Hematology and some blood chemical parameters as a function of tick-borne disease (TBD) signs in horses

Abstract Two statements provide the context within which this investigation was carried out: (i) Apulia is an enzootic region for tick-borne diseases (TBD); (ii) the principles of enzootic stability and the study of resilient/resistant breeds are among the tools for future pest control strategies. Thus, a trial protocol was established to check the amount of variation in hematologic and biochemical parameters serving as a function of TBD signs in resilient horses. Blood samples were collected from 109 horses belonging to the Apulian native Murgese breed. Hematologic and biochemical parameters were screened and microscopic search for the parasites in the red cells was performed. Differences in clinical manifestations and hematological and biochemical responses were recorded. The following disease classification was used: infection-free horses (class 0), infected horses (presence of Theileria equi and/or Babesia spp in the red cells) without clinical signs (class 1), and horses suffering from clinical disease (class 2). Seventy-one horses (65.1%) showed no TBD signs; hemoparasites were found in 38 horses (34.9%), of which only five (4.6%) showed clinical signs. A significant decreasing trend was shown from class 0 to class 2, where animals with clinical signs presented highly reduced values of some relevant blood parameters. The similarity of the blood values of class 0 and 1 animals is the most striking result of this work and calls for more extensive, detailed research into the mechanisms through which infected horses with no clinical signs of disease can cope with the condition.