Circulating and bone marrow myeloid cells containing Leishmania amastigotes in a case of advanced canine leishmaniosis

Ioannis Oikonomidis, Theodora Tsouloufi, Mathios Mylonakis, Dimitra Psalla, Nectarios Soubasis, Timoleon Rallis, Maria Kritsepi-Konstantinou

Research output: Contribution to journalArticlepeer-review

Abstract

Abstract. A 5-y-old male Poodle mix was presented with intermittent vomiting, anorexia, and weight loss. Physical examination revealed emaciation, lethargy, dehydration, hypothermia, respiratory distress, and splenomegaly. Based on clinicopathologic, serologic, and parasitologic findings, diagnoses of severe leishmaniosis and dirofilariasis were made. Extracellular, intraneutrophilic, and intramonocytic Leishmania amastigotes were observed on direct and buffy coat blood smear examination. On direct blood smears, 0.2% of neutrophils had cytoplasmic infection. In buffy coat smears, 0.5% of neutrophils and 0.1% of monocytes were found to be infected. Leishmania amastigotes were also found engulfed by eosinophils and neutrophil precursors in bone marrow aspiration cytology. The detection of Leishmania amastigotes in blood smears is rare and the clinical significance is uncertain. In circulating blood, Leishmania amastigotes are primarily found phagocytized by neutrophils. Although debatable, there is growing evidence that neutrophils are used as carriers enabling the “silent entry” of the protozoa into macrophages (“Trojan horse” theory). Cytologic screening of blood smears for the diagnosis of canine leishmaniosis is not currently a routine practice. Clinical pathologists and practitioners should be aware that Leishmania amastigotes may be in neutrophils and less frequently monocytes during blood smear evaluation; neutrophil precursors and eosinophils may also be parasitized in bone marrow specimens.
Original languageEnglish
JournalJournal of Veterinary Diagnostic Investigation
Early online date5 Jul 2019
DOIs
Publication statusE-pub ahead of print - 5 Jul 2019

Keywords

  • bone marrow amastigotes
  • canine leishmaniosis
  • intracellular amastigotes

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