African tick-bite fever

African tick-bite fever (ATBF) is an acute, influenzalike illness that is frequently characterized by fever, regional lymphadenopathy, and inoculation eschars [2]. The symptoms may include fever, headache, muscle pain, and a rash [6]. At the site of the bite there is typically a red skin sore with a dark center [6].

The disease is caused by a bacterium called Rickettsia africae [5], which was first identified in southern Africa in 1911 [5]. It is most often observed in North American and European tourists returning home from the southern parts of Africa, where they have been bitten by infected ticks [7].

Common clinical characteristics of ATBF include fever, headache, myalgias, lymphadenitis, and an inoculation eschar with cutaneous rash—the classic tache noire [4]. The disease can also present with multiple eschars in travelers returning from southern Africa [8].

Symptoms may vary depending on the individual, but generally, people infected with ATBF experience fever and chills, along with multiple crusty skin sores or ulcers, and swelling in the area of the skin sores [9].

African tick-bite fever (ATBF) is characterized by several signs and symptoms, which can vary in severity and duration.

Common symptoms:

• Fever [1]
• Headache [5]
• Muscle pain (myalgia) [5]
• Rash [2]
• Regional lymphadenopathy (swollen lymph nodes) [1]

Specific skin manifestations:

African tick-bite fever (ATBF) can be challenging to diagnose, but various tests can help confirm the infection. Here are some diagnostic tests for ATBF:

• PCR (Polymerase Chain Reaction): PCR is a molecular test that can detect the genetic material of Rickettsia africae bacteria, which causes ATBF. A biopsy of the eschar (the tick bite wound) or blood sample can be used for this test [4].
• Serologic tests: Serologic tests, such as immunofluorescence and enzyme-linked immunosorbent assay (ELISA), can detect antibodies against Rickettsia africae in the blood. However, these tests are not specific to ATBF and may cross-react with other rickettsial species [1][2].
• Clinical diagnosis: Diagnosis of ATBF is often based on symptoms, such as fever, headache, rash, or painful lymph nodes, accompanied by a tick bite wound (eschar) [9]. A low white blood cell count can also be indicative of the infection [7].

It's worth noting that laboratory tests may not always confirm the diagnosis, and ATBF is often diagnosed clinically based on symptoms and exposure to ticks. If you suspect you have been bitten by an infected tick, it's essential to consult a healthcare professional for proper evaluation and testing.

References:

[1] CE Owen (2006) - Laboratory diagnosis of ATBF may be made with non-PCR serologic tests; however, other rickettsial species cross-react, and the results are not positive until 3 weeks after the tick bite [1].

[2] DZ Uslan (2004) - No readily available serologic diagnosis exists except in research laboratories, although a serologic test for RMSF will occasionally be positive [2].

[3] MS Fralish (2020) - African tick bite fever in a Taiwanese traveler returning from South Africa: molecular and serologic studies [3].

[4] F Althaus (2010) - PCR of a biopsy of the eschar is an alternative way to confirm the diagnosis of ATBF. To achieve an optimal sensitivity, a specific nested PCR can be used [4].

[7] by N Harrison (2016) - For serological testing the immunofluorescence test is the preferred method but seroconversion usually occurs about 2–3 weeks after the tick bite [8].

[9] Tick bite fever is usually diagnosed clinically by the presence of the eschar, accompanied by one or more symptoms like fever, headache, rash, or painful lymph nodes [9].

African tick-bite fever (ATBF) is a disease caused by the bacterium Rickettsia africae. The standard therapy for adult patients with ATBF is doxycycline 100 mg twice daily [1][8]. This antibiotic is very effective in treating the infection, although it may take a day or two for the patient to feel better [7].

Alternatives to doxycycline for the treatment of ATBF are limited. However, other antibiotics such as chloramphenicol or azithromycin may also be used [2]. It's worth noting that the disease will also tend to resolve without treatment [2].

The standard treatment duration is not specified in all sources but it seems like 7-10 days is a common duration for doxycycline therapy. For example, one source mentions 7 days of doxycycline (100 mg twice daily) as the initial therapy [6], while another source recommends 10 days of doxycycline 100 mg twice daily for Rickettsia africae infection [3].

It's also important to note that antibiotics should be started as soon as the infection is suspected, and treatment should not be delayed [4].

African tick-bite fever (ATBF) is a spotted fever rickettsiosis that can be challenging to diagnose due to its similarity in symptoms with other tropical fevers. Here are some conditions that should be considered as part of the differential diagnosis for ATBF:

• Malaria: Malaria is an important differential diagnosis, especially in travelers returning from endemic areas [2]. Early serological tests may be negative, and repeat testing is often required to confirm the diagnosis.
• Scrub typhus: Scrub typhus should also be included in the differential diagnosis of patients with a fever, as it can present with similar symptoms to ATBF [9].
• Other tropical fevers: African tick-bite fever should be considered along with other tropical fevers such as dengue fever, chikungunya, and Zika virus infection in the differential diagnosis of all febrile patients returning from endemic areas [10].

It's essential for clinicians to consider these conditions when evaluating patients suspected of having ATBF. A comprehensive medical history, physical examination, and laboratory tests (such as serology and PCR) can help differentiate between these conditions.

References:

[1] Althaus F et al. (2010). African tick-bite fever: a new entity in the differential diagnosis of multiple eschars in travelers. [3]

[2] Frean J et al. (2019). Malaria is an important differential diagnosis of the non-specific prodrome in travellers. [2]

[3] Althaus F et al. (2010). African tick-bite fever: a new entity in the differential diagnosis of multiple eschars in travelers. [4]

[4] Althaus F et al. (2010). African tick-bite fever: a new entity in the differential diagnosis of multiple eschars in travelers. [5]

[9] Clinicians should include scrub typhus in the differential diagnosis of patients with a fever ... [9]

[10] African tick-bite fever should be considered along with malaria and other tropical fevers in the differential diagnosis of all febrile patients returning from ... [10]