What is Rickettsial Infection?
Rickettsia refers to a group of bacteria that are spread by bugs like ticks and fleas, causing diseases that come with high fever. These diseases are found all over the world. Even though the signs and symptoms of Rickettsia infection are often similar, the specific bacteria and how common the disease is can differ from place to place. Therefore, it’s essential to be familiar with the usual symptoms and know the common diseases in your area to make sure these infections are diagnosed and treated quickly. This is significant because if they’re not treated right away, these infections can lead to serious health problems, and in some cases, can even be fatal.
What Causes Rickettsial Infection?
Rickettsial infections are infections caused by a group of bacteria that can only live inside other cells, specifically the Rickettsia bacteria. These come in four types: spotted fever group, typhus group, ancestral group, and transitional group. One of these, the Rickettsia rickettsii bacteria, leads to a disease called Rocky Mountain spotted fever. This is the most severe and best-known type of rickettsial infection here in North America.
However, there are many other types of Rickettsia bacteria that cause illness in different parts of the world. For example, Rickettsia africae causes African tick bite fever in sub-Saharan Africa, and Rickettsia conorii is responsible for Mediterranean spotted fever, found in Europe and North Africa. There are also Rickettsia prowazekii and Rickettsia typhi that cause types of illnesses known as typhus syndromes.
Scientists are continually discovering new species of Rickettsia bacteria as we develop more advanced methods of studying these tiny organisms.
Risk Factors and Frequency for Rickettsial Infection
Rickettsia is a type of bacteria that is usually carried and spread by ticks, lice, mites, and fleas. Humans often get infected accidentally. The specific type of tick that transmits this bacteria can vary depending on the region and the specific type of rickettsia bacteria. In the United States, most cases of a disease caused by rickettsia, called Rocky Mountain spotted fever, are associated with the American dog tick, the Rocky Mountain wood tick, and the Lone Star tick.
In South America, the tick that is commonly linked with spotted fever is Amblyomma cajennense, while in South Africa, the ticks are Amblyomma hebraeum or Amblyomma variegatum. Infections are more likely to occur during warmer months and in people who spend a lot of time outdoors because of the involvement of ticks and other bugs.
Epidemic typhus, caused by the R. prowazekii bacteria, is spread by body lice and is more common in crowded places with poor hygiene. Murine typhus, caused by the R. typhi bacteria, usually happens in tropical and subtropical places and is associated with flea bites.
Signs and Symptoms of Rickettsial Infection
After being exposed to Rickettsia species, usually through a tick or flea bite, people will usually start to show symptoms within four to ten days. These symptoms often appear similar to those of the flu and may occur more frequently during the summer months. Whether or not you’re aware of being bitten by a tick or flea, it’s crucial to be aware of these symptoms. The classic signs include fever, headache, and a distinctive rash that may look like tiny pinpricks or a more widespread rash. Other symptoms might include:
- Swelling of the lymph nodes
- Confusion or stiffness in the neck
- A sore or scab at the place of the tick or flea bite
- Muscle and joint pain
- Liver inflammation
- Vomiting
- Unstable heartbeat or blood pressure
Although these symptoms are generally consistent when caused by any Rickettsia species, the specific symptoms and the patient’s travel and outdoor exposure history can help identify the exact cause.
Testing for Rickettsial Infection
Most of the time, rickettsial infections, a type of bacterial infection, are diagnosed based on your body’s immune response to the bacteria. This is typically measured through blood tests looking for certain infection-fighting cells, known as IgG and IgM, that react to the R. rickettsiae – the specific bacteria that causes rickettsial infection. Doctors strongly suspecting this infection usually rely on these tests for diagnosis.
While it’s possible to grow the bacteria in a lab, this method isn’t often used because it’s challenging and requires strict safety measures due to the risk of exposure to the bacteria itself. Some centers may use a technique known as a PCR test, which looks for the bacteria’s genetic material. Another option might be a skin biopsy, where a tiny piece of skin is removed for examination.
Patients with rickettsial infections can also have a lower than normal level of platelets, the blood cells that help with clotting, and sodium in their bodies, along with an increase in white blood cells in the fluid that surrounds their brain and spinal cord. However, it’s important to note that the count of white blood cells, when checked in a regular blood test, may be high, normal, or low. So, this test doesn’t always help accurately rule in or out the infection. That’s why doctors follow their clinical judgment derived from other symptoms and tests.
It’s crucial to suspect and diagnose rickettsial infection early due to its high severity and associated risk of death, along with the possibility of the immune response tests (serology tests) giving negative results early in the disease. A negative test result doesn’t necessarily mean you don’t have the disease; therefore, if the doctor strongly suspects a rickettsial infection, they may start treatment anyway.
Treatment Options for Rickettsial Infection
The preferred medicine for treating rickettsial infections, a type of infection caused by bacteria, is doxycycline. However, how much you take and for how long often depends on the bacteria causing the infection. If a patient is allergic or the disease is severe, another option is a medicine called chloramphenicol. If the infection is not as severe, clarithromycin, which is a part of a medicine group known as macrolides, can be considered as an alternative.
It’s important to keep in mind that fluoroquinolones, a different group of antibiotics, have been linked to negative outcomes and therefore, are not recommended for rickettsial disease. Moreover, serious rickettsial diseases like Rocky Mountain spotted fever have death rates up to 20-30% if appropriate antibiotic treatment is not given immediately.
Pediatrics (children under 8 years old) usually do not take doxycycline due to concerns about side effects. However, in cases with severe rickettsial infections, the potential benefits of doxycycline treatment often outweigh the risks, because these diseases can be life-threatening. As a result, treatment with doxycycline may be started in children below 8 years old with the suspicion of a rickettsial infection, while waiting for lab results to confirm the diagnosis.
What else can Rickettsial Infection be?
There are several conditions that are important to consider and manage promptly. These include:
- Dengue
- Malaria
- Group A streptococcal infection
- Kawasaki disease
- Leptospirosis
- Measles
- Meningococcal infection
- Rubella in children
- Syphilis in children
- Toxic shock syndrome in children
- Vasculitis and thrombophlebitis
What to expect with Rickettsial Infection
Rickettsial infections, which are caused by the Rickettsia type of bacteria, can range from mild to severe. The severity often depends on two main factors: the harmfulness of the specific Rickettsia species and the strength of the patient’s immune system. The most harmful types include R. rickettsii and R. prowazekii, which can have very serious consequences if not diagnosed and treated quickly.
Take for example, Rocky Mountain spotted fever, which is caused by the R. rickettsii bacteria – it can have a mortality rate as high as 30% if not diagnosed quickly and treated with antibiotics. However, if diagnosed and treated with the right antibiotics during the first week of illness, patients typically have very positive results, showcasing how important speedy treatment is to the recovery process.
Possible Complications When Diagnosed with Rickettsial Infection
The seriousness and type of complications arising from a Rickettsia infection largely depend on the specific Rickettsia species and the overall health of the infected individual. If the infection is identified and treated early, serious complications are usually avoided. However, in some cases, long-term health issues might occur. These can range from gangrene (death of body tissue due to lack of blood flow), hearing loss, loss of control over bowel or bladder function, to partial paralysis of the lower body.
Possible Long-term Health Issues:
- Gangrene
- Hearing loss
- Bowel or bladder incontinence
- Partial paralysis of the lower body
Preventing Rickettsial Infection
The best way to avoid rickettsial infections, diseases caused by bacteria spread through the bite of insects like ticks, lice, mites, and fleas, is to prevent them in the first place. This basically means avoiding contact with these insects, especially if you are living in or travelling to areas where these diseases are common. At this time, there are no available vaccines to prevent diseases like Rocky Mountain spotted fever or other rickettsial infections, and taking antibiotics to prevent these infections is not commonly recommended in the United States.
To minimize the chances of getting a rickettsial infection, it’s important to check your body for insects after spending time outdoors. It’s also key to dress appropriately to prevent bites; for instance, by wearing long-sleeved shirts, pants, socks, and shoes that completely cover your feet. Applying insect repellent can also reduce your risk. Additionally, it’s vital to be aware of locations where Rickettsia bacteria – the type of bacteria that cause these diseases – are commonly found.
