# Molecular Detection of Pythium insidiosum in Cutaneous Lesions of Horses from Northeastern Brazil

## TL;DR

This study confirms the presence of Pythium insidiosum in horse skin lesions in Northeastern Brazil using DNA-based testing, showing the need for better diagnostics.

## Contribution

First molecular confirmation of Pythium insidiosum in horses from Northeastern Brazil using nested-PCR.

## Key findings

- Nested-PCR detected P. insidiosum in four out of five samples, showing higher sensitivity than microbiological culture.
- This is the first molecular confirmation of P. insidiosum in equine pythiosis in the Brazilian Northeast.
- The study highlights the importance of molecular methods for diagnosing pythiosis in neglected regions.

## Abstract

Pythiosis is a serious but often overlooked disease that affects horses living in flooded or swampy areas. It is caused by a microorganism found in water, which infects the skin and produces large, painful wounds that are difficult to heal and can be fatal without proper treatment. In this study, we describe cases of horses from Northeastern Brazil with skin lesions suspected of pythiosis. Using a modern DNA-based test, we confirmed the infection in four animals. These are the first molecularly confirmed cases in this region, highlighting the need for faster and more reliable diagnostic tools to improve horse health and welfare.

Pythiosis is an underestimated and neglected disease in Brazil, both in horse breeders and in horses. The molecular detection of P. insidiosum in horses in the Brazilian Northeast represents a milestone in the epidemiology of equine pythiosis in the country. This study reports novel cases of equine pythiosis, diagnosed by molecular methods, in five states of Northeastern Brazil. Clinical samples were submitted to microbiological culture, DNA extraction, and nested-PCR for molecular detection of P. insidiosum. The nested-PCR successfully detected P. insidiosum in four out of five equine lesion samples, demonstrating higher sensitivity compared to microbiological culture, which confirmed the pathogen in only one case. These findings reinforce the effectiveness of molecular diagnosis for equine pythiosis compared to conventional methods. This is the first molecular confirmation of P. insidiosum in horses from Northeastern Brazil, emphasizing the need for broader surveillance and improved diagnostic approaches in neglected regions.