Incidental Finding of Dirofilaria immitis (Spirurida: Onchocercidae) Microfilariae in the Bone Marrow of a Dog with Mixed Leishmania infantum - Dirofilaria immitis Infection.

Simple Summary: Canine leishmaniasis and cardiopulmonary dirofilariasis are common parasitoses in dogs and are endemic in various regions of Italy. Although Leishmania infantum and Dirofilaria immitis have commonly been reported as single infections in dogs in Italy, mixed infection with both parasites is seldom reported. This case report describes a very rarely reported localization of Dirofilaria immitis microfilariae in the bone marrow of an adult dog, which was serologically and PCR-positive for Leishmania infantum. This is the second reported case of the localization of D. immitis microfilariae in the bone marrow of a Leishmania-infected dog. We report a rare and interesting case of mixed infection with Leishmania infantum and Dirofilaria immitis associated with the incidental finding of microfilariae in the bone marrow of a 9-year-old, intact, male Bullmastiff which was seropositive to L. infantum. Clinical signs showed progressive weakness, pale mucosae membranes, and a very low body condition score. Laboratory abnormalities included moderate, normocytic, normochromic, non-regenerative anemia; mild leukocytosis, neutrophilia, monocytosis, and eosinopenia; low platelet count; elevated C reactive protein; mild hyperkalemia, hypoalbuminemia, and hyperbeta-2-globulinemia; and a low A/G ratio. Hypoadrenocorticism, euthyroid sick syndrome, and alteration in the fibrinolytic phase of hemostasis were also detected. Microfilariae were incidentally found in bone marrow cytology aspirate in the absence of clinical features indicative of co-infection with D. immitis. PCR confirmed the identification of the Dirofilaria species. It is assumed that the microfilariae may have left the microcirculation and migrated to bone marrow tissues by crossing the vessel wall. To the best of our knowledge, only one such case has been previously reported in dogs. [ABSTRACT FROM AUTHOR]