This week’s podcast discusses ticks and Lyme Disease, which are both found in Ireland, the UK, and much of the rest of the world.
To listen, click here or on the podcast at the foot of this page. I’ve written fairly detailed notes on this topic below: I sourced this information when preparing for the radio show, and it’s too useful not to share it in a written blog post.
As a new graduate vet, I spent eight months in Swaziland (between South Africa and Mozambique) working on a project involving cattle ticks. At that point, every cow in the country was plunged through a dip tank full of chemicals to kill ticks, and our research aimed to find a better way of dealing with this issue. I learned a lot about ticks during my time in Africa, including seeing dogs carrying massive tick burdens, like bunches of grapes hanging from their bodies (see the photo at the top of this page).
Problems caused by ticks
- Direct harm by the ticks themselves
a) Ticks usually just cause a minor irritation to animals, but sometimes the bite wound can become infected, causing a painful abscess, especially if the tick is brushed off or carelessly removed, breaking off the tiny mouth parts and leaving them embedded in the skin.
b) Sometimes, if a high number of ticks attach, the bloodsucking can cause anaemia due to blood loss (similar to an animal bleeding from a wound for days on end).
c) With some African, North American and Australian tick species there is a nasty neurological condition of dogs called Tick Paralysis caused by salivary neurotoxins.
d) Finally, a peculiar correlation between tick bite and mammalian meat allergy in humans has been described recently: this is not fully understood.
- Harm caused by tick borne diseases (TBD’s)
The biggest problem with ticks is that when they suck a blood meal, they also inject small amounts of tissue fluid and saliva from their own bodies, which may include pathogenic organisms such as bacteria, protozoa and viruses.
In Africa, where I was working, these organisms included serious protozoal parasites called Babesia, which themselves survive by attacking red blood cells once they arrive in the bloodstream. The cattle suffered a high mortality due to anaemia caused by loss of red blood cells. In Ireland, this is also seen in cattle: it’s known as Red Water because the cattle pass red-coloured urine due to the destruction of their red blood cells. (see below for more on this).
Common tick species
The potential of ticks to cause disease problems is closely linked to the precise species of tick: those that are able to attach to a widest range of species are the most dangerous because they are able to pass on the widest number of diseases to the most creatures.
- In Ireland, the most common tick species by far is the castor bean tick, Ixodes ricinus, which can attach to reptiles, birds and mammals. This is the most important tick-borne disease (TBD) vector, able to pass disease between wildlife, humans, livestock and pets. This is the most common tick species infesting dogs, especially those that visit woodland and bogland,
- A second common tick species in Ireland, which also has a broad host range, is the hedgehog tick, Ixodes hexagonus. This infects cattle, sheep, horses, donkeys, cats and dogs as well as humans, and wild mammals and birds. It’s the most common tick seen on cats
- Other species of tick are less common and are not thought to carry disease.
- It’s worth having this helpful new app on your phone when out and about in tick country: the ”TickTracker by LivLyme Foundation” allows you to record and submit information about ticks which will help to map the problem areas for future visitors to an area.
Tick Borne Diseases in Ireland
- Borreliosis – also known as Lyme Disease. The only one that commonly affects humans as well as animals. See more detail below.
- Louping ill – a brain disease caused by a virus that can affect sheep (mostly lambs), cattle, goats, pigs, horses, mountain hare and red grouse. Only exceptionally affects humans, if they have contacted an affected mammal carcass, not from tick bites. Recently weaned lambs moved to tick-infested pastures are most susceptible to disease while animals growing up in endemic areas usually develop some level of immunity resulting in reduced mortality rates of 5 to 10% as compared to 60% in newly introduced stock. There is no effective treatment but a vaccine is available for those animals judged to be at higher risk.
- Anaplasmosis – a bacterial disease seen in sheep, cattle and goats, also known as tick-borne fever (TBF), are characterized by fever, weakness, anorexia, and occasionally, respiratory distress, again mostly seen in animals that are not used to an area so they have no endemic immunity.
- Bovine Babesiosis – a protozoa that causes redwater in cattle, including anaemia, jaundice, and fever, with a mortality rate of around 10% Used to be very common in some parts of Ireland especially in the west and north west. Used to be 1.7% incidence but less common now (down to 0.06%), thought to be due to wide use of ivermectin as a wormer in cattle decreasing the overall numbers of ticks.
- Canine Babesiosis is common in dogs in some Eastern European countries, and some imported dogs in Ireland have been reported to bring this disease back with them (I diagnosed one from Poland a few years ago)
Lyme disease is caused by spirochaete bacteria called Borrelia burgdorferi. It occurs in a wide variety of mammals but dogs and humans are more susceptible to disease. The signs of disease – in dogs and people – are immune mediated i.e. rather than the bacteria actually causing damage itself, it’s the way the immune system of the body reacts to the bug that causes problems. Signs include acute arthritis in one or more joints with lameness, joint swelling and heat. Other signs include fever, anorexia, lethargy and enlarged lymph nodes.
The strange thing is that treatment is easy: a 3 – 4 week course of antibiotic provides a complete cure if given early. The challenge is to make the diagnosis in the first place. The condition often remains undiagnosed, or worse, misdiagnosed, so that the wrong treatment is given, and serious, chronic damage takes place in the body.
Most canine infections are sub-clinical (i.e. animals are not visibly unwell) with only 5 to 10 percent of infected dogs developing clinical signs. Or to put it the other way, 90 -95% of dogs infected with Lyme Disease show no sign of illness and do not need to be treated.
In humans, the most common initial sign is a circular skin rash known as erythema migrans, which can act as an early sign of infection. This is not always seen, but people should be alert to this possibility and let their doctor know if they see it. Dogs don’t get this.
It has been suggested that dog owners might be at greater risk of infection from Lyme disease than people without dogs, but studies have found no correlation between dog ownership and risk of infection, and infected dogs pose little or no direct risk to humans. The risk to humans comes from direct contact with ticks, so if a dog brings lots of ticks back to a home, that causes a risk, or if a human accompanies a dog to an areas where there are lots of ticks, this will also put them at increased risk of picking up ticks.
Use of tick preventative products
In dogs and humans, the risk of infection with Lyme Disease can be reduced significantly by rapid removal of any ticks that attach. Most Lyme Disease infection is thought to be transmitted at least 24 hours after attachment.
In dogs at high risk, the use of routine preventative products that rapidly kill or repel ticks makes sense, to reduce the time that ticks spend feeding and therefore to minimise any transmission of infection.
- Tablets, to be given once a month or every 3 months- a type of drug in a group called isoxazoline (eg Bravecto, Nexgard, Nexgard Spectra and Simparica).
- Topical insecticides (spot ons or collars) e.g. permethrin (Advantix and Vectra 3D), deltamethrin (Scalibor collar) and flumethrin (Seresto collar)
Any dog with a history of picking up high numbers of ticks should be routinely given tick preventive products to avoid recurrent exposure to ticks. They are potent medications and are often prescription-only, so you’ll need to get them from your vet.
Check your dog and yourself for ticks every day
Pet owners should check their dogs every 24 hours and carefully remove any ticks found with a tick removing tool, using a “twist and pull” action. The O’Tom Tick Hook is the most widely available. After removal, ticks should be handled with care, using gloves, and disposed of safely (e.g into fire, or squashing while inside plastic bag then into bin).
Vaccination against Lyme Diseaes
A dog vaccine is available for Lyme disease prevention (Merilym3) if a dog is judged to be at high risk. The vaccine produces antibodies in the dog, and uniquely, these work in the ticks themselves, not in the dogs. The tick has a blood meal, swallowing antibodies in the dog’s blood. These antibodies prevent migration of the Lyme Disease bacteria to the salivary glands of the ticks, reducing the risk of them passing the infection on to dogs.
The vaccine is given as a primary series of 2 vaccines, 2-4 weeks apart, with an annual booster. Vaccination against Lyme disease is not used to treat the condition at all, and Lyme vaccines are not considered core vaccines for dogs. And even if the vaccine is used, effective tick control is still important
Lyme Disease vaccination in humans
A vaccine for humans is not currently available. However, twenty five years ago, a vaccine called LYMErix was on the market, preventing between 76 and 92 percent of infections. Rumours (later disproved) that the vaccine might actually cause arthritis in humans meant that it became difficult to sell the vaccine and it was taken off the market. The vaccine for dogs is almost identical to this old human one.
A new Lyme vaccine for humans is currently being developed in France.
In the absence of a vaccine, people should remove ticks if they find any attached to them, and they should tell doctors that they have a history of contact with ticks if they ever develop odd signs (e.g. skin rash, arthritis)
Questions about pets from listeners
The following questions were asked this week:
- My elderly dog has a long list of issues: what options do I have to help her?
- Our terrier is terrified and excited by a local goat in Connemara. What can I do to stop him barking at it so much?
- I also did a Facebook Live session of questions and answers, which you can watch here.