# Diagnosis of a Rare Rickettsia felis Infection Complicated with Unusual Pericardial Effusion and Cardiac Tamponade Using an mNGS Test

## TL;DR

A rare Rickettsia felis infection was diagnosed using advanced sequencing after unusual heart symptoms, highlighting the underappreciated threat of rickettsial diseases.

## Contribution

This case demonstrates the utility of metagenomic next-generation sequencing in diagnosing rare rickettsial infections with atypical clinical presentations.

## Key findings

- Metagenomic next-generation sequencing confirmed Rickettsia felis infection in a patient with pericardial effusion and cardiac tamponade.
- The case highlights the underdiagnosed and underreported nature of sporadic rickettsial infections in clinical practice.
- Rickettsia felis is increasingly transmitted to humans due to the rising population of domesticated animals.

## Abstract

The occurrence of sporadic rickettsial infections has been consistently undervalued and overlooked, primarily owing to a limited emphasis on routine examinations for rickettsioses in clinical practice. At present, the immunofluorescence assay is the prevailing diagnostic method for suspected rickettsioses that enables the detection of specific antibodies against rickettsia in human serum. Herein, we present an exceptional instance of rickettsial infection that was characterized by a rare manifestation of extensive pericardial effusion leading to dyspnea and cardiac tamponade. A diagnosis of chronic fibrosing pericarditis was established based on pericardium tissue obtained through pericardiotomy, and a conclusive metagenomic next-generation sequencing test confirmed the presence of Rickettsia felis infection. The cat flea, scientifically known as Ctenocephalides felis, is the predominant carrier of R. felis. An escalating incidence of human R. felis infections has raised concerns, particularly in light of the burgeoning population of domesticated animals in many contemporary societies.