Pythiosis in Equidae in Northeastern Brazil: 1985-2020.

This research describes the findings related to the occurrence of pythiosis, a serious infectious disease, in equidae (horses, donkeys, etc.) in northeastern Brazil between 1985 and 2020.

Epidemiology

• The study was conducted by the Laboratory of Animal Pathology of the Federal University of Campina Grande, who received 1,331 tissue samples from equidae from January 1985 to December 2020.
• Of these samples, 202 or 15.17% were diagnosed with pythiosis, indicating that the disease is endemic in this region.
• The disease was found in male and female equidae of different ages, from 4 months to 25 years old.
• Most of the affected animals were of mixed breed (79.7%) and typically reared in an extensive system (73.26%).
• Although the disease was present throughout the year, the majority of the cases (70.29%) were observed after the rainy season, indicating a seasonal trend in infection rate.

Clinical Pathology

• The clinical course of pythiosis in equidae was observed to be chronic.
• The lesions caused by the disease were primarily located on the limbs and ventral thoracoabdominal wall and were characterized by the creation of nodules or tumor-like masses with ulcerations and serosanguineous discharge.
• Upon examination, fistulous tracts containing kunkers were found on the cut surface of these masses.

Microbiological and Histopathological Findings

• The direct assessment of these kunkers and subsequent microbiological culture revealed the presence of sparsely septate and branched hyaline hyphae, indicating the fungal nature of the pathogen.
• Through histopathological analysis, a marked inflammatory infiltration of eosinophils with well-defined regions of eosinophil necrosis and collagenolysis were observed, revealing the immune response and tissue damage caused by the pathogen.
• Immunohistochemistry specifically labelling Pythium insidiosum, the causal agent of pythiosis, showed a strong response towards the hyphae.

Diagnosis

• The presence of intralesional kunkers could assist in an accurate presumptive diagnosis of the disease.
• However, for a definitive diagnosis, histopathology in association with immunohistochemistry, culture-based, or molecular methods are recommended.

Summary

• The study highlights pythiosis as a significant issue in the equine population of northeastern Brazil.
• Understanding the epidemiological, clinical, pathologic, microbiological, and immunohistochemical aspects of the disease could help in developing effective diagnostic procedures and treatment strategies to control the disease effectively in this region.