Leishmaniasis is a parasitic disease in dogs caused by microscopic organisms from the genus Leishmania, most commonly Leishmania infantum. It spreads primarily through the bite of infected sand flies and can affect the skin, internal organs, or both. The disease is found in roughly 50 countries across four continents, with millions of dogs infected worldwide, and it ranges from mild skin sores to life-threatening organ damage.
How Dogs Get Infected
Female sand flies pick up the parasite when they feed on an infected animal. Inside the fly, the parasite changes form, and when the fly bites a new host, it injects the infectious stage into the skin. In the Old World (Europe, Africa, Asia), sand flies of the genus Phlebotomus carry the parasite. In the Americas, the genus Lutzomyia fills that role.
Sand fly bites aren’t the only route. Dogs can also pass the infection vertically from mother to puppies during pregnancy, and dog-to-dog transmission through biting has been documented. These alternative routes help explain why the disease has turned up in places without established sand fly populations. The CDC confirmed a case of Leishmania infantum in a dog born in California that had never traveled to a known endemic area.
Where the Disease Is Found
Canine leishmaniasis is endemic across southern Europe, North Africa, the Middle East, Central and South Asia, and large parts of Central and South America. In some regions the infection rates are striking: seroprevalence reaches 36% in parts of Brazil, 33% on Margarita Island in Venezuela, and nearly 60% in certain areas of Tunisia. The disease is also expanding. Countries like Uruguay, where it was previously absent, now report cases, driven by factors like migration, deforestation, drought, and warming temperatures.
In North America, a survey of more than 12,000 foxhounds and other canids found infected dogs in 18 U.S. states and 2 Canadian provinces. So far, transmission in North America appears limited to dog-to-dog contact rather than sand fly bites, but if the parasite adapts to local sand fly species, the risk to both dogs and humans would increase significantly.
Symptoms to Watch For
Infected dogs typically develop both skin and internal (visceral) signs, though some remain asymptomatic for months or even years while still carrying the parasite. The clinical picture varies widely, from a single self-healing skin ulcer to severe, multi-organ disease.
Skin signs are often the most visible. These include hair loss (especially around the eyes and muzzle), scaly or flaky skin, non-healing ulcers on the ears, feet, nose, and scrotum, and abnormal nail growth where the nails become long and brittle. Some dogs develop raised, nodular lesions that range from white to grayish or reddish.
Internal disease shows up as weight loss despite a normal appetite, swollen lymph nodes, enlarged spleen and liver, eye inflammation, nosebleeds, and eventually kidney damage. Kidney failure is the most common cause of death in dogs with advanced leishmaniasis. Because these symptoms overlap with many other conditions, the disease is easy to miss without targeted testing.
How It’s Diagnosed
Diagnosis can be tricky. The gold standard is finding the parasite directly in tissue samples, usually taken from bone marrow or lymph nodes. A veterinarian examines the sample under a microscope looking for the parasite’s characteristic amastigote form inside cells. This method is highly specific, but it requires skilled personnel and specialized equipment, so it’s not available everywhere.
Blood tests that detect antibodies against the parasite are more practical and widely used. The most common options include ELISA and an indirect immunofluorescence test recommended by the World Organisation for Animal Health. Rapid point-of-care tests exist too, though they’re less sensitive. High antibody levels strongly correlate with active disease, but lower levels can be harder to interpret and often require follow-up with additional methods like PCR, which detects the parasite’s DNA.
Veterinarians use a four-stage classification system to guide treatment decisions. Staging accounts for clinical signs, blood work abnormalities (particularly kidney values), and antibody levels. A dog in stage one may look healthy with only mild antibody elevation, while a dog in stage four has severe organ damage and a much poorer prognosis.
Treatment and Long-Term Management
Leishmaniasis in dogs is treatable but rarely curable. The goal of treatment is to control symptoms, reduce the parasite load, and maintain quality of life, often for years. Most dogs require long-term medication and regular monitoring.
The first-line treatment in most of Europe combines an injectable antimony-based drug with allopurinol, a daily oral medication. A second widely used option pairs miltefosine (an oral antiparasitic) with allopurinol. In a long-term study of 173 dogs treated with this combination, 98% showed clinical improvement within an average of 3 months, and 88% were considered clinically recovered after about 17 months. The miltefosine course typically lasts 28 days, while allopurinol continues for months to over a year. Relapses do occur. In that same study, 30 dogs relapsed, with the earliest relapse at about 5 months, though the average relapse-free period was over 7 years.
Because kidney disease is a major complication, your vet will check kidney function regularly throughout treatment. Dogs caught at an earlier stage respond better and live longer with appropriate management.
Prevention Options
Preventing sand fly bites is the most effective way to protect your dog. Insecticide-impregnated collars containing deltamethrin are widely used in endemic areas. Studies show these collars provide around 50 to 63% overall protection, but that number climbs to 74 to 100% in dogs that actually keep their collars on consistently. Dogs that lost their collars between checkups saw protection drop dramatically, sometimes to near zero. A different collar type using imidacloprid combined with flumethrin has shown efficacy above 90%.
Topical spot-on treatments containing insect repellents also reduce sand fly feeding. Keeping dogs indoors during peak sand fly activity, which is dusk to dawn, adds another layer of protection. Fine-mesh screens on windows and doors help keep sand flies out of living spaces.
Two vaccines are currently on the market: Neoleish and LetiFend. Both aim to stimulate the type of immune response (cell-mediated, or Th1) that’s most effective against the parasite. Two previously available vaccines, Leish-Tec in Brazil and CaniLeish in Europe, were pulled from the market in 2023. Vaccination doesn’t replace bite prevention but can be used alongside it in high-risk areas.
Risk to Humans
Dogs are the primary reservoir for the form of leishmaniasis that infects people, particularly visceral leishmaniasis, the most dangerous type in humans. The parasite doesn’t jump directly from dog to person through casual contact. Instead, a sand fly bites an infected dog, picks up the parasite, and later transmits it to a human through another bite. Research has shown a direct relationship between the number of infected dogs in an area and the rate of human disease. Even dogs that appear perfectly healthy can carry enough parasites to infect sand flies that feed on them.
People with weakened immune systems, particularly those living with HIV, face the highest risk. In the North American foxhound survey, no human infections were found despite widespread canine infection, likely because sand fly transmission hasn’t become established there. But in endemic regions of South America, southern Europe, and parts of Africa and Asia, controlling canine leishmaniasis is considered a key part of protecting human health.