Intoduction to Leishmania
Leishmania spp. are the causitive agent of leishmaniasis in animals and humans. The three most important species from a medical standpoint are Leishmania tropica which causes Oriental sore or cutaneous leishmaniasis, L. donovani which causes Kala-azar or visceral leishmaniasis, and L. braziliensis, the causative agent of espundia or mucocutaneous leishmaniasis. The disease is widespread in the tropics. In the U.S. there have been reported cases in dogs, cats and humans in Texas. Infection in dogs has also been Ohio and Oklahoma. Diagnosis is based on demonstration of the organism in spleen pulp, lymph nodes, liver, or peripheral blood , these species cannot be differentiated morphologically. They are separated on the basis of the disease produced, the host and its immune response, and on the geographical distribution. In addition, ELISA and PCR based methods are available for detection in dogs and humans, respectively. Treatment is difficult and involves using antimony compounds (Glucantime, Allopurinol) which are toxic. Relapse may occur and infection may persist despite treatment.


Leishmania forms


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Visceral form




Leishmaniasis in macerated hamster spleen.
The visceral form occurs in humans (kala-azar) and animals and causes a progressive systemic disease that can be fatal. The prognosis is poor. In dogs chronic wasting, exercise intolerance, anorexia, lameness, lymphadenopathy, epsitaxis (node bleed), and nonpruritic skin lesions may be observed. In humans, some of the cured cases show a post-kala-azar dermal "leishmanoid" which contains numerous parasites. There have also been cases of blood transfusion-aquired leishmaniasis reported. to see images of post visceral Leishmaniasis.



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Cutaneous form


The cutaneous form has been reported in dogs, cats and humans. Symptoms may include the development of multiple, rounded, alopecic cutaneous lesions on the pinna of the ear, muzzle, and footpads. In addition, the haircoat may be dry and brittle, with areas of depigmentation. Slow choronic disease progression occurrs in the absence of visceral involvement. Mucosal involvement may occur resulting in fever, splenomegaly, diarrhea and abdominal pains. Lymphadenopathy (enlarged lymph nodes) may also be observed.



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Mucocutaneous form




Symptoms of the mucocutaneous form, sloughing of cartilaginous tissues. .
The mucocutaneous form has been reported in humans, dogs, rodents, and wild animals. Symptoms may include ulcers and sloughing of cartilaginous tissues (nose).



Life Cycle

Leishmania is primarily a parasite of mammals, most commonly humans, dogs, and rodents, but several species are now known from lizards. The amastigote stage is the only one found in the definitive host's tissues. Leishmania spp. is vectored principally by sandflies (Phlebotomus and Lutzomyia). Within the gut of these flies the parasite assumes the promastigote form. Promastigotes are inoculated into the vertebrate host when the sandfly takes a blood meal.




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Please refer questions or comments to Rhonda Pinckney DVM, PhD.