Acute Myeloid Leukemia in a Dog Chronically Infected with Leishmania spp. and Other Infectious Agents

Abstract

Background: Rare studies have described the association of hematopoietic tumors and canine visceral leishmaniosis, however the association between the parasitary disease and neoplasia is still not well established in dogs. Thus, the aim of the present study was to report a case of acute myeloid leukemia (AML) in a dog infected by Leishmania spp. and other
infectious agents.
Case: A 8-year-old, male Poodle, was brought to the Veterinary Hospital from Universidade Federal Rural do Semi-Árido. The dog had a history of recurrent tick-borne diseases, such as anaplasmosis, over the previous ten months. On physical examination, pale mucosa, enlargement of popliteal lymph nodes, onychogryphosis, purulent nasal discharge, and bilateral
blepharitis with purulent discharge were observed. The dog was skinny and infested with ticks. The blood cell count revealed normocytic, normochromic anemia and leukocytosis (38.000/mm3) with neutrophilia (30.020/mm3). Serum biochemical tests demonstrated hyperproteinemia due to hyperglobulinemia, hypoalbuminemia, and an albumin:globulin ratio of 0.30. The immunochromathographic test for leishmaniasis was negative. The alterations observed in the bone marrow cytological analysis were suggestive of AML, and Anaplasma spp., Hepatozoon spp., and amastigote forms of Leishmania spp. were observed inside bone marrow cells. After diagnosis, a decision to euthanize the animal was made.
Discussion: Few studies have demonstrated the presence of hematopoietic neoplasia in dogs chronically and simultaneously infected with multiple pathogens. A case of multiple myeloma in a dog associated with infection by Ehrlichia canis, A. phagocytophilum, L. infantum, and Dirofilaria immitis is described. Another study reported B-cell lymphoma in a dog with E. canis and Histoplasma capsulatum infection. The pathogenesis of AML in the reported dog might be associated with continuous antigenic stimulation and chronic inflammation caused by the infectious agents. The pathological changes in bone marrow caused by Leishmania are well described, and different combinations of hypoplasia, hyperplasia, or dysplasia of all hematopoietic lineages can occur. The inflammation and chronic stimulation of hematopoiesis can lead to an increased risk of changes in the genetic material of the hematopoietic precursor cells. Thus, there is an increased chance of generation of mutated clones, resulting in hematopoietic malignancies. Immunosuppression is a common condition present in numerous types of neoplasia, especially in those with hematopoietic origins, which increases the vulnerability to opportunistic diseases. In humans, the presence of concomitant neoplasia and leishmaniasis is well documented, However, there are very few veterinary medicine studies on the association between neoplasia and canine visceral leishmaniosis. Cases of hematopoietic tumors, such as multiple myeloma, and multicentric, cutaneous, and cardiac lymphomas, have been described in dogs with leishmaniasis. To the best of our knowledge, this is possibly the first report implicating pathogens of the genera Leishmania, Anaplasma and Hepatozoon as contributors in the etiopathogenesis of AML in the studied animal. Based on all clinical and laboratory findings, we theorize that the prolonged antigenic stimulation and chronic inflammation
caused by the infectious agents played a crucial role in the development of leukemia in the dog.
Keywords: myeloproliferative disorder, hemoparasites, canine leishmaniasis.