Caracterização das lesões vasculares na pitiose em cães e eqüídeos

Abstract

Pythiosis is an infectious disease caused by the oomycete Pythium insidiosum. This disease affects humans and several animal species. In humans, the vascular form is the most common clinical presentation of pythiosis, where hyphae are observed on the artery wall, with the development of aneurysms and thrombosis, which can lead to limb amputation, among other consequences. In animals, the occurrence of vascular lesions has already been cited by several authors, however, the details of these lesions and their possible role in the pathogenesis of pythiosis have not been studied further. Thus, the objectives of this study were (1) to characterize the vascular lesions in dogs and horses, determining the presence and location of hyphae in the wall of the affected blood vessels; (2) to investigate how canine pythiosis lesions evolve and spread to adjacent tissues, (3) as well as to seek to understand the role of blood vessels in the development of kunkers in equine pythiosis; (4) and describe an unusual case of intestinal pythiosis in a horse. In the first study, the histological reassessment of the lesions made it possible to determine the location of the hyphae, mainly in the artery wall, rather than in the lumen of the vessels or inside thrombi, suggesting that in canine pythiosis, the occurrence of embolism is uncommon in comparison to pythiosis in humans or fungal infections in dogs. The observation of intense inflammation and hyphae adjacent to blood vessels (perivasculitis) strongly suggests that hyphae use the blood vessel wall as a pathway and that lesions and hyphae spread to adjacent tissues by extension (contiguity). In the second study, hyphae were observed on the wall of the arterioles and on the periphery of the kunkers, often slightly protruding out of the kunkers, in addition to remaining in the longitudinal direction of the collagen fibers, present inside some kunkers. These findings, added to the observation of kunkers with blood vessel-like ramifications, indicate that hyphae use arteries as a pathway and that the formation of kunkers occurs through the extension of the inflammatory process, similar to what occurs in dogs, forming the concretions of threedimensional shape. In the third article, the first case of intestinal segmental pythiosis was described in an equine, at the Veterinary Pathology Laboratory of UFSM, in 56 years of diagnostic routine.