Despite haemolytic anaemia being the main consequence of Babesia rossi infection
in dogs, the bone marrow response has been reported to be mild in the face of severe
anaemia. A similar finding has been described in falciparum malaria and has been
ascribed to either a decreased production of erythroid precursors or an inability of
erythroid precursors to respond to hormonal stimulus.
Recently, more information has become available on the use of various reticulocyte
indices in an attempt to describe and explain the underlying pathogenesis of various
anaemias as their release describes the recent functional state of the bone marrow.
The objective of this study was to compare the admission absolute reticulocyte count
(ARC) and reticulocyte indices in dogs naturally infected with B. rossi with dogs
suffering from immune-mediated haemolytic anaemia (IMHA), unrelated to babesiosis,
as well as healthy control dogs. The ARC and reticulocyte indices were also evaluated
in five experimentally B. rossi infected dogs throughout the disease course.
This was a retrospective observational study looking at the records generated on a
haematology analyser, the ADVIA 2120 (Siemens, Munich, Germany). The
haematocrit (HCT), ARC and other reticulocyte indices for 103 dogs, naturally infected
with B. rossi was compared to 16 dogs with IMHA and 14 control dogs. The
experimentally infected dogs consisted of five purpose-bred beagles that were infected
with high and low dose B. rossi parasite inoculum. Differences between groups were
assessed using the Mann-Whitney U test, whereas the Friedman’s ANOVA was used
to assess the change over time during the disease course in the experimentally
infected dogs. The Wilcoxon Signed Ranks test was then used to determine the
differences within the experimentally infected groups.
The median (IQR) HCT for the Babesia (0.16 L/L; 0.12 – 0.27; P < 0.001) and IMHA
(0.15 L/L; 0.12 – 0.17; P < 0.001) groups were significantly lower than the control group (0.52 L/L; 0.45 – 0.57). For the Babesia and IMHA groups the HCT did not differ
significantly. Compared to the control group (42.1 x109/L; 33.8 – 62.6), the median
(IQR) ARC was significantly higher in the Babesia (82.1 x109/L; 48.6 – 174.9; P =
0.006) and IMHA (256.7 x109/L; 79.0 – 436.9; P = 0.004) groups. The ARC was
significantly lower in the Babesia group compared to the IMHA group (P = 0.011),
despite no significant difference for HCT between groups.
On day four of the experimentally infected group, approximately 24 – 48 hours after a
peripheral parasitaemia was observed, there was a sudden decrease in the ARC to
less than its value on day one, which was inappropriate for the degree of anaemia
observed.
The reticulocytes of B. rossi naturally infected dogs were larger and more hypochromic
with a greater difference in cellular haemoglobin (CH) between reticulocytes and
mature erythrocytes compared to the control group, whereas the reticulocytes of the
experimentally infected dogs were smaller and more hypochromic than day one of
infection. All reticulocyte indices demonstrated significant differences on day four
compared to day one of the experimental study. The changes noted in the reticulocyte
indices are postulated to be a contribution of anaemia of inflammation (AID), shift
reticulocytosis and iron-restricted erythropoiesis.
This study concludes that the regenerative response in dogs naturally infected with B.
rossi is inappropriate, despite the severity of anaemia observed, compared to dogs
with IMHA. Furthermore, the findings of the experimentally group may indicate a
possible direct suppressive action of the Babesia parasite on the bone marrow during
the time of parasitaemia, resulting in insufficient erythropoiesis. Similar findings have
been reported in falciparum malaria and other factors will require further investigation. / Dissertation (MSc)--University of Pretoria, 2020. / Companion Animal Clinical Studies / MSc / Unrestricted
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:up/oai:repository.up.ac.za:2263/82588 |
| Date | January 2020 |
| Creators | Seejarim, Chandini |
| Contributors | Goddard, Amelia, chandiniseejarim@yahoo.com, Rautenbach, Yolandi |
| Publisher | University of Pretoria |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | © 2021 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
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