On 16th March 2016, newspapers and news feeds across the UK broke the news that a new “deadly tick-borne disease” had been diagnosed in dogs in Essex. The disease turned out to be babesiosis – a parasite of the red blood cells, similar in many ways to malaria, transmitted by tick bites. The condition has now, apparently, reached the UK for the first time. So, how seriously should we take the stories, and are they accurate?
Is this a new disease?
Not at all – it has been fairly common in continental Europe and across the world for many years; as an island, the UK has been lucky enough to avoid it (until now). There have, however, been “mini-outbreaks” before in the UK, so it’s not something we’ve never seen before. The difference is that the previous outbreaks have been in dogs who had travelled to Europe on the PETS Passport Scheme; the new outbreak appears to be “native” to the UK, with infected ticks surviving in the environment.
Babesiosis is caused by a microscopic parasite called Babesia canis. The parasite infects the dog’s red blood cells, destroying them and triggering the immune system to respond. Unfortunately, in its efforts to destroy the parasites, the immune system also destroys many red blood cells – this is called immune mediated haemolytic anaemia (IMHA). The symptoms are generally those of anaemia, and include:
- Lethargy and shortness of breath
- Loss of appetite
- Weight loss
- Pale gums (due to anaemia)
- Jaundice (yellowing of the gums, eyes and pink skin; caused by breakdown of the red blood cells)
- Discoloured urine and stools
- Swollen lymph nodes.
- Sometimes, liver failure, brain damage, or kidney failure may occur.
In some cases, it is fatal even with treatment; however, occasionally a dog will not show any symptoms, but will still spread the parasite.
How is it diagnosed?
There are a number of ways your vet can diagnose the infection; often, the parasites can even be seen in blood cells under the microscope. Other techniques include PCR tests for the parasite’s DNA, and immune tests to determine if a dog has antibodies against the infection (although this often requires repeated samples several weeks apart, so is less useful in the emergency situation).
Can it be treated?
Yes, but many affected dogs are very, very sick, and so the prognosis is guarded. Use of certain anti-protozoal drugs (such as imidocarb and diminazine) is combined with intensive care, medications to reduce the immune system’s attack, intravenous fluids and often blood transfusions. These specific anti-babesia drugs are not licensed for use in dogs in the UK, and may need to be imported from France or Spain, where the condition is more common.
How is it spread?
The good news is that Babesia canis is not usually spread from dog to dog – it is transmitted via a tick bite. However, infected blood-blood transmission is theoretically possible (e.g. in a dog fight); and a bitch can infect her unborn pups.
The second piece of good news is that the most common UK tick (the Sheep or Castor Bean Tick, Ixodes ricinus) doesn’t carry the infection. It’s only the relatively rare Meadow Tick (Dermacentor reticulatus) that carries the parasites. This is more limited in area, and is most common in the southwest of England, Wales, and in Kent and Essex.
Can it infect people?
Fortunately, Babesia canis does not usually infect people – humans are at very low risk, even if bitten by an infected tick; however, other Babesia species (especially B. microti) have managed to “jump the species barrier” into people with weakened immune systems. That said, as ticks can carry other serious diseases, care should still be taken to avoid being bitten.
Will it spread?
Almost certainly, yes. Ticks don’t just bite dogs – they bite all sorts of different wildlife; which can carry them, or the infection, further afield. If the disease is truly established in the UK, it will spread wherever there are Meadow Ticks to carry it.
How can it be prevented?
Although there’s no licensed vaccine in the UK, ticks do not usually start transmitting the infection for 24-48 hours after attaching to the dog’s skin. Therefore, any product that will repel them, or kill them rapidly, will minimise the risk of infection. There are a range of highly effective products available on prescription from your vet, as spot-ons, collars, and tablets. Removal of attached ticks as soon as possible, using a tick-hook or tweezers to twist it out, is also important – if in doubt, get your vet or vet nurse to show you how.
What should I do if I think my dog’s been infected?
Get them to your vet as soon as possible! Remember, anaemia can be caused by many other conditions, but they all need rapid treatment if your dog is to make a rapid and full recovery.
UPDATE – 2019
There have now been other cases, which may suggest the infected ticks are spreading:
There is also evidence that infected ticks may be much more widespread than originally thought.