Aspectos macro e microscópicos de lesões em hospedeiros naturalmente infestados por carrapatos

Abstract

Ticks are hematophagous ectoparasites with a wide geographical distribution, capable of causing skin lesions, transmitting pathogens, and actively modulating the host's immune response. Although experimental models have elucidated some of the inflammatory mechanisms involved in resistance to parasitism, little is known about these reactions in naturally infested wild hosts. In this context, the present study aimed to characterize macroscopic, histopathological, and inflammatory infiltrate composition changes in different species of wild and domestic animals naturally parasitized by ticks. A total of 57 skin samples from 74 necropsied animals were analyzed, covering nine host species, including giant anteaters, wild boars, capybaras, horses, cattle, brown brocket deer, porcupines, lesser anteaters, and tapirs. Samples were collected at tick attachment sites (visually identified) and processed for histological analysis. Macroscopic changes were generally mild across all hosts, primarily presenting as swelling, crusts, and, to a lesser extent, hypotrichosis. More pronounced lesions were observed in horses parasitized by Dermacentor nitens and in wild boars infested by Amblyomma sculptum. Microscopic evaluation revealed more severe cutaneous alterations than those observed macroscopically, particularly in tapirs, wild boars, and cattle, whereas lesser anteaters exhibited milder lesions. Wild boars displayed more intense hemorrhage, acanthosis, and necrosis than giant anteaters, though individual variations were observed within the same species. In horses, inflammation was more severe with A. sculptum than with D. nitens. Brown brocket deer exhibited moderate spongiosis and mild necrosis. Porcupines and capybaras had high scores for necrosis, edema, and acanthosis, respectively. Cattle parasitized by Rhipicephalus microplus showed mild changes, except for inflammation in one case. The evaluated tapir exhibited severe alterations (score 3), except for hemorrhage (score 2). Hemorrhage was generally less intense, except in capybaras and deer. Statistical analysis comparing giant anteaters and wild boars parasitized by A. sculptum revealed significant differences in inflammatory infiltrate composition. Wild boars had higher proportions of eosinophils (p < 0.001) and neutrophils (p = 0.011), whereas anteaters exhibited higher mast cell concentrations (p = 0.001). Lymphocytes and macrophages did not differ significantly between groups. In brown brocket deer and porcupines, the infiltrate was more heterogeneous, including macrophages, lymphocytes, and neutrophils. Horses showed an eosinophil-dominated response, while cattle displayed a mixed infiltrate of mild to moderate intensity. The cutaneous inflammatory response to tick attachment varies substantially among hosts, suggesting possible host-specific immunological adaptations. The absence of basophils often highlighted in experimental models as key players in resistance to parasitismo raises important questions about differences between laboratory-induced responses and natural infestations.