According to the Pet Food Manufacturers’ Association’s estimates, 2021 saw over 3 million households getting a new pet. That’s at least 3 million new cats and dogs (and other creatures!) in the UK. We’ve discussed where these lockdown dogs and cats have come from before. And we know that some are linked to the big increase in the number of pets imported from abroad. We’ve also had discussions about this, as well as the potential issues it causes (puppy farming, ear cropping, lockdown puppies etc.). Today, we will discuss another issue associated with imported dogs – parasites. The control of parasites is important, for the health of your own dog, other dogs in the country, and even sometimes humans. Here are 7 exotic parasites you should check your imported dog is not carrying.


Leishmania are a group of tiny protozoan (single-celled) parasites commonly found in Eastern and Southern Europe, but are present worldwide. The parasites cause a disease called Leishmaniasis that affects multiple body systems, including the skin, eyes and blood. It is generally spread by sand fly bites. It can rarely be transmitted from dog to dog by sexual reproduction or from mother to pups, and possibly via biting and blood transfusions. Luckily, the sand fly is not currently present in the UK. So most cases of Leishmaniasis occur in imported dogs. Although direct dog to dog transmission can occur here. It can infect humans as a zoonosis too, but this is rare.

A dog with Leishmaniasis may have dermatitis, hair loss, ulcers and thickened skin. The eyes can be affected by conjunctivitis and uveitis. The lymph nodes may be swollen as well. Inside the dog, it causes damage to the kidneys and liver, and can cause multiple joint problems. The biggest risk is the kidney damage, which can lead to kidney failure and death if not managed. Dogs with Leishmaniasis have shortened life expectancies for this reason.

Dogs that are infected may show symptoms straight away, but can also be infected with no signs for many years, only becoming sick in later life 

Treatment is difficult or sometimes impossible. Certain drugs can reduce the chance of the protozoans causing disease and specific symptoms can be managed, but often if the kidney damage is too great there is little that can be done. Even if the symptoms can be controlled, treatment often has to be lifelong.

Diagnosing Leishmaniasis is difficult

We can get clues based on the clinical signs of the dog, like the skin lesions. Testing the skin via sampling or biopsy can also detect the disease. We can even sample the lymph nodes or bone marrow. The best test is antibody counts (quantitative serology), where antibodies to Leishmania are measured. If the level is high, the dog likely has encountered the parasite in its life. If the level increases after a second test, the disease is probably progressing. Serology, therefore, can be used to detect when an infected dog may be starting to develop symptoms. It is recommended that all dogs are tested when first imported into the country. Then again 6 months later if they are negative, to see if the antibody level has increased and identify early infections.


Dirofilaria immitis is a tiny roundworm that lives in the hearts of dogs, as well as other animals. It is spread by mosquitoes, so is found mostly in the warmer parts of the world. A mosquito bites an infected animal and ingests the worm’s larvae. When it bites another animal, the larvae enter its blood and start to develop. The worms migrate mainly to the right side of the heart. The worm cannot currently live outside in the UK as it is too cold. There is an increasing risk that as the UK’s average temperature increases with climate change, D. immitis may start to reside in the UK, increasing the risk of dogs becoming infected here. As of now, the biggest risk is dogs travelling to and from abroad, especially the Mediterranean. D. immitis can infect humans, but it cannot be caught from dogs.

A dog infected with heartworm may start to show signs of exercise intolerance and chronic coughing. Inside, their heart is starting to fail as the worms block the flow of blood. This can result in fluid build-up in the lungs, high blood pressure, and even heart failure. In extreme cases, the vessels of the heart can rupture, leading to sudden death.

Suspicion of heartworm can be based on clinical signs, imaging the chest or looking at blood under a microscope. Proper diagnosis can be done via an antigen test, detecting proteins found on the worm (a bit like the lateral flow tests we’re all used to for Covid). Treatment is difficult, so regular prevention with worming tablets or spot-ons is critical, particularly for dogs travelling abroad or coming from other countries.

Tick-Borne Parasites

The next few parasites are all related, so we will group them together. The common factor linking these parasites is that they are all spread by ticks. There are many kinds of tick-borne parasites, but these in particular are mainly found outside the UK, often in imported dogs from bad backgrounds. They are Ehrlichia canis, Hepatozoon canis, Babesia and Anaplasma, though there are others too. Most of these are spread when an infected tick bites a dog (Hepatozoon is spread by dogs eating infected ticks). The ticks that spread these parasites are not generally found in the UK.

The diseases caused by these parasites vary, but tend to cause fever and lymph node swelling, anaemia, thrombocytopenia (platelet destruction), weight loss and neurological signs. The anaemia and thrombocytopenia can lead to weakness, collapse, uncontrolled bleeding and even death.

Diagnosis of these diseases can be done via a blood smear. We can sometimes see the parasites infecting various blood cells. A more sensitive test is to measure the antibodies with paired quantitative serology a few weeks apart, like with Leishmania. The best test is a PCR test on blood or other fluids. This advanced test will detect small amounts of the parasites’ DNA, indicating infection.

Treatment is  via antibiotics or anti-protozoan drugs, depending on the specific agent involved. We can prevent them with regular tick control drugs and avoidance. 


Brucella canis is perhaps the most important parasite on the list for a number of reasons. First, it causes a lot of reproductive issues, which is a concern for people who import dogs for breeding. Secondly, the cases in the UK appear to be increasing, thought to directly be because of imported dogs. Before 2020 there were 2 cases in the UK, since 2020 there have been over 40. And thirdly, this bacteria can spread to humans and cause serious disease. B. canis is spread between dogs via sexual reproduction, or contact with infected fluids.

It mainly causes reproductive problems, including swollen genitals, infertility, discharge, and abortion. It can also cause damage to the kidneys, brain, eyes and spine. In humans, it results in fever, pain, lethargy, genital swelling, heart swelling, depression and even eye and neurological problems, which can be very long lasting.

There is no effective treatment for B. canis. Antibiotics can help reduce symptoms, but the dog is still vulnerable and can also still spread it to other dogs. Dogs infected should be fully isolated from other dogs for life, or put to sleep on welfare and safety grounds. Testing for B. canis is performed via antibody paired serology again. Any dog from abroad or that has visited areas where B. canis is found, and is struggling to be bred from, should be tested.


Currently, all of these diseases are non-endemic in the UK. This means that infection cannot occur from the environment, usually because our climate is too cold. This may change due to climate change, but we want to keep these diseases out as long as possible. It is therefore important to screen any imported dogs for the above parasites.

However, you might be questioning the cost of this. Adopting a dog from abroad can be expensive already, so adding testing may increase this further. And in truth, testing for these parasites is not cheap, particularly for the more advanced tests like PCR or paired serology. Although we recommend performing a screen for all these parasites before bringing an imported dog into the country (and if you cannot afford this, we advise looking for a dog closer to home…), there are things we can do to keep costs down.

The first is to only test for certain diseases based on risk 

We can look at the country the dog came from and which diseases are present there, and only test for those. However, this isn’t foolproof as a dog’s history can be incorrect or even falsified, particularly with some mistreated animals, so they may have been to multiple countries and picked up multiple diseases already. Unfortunately, many of these diseases are found worldwide, and all are found in Eastern Europe where most imported dogs are from. The history of the dog, such as its reproductive status, history of parasite treatments and preventatives, and previous testing, can also indicate which diseases we should test for. 

The next method is to base what we test for on clinical signs

A dog imported from abroad with skin issues should be tested for Leishmania, a dog with many ticks over it should be tested for the tick-borne diseases. One that has aborted should be tested for Brucella canis. This is risky though, as many of the diseases remain dormant for many months or years, and if symptoms are present, treatment may be more difficult.

We can also start with cheaper tests 

For example, general blood screening for signs of infection, or looking at blood smears under the microscope. These can often be performed by vets in their practices, which is cheaper than using an internal lab. These tests are often poorly sensitive (high false negatives) but are quite specific (low false positives) – if we see a parasite on a blood smear the dog is likely to have an infection, but just because we don’t see them on a smear doesn’t mean they aren’t there. Certain tests are coming out now that combine multiple tests at once, testing for multiple parasites – these are quick and easy to use, and provide a lot of information for a much cheaper cost than many individual tests.

Certain diseases are commonly seen together, so diagnosing one on a test is a good reason to test for the other as well

Hepatozoon canis and Anaplasma are commonly seen together as the same tick spreads them both – if one is spotted, we should check for the other. The same is true of Ehrlichia and Leishmania, though we aren’t exactly sure why they are related. Dirofilaria immitis can be easily confused with other similar worms on testing, like Dirofilaria repens that causes skin disease – if we identify one, it is sensible to test for the others to ensure there aren’t multiple worm species infecting the dog.

Finally, we can prioritise 

Of the 7 parasites listed above, Brucella canis is the disease most significant to human health. Due to the symptoms it causes, it may be sensible to test all dogs coming into the country for the bacteria, to prevent any spread to humans. Leishmania may be the next one to test for, as it can cause reduced life expectancy and the need for lifelong treatment.

Final Thoughts

Although we know that everyone’s hearts are in the right place, we hope this article has shown you another potential issue that adopting a dog from abroad can create. These parasites are certainly nasty, and cause problems ranging from fevers, abortion, skin issues, organ failure and even death. We want to keep them out of the country as long as we can, but unfortunately the increased adoption of dogs from abroad is causing an increased number of cases. 

Testing for at least some of these parasites before or upon entry to the UK will go a long way to reducing the risk, but we want to again ask you to consider whether getting a dog from abroad is right for you. If you do it correctly, the testing could cost you hundreds of pounds – if you don’t, there is risk to your dog’s life, yourself, as well as other UK pets.  

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