Sequencing Test Identified Malaria in Heart Fluid

Clinicians in Canada diagnosed a patient using bacterial DNA sequencing after standard malaria tests returned negative results.

Updated on Oct. 14, 2026 in Heart Disease

A clear medical specimen vial on a clean white laboratory surface, emphasizing the precision of modern diagnostic procedures. — Clinicians in Canada used 16S rDNA sequencing to diagnose a malaria infection in a patient after standard tests failed to identify the parasite. AI Illustration. Upload story photo >

A patient in his 70s was diagnosed with malaria after doctors found the parasite DNA in fluid surrounding his heart. The diagnosis was confirmed using 16S rDNA sequencing, a method that detects bacterial genes within the parasite, after initial standard blood tests failed to detect the infection.

Why it matters

This case highlights the diagnostic challenge of low-level malaria infections, which can occur in patients with partial immunity due to past exposure in high-burden regions like Nigeria. Pericardial effusion, the accumulation of fluid around the heart, is an infrequent but serious complication that can be missed by standard screening.

Doctors successfully drained 240 millilitres of fluid from the heart sac, identifying Plasmodium falciparum DNA via a 286-letter genetic match. This method bypassed standard microscopy, which typically detects malaria at an 85% to 93% rate.

The players

Plasmodium falciparum

This is the most lethal species of the malaria parasite and is responsible for the highest number of malaria-related illnesses globally.

The details

Clinicians performed the sequencing after identifying bacterial genes in the parasite's apicoplast, an organelle that carries 16S genes. The patient, who had previous exposure in Nigeria, eventually responded to a three-day course of atovaquone-proguanil.

Day 25: The patient was admitted to a hospital in Canada with heart and lung issues.
Day 26: Medical staff collected heart fluid for testing.
Day 34: The patient developed a fever.
Day 54: DNA sequencing identified the malaria parasite in the collected fluid.
Day 62: The patient was discharged home.

Health Landscape

This case demonstrates a rare diagnostic outlier in the context of the estimated 282 million global malaria cases in 2024. While most infections are identified via standard blood tests, this instance marks a departure from typical screening protocols for global malaria cases.

Patients with a history of residence in malaria-endemic regions like Nigeria should inform their doctors, even if they have developed partial immunity. This case underscores the importance of advanced sequencing when standard tests return negative results for patients with unexplained heart fluid.

The takeaway

Advanced genetic sequencing can be a life-saving tool for identifying infections that evade standard medical screening. Patients with recurring health issues after travelling to high-burden regions should persist in seeking specialized diagnostic tests.