the same family as spiders, mites and scorpions. Size wise they are pretty small at around 0.5mm to 3mm but will be bigger when fully fed- they are certainly visible to the naked eye. Fully fed they are often described as baked-bean size.
Depending on the life-cycle stage they will either have 6 or 8 legs (this is explained below). They do not have wings, cannot “jump” and are blind– so to find their hosts they will climb onto grass/plants/shrubs from which they will attach to passing animals. They use special sensory organs on their front legs to detect stimulants such as carbon dioxide, changes in light and body heat that are given off by their larger hosts. This process is known as “questing” and is a host-seeking set of behaviors.
Their colour is somewhat species dependent and they vary from reddish to dark brown or black. There is often a colour change apparent when feeding or fully fed, with them often looking pearly-grey, opalescent.
The most common tick in the UK is Ixodes ricinus, which is also known as the sheep, castor bean or deer tick. However, unlike its name suggests, this tick will feed on a wide range of mammals, birds and some reptiles, as well as people. Ixodes hexagonus (the hedgehog tick) and Dermacentor reticulatus (the marsh tick) are the next most common species in the UK, respectively.
Ticks feed on blood, and each of their active life-cycle stages (larva, nymphs and adults) requires them to be on an animal host.
Tick Life-Cycle, Risks & Treatment
Is there a tick “season”?
Yes and No….. Ticks can be found throughout the year but are most active between spring and autumn so there is a degree of seasonality, but more around the level of activity.
In the UK, generally speaking, nymphal tick activity increases during spring, peaking from April to June. So during this period, the risk of acquiring a tick bite is highest. Activity reduces during the summer months but can then pick up again in early autumn. Activity continues over the winter months but at a reduced level. Adult ticks can be active at all times of the year but are more active in summer which is also the peak time for larval activity.
Where on the body are they found?
Once a tick has found a host they look for a suitable place to attach and puncture the skin to get a blood meal.
The most common areas for ticks to be found on horses are considered the chest, underbelly, head, ears, throatlatch, mane and tail.
On dogs the most common place for tick bites are the head, neck, ears and feet. The most common bite places on humans are the back of the knees, between the legs/groin, and around the waist.
Image Courtesy of the CDC
Geography plays a large part in tick prevalence in the UK, with some areas known as “hot spots”
The attachment of ticks to a host generally relies on suitable vegetation being present for them to quest from- e.g forests, woods and areas of grassland such as heath and moorland. The other key driver is the presence of other hosts for example high livestock numbers and/or wildlife populations.
Within the UK there are a few areas that have been identified as tick hotspots:
- New Forest
- Exmoor
- Thetford Forest
- Lake District
- North Yorkshire Moors
- Highlands and Islands of Scotland.
Generally speaking, any grassy or wooded area should be considered a risk, especially in the period April through August.
Ticks are very sensitive to temperature and relative humidity, requiring areas with dense ground layer coverage of vegetation for survival, reproduction or establishment. Without larger hosts such as deer/cattle/horses etc that adult ticks feed on, tick populations are unable to establish, even when suitable vegetation and temperature and environmental conditions are met.
The tick life-cycle & how infection occurs
The tick lifecycle is actually pretty complex involving three active stages – larvae, nymphs and adults (the 4th stage- pupa- is non-active) with all three stages needing an animal host to feed from before the next life cycle stage can take place.
The cycle takes on average three (3) years!
A stylised tick life cycle would look like the following:
- An adult tick is attached and takes a blood meal from its large host (horse, deer, cattle)
- The engorged adult detaches and falls to the ground to lay its eggs.
- The young seed ticks (larva) emerge from the eggs and attach themselves to a host (small mammal, bird), and takes a blood feed. They are thought to remain on this host for up to 5 days.
- Once full the larval stage detaches and falls to the gound where it molts to reach the nymphal stage.
- The nymph ticks again look for a host- this time often slightly larger like a rabbit, or hedgehog where they feed for up to a further 6 days.
- The fed nymph tick again detaches and falls to the ground and molts into either a female or male young adult.
- The young adult ticks “quest” and attaches to their final large host. On the preferred host the adults mature and mate. They can stay on the host for up to 11 days before the gravid females fall to the ground.
- Each adult female tick is though capable of laying around 2000 eggs.
Removal and Treatment of Ticks
Any attached ticks should be removed as quickly as possible. The longer a tick stays attached the greater the risk of disease transmission is thought to be. Likewise, the longer the tick is attached the greater the risk of skin irritation and general infection.
The safest way to remove ticks from your horse- and dogs or yourself- is by utlising a tick twister/tick remover. There are lots of “old school” tips such as- covering the tick with vaseline/petroleum jelly, burning or freezing the tick, and bursting it on the host and none of these should be undertaken for a variety of reasons!
Once removed the bite area is likely to remain irritated and often red. Usually, this is nothing to be concerned with but do keep an eye out for further infection. If you have doubts contact your vet. It can be worthwhile to apply an antiseptic to the bite to prevent further infections and to apply a topical bit cream to soothe the area.
If after a few days post tick removal there are signs of continuing irritation or infection- key symptoms being reddening of the area, swelling and heat, or weeping at the bite site- then you should contact your vet. It may be useful to keep the removed tick for identification purposes.
Preventing Ticks on Horses?
Preventing ticks on horse is difficult and it should be noted that there are currently no Veterinary Medicines Directorate (VMD) licensed products (POM-V, POM-VPS for example) that are indicated for the control or treatment of ticks on horses. The product Deosect 5% w/v Concentrate for Cutaneous Spray Solution is a licensed veterinary medicine (POM-VPS) that is indicted to “control flies and lice on horses”, so not ticks…
So this leaves the horse owner with a number of retail-only products. These are really fly prevention sprays and contain DEET, permethrin, citronella or proprietary blends of natural or synthetic oils and chemicals. With severe cases of tick infestation, your veterinarian will be able to assist with a product prescribed under the cascade system.
Lyme Disease
Lyme disease is probably is the most well known condition associated with ticks. Lyme disease is a serious infection of animals including humans, although routinely treatable in most cases with antibiotics. It is caused by the bacterium Borrelia burgdorferi.
In infected horses, clinical signs do not often appear, but the most common ones are lameness, sometimes with fever, and behavioral changes (irritability, uneager to work) which can be difficult to diagnose. The lameness is usually associated with the larger joints and frequently shifts. Laminitis has occasionally, been associated with Lyme disease.
Whilst in humans the early symptoms may include mild flu-like symptoms, including fever, headache and fatigue. Early symptoms in humans are usually accompanied by a characteristic spreading bulls-eye rash (called erythema migrans) at the site of the tick bite
Definitive confirmation of Lyme disease in horses is problematic and the current diagnosis is based upon finding a positive antibody titre for the suspected organism in a horse with suspicious clinical signs in an area where the disease, or at least Ixodes ticks, are known to be endemic. Diagnosis will require a blood test from your vet.
There are some limitations to the standard methodology:
- it can take 3 months for infected horses to seroconvert i.e. many cases where the infection is newly established will be returned as “negative”
- Many infected and seropositive horses will never exhibit any clinical signs. This can mean a misdiagnosis of Lyme disease when the causative conditon may not be that pathogen
- As with other serology tests used in horses, the horse can remain seropostive for a very long time after the the infection has occurred and been successfully treated.