# First Detection of Rhodococcus equi in a Foal in Bulgaria—A Case Report

## TL;DR

This case report documents the first occurrence of a virulent Rhodococcus equi infection in a foal in Bulgaria, highlighting diagnostic and treatment challenges.

## Contribution

The first documented case of VapA-positive Rhodococcus equi infection in a foal in Bulgaria is reported.

## Key findings

- A 56-day-old Arabian filly died despite antimicrobial treatment, with post-mortem revealing severe bronchopneumonia.
- PCR confirmed R. equi carrying the VapA gene, which is associated with virulence.
- The isolate showed resistance or intermediate susceptibility to several antimicrobials but was sensitive to macrolides and fluoroquinolones.

## Abstract

This report presents the first documented case of VapA-positive Rhodococcus equi infection in a foal in Bulgaria. The pathogen is known to often cause fatal pyogranulomatous bronchopneumonia and extrapulmonary disorders in foals, as well as in immunocompromised humans.

This case report describes the following scenario: A 56-day-old Arabian filly presented with classical symptoms of respiratory distress and a rapidly deteriorating condition, despite intensive antimicrobial treatment, resulting in death. The post-mortem examination revealed severe bronchopneumonia with characteristic disseminated pus-containing nodules. Microbiological tests and PCR confirmed the presence of R. equi carrying the virulence-associated protein A (VapA) gene. The isolate was sensitive to macrolides and fluoroquinolones but showed resistance or intermediate susceptibility to several commonly used antimicrobials. This case highlights the diagnostic and therapeutic challenges posed by this intracellular pathogen and emphasizes the importance of early detection, targeted therapy, and biosecurity measures—especially in the absence of an effective commercial vaccine.