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Clinical investigation and comparison of blood smear and PCR to diagnose haemoparasites in Sports Horses and Traction Horses (Cart Horses)

Abstract:

The blood profile is usually explored in equine medicine to find changes not detected through clinical examination. The haematozoa search in horses, often presents conflicting results between the clinical picture presented by the animal and the laboratory result, raising the hypothesis that the hematozoa search technique is responsible for diagnostic failures. Thus, this study aims to compare the values obtained from blood tests in 15 sports horses and 15 traction horses (cart horses), taking into account differences such as nutritional characteristics, state of health and type of activity performed, and to compare the different techniques with hematozoa search, as blood smear and PCR. It was found that only the traction horses showed mean values of red blood cells, hematocrit and hemoglobin below the considered physiological for the species, although 100% of the animals of both experimental groups were considered positive for hemoparasitoses by PCR. It was verified the superiority of hemoparasites search method by PCR, compared with blood smear performed by different techniques, since only 33.3% of the horses were considered positive for Theileria equi by this technique, while the PCR showed 100% positive for Theileria equi, Babesia caballi and mixed infection. None of the animals studied was diagnosed with Anaplasma phagocytophilum (Ehrlichia equi) and Ehrlichia risticcii (Neoricketsia risticii). It is shown that many cases of hemoparasitosis absence of diagnostic by hematological exams and or blood smears are erroneous due to the low sensitivity of the technique and may impact on treatment failure or spread of blood parasites and hemoparasitoses. It is noteworthy to stres the importance of tests such as PCR for the definitive diagnosis.

Index Terms:
Blood smear; hematology; horse; PCR (polymerase chain reaction).

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