Most people know that you contract Lyme disease through a tick bite. But Borrelia burgdorferi, the Lyme-causative bacteria, is not the only pathogen that can be transferred via tick saliva. Other diseases can occur simultaneously with Lyme; these are called co-infections. Unfortunately, the public and medical professional education surrounding co-infections is scant at best. They can often compound the symptoms of Lyme disease, or cause disturbing new symptoms in their own right. Left untreated, they can also cause old symptoms to resurge, complicating treatment and prolonging patients’ suffering.
A subset of these co-infections is caused by bacteria called Rickettsia. Although it’s a somewhat obscure pathogen, it’s important to give it visibility so that people know how it’s contracted, and how it can be identified and treated.
What Is Rickettsia?
First of all, let’s define “Rickettsia”. People might immediately conflate it with the vitamin D deficiency disease called rickets, but the two actually have nothing to do with each other. Rickettsia was named after Howard Taylor Ricketts, who pioneered the study of tick-borne spotted fever. But is Rickettsia a bacteria or virus? The term Rickettsia refers to a genus of bacteria that can occur in three different shapes: cocci, bacilli, or threads. Traditionally, it’s the name used to describe this single genus of pathogen, though the term “Rickettsia” is often used informally when talking about any member of the order Rickettsiales. They are responsible for a spectrum of diseases in both humans and plants, and can be transmitted in a number of ways.
What Are The Three Main Groups Of Rickettsia?
There are three paramount groups of rickettsia: typhus group, spotted fever group, and scrub typhus group. The two typhus groups are far less common in the U.S. than the spotted fever group, which is the one we’ll be focusing on.
How Do You Contract Rickettsia?
The most prominent form of Rickettsia transmission is via ticks, the same method as Lyme disease. However, Lyme is not considered a rickettsial disease, as it is caused by the Borrelia burgdorferi bacteria, not the Rickettsia genus. Rickettsia-related illnesses can also be transmitted through lice, mites, and fleas, though this is far less common. Spotted fever rickettsioses (commonly known as simply spotted fevers) are caused by a closely related group of bacteria carried by vectors. In the U.S., these are most commonly the American dog tick, the Rocky Mountain wood tick, or the brown dog tick.
Similar to Lyme, incidents of the disease rise during the summer, which is traditionally tick season. It’s believed that transmission occurs very quickly after a bite, with the bacteria gaining rapid entry into the human host’s endothelial cells (cells that line the interiors of the blood vessels). The disease is not contagious from person to person, though questions remain about potential STD transference, as well as complications passed from mother to child in the womb and through breast milk. It’s also important to note that human hosts are accidental; the pathogen does not aim for the human system, but can wreak havoc there nonetheless.
What Are The Symptoms of Rickettsia?
Spotted fevers are some of the more serious complications from infected tick bites, and can range from mild to life-threatening. The first sign of a large subset of spotted fevers is a dark scab at the site of the bite, known as an eschar. These develop shortly after the bite, from a few days to a couple of weeks. Following the appearance of an eschar, patients will also develop more generalized symptoms that conform to standard vector-borne infections. These symptoms often mimic the flu and can include fever, headache, rash, and muscle aches. The infections of the endothelial cells can also lead to disseminated inflammation, as well as complications in the central nervous system. Rocky Mountain spotted fever is one of the most deadly tick-borne illnesses out there; before the introduction of antibiotics, mortality rates were as high as 30%. Even in 2019, these rates remain high – on average, 3-5% of people who contract RMSF will die.
How Is Rickettsia Diagnosed?
As it stands, most cases of Rickettsia-related diseases are diagnosed based on Immunoglobulin M (IgM) and IgG serologic responses to R. rickettsiae. However, these tests can return false negatives if performed too early in the disease’s life cycle. Another method is through polymerase chain reaction (PCR), although this is complex and time consuming. As the disease can be so damaging, early and certain identification is critical.
Infectolab, partnering with BCA-clinic in Germany, are releasing a new Rickettsia test in January. This will build on the foundations of their successful Lyme ELISpot method, and will test for both attacking T-cells and memory T-cells. The result is a much clearer picture of the stage a patient is at with the disease, as well as a reduced risk of a false negative.
How is Rickettsia Treated?
Once Rickettsia is successfully identified, it can be treated with the antibiotic doxycycline. The treatment course spans a week to ten days, and should be administered as soon as possible, even in cases where RMSF is suspected and not yet confirmed. This is especially pertinent with children, who are at a higher risk of dying from the disease than healthy adults.
Rickettsia can be a particularly dangerous and insidious pathogen, especially when paired with other co-infections like Lyme. Robust education around vector-borne diseases, concrete diagnosis and rapid treatment, is the key to defeating it.