Leishmaniasis in Dogs: Signs, Treatment and Prevention

How dogs get infected

The cause is a single-celled parasite. In Europe, almost all cases in dogs come from one species, Leishmania infantum. It spreads through the bite of infected female sand flies. These insects are about a quarter the size of a mosquito and make no sound, so bites usually go unnoticed. They are most active from dusk to dawn and like to bite where the hair is thin, such as the nose, the ears and the belly.

During the day, sand flies hide in shady, humid spots such as gaps in stone walls, firewood stacks and animal sheds. Their larvae grow in soil rich in organic matter. Outdoor, stray, hunting and shelter dogs in affected areas are the most exposed.

Signs may appear a few months after the bite or only after several years. Many infected dogs never look sick, yet they can still carry the parasite and pass it on to sand flies.

Where it is found

Leishmaniasis is established across southern Europe, from Portugal and Spain to Greece. In some exposed dog populations there, up to six in ten dogs carry the infection.

In Greece, a countrywide study found dogs with antibodies to the parasite in every region, with the highest rates in the north of the country. Infected dogs have also been found in North Macedonia. In Serbia and Bulgaria, fewer infected dogs have been reported, and published data are limited. In Serbia the parasite has been found in sand flies and jackals, and researchers see a growing risk for local dogs.

In southern Europe the sand fly season usually runs from about April to November. In the warmest areas, including Greece, vets may recommend protection all year. Farther north, most cases are in dogs that lived in or traveled to affected areas. Sand flies have also been found outside their usual range, for example in parts of Germany and Switzerland.

Signs to watch for

Leishmaniasis looks different from dog to dog. The first sign is sometimes a small sore or bump on the ear, nose or belly where the sand fly bit. It heals by itself within a few weeks and is easy to mistake for a tick or insect bite. Later, owners may notice some of these signs.

• Hair loss and dry, flaky skin, often starting on the head
• Thick, crusty skin or open sores, often on the muzzle, ears or paw pads
• Nails that grow unusually long or become misshapen
• Weight loss and loss of muscle
• Swollen lymph nodes, felt as lumps under the jaw or behind the knees
• Tiredness and a poor appetite
• Drinking and urinating more than usual
• Nosebleeds
• Red, sore or cloudy eyes
• Limping or stiff joints
• Vomiting or diarrhea that keeps coming back

The skin changes are usually not itchy, which can be a useful clue. Other diseases spread by ticks and insects in the same regions can look similar, and a dog can have several at once. Tests by a vet are needed to find the cause.

When it is an emergency

Leishmaniasis usually progresses slowly, but it can damage the kidneys, the blood and the eyes. Kidney failure is a common cause of death in dogs with this disease. A heavy or repeated nosebleed, pale or white gums, sudden weakness or collapse, and refusing food along with vomiting all need a vet the same day. The same applies to a sudden change in thirst or urination, very little urine, blood in the urine, or an eye that looks painful, red or cloudy.

How vets diagnose and treat it

Diagnosis usually starts with an exam, blood tests and a urine test. These show how the blood, kidneys and liver are affected. To confirm the infection, vets may use an antibody test, a test for the parasite's genetic material, or a microscope check of a sample from a lymph node or the bone marrow. If your dog has been vaccinated against leishmaniasis, tell the vet, as this can affect some results.

Vets then grade how severe the disease is, largely based on kidney health. Dogs with mild disease usually do well, while serious kidney damage makes the outlook poorer.

Treatment usually combines medicines. One type reduces the number of parasites over several weeks. Another is given by mouth for many months to keep the parasite in check. Supportive care and a special diet are often added. Many dogs start to improve within a few weeks, but the signs usually take several months to clear. Some of these medicines have side effects, so the vet will usually check blood and urine along the way.

Treatment controls the disease, but the dog stays infected for life and the disease can come back. Regular checks, often every few months at first and then once or twice a year, help catch a relapse early. Care takes time and money, so it helps to discuss the plan and the likely costs with the vet.

How to prevent it

No single method gives full protection. Vets usually recommend several steps together.

• Use a collar or spot-on that repels sand flies, chosen with your vet. A collar works best if it goes on one to two weeks before the season or a trip, and a spot-on at least two days before.
• Keep dogs indoors from dusk to dawn during the sand fly season.
• Fit fine mesh screens on the windows and doors of the room where the dog sleeps.
• Clear away rubbish and rotting organic matter near the house, since sand flies breed there.
• Ask the vet about vaccination. Vaccines are available in Europe for healthy dogs from six months of age, with regular boosters. Vaccination lowers the chance that an infection turns into illness. It does not stop infection, so bite protection is still needed.

Some sand fly products for dogs are toxic to cats, so dog products should not be used on cats. Your vet can advise how to keep a cat safe around a treated dog.

Risk to other pets and people

In Europe, leishmaniasis almost always spreads through sand flies. A sand fly that bites an infected dog can pick up the parasite and later pass it to another dog or to a person. This is why dogs are the main source of the parasite in southern Europe. For the same reason, vets recommend bite protection for infected dogs even after successful treatment.

The parasite can also pass between dogs without sand flies. It can go from a mother to her puppies, through mating, or through a blood transfusion. These routes matter most in places without sand flies. Vets also recommend screening dogs before they give blood.

Owning an infected dog has not been shown to raise the risk for the family. In countries without sand flies, such as the UK, spread from dogs to people has not been reported. In sand fly areas, people can be bitten too, so the same evening precautions help the whole household. In people the disease can be serious, especially for young children and people with a weak immune system. Cats can also be infected, but they rarely become ill.

Rescued and adopted dogs

European parasite guidelines name shelter dogs from affected areas that move to new countries as a higher-risk group. Many rescued dogs lived outdoors or on the street, where they were more exposed to sand flies. Because signs can take months or years to appear, a dog can look healthy on adoption day and still carry the parasite.

Testing has limits too. Antibodies usually take several months to appear, sometimes much longer, so an early test may miss a recent infection. Many vets suggest a test soon after the dog arrives and a repeat test some months later. Your vet can advise on timing based on where the dog came from.

At Paw Squadron, the first stops after every rescue are the vet and a bath, with a checkup, deworming and treatment against fleas and other parasites. Before adoption, every animal gets a checkup, treatment, vaccinations and a microchip. It is still worth telling your own vet where the dog came from and asking whether leishmaniasis testing makes sense. Many dogs that test positive stay well for long periods with regular vet checks, bite protection and early treatment if signs appear.

You can find more guides on parasites and pet health in PawPedia. If you are thinking about giving a rescued dog a home, visit our Adoptions page.