Chronic Myelogenous Leukemia in a Great Horned Owl (Bubo virginianus)

Abstract

A free-ranging adult female great horned owl (Bubo virginianus) was presented to the Wildlife Medical Clinic at the University of Illinois after being observed with anorexia and decreased activity. A severe leukocytosis (212 400 cells/microl), primarily comprised of mature heterophils, was found at presentation. Results of various diagnostic tests including radiographs, Chlamydophila serologic testing, measurement of Aspergillus antibody and antigen titers, plasma protein electrophoresis, fecal culture and acid-fast staining, coelioscopy, endoscopy, tracheoscopy, exploratory coelomotomy, nuclear scintigraphy, tissue cultures, bone marrow biopsy, and histopathology revealed no underlying cause for the persistent leukocytosis. No response to treatment with antibiotics or antifungal agents was observed, although a transient, significant decrease in the leukocyte count (6200 cells/microl) was observed after treatment with fenbendazole. A presumptive diagnosis of chronic myelogenous leukemia was made based on 3 factors: disease duration of greater than 3 months, a lack of identifiable foci of inflammation, and a lack of response to conventional therapy. The diagnosis was confirmed based on postmortem examination and testing 177 days after initial presentation.

Anti-parasite treatment results in decreased estimated survival with increasing lead (Pb) levels in the common eiderSomateria mollissima

“…There was even evidence of a survival benefit in the years following APT among common eiders that presumably results from the alleviation of effects of parasitism [16]. Notwithstanding, evidence of fenbendazole toxicosis has been found in other birds where it lowered condition and survival [58][59][60][61][62]. Subtle, longer-term health consequences of the antihelminthic may include increased sensitivity to Pb toxicity, thereby causing the decreased returns to the breeding colony observed among eiders with higher Pb.…”

Microsporidiosis in Vertebrate Companion Exotic Animals

“…Of note, fenbendazole, albendazole and other benzimidazoles are toxic in some avian species [ 156 ] and can cause medullary aplasia, digestive signs, and death. Toxicity has been reported in some columbiformes [ 157 , 158 ], some vultures [ 159 ], storks [ 159 , 160 ], pink-backed pelicans ( Pelecanus rufescens ) [ 161 ], a leukemic great-horned owl ( Bubo virginianus ) [ 162 ], and, anecdotally, in cockatiels ( Nymphicus hollandicus ) [ 156 ] and keas ( Nestor notabilis ) [ 151 ]. Because columbiformes are suspected to excrete microsporidia more frequently than other birds [ 142 ], finding a viable treatment for this order would be important.…”

What is Your Diagnosis?

“…19 In humans, lymphoma commonly causes ischemia and necrosis of the digits as a paraneoplastic syndrome, and this condition also has been reported in a cat with multicentric follicular lymphoma. 21 Lymphoid neoplasia is the most common form of hemolymphatic neoplasia reported in birds, 13,14 but, to our knowledge, this is the first reported case of suspected HVS secondary to CLL in an avian species. This case also represents the second report of lymphoid neoplasia in a European starling.…”

“…10,11 Severe leukocytosis in birds is often associated with diseases such as aspergillosis, avian mycobacteriosis, salmonellosis, chlamydiosis, and sepsis, 12 but herpesviruses (ie, Marek disease) and retroviruses (ie, avian leukosis virus, reticuloendotheliosis virus) can specifically cause a lymphocytic leukocytosis in chickens. [12][13][14] A multicentric lymphoma has been reported in a European starling in which case retroviral nucleic acid was found in the neoplastic tissue. 15 Further virological testing was not performed in this case.…”