Abstract:
Babesiosis caused by the virulent tick-borne hemoprotozoan, Babesia rossi, results
in a marked systemic inflammatory host response in dogs. Neutrophils form part of
the innate immune response and contains myeloperoxidase (MPO) as the predominant
component of the neutrophil lysosomal protein in azurophilic granules. The neutrophil
myeloperoxidase index (MPXI), determined on the ADVIA hematology analyzer, is a
quantitative estimate of intracellular MPO content. Objectives of this study were to: (a)
compare MPXI in dogs with babesiosis with healthy control dogs; (b) compare MPXI in
dogs that died from babesiosis with dogs that survived and controls; and (c) correlate the
MPXI with the previously determined segmented and band neutrophil count and cytokine
concentrations in dogs with babesiosis. Data for 140 dogs naturally infected with B. rossi
and 20 healthy control dogs were retrospectively evaluated. Neutrophil counts and
MPXI were determined on an ADVIA 2120 analyzer. Cytokine concentrations [interleukin
(IL)-2, IL-6, IL-8, IL-10, IL-18, granulocyte-macrophage colony stimulating factor
(GM-CSF), and monocyte chemo-attractant protein-1 (MCP-1)] were determined using a
canine-specific multiplex immunoassay. The mortality rate of the Babesia-infected dogs
was 11% (15/140). MPXI was significantly higher in Babesia-infected dogs (P = 0.033),
and in Babesia-infected non-survivors (P = 0.011), compared with healthy control dogs.
In Babesia-infected dogs a significant positive correlation was found between MPXI and
IL-10 (r = 0.211, P = 0.039) and a significant negative correlation was found between
MPXI and IL-8 (r = −0.350, P < 0.001). In Babesia-infected non-survivors, significant
positive correlations were found between MPXI and IL-2 (r = 0.616, P = 0.033), IL-6
(r = 0.615, P = 0.033), IL-18 (r = 0.613, P = 0.034), GM-CSF (r = 0.630, P = 0.028),
and MCP-1 (r = 0.713, P = 0.009). In Babesia-infected survivors, a significant negative
correlation was found between MPXI and IL-8 (r = −0.363, P = 0.001). MPXI was
correlated with pro-inflammatory cytokines in Babesia-infected dogs that died. The
potential of MPXI as a novel marker of inflammation and prognosis in dogs infected with
B. rossi, thus warrants further investigation.
