What is Rickettsia akari (Rickettsialpox)?
Rickettsia akari is the germ that causes a disease known as rickettsialpox. This germ is spread to humans by a mite commonly found on house mice, known as Liponyssoides sanguineus. Approximately one week after being bitten by this mite, an infected person develops a blister which then dries up and leaves a hard, dry patch of skin, also known as an eschar. The rash associated with this disease can vary, appearing as raised spots or blisters, which is why the condition is referred to as rickettsialpox.
Similar to other types of Rickettsiae (the scientific group it belongs to), R. akari is a type of germ that lives inside cells and has properties of both viruses and bacteria. It was initially grouped with those causing the spotted fever group of diseases. However, it now falls into another category known as the ‘transitional group’. This new group displays characteristics of both the spotted fever and the typhus group of diseases. Moreover, this germ carries a piece of genetic material similar to the one found in Rickettsia felis, another member of the transitional group.
What Causes Rickettsia akari (Rickettsialpox)?
R. akari, a type of bacteria, is spread through the bite of Liponyssoides sanguineus, commonly known as the mouse mite. The word ‘akari’ is Greek for mite, which is how it got its name. Unlike other similar bacteria types, R. akari primarily affects what’s known as the macrophage – a type of cell in our bodies that kills harmful bacteria.
The first reported cases of R. akari infections were in 1946 in New York City. The infection causes blister-like sores which may resemble chickenpox. Because of these similar symptoms, the disease caused by R. akari is commonly called rickettsialpox.
It is also important to note that besides the mouse mite, there may be other ways this bacteria can be transmitted. This assumption comes from the fact that there is a high occurrence of R. akari found in dogs in New York City and pet cats in California.
Risk Factors and Frequency for Rickettsia akari (Rickettsialpox)
Rickettsialpox is a disease first discovered in New York City, but it has since been found in several other towns, states, and even continents like Europe, Asia, Africa, and South America. Rickettsialpox tends to be particularly prominent among intravenous drug users and the homeless. Cities such as Baltimore and Los Angeles have reported high occurrence rates of R. akari, the bacterium that causes the disease.
This illness isn’t officially tracked as some are, and it’s usually caused by rodents. Specifically, colorless, bloodsucking mouse mites pass the disease from rodents to people, though it can also spread in labs due to inhalation. Even though rickettsialpox isn’t common (New York City, for instance, records about five cases each year), it can increase if the mouse population decreases. The disease takes about seven to 14 days to show up after a person is infected.
- Rickettsialpox was first seen in New York City and has been reported worldwide.
- The disease is usually seen in intravenous drug users and homeless people.
- Baltimore and Los Angeles County have high occurrence rates of R. akari, the bacterium causing rickettsialpox.
- Rickettsialpox is spread by the bloodsucking mouse mite from rodents to humans and can be inhaled in lab environments.
- In New York City, there are about five cases reported each year.
- The number of cases can increase if the mouse population decreases.
- The disease takes about one to two weeks to show symptoms after infection.
Signs and Symptoms of Rickettsia akari (Rickettsialpox)
R. akari infection, which is quite rare, often causes three main symptoms: fever, a rash filled with small blisters, and a skin lesion known as an eschar. This trio of symptoms was found in 92% of patients studied in New York City. However, only a handful of doctors were able to correctly identify these cases, indicating that many physicians may not be thoroughly familiar with this type of infection.
When a person gets R. akari infection, they may experience additional symptoms such as headache and muscle pain at the beginning. The eschar, or skin lesion, shows up about a week after the silent bite of a mouse mite. It starts as a small raised spot which then develops a blister at the center. This blister then dries, leaving a brown or black crusty skin sore. The lymph nodes in the region of the eschar may be swollen.
The rash, which usually transforms into small blisters with a dry black crust, typically starts on the third or fourth day after the mouse mite bite. But there’s variability in the timing of the rash, which can appear anywhere from the first day to the tenth day after the bite. This makes diagnosis more challenging. The rash resolves in about two to three weeks and these skin lesions do not leave scars after healing. The rash is generally not present on the palms and the soles of the feet.
On the other hand, it’s essential to note that not all patients develop the typical blister-filled rash. A study of 13 patients found the rash in 92% of cases, suggesting there can be variation in the rash’s appearance. Another study involving 178 patients also found that the rash could look different.
In the most extensive study involving 144 patients, almost all patients (99.9%) had the trio of fever, rash, and eschar, and 90% reported having headaches. Some patients showed temporary abnormalities in their blood cell counts, such as a decreased level of white blood cells or platelets. Some also exhibited a temporary spike in their liver enzymes.
R. akari infection usually resolves on its own within 7 to 10 days. In one particular case, a patient with HIV was given the antibiotic doxycycline and recovered from the infection. In a study with 34 patients, about a third were admitted to the hospital, probably to rule out more severe diseases like cutaneous anthrax and chickenpox.
Testing for Rickettsia akari (Rickettsialpox)
R. akari infections are typically diagnosed by detecting a significant increase in special types of antibodies in your blood. These antibodies react specifically to certain ‘antigens’ or foreign substances which are linked to R. akari, a type of bacteria. You can get tested for this through the Centers for Disease Control and Prevention (CDC). R. akari doesn’t trigger the production of certain other types of immune response elements, so tests looking for those wouldn’t be helpful.
Unlike some other types of bacteria, R. akari isn’t usually visible in blood samples, even with most conventional staining techniques. Unfortunately, there are no quick tests to diagnose infections caused by R. akari.
Specialized staining techniques can be used on a skin biopsy sample collected from a skin sore and can help identify the presence of rickettsial organisms, which include R. akari. However, these tests can’t specify which species of rickettsia is causing the infection. They also require considerable time and high expertise.
A very precise genetic testing technique using Polymerase chain reaction (PCR) can accurately identify R. akari in skin biopsy samples. This technique can distinguish R. akari from other similar bacteria species. For this test, a swab of the skin sore can be used as the sample for testing. Skin sores are typically more likely to show the presence of R. akari since these areas have a higher concentration of the bacteria compared to fluid samples from skin rashes.
R. akari can also be grown in a lab using a type of cell system involving the blood or skin sore specimen. However, this process can take several weeks, making it unsuitable for helping doctors make immediate treatment decisions. Plus, growing rickettsial organisms in labs can create safety risks for laboratory staff since the bacteria can be transmitted by inhalation and through contact with skin cuts. Rickettsia can penetrate the host cell membrane and invade it, once attached to the respiratory mucosa.
Treatment Options for Rickettsia akari (Rickettsialpox)
Rickettsialpox is a disease that usually resolves on its own. However, taking antibiotics can shorten the time a person experiences symptoms from about a week to less than two days. A preferred medication to treat Rickettsialpox is doxycycline, as it can lead to a marked decrease in fever within one day of starting treatment.
Children older than eight years can also take doxycycline. The dosage is adjusted based on their body weight but should not go over a certain amount per day. Doxycycline is not recommended during pregnancy or for children below eight years old.
Like other similar infections, Rickettsialpox can be treated with several different antibiotics, though the effectiveness varies. Chloramphenicol and josamycin are some examples. Certain antibiotics like penicillin, aminoglycosides, and vancomycin, though often bacteriostatic (limiting bacterial growth but not killing them), are less effective and only limit bacterial growth at high doses. These antibiotics might not entirely stop the progression of the disease even at a high dose, as seen in lab tests on mice.
What else can Rickettsia akari (Rickettsialpox) be?
When trying to diagnose a feverish illness that also involves a rash, doctors must consider a wide range of potential causes. These could be due to viruses like infectious mononucleosis or chickenpox, or bacterial diseases like Lyme disease and streptococcal infection. It could also be because of conditions related to connective tissues, such as systemic lupus erythematosus.
- Diseases caused by other types of rickettsiae (a type of bacteria) that also come with a rash or a wound known as an eschar
- Ehrlichial infections, which are characterised by fever and a low platelet count
- Infections caused by the bacteria Orientia, which also produce an eschar
- Leptospiral infections, which present with fever and abnormal liver enzymes
- Febrile illnesses that affect multiple body systems, like dengue
These are all possibilities that need to be taken into account to accurately diagnose the patient’s condition.
What to expect with Rickettsia akari (Rickettsialpox)
If antibiotics are started immediately, most people will start to feel better within two days from the infection caused by the Rickettsia akari bacteria. However, postponing the start of antibiotic treatment can worsen the health outcome for the patient. Therefore, treatment should begin even if we’re only suspecting the presence of the infection without waiting for lab test results. This is to ensure the best possible health result for the patient.
Possible Complications When Diagnosed with Rickettsia akari (Rickettsialpox)
Rickettsialpox is usually not a severe disease and most people get better on their own within 2 to 3 weeks. It’s quite unusual for someone to have complications or die from this condition.
Preventing Rickettsia akari (Rickettsialpox)
It’s important for patients to understand the cause of the condition and take necessary steps to eliminate mites, which are tiny insects that can cause disease. One of these steps includes using bug sprays effectively. Furthermore, it’s essential to take measures to prevent mice from inhabiting your house. You can do this by cleaning up tall grass and brush near your home, clearing trash promptly, and sealing any holes or hiding places for mice. Understanding and following these guidelines can help in maintaining a healthier living environment.
