African tick bite fever

CASES/YEAR
0 (US); 60,000 (Global)
CATEGORY
Arthropod-Borne
AGENT TYPE
Rickettsiae
OTHER NAMES
Rickettsia africae infection; ATBF;
ACUITY
Acute-Moderate
INCUBATION
5-7 days
INITIAL SYMPTOMS
Fever, headache, black eschar (may be many), regional adenitis, vesicular rash, and aphthous ulcers; [ABX Guide: Rickettsia species]
PRECAUTIONS
Standard; "Not directly transmitted from person to person." [CCDM, p. 518]
COMMENTS
Similar to Mediterranean spotted fever with fever, myalgia, nausea, and headache, but milder course; Rash (may be vesicular) in about 1/2 of cases; Other symptoms are aphthous stomatitis, one or more eschars, and lymphangitis. [CCDM, p. 516] Reported features of ATBF are fever (81-88%), headache (83%), rash (26-46%), vesicular rash (16-45%), tache noire (32-95%), multiple eschars (21-54%), myalgia (63-87%), and lymphadenopathy (43-49%). [PPID, p. 2352t] The rash of rickettsial infections can involve the palms and soles in the later stages of infection. [PPID, p. 813] Outbreaks have been reported among soldiers and travelers in endemic rural areas throughout Africa south of the Sahara. [Guerrant, p. 324] It is the most frequently diagnosed travel-related rickettsiosis. Patients have a fine petechial or papular rash. [CDC Travel, p. 329, 639] Common in Safari tourists to southern Africa; Fever frequently absent; Some patients have draining lymphadenitis in inguinal lymph nodes. [Cecil, p. 2021] Patients may have "nuchal myalgia" (81%), nausea-fatigue-headache (62-83%), maculopapular rash (14-26%), vesicular rash (0-21%, and aphthous stomatitis (0-11%). [Guerrant, p. 326] Fatality rates without treatment: Rocky Mountain (20-25%), Mediterranean spotted fever (1-2.5%), African (none); [Cohen, p. 1667]
DIAGNOSTIC
Serology (indirect immunofluorescence assay); Skin biopsy (direct immunofluorescence); PCR or culture; Common in rickettsial infections: elevated transaminases, thrombocytopenia, leukopenia, or leukocytosis; [ABX Guide: Rickettsia Species]
SCOPE
Sub-Saharan Africa & West Indies; Maculataum disease (R. parkeri) is a similar disease in North and South America; [Guerrant, p. 323-8] R. africae infections occur in the Caribbean; [Harrison ID, p. 692]
SIGNS & SYMPTOMS
  • >fatigue, weakness
  • >fever
  • >myalgia
  • E stomatitis
  • G liver function test, abnormal
  • G nausea, vomiting
  • H leukocytosis
  • H leukopenia
  • H lymphadenopathy
  • H thrombocytopenia
  • N headache
  • S entry wound with lymph nodes
  • S lymphadenitis, acute
  • S lymphangitis
  • S papules or plaques
  • S petechiae and ecchymoses
  • S rash (exanthem)
  • S rash on palms
  • S skin blister or vesicles
  • S ulcer of skin
ANTIMICROBIC

Yes

VACCINE

No

ENTRY
SOURCE
RESERVOIR
Cattle, Goats and Sheep, Dogs, Rabbits, Rodents, Wild Animals
RISK FACTORS
  • Travel to endemic area
  • Work or play in tick-infested area
REFERENCES FOR CASES/YEAR
1.
2. (Global) May cause most of rickettsial infections worldwide; [Cecil, p. 2021] Probably causes a high incidence of infections in indigenous people, and is the most common travel-related rickettsiosis; [Guerrant, p. 324] Guesstimate: Use US rate (about 3000/year) for Rocky Mountain spotted fever X 20= 60,000;