Many diseases can be passed on to humans through the bites of ticks, lice, mites, and fleas. Although these creatures are tiny, the bacteria they carry can wreak havoc in humans, leading to several serious diseases. This group of disorders is known as vector-borne diseases, which run the gamut from mild to fatal. One of the most difficult aspects of this group of diseases is how to quantify them all separately. Many begin with generalized symptoms that resemble a traditional infection. If patient and doctor alike are not careful, a disease can subsequently be misdiagnosed and left to develop unchecked. This is why it’s important that vector-borne illnesses are visible to the general public, and that there is plenty of readily accessible information about them.
Rickettsia is a genus of bacteria that can cause several serious disorders. But where is rickettsia found in the U.S.?
What is Rickettsia?
Before we ask “What states have rickettsia?”, we’ll answer another important question: is rickettsia a bacteria or a virus? The two are often easy to confuse, but the umbrella term “rickettsia” refers to a diverse group of intracellular bacteria found in ticks, lice, fleas and mammals. The rickettsial group of pathogens differs from other types of bacteria in that they can live and multiply only within the cells of their host organism, and can’t survive outside it. Some of these bacteria and their associated infections occur worldwide, while others occur only in specific geographical areas.
Although there are many variations of rickettsial diseases, they can primarily be separated into two groups, based on serological characteristics: the typhus group and the spotted fever group. While the typhus group contains only two pathogens capable of infecting humans, the spotted fever group encompasses at least 32. One of these is R. rickettsii, the agent of Rocky Mountain Spotted Fever.
What is Rocky Mountain Spotted Fever?
Rocky Mountain Spotted Fever (RMSF for short) is a bacterial infection that can cause severe complications for patients. Symptoms begin with flu-like presentations before worsening over time. Neurological complications, nausea, stomach pain, and widespread pain are common in the latter stages. Death can ultimately occur if the disease isn’t treated with antibiotics. RMSF still retains one of the highest mortality rates for tick-borne diseases, with 5% of patients dying from the disorder.
Where is RMSF Found in the U.S.?
Because there are so many variations of rickettsial diseases, geographically placing them can be a tall order. During 2008–2012, passive surveillance estimated that the average incidence of Spotted Fever Group rickettsiosis was close to nine million people per year. This high incidence rate, coupled with the wide range of pathogens that make up the rickettsial genus, makes it challenging to definitively say where exactly in the country rickettsial diseases can occur. If we first look solely at RMSF, the most dangerous disease in the group, then we can get a little more specific.
As we’ve already mentioned, the bacteria that causes RMSF is called R. rickettsii. The vector most commonly associated with the transmission of this pathogen is the American dog tick. Primarily, this tick is found in the Eastern, Central and Pacific Coastal states. In the Western states, the Rocky Mountain wood tick is associated with transmission, and more recently the brown dog tick, found all across the country, has been recognized as a significant vector. The American dog tick makes its home primarily in shrubbery, woodland, and grassy areas. These ticks often congregate along pathways and trails, where they extend their front legs in a process known as “questing”. Contrary to popular thought, ticks cannot jump or fly. Questing is their only means of attaching themselves to a host, which means direct contact is necessary.
Ehrlichiosis is another commonly occurring rickettsial condition caused by the Ehrlichia species of bacteria. The lone star tick is a prime carrier of a particular species of that pathogen known as E. chaffeensis. This tick is among the most common in the southeastern U.S., and is particularly prominent in states such as Arkansas, Delaware, Missouri, Oklahoma, Tennessee, and Virginia. The white-tailed deer is the major host of the lone star tick.
How is Rickettsia Diagnosed?
Rickettsia is traditionally diagnosed with a series of blood tests. Early identification (and subsequent antibiotic intervention) is often crucial with some of the more dangerous rickettsial infections, including RMSF. As per the CDC website, “the standard serologic test for diagnosis of RMSF is the indirect immunofluorescence antibody (IFA) assay for immunoglobulin G (IgG) using R. rickettsii antigen”.
However, Infectolab Americas and BCA-clinic in Germany are planning to release a new Rickettsia test in January 2020, which can help doctors receive a clearer picture of their patient’s condition. BCA-clinic has a reputation as Lyme specialists, and this new test builds upon the clinic’s progressive ELISpot blood test, which aids diagnosis in Lyme patients.
The new Rickettsia ELISpot examines the patient sample for both attacking T-cells and memory T-cells. These specific antigens are both produced in response to infection, but at different times. Attacker cells are sent forth upon detection of foreign pathogen, while memory cells are created in the aftermath, in order to protect against any recurring infections in the future. By testing for the presence of specific molecules (specifically IFN-gamma and IL-2 molecules), medical professionals are able to more accurately assess their patient and plan treatment accordingly.
How Can You Protect Yourself from Rickettsia?
Protecting yourself from rickettsial infections is all about education. If you know how the infections are spread, you can do your best to avoid being infected in the first place. Be aware that you may be putting yourself at risk whenever you go outside in woodland or grassy areas, anywhere in the U.S. If flu-like symptoms flare up inexplicably, make sure to check yourself for tick bites and inform your doctor about any outdoor activities you may have been involved in recently. Although many of these vector-borne diseases can become critical, almost all of them, including RMSF, are easily treatable with antibiotics as long as they’re caught early.