Leishmaniosis, also called leishmaniasis, is a disease caused by a tiny single-celled parasite, Leishmania infantum. It can pass between animals and people, so vets treat it as a shared health issue [1]. Many dogs carry the parasite quietly for a long time, and some of them become sick months or years after they were infected [1]. In sick dogs, the skin is the part most often affected [1].
If your dog has scaling, hair loss, sores that do not heal or overgrown nails, see your vet, and tell them where your dog has lived or travelled.
Where it occurs
The parasite spreads mainly through the bite of sand flies. Dogs are its main animal host in areas such as the Mediterranean region and Brazil [1][2]. In the United States, cases that started at home are uncommon. Most of them have been in Foxhounds, and many other US cases were in dogs that had been to Spain, Italy, Greece or other affected countries [2].
Sand flies are not the only route. The parasite can also pass from a mother dog to her puppies before birth, and through blood transfusions, and it may spread through bites between dogs [1][2].
For more on biting insects, see fly and mosquito bites on dogs and cats.
Skin signs
Skin problems and swollen lymph nodes are the signs vets see most often in dogs with leishmaniosis [1]. The skin changes can include [1]:
- dry, flaking or scaling skin, in one area or all over;
- open sores, often at the edges of the lips, nose and eyelids, on the legs and feet, or over spots that get knocked or rubbed;
- small raised bumps, larger lumps or pimples;
- crusting and sores on the nose;
- a thick, hard layer on the nose and paw pads;
- nail problems, most typically nails that grow too long and curve.
Less common forms can turn up on the skin, in the mouth or in the eyes, so vets in affected areas keep leishmaniosis in mind even when the signs look unusual [1]. For crusting and sores on the nose, see dry, crusty nose in dogs.
Signs beyond the skin
The disease can affect the whole body. Signs listed by a veterinary expert group include [1]:
- weight loss and muscle wasting;
- tiredness and pale gums;
- enlarged lymph nodes;
- nosebleeds;
- lameness or swollen joints;
- fever;
- eye problems, such as red, swollen or dry eyes;
- kidney problems.
The time from infection to the first signs ranges from about 3 months to 7 years [1]. This means a dog can show signs long after it left an affected region.
How vets diagnose it
Vets use blood tests that look for antibodies against the parasite, together with tests that look for the parasite itself in samples such as lymph node, bone marrow or skin [1]. Results can be hard to read. Some dogs with other skin diseases look similar, and antibody levels in dogs that live in affected areas can rise and fall with the sand fly season [1]. Your vet may need more than one test.
Can people catch it?
Leishmaniosis can affect people as well as dogs, and dogs are the main animal source of this parasite [1]. People usually catch it from the bite of an infected sand fly. If you have questions about your own health, talk to your doctor. For your dog, talk to your vet.
Treatment
Your vet will advise on treatment for your dog. They will first decide how sick your dog is, as this guides whether and how to treat [1].
At home, as directed by a vet:
- do not give your dog human or leftover medicines unless your vet says so;
- do not stop or change any medicine without talking to your vet;
- give any treatment exactly as your vet prescribes;
- go back for any recheck or blood test your vet books.
Cutting down sand fly bites is the main way to lower the risk of infection [1]. Ask your vet what fits your dog and where you live.
Outlook
With treatment, many dogs improve and stay stable for a long time, but the disease can come back, so regular checkups matter [1].
These are statements about groups of dogs. They cannot predict how one dog will do. Your vet can explain what this means for your dog.
When to see your vet
See your vet if your dog has:
- scaling skin, hair loss or sores that do not heal [1];
- overgrown, curved nails [1];
- weight loss, tiredness, nosebleeds or lameness [1];
- red, swollen or cloudy eyes [1];
- any skin change you are unsure about, especially if your dog has lived in or travelled to an affected region.
The bottom line
Leishmaniosis is a long-lasting parasite disease, spread mainly by sand flies, that can affect a dog’s skin, nails and organs. Only a vet can confirm it with the right tests.
This article is for general information only and does not replace advice from your veterinarian. If your dog has skin sores, scaling or hair loss, see your vet.
Sources
- Roura X, Paltrinieri S, Cortadellas O, et al. Updated Canine Leishmaniosis Working Group recommendations for leishmaniosis in dogs: Q&A on clinical management. Parasites & Vectors. 2026;19. CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC13411665/
- Yao C, Yang Y, Du A. Autochthonous Leishmaniosis in Dogs, Cats, Horses, and Wildlife in the United States of America. Microorganisms. 2026;14(4). CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC13118834/