September 25, 2021

I, Science

The science magazine of Imperial College

Ticks in fur
The dreaded mini vampires

Vampires are on the loose and at a time when most things are being blamed on either climate change or the EU (not anymore…), it’s been suggested that a combination of both may have caused the uprising. But the rise of the tick is not sexy news fodder, and tick diseases only affecting dogs even less so. Canine Babesiosis is no Lyme’s Disease- humans can’t catch it and it’s unlikely to hit the national news by infecting Avril Lavigne. But what is worrying is that until recently, Babesiosis has not been seen on UK shores. So with another suspect case at the Barrier Vet Clinic in London this month, why now? And perhaps more importantly, what next?

dog at the Vet

The bloodthirsty tick is second only to the mosquito at transmitting disease to both humans and animals. The insects work as vectors carrying parasites which they can transmit to humans and animals when they feed. Babesia canis, a single celled protozoon,  is one such parasite transmitted by the tick Dermacentor reticulatus. This causes Babesiosis, a malarial-type disease which damages a dog’s red blood cells and also causes the dog’s immune system to attack its own red blood cells resulting in anaemia, reduced blood clotting, fever and lethargy.

Being separated from mainland Europe by a body of water has served the UK well as a form of protection from infectious diseases and, historically, Babesiosis has only affected dogs in mainland Europe, Asia and Africa.  Writing in an online pet health blog, Holly Wilson recalls the time her dog Olive was infected whilst on a trip to France last year. “It was when we began the journey home that Olive started to show worrying symptoms. By the time we had arrived she was weak and her eyes were glazed. Then I looked at her gums and to my horror they were completely white.”

Holly and her pointer, Olive courtesy of The Telegraph
Holly and her pointer, Olive courtesy of

In March this year, Harlow in Essex saw four dogs infected by the disease. A tick recovered later was identified by the Animal and Plant Health Agency as Dermacentor reticulatus. The difference? None of these dogs had a history of travelling abroad.

Pets must, like us, travel with passports. The Pet Travel Scheme (PETS) was introduced in 2001 to allow for transport of animals across borders whilst ensuring protection against rabies, the tapeworm echinococcus multilocularis, and ticks harboring exotic blood-borne disease. In January 2012, however, restrictions were relaxed to comply with EU regulations meaning that pets no longer needed to receive tick treatment prior to returning to the UK. Vets lobbied hard against the change, concerned that the relaxation of restrictions would lead to inevitable outbreak of exotic disease as dogs brought infected ticks back into the country. Chief Medical Officer Professor Dame Sally Davies reassured them that “the wider public health risks from exotic tick-borne infections and the need for tick controls for pets entering the UK will be kept under review.” Four years on, Sean Wensley, President of the British Veterinary Association (BVA) says “it is disappointing to see our concerns potentially becoming a reality.”

Pet Passport pet,animal,dog,cat,horses,travel,holiday,blue,star,gold, europe,european,united,kingdom,britain,

Fortunately for Olive, alarm bells rang when Katyia, her Polish vet, recognised the symptoms and suggested testing for Babesiosis. Caught early and with appropriate treatment, the prognosis can be good. Olive thankfully survived the disease. “But,” said Clive Swainsbury, partner at Forest Veterinary Centre in Harlow where the first case of Babesiosis from a UKonly based dog was reported, “it’s easy to miss it”. Talking to The Guardian, Swaisbury goes on- “it’s a new disease to this country, so we aren’t used to looking for it on a regular basis.” If acute, or left untreated, the disease can be fatal. Sadly, three of those four dogs diagnosed in Harlow did not survive.

Dr Helen Roberts, who works in International Disease Monitoring and Risk Analysis at the Animal and Plant Health Agency counters claims that the incidence is purely due to relaxation of PETS restrictions. “I would happily go on the record to say no, the change in EU rules was not responsible (…) the ticks were already present in the UK; the PET scheme (would not have resulted in) an infected dog entering and passing on infection to local ticks.”

So if it’s not the relaxation of restrictions, what is it? A study published in the International Journal of Medical Microbiology in 2004 by Sarah Randolph, Professor of Zoology at Oxford University, found that tick-borne disease systems are “highly susceptible” to climactic influences such as temperature and moisture stress. Randolph is careful to point out, however, that climate change is “not necessarily” the cause of the increased incidence of tick-borne disease in many parts of Europe. In the absence of an absolute link to specific climate variables, Randolph urges us instead to examine the impact of biotic factors, such as “increases in deer abundance and changing habitat structure”, even “socio-political change” amongst European populations.

Chris Packham and Professor Richard Wall search for ticks that may have infected dogs in the Harlow area (courtesy of
Chris Packham and Professor Richard Wall search for ticks that may have infected dogs in the Harlow area. Photo courtesy of

Regardless of cause, it seems the mainland tick is here to stay. Richard Wall, Professor of Zoology at the University of Bristol, is leading the charge on tick research in the UK with his initiative The Big Tick Project.  “The fact that we now appear to have established populations of Dermacentor reticulatus acting as vectors of the introduced pathogen Babesia canis”, he says in The Guardian,is a new and important development and a major concern for animal health.”

“The problem in the future”, Sainsbury says. “The very (infected) female tick will lay around 2000 infected eggs. Even if you do all you can, you’re not going to stop the spread of the disease.” So, although the PETS scheme may well be up for debate in two years pending the current political climate, it would be prudent to keep your eyes peeled and keep treating your dogs for ticks. That includes you, Avril Lavigne.

Images: Tick yingphoto; dog at the vets Ivonne Wiring; PETS Passport Peter Baxter.

Sophie Walsh is studying for an MSc in Science Communication.