What Is Trench Fever? Rare Disease Spread by Lice Found in Colorado—Here's What You Need to Know

The entire world may be occupied with the COVID-19 pandemic, but that doesn’t mean outbreaks of other serious diseases have completely stopped—and Colorado officials are currently witnessing that truth first-hand.

The concern began in early June, when Michelle Barron, MD, medical director of infection prevention and control at UCHealth University of Colorado Hospital received the information that the health system's microbiology lab confirmed a third diagnosis of trench fever, an infection caused by the bacterium Bartonella quintana, and transmitted by human body lice.

According to Dr. Barron, the two cases diagnosed before signaled an issue—but the third solidified her concern. "Because this is an unusual organism, we considered two cases enough to perform an outbreak investigation,” Dr. Barron tells Health. She says it’s likely that the Denver cases are connected, but she and her colleagues are still actively investigating each one. Since the third case was diagnosed, a fourth suspected case has been identified.

In a recent interview with Kaiser Health News, Dr. Barron said she'd never before seen a case of trench fever in her 20 years of work—and that's why she notified public health officials. Colorado Public Health officials issued a health advisory on July 16 for physicians to be on the lookout for more cases. Here's what you need to know about the rare illness.

What is trench fever?

Trench fever is rare condition that plagued soldiers in World War I, after European trenches were infested with body lice, according to a 2016 review published in The Lancet. It infected more than one million troops during World War I, rendering each affected soldier unfit for duty for more than two months.

Since then, trench fever has occurred worldwide, with cases reported from Europe, North America, Africa, and China, per the Centers for Disease Control and Prevention (CDC). It's rare, but the European Centre for Disease Prevention and Control (ECDC), says since the 1990s it has been recognized as a reemerging pathogen among impoverished and homeless populations. In recent years, outbreaks have also been identified in San Francisco and Seattle homeless camps.

“This organism is not spread from person-to-person but from a body louse,” Dr. Barron says. “This commonly is seen in transient populations, like the homeless, that are living in sub-optimal hygienic conditions.” The ECDC also clarifies that B. quintana is only transmitted by the body louse, Pediculus humanus humanus. It is not transmitted by the more common head louse, known as Pediculus humanus capitis.

B. quintana is also close relative of Bartonella henselae, the bacterium that causes cat scratch disease (CSD), an illness that can result from the scratches of domestic or feral cats. B. quintana colonies live in the digestive systems of body lice, are excreted in their feces, and can then enter the human body through the eyes, nose, or a scratch in the skin.

What are the symptoms of trench fever?

The ECDC says that the incubation period for B. quintana is usually between 15 and 25 days. Symptoms of trench fever commonly include a recurrent fever (the illness has the nickname "5-day fever"). In non-immunocompromised people, the fever is also accompanied by nonspecific symptoms including severe headache, tenderness or pain in the shin, weakness, lack of desire to eat, or abdominal pain.

Other more serious complications include chronic bactremia (a continuous presence of bacteria in the bloodstream), endocarditis (an infection of the inner lining of the heart chambers and valves), and, among immunocompromised people, a condition known as bacillary angiomatosis, characterized by lesions on the skin or internal organs.

How is trench fever diagnosed—and how is it treated and prevented?

Trench fever can be diagnosed by serology (an examination of blood serum) or blood culture for B. quintana, and treated with antibiotics. However, making a diagnosis can be challenging.

“B. quintana is slow-growing,” Dr. Barron says. “It can be recovered from standard blood culture media, but normally labs have to hold onto the bottles for longer periods of time (14 days) rather than the standard length of time (5-7 days) to recover it. So you have to notify the lab ahead of time that you suspect the diagnosis so that they can incubate the specimens longer.” In fact, the bacteria in two of the confirmed Denver cases grew just before the cell cultures were due to be thrown out.

According to the ECDC, the primary way to prevent trench fever is to avoid infestation with body lice—and those infestations are linked to low socioeconomic status, over-crowding and poor personal hygiene. Because body lice are commonly found on clothing and human skin, it's essential to discard any infested clothes or wash them in very hot water. In outbreak situations, the ECDC says areas have benefitted from insecticide treatment of the area and removing those infected from the area.

While the current outbreak in Colorado is a concerning public health issue, "the general public is unlikely to be affected by this disease," Dr. Barron says. "At the same time, it is important for the medical community at large to be aware of it so that cases can be identified and treated appropriately.”