An overview of clinical features of equine pythiosis (Pythium insidiosum)
TL;DR
The biological and infectious aspects of Pythium insidiosum are analyzed and the immunopathogenesis of equine pythiosis is characterized, focusing on the interaction between the etiological agent and the host immune response.
Abstract
Pythiosis is a chronic granulomatous disease affecting various animal species, most commonly equines. It occurs in tropical, subtropical, or temperate climates and is associated with waterlogged areas, such as swamps and ponds. The causative microorganism parasitizes aquatic plants and produces motile zoospores capable of infecting hosts through cutaneous lesions. Pathogenesis is associated with a predominant Th2-type immune response, characterized by the production of interleukins such as IL-4, IL-5, and IL-13, as well as intense eosinophilia and granulomatous inflammation, which contributes to the agent’s persistence in tissues. Clinically, the disease is characterized by the formation of eosinophilic granulomas containing “kunkers”, necrotic masses composed of hyphae, collagen, and inflammatory cells. Various therapeutic approaches have been employed, including the use of antifungals, surgery, and immunotherapy. Surgical removal combined with immunotherapy is considered the most effective strategy, although treatment poses challenges due to the agent’s unique characteristics; unlike true fungi, its cell wall contains cellulose and β-glucans. This study aims to analyze the biological and infectious aspects of Pythium insidiosum and to characterize the immunopathogenesis of equine pythiosis, focusing on the interaction between the etiological agent and the host immune response.