Keynote Message

Canine and feline rickettsial (Ehrlichia canis), protozoal (Leishmania infantum), viral (canine and feline parvoviruses, feline retroviruses), and fungal (Histoplasma capsulatum) agents may affect the bone marrow, resulting in a range of haematological abnormalities of various severity and duration. The nature of bone marrow injury in these diseases has yet to be fully elucidated and one or more pathogenetic mechanisms may underlie the bone marrow pathology. Acute or chronic refractory aplasia is the major bone marrow disorder, associated with the myelosuppressive (chronic) canine monocytic ehrlichiosis (Ehrlichia canis), feline and canine parvoviral infections, feline leukaemia virus (FeLV), and feline immunodeficiency virus infections. Marrow necrosis, myelofibrosis, pure red cell aplasia, myelodysplastic syndromes, and myelophthisic diseases may also be associated with FeLV infection. Histiocytic inflammation, along with erythroid hypoplasia and mild-to-moderate multilineage myelodysplastic changes are the major cytopathological changes in leishmaniosis, while an intense granulomatous inflammation has been documented in histoplasmosis. Importantly, however, none of the aforementioned bone marrow disorders is disease-specific and they can be induced by numerous non-infectious diseases. In this session, the pathogenesis of bone marrow injury associated with common canine and feline infectious diseases will be updated. Moreover, the disease-specific haematological abnormalities will be discussed, aiming to enhance the ability to make evidence-based diagnostic recommendations in the clinical setting.

Key References

1.  Gleich S, Hartmann K. Hematology and serum biochemistry of feline immunodeficiency virus-infected and feline leukemia virus-infected cats. Journal of Veterinary Internal Medicine. 2009;23:552–558. DOI: 10.1111/j.1939-1676.2009.0303.x.

2.  Mylonakis ME, Koutinas AF, Breitschwerdt EB, et al. Chronic canine ehrlichiosis (Ehrlichia canis): a retrospective study of 19 natural cases. Journal of the American Animal Hospital Association. 2004;40:174–184.

3.  Mylonakis ME, Koutinas AF, Leontides LS. Bone marrow mastocytosis in dogs with myelosuppressive monocytic ehrlichiosis (Ehrlichia canis): a retrospective study. Veterinary Clinical Pathology. 2006;35:311–314. DOI: 10.1111/j.1939-165X.2006.tb00137.x.

4.  Mylonakis ME, Day MJ, Siarkou V, et al. Absence of myelofibrosis in dogs with myelosuppression induced by Ehrlichia canis infection. Journal of Comparative Pathology. 2010;142:328–331.

5.  Frezoulis PS, Angelidou E, Karnezi D, et al. Canine pancytopoenia in a Mediterranean region: a retrospective study of 119 cases (2005 to 2013). Journal of Small Animal Practice. 2017;58:395–402. DOI: 10.1111/jsap.12647.

6.  Fujino Y, Horiuchi H, Mizukoshi F, et al. Prevalence of hematological abnormalities and detection of infected bone marrow cells in asymptomatic cats with feline immunodeficiency virus infection. Veterinary Microbiology. 2009;136:217–225.