UTMB study shows flea-borne murine typhus can become life-threatening

A new study by researchers at The University of Texas Medical Branch (UTMB) found that murine typhus, a flea-borne disease many people have never heard of, can quickly become life-threatening.

The study, published in the journal Emerging Infectious Diseases, examined adults treated for murine typhus in the Galveston area over a four-year period. Researchers found that the flea-borne illness frequently led to hospitalization and, in many cases, life-threatening complications requiring intensive care.

The findings underscore the importance of recognizing the disease early and beginning treatment before laboratory tests confirm the diagnosis.

Murine typhus is caused by the bacterium Rickettsia typhi and is spread to humans through infected fleas. While the disease was historically linked solely to rats, today most cases in Texas are associated with both rats and opossums. People become infected when flea feces containing the bacteria enter the body through a flea bite, broken skin, or the mucus membranes around the eyes. The disease cannot be spread directly from person to person.

Although the disease nearly disappeared from the United States decades ago, it has reemerged in southeastern Texas and parts of California in recent years, an issue that researchers attribute to a confluence of circumstances:

• The disease has moved from rats to opossums and the fleas they carry.
• Opossums are well adapted to thriving in urban and suburban environments.
• Fleas are abundant and infect many different animals.
• Environmental changes may be helping fleas thrive.

Not always mild

Researchers reviewed 149 adult cases of murine typhus treated at UTMB between 2019 and 2023. Nearly 80% of those patients were hospitalized, and 28% of hospitalized patients became critically ill and required care in the intensive care unit. Severe complications included shock, acute kidney injury, and respiratory failure. Some patients required mechanical ventilation, medications to support blood pressure, or dialysis. Two patients died from severe manifestations of the disease.

"Murine typhus has long been viewed as a relatively mild illness, but our findings show that's not always the case," said Alexander Duarte, MD, vice chair for Faculty Development in the Division of Pulmonary Critical Care & Sleep Medicine at UTMB and one of the study authors. "In areas where this disease is common, clinicians should keep it on their radar when evaluating patients with unexplained fever and other flu-like symptoms. Recognizing it early can make a tremendous difference in preventing serious complications."

One of the biggest challenges is that murine typhus symptoms are similar to those of many other illnesses. Patients typically develop fever, headache, muscle aches, fatigue, and nausea - symptoms that overlap with viral infections and other common conditions. Laboratory tests that confirm the diagnosis often take several days, making early clinical recognition especially important.

The study found that older adults were more likely to develop severe disease. Patients with lower platelet counts when they first sought medical care also faced a greater risk of serious complications.

Early treatment is critical

Because waiting for laboratory confirmation can delay treatment, the researchers emphasize that physicians practicing in areas where murine typhus is common should consider starting doxycycline when the disease is clinically suspected. Early treatment can dramatically reduce the risk of complications.

"The challenge is that we often can't wait for laboratory confirmation because those results may not be available for several days," said Lucas Blanton, MD, associate professor in the Division of Infectious Disease at UTMB and co-author of the study. "If murine typhus is suspected, starting doxycycline promptly can prevent patients from becoming critically ill. That's why awareness among both healthcare providers and the public is so important."

Because murine typhus is spread by infected fleas, researchers say prevention starts with reducing flea exposure. That includes using veterinarian-recommended flea control for pets, avoiding contact with stray or wild animals, discouraging opossums and rodents from nesting around homes by securing trash and removing outdoor food sources, and wearing insect repellent when appropriate.

Anyone who develops a fever, headache, and body aches after possible flea exposure, particularly in areas where murine typhus is common, should seek medical attention promptly as early treatment with doxycycline is highly effective.

"We hope these findings increase awareness of murine typhus among healthcare providers and the public," Duarte said. "Most people recover with prompt treatment, but this disease has the potential to become life-threatening. Recognizing it early and treating it quickly can save lives."

Additional UTMB study co-authors: Efstathia Polychronopoulou, PhD, MPH. biostatistician II, and Shawn P. Nishi, Division Chief of Pulmonary, Critical Care & Sleep Medicine. Lead author Matthew Pickich and co-author Puneet Singh have since graduated from the UTMB pulmonary fellowship program.