Leishmaniasis in Dogs

What is leishmaniasis?

Leishmaniasis is a disease caused by a protozoan (single-celled) parasite that infects dogs, cats, and certain rodents in many parts of the world, most commonly in rural areas. The parasite is transmitted by small, biting sand flies. It is important to be aware of this disease because humans can also become infected.

Leishmaniasis can cause one or two types of infections: a cutaneous (skin) infection and a visceral (organ) infection. Leishmaniasis is common in tropical and subtropical regions of the world but is increasingly found in North America and Northern Europe. In North America, the disease is commonly reported in foxhounds.

What are the clinical signs of leishmaniasis?

Clinical signs of visceral leishmaniasis include:

• Fever
• Anorexia (lack of appetite)
• Weakness
• Decreased stamina
• Severe weight loss
• Diarrhea
• Vomiting
• Increased drinking and urination
• Bleeding from the nose
• More than half of dogs develop swollen lymph nodes, and these cases may also develop an enlarged spleen and will progress to kidney failure. Muscle pain, joint inflammation, and swelling of the testicles may also be present.

Clinical signs of cutaneous leishmaniasis include:

• Thickening and hardening of the tissues on the muzzle and footpads (hyperkeratosis)
• Loss of pigment or dark coloring of the tissues on the muzzle and footpads as the disease progresses
• Nodules or hard lumps in the skin
• Dull and brittle coat with areas of hair loss
• The nails may grow long and curve abnormally
• Ocular (eye) signs may develop, including blepharitis (swollen eyelids), conjunctivitis, inflammation of the cornea, uveitis (inflammation within the eye), loss of hair around the eyelids, and nodules on the eyelids.

There are four classified stages of leishmaniasis based on clinical signs and diagnostic tests:

• Stage 1: Mild disease with little or no change seen in bloodwork.
• Stage 2: Moderate disease with antibodies seen in the blood, along with elevated protein and mild anemia. Signs include skin changes, weight loss, and bleeding from the nose.
• Stage 3: Severe disease that includes Stage 2 changes as well as more severe signs, such as kidney disease, eye inflammation, enlarged lymph nodes, and an enlarged spleen.
• Stage 4: Extremely severe disease, with more severe clinical signs, including difficulty breathing and bloodwork consistent with kidney failure.

How is leishmaniasis diagnosed?

Leishmaniasis is diagnosed based on a dog’s clinical signs, medical history, and travel history — especially travel to an area where leishmaniasis is common. Initial blood and urine testing (CBC, biochemistry, urinalysis), may reveal changes that suggest leishmaniasis, such as elevations in kidney values or liver enzymes, but confirmation requires additional testing.

• Your veterinarian may also collect small samples from enlarged lymph nodes using a needle (fine-needle aspirates) or prepare samples from skin lesions. Examining these samples under a microscope can demonstrate the organism, but this method does not detect every infected dog.
• A PCR blood test can also be sent to a laboratory. This test detects the genetic material (DNA) of the organism and has the best chance of identifying leishmaniasis, but it is not 100% accurate.
• Blood tests may also detect antibodies against the organism, depending on how long the dog has been infected. High antibody levels can indicate active infection; however earlier in the disease, antibody levels may be low so your veterinarian may recommend repeating this test in two weeks to see if they have increased in response to infection or if the antibodies are left over from a previous exposure.

Is there any treatment for leishmaniasis in dogs?

Unfortunately, it is unlikely that treatment will completely remove the parasite. The goal of treatment is to control the infection and resolve the clinical signs of leishmaniasis. Several treatments are available and are often used in combination.

• Allopurinol, meglumine antimonite, and miltefosine are medications used to slow down or kill the parasite.
• Marbofloxacin (an antibiotic) and domperidone (an immune stimulant) are also used in treatment.
• Supportive care may include intravenous fluids, special therapeutic diets, and antibiotics to treat infected skin lesions.
• Surgery may be required to remove solitary skin lesions.

Dogs must be closely monitored after treatment because relapse can occur.

What is the prognosis?

The prognosis for a dog diagnosed with leishmaniasis is guarded (uncertain) to grave, depending on the stage of disease when it was diagnosed. Many dogs die from the resulting kidney failure. Severely ill dogs may not be able to undergo treatment. Your veterinarian will provide you with specific treatment recommendations based on your dog’s condition.