Preliminary study on tick ectoparasites of horses: effects on tick development and on the haematological parameters of hosts

Amblyomma sculptum and Dermacentor nitens are the most common tick species that affect horses in Brazil. They induce immunological responses, which reflect the intensity of tick infestation and their life cycle. This study compares the development of these ticks feeding on two horse breeds, and the influence of biological parameters and infestation on haematological values. A total of 12 female horses (6 Mangalarga Marchador and 6 Breton Postier) were subjected to natural tick infestation, counting, and collection. Additionally, blood samples from each animal were collected. Engorged female ticks were kept in a Bio-Oxygen Demand incubator to monitor their development. A significant negative correlation was found between the tick count and the haematological parameters of horses: White Blood Cell, Red Blood Cell, Haemoglobin, and Packed Cell Volume. Our results demonstrate that the animals of two breeds have a similar influence on the development of ticks and that although haematological parameters are correlated with parasitism, the variation in resistance and susceptibility of these animals is probably related to specific characteristics of each animal and not because of the breed.