Toby, a fun-loving Labrador, was a beloved member of the Murphy household. So, when the family noticed patches of hair loss and red, itchy skin on his paws and legs, they were concerned. Still, they thought: "All dogs get itchy sometimes." A medicated shampoo and a modified diet seemed to help.
Author
- Nikki Walshe
Associate Professor in Equine Science, Department of Biological Sciences, University of Limerick
But by the following winter, Toby's condition worsened. He began losing more hair around his head, dropped weight rapidly and his lymph nodes became swollen. The family sought further veterinary help. Blood tests and tissue samples revealed something unexpected: Leishmania infantum , a parasite typically found in southern Europe, transmitted by the bite of sand flies.
Toby had never left the UK, but his owners had visited the Jalón Valley, Spain just months earlier. Toby hadn't gone with them, but the possibility arose: could an infected sand fly or contaminated item have made its way back in luggage or belongings? Toby was treated and recovered well.
This is an adapted version of one of just three recorded cases of leishmaniasis in UK dogs since 2019. Canine leishmaniasis causes chronic, sometimes fatal disease in dogs and can infect humans , particularly those with a weakened immune system . Once confined to the Mediterranean basin, it is now spreading northwards through Europe .
The rise of vector-borne diseases
One growing concern in both the veterinary parasitology and public health sector is vector-borne disease (illness spread by arthropods like flies, ticks and mosquitoes). These diseases don't respect borders; instead, they migrate with changing habitats and climates .
The UK's island geography has historically offered a degree of natural protection . But global warming , increased international travel and trends like cross-border pet rehoming are eroding that protection. What was once "exotic" is now edging closer to home.
In fact, the international rehoming of animals and routine pet travel are now major contributors to the rise of exotic diseases in domestic animals. In one large group of imported dogs , more than a quarter tested positive for conditions not typically seen in the UK, including heartworm Dirofilaria immitis . Spread by mosquitoes, heartworm damages the heart and lungs of dogs. Once restricted to southern Europe, it is now being reported in central and eastern Europe , with sporadic cases further north and west.
It's not just dogs. Horses are also vulnerable.
Equine piroplasmosis (EP) - transmitted by ticks - can cause severe illness or death. Once considered a southern European problem, it is now a concern for the UK's equine industry due to expanding tick habitats, increased animal movement and blood tests showing antibodies to the parasite in some horses in Britain and Ireland - a sign they have been exposed to the disease.
African Horse Sickness , a midge-borne virus, has caused devastating outbreaks, such as in Spain, Portugal and Morocco , in the late 1980s, killing hundreds of horses. While the current risk of the virus spreading in the UK is low, species of midges capable of transmitting it are already found in parts of Europe. Climate and environmental modelling suggest that conditions across the region are becoming increasingly suitable for the virus to establish and spread.
When pets and people share risks
Our close relationships with companion animals mean some parasites can leap from them to us.
Exotic parasites like Echinococcus multilocularis , Leishmania infantum and Dirofilaria immitis can infect humans, sometimes with serious consequences.
Take Echinococcus , for example. Dogs often carry it without symptoms, shedding eggs in their faeces that can contaminate soil, water, or food. Humans may become infected by accidentally ingesting these eggs, such as through contact with infected dogs or unwashed produce.
The two species of greatest concern for zoonotic transmission are Echinococcus granulosus, which causes Cystic echinococcosis, and E. multilocularis, which can cause a more serious, invasive form of the disease affecting the liver and other organs. In the UK, E. granulosus is present at low levels, with isolated cases reported in imported and farm-associated dogs.
E. multilocularis has not been detected in the UK and remains under active surveillance. In Ireland, there are no confirmed cases of Echinococcus in dogs, yet a 2019 case involving a woman with no travel history suggests the parasite may already be circulating undetected highlighting the importance of continued surveillance.
And what of exotic parasites that have already entered our domestic animal population? The first recorded UK case of a cyst-forming parasite in donkeys was documented in 2020 , the first recorded Irish case was in 2023 and researchers are investigating suspected Onchocerca cervicalis in Connemara ponies. Initially mistaken for "sweet itch" - a common allergic skin condition in horses caused by midge bites - these cases presented with unusual symptoms but responded to deworming.
Protecting the UK
Protecting the UK from emerging vector-borne threats requires a proactive approach:
screen animals before importation to reduce the risk of bringing parasites into the country
formally monitor insect vectors - flies, ticks and mosquitoes - to track and predict spread
test local animal populations to establish a clear disease baseline
educate vets and owners about the risks of animal movement and encourage responsible practices, especially for dogs and horses.
Most importantly, we need a true One Health approach - a framework that recognises the health of people, animals and the environment are deeply interconnected. This approach brings together veterinary and human health professionals, environmental scientists and policymakers to share data, monitor threats and design coordinated prevention strategies. By acting early, we can limit the spread of parasites before they become established in the UK and Ireland.
If we wait until disease emerges, the horse will have truly bolted and we may discover the infection has already spread to our animals, our communities and, potentially, ourselves
Nikki Walshe is affiliated with ESCCAP (European Scientific Counsel Companion Animal Parasites)
