Leishmaniasis in Dogs
What is leishmaniasis?
Leishmaniasis is a disease caused by a protozoan parasite found in dogs and certain rodents in many parts of the world, most commonly in rural areas.
"The parasite is transmitted by a small biting sand fly."
The parasite is transmitted by a small biting sand fly and is an important disease because humans can also contract Leishmaniasis. You cannot become infected with leishmaniasis from your dog or cat.
Leishmaniasis can cause one or two types of infections, a cutaneous or skin infection and a visceral or organ infection.
Leishmaniasis is common in the Mediterranean, South and Central America, and southern Mexico. It has been reported in Oklahoma, Ohio, and Texas and is considered endemic in foxhounds in the United States.
What are the clinical signs of leishmaniasis?
Virtually all dogs that acquire leishmaniasis will develop the visceral form of the disease. Ninety percent of those dogs will also have cutaneous involvement. The clinical signs associated with the visceral form include fever, anorexia (lack of appetite), weakness, exercise intolerance, severe weight loss, diarrhea, vomiting, bleeding from the nose, and blood in the stool (usually seen as dark, tarry stools, called melena). About one-third of dogs will develop swollen lymph nodes and an enlarged spleen, and will progress to kidney failure. Muscle pain, joint inflammation, and swelling of the testicles may also be seen.
Clinical signs of the cutaneous form most commonly include thickening and hardening of the tissues on the muzzle and foot pads, called hyperkeratosis. Many dogs will lose the pigment or dark coloring of these tissues as the disease progresses. Nodules or hard lumps may form in the skin and the coat often appears dull and brittle with areas of hair loss. The cutaneous form more commonly affects cats.
How is the disease diagnosed?
Leishmaniasis is diagnosed on medical history, especially recent travel to an area with endemic leishmaniasis, and clinical signs. Blood and urine tests are usually performed along with tissue biopsies. In the United States, if your pet is diagnosed with leishmaniasis, it must be reported to the Centers for Disease Control and Prevention (CDC). In Canada, leishmaniasis has not been reported to occur, and the Canadian Food Inspection Agency (CFIA) lists it as one of the "Non-reportable List B" diseases.
Occasionally, the organism can be found on aspirates of lymph nodes or smears made from skin lesions but these are not very sensitive. A blood test called a PCR can be sent away to an outside laboratory. This test has the best chance of diagnosis of leishmaniasis, though the test is not 100%. General blood tests may reflect changes if specific organs are affected.
Is there any treatment?
The treatment requires administration of a special drug, sodium stibogluconate, which is available from the CDC. Alternative treatments include meglumine antimonite (not available in the USA or Canada), allopurinol and/or amphotericin B, most often in combination. Supportive treatments including intravenous fluid support, special diets and antibiotics if the skin lesions are infected. Solitary skin lesions can be removed surgically.
What is the prognosis?
The prognosis for a pet diagnosed with leishmaniasis is very guarded to grave. Most dogs die from kidney failure. Severely ill pets may not be able to undergo treatment. Your veterinarian will provide you with specific treatment recommendations based on your pet's condition.
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