In the First World War, soldiers were afflicted by a new illness called trench fever. The condition was characterized by re-curring bouts of fever, dizziness and head, lower back and shin pain that sidelined soldiers for months.
It wasn’t until the end of the war that a tiny bacterium, called Bartonella, was identified as the cause. Human lice spread the bacteria between soldiers in the unsanitary conditions at the front. Altogether, trench fever affected more than one million soldiers and was one of the most common infections of the war.
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This condition also sprung up occasionally during the Second World War. Most recently, an outbreak among homeless people in Los Angeles spawned the name “urban trench fever” for this modern affliction.
Bartonella infection may seem like a disease of history and marginalized individuals, but the species of Bartonella associated with trench fever was the first of many that have been recently discovered.
There is a growing understanding about the role this small pathogen plays in other health conditions in people and animals.
Perhaps the most interesting thing about Bartonella is that it infects red blood cells. It does so without stimulating the immune system. Other blood pathogens stimulate a vigorous immune response. The immune system seeks out and destroys infected red blood cells, often leading to anemia and jaundice, which is yellowing of normally white tissues like the sclera (white) of the eye.
Animals and people infected with Bartonella do not become anemic or jaundiced because the infected red blood cells are not destroyed. To this end, some researchers refer to it as a “stealth pathogen.”
Besides the Bartonella associated with trench fever, there are many more species found in animals. Cat scratch disease is likely the most significant illness associated with Bartonella today.
As the name suggests, this infection occurs when infected cats scratch or bite people. Infections in people are usually self-limiting and result in localized lymph node swelling, pain and fever. Fleas spread the bacteria between cats, which remain outwardly healthy even when infected.
Bartonella causes sporadic disease in dogs and cattle. All Bartonella species that cause disease in dogs have also been found to cause illness in people.
There is speculation that these dog-associated Bartonella originated by spilling over from wild animals.
In nature, this bacterium has been recovered from a diversity of wild animals ranging from bats to porpoises. In fact, there are so many Bartonella species that scientists believe they co-evolved with their natural hosts.
Among wildlife hosts, rodents are perhaps the most diverse. Representing more than 40 percent of all mammals, the extreme diversity in rodents is mirrored by the variety of Bartonella they carry.
In Saskatchewan, rodents like Richardson ground squirrels (commonly referred to as gophers) carry Bartonella.
Recent studies in Vancouver by the Vancouver Rat Project found that 25 percent of rats in that city are infected.
Given the diversity of Bartonella carried by rodents and their sheer numbers, there is growing concern about the role of rodent-associated Bartonella as a cause of illness in people.
Just as lice control reduced cases of trench fever during the Great War, the cornerstone of preventing Bartonella infection in domestic animals is carried out by controlling fleas and ticks.
Overall, this pathogen is more of a problem in warmer regions but as climate change influences the distribution of fleas, ticks and the infectious agents they carry, pathogens like Bartonella may become more of an issue in Canada.
