Leishmaniosis (Visceral Leishmaniasis) in Dogs
Leishmaniosis is a chronic, severe disease of humans, dogs, and certain other mammals caused by single-celled protozoa of the genus Leishmania. Canine leishmaniosis (also called viscerocutaneous leishmaniosis) is characterized by skin lesions and disease of internal organs.
Infection in dogs is prevalent in Central and South America, the Middle East, Asia, and the Mediterranean region. The disease is found intermittently in North America, especially in Foxhounds. Isolated cases are diagnosed around the world in animals that have visited areas where the disease is well established.
Leishmaniosis can be transmitted from dogs to people. Humans most frequently catch this disease when they are bitten by a sand fly or other insect that has previously bitten an infected animal or human. While there are only a very few human or animal cases in the US each year, worldwide there are about 700,000 to 1 million new cases of human leishmaniasis and 20,000 to 30,000 deaths a year. Most human cases of visceral leishmaniosis are reported in Brazil, Ethiopia, India, Kenya, Somalia, South Sudan, and Sudan.
The incubation period is quite variable, ranging from months to several years. The signs vary but may include skin lesions, weight loss, reluctance to exercise, lethargy, poor appetite, local or generalized disease of the lymph nodes, eye lesions, kidney failure, nosebleed, lameness, and anemia. Occasionally, some dogs have chronic diarrhea or liver disease. The most common skin lesions are areas of baldness with severe dry skin shedding, usually beginning on the head and extending to the rest of the body. Other animals develop chronic ulceration, located particularly on the head and limbs. Ulcers on the ears can bleed considerably. The signs invariably progress slowly.
Canine leishmaniasis is diagnosed using specialized blood tests that identify the parasite or the dog's immune response to the parasite. Direct observation of the parasite is more difficult, even in dogs with full-blown disease.
Drug treatment is available for dogs with visceral leishmaniosis and may last 6 to 12 months or longer. Treatment usually only improves the dog's signs and does not eliminate the parasites. Treated dogs can remain carriers of the infection, allowing it to spread to others. Relapses after treatment are common. Topical insecticides against sand flies are critical for dogs that live in areas where leishmaniasis is common, dogs traveling to these regions, and infected dogs (to reduce likelihood of transmission). In areas where the disease is common, rapid treatment of infected dogs, control of stray and homeless dogs, and control of sand flies are recommended. Vaccines against canine leishmaniosis are available in Europe and Brazil, and other vaccines are under development. Because dogs can serve as a source of infection for people, especially young children, preventing canine infections is important for human health in areas where leishmaniasis is prevalent.
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