Hematologic indices in clinically healthy outdoor dogs exposed to vector-borne pathogens

Abstract

Haematologic abnormalities possibly associated with exposure to vector-borne pathogens are rarely reported in clinically healthy outdoor dogs. Therefore, we analysed changes in the complete blood count (CBC) of clinically healthy outdoor dogs seroreactive to Anaplasma spp. and Babesia spp., with or without microfilariosis. Stray, shelter and hunting dogs, 81 in total, that were polymerase chain reaction negative for Anaplasma spp. and Babesia spp. were divided into groups according to their seroreactive status and results of a modified Knott’s test: seronegative to both Anaplasma spp. and Babesia spp. SN (N=26); seroreactive to A. phagocythophilum SR-A (N=12); seroreactive to B. canis, B. gibsoni and/or B. vogeli SR-B (N=25); and seroreactive to both of the pathogens SR-AB (N=8). These four groups were negative to microfilariosis, unlike the fifth group, seroreactive to either or to both of the pathogens and with microfilariosis SR-M (N=10). The frequencies of CBC alterations among all analysed dogs were: 0.35 – leucocytosis, 0.44 – granulocytosis, 0.28 – anaemia, 0.74 – microcytosis, 0.37 – increased mean cell haemoglobin concentration (MCHC) and 0.33 – thrombocytopenia. The frequency of alterations did not differ across the groups. An exception was the SR-M group wherein increased MCHC peaked with a frequency of 0.80, while in the other four groups, the frequency ranged between 0.10 and 0.50. Clinically healthy outdoor dogs have multiple CBC abnormalities, consistent with stress and low-level chronic inflammation, but not associated with a previous exposure to Anaplasma spp. or Babesia spp. The presence of microfilaria increases haemolysis in vitro.