Acute Spotted Fever Rickettsiosis among Febrile Patients, Cameroon

Abstract

Although potential arthropod vectors are abundant in Cameroon, acute febrile illnesses are rarely evaluated for arboviral or rickettsial infections. Serum samples from 234 acutely febrile patients at clinics in Tiko and Buea, Cameroon, were examined for antibodies to Rickettsia africae and African alphaviruses and flaviviruses. These serum samples did not contain antibodies against typhoid, and blood malarial parasites were not detected. Serum samples of 32% contained immunoglobulin M antibodies reactive with R. africae by immunofluorescence assay and were reactive with outer membrane proteins A and B of R. africae by immunoblotting. These findings established a diagnosis of acute rickettsiosis, most likely African tick-bite fever. Hemagglutination inhibition testing of the serum samples also detected antibodies to Chikungunya virus (47%) and flaviviruses (47%). High prevalence of antibodies to arboviruses may represent a major, previously unrecognized public health problem in an area where endemic malaria and typhoid fever have been the principal diagnostic considerations.

Human Ehrlichioses and Rickettsioses in Cameroon

“…The report based on a serologic survey that used an unreliable technique demonstrated rickettsial antibodies in cattle and humans in the northern region of Cameroon and in other animals in the south of the country ( Maurice et al, 1968;Le et al, 1977). Efforts to determine the epidemiology and ecology later re-emerged in 2004 when anti-rickettsial IgM antibodies were detected in some Cameroonian patients along the coastal region of Cameroon (Ndip et al, 2004a). These results were further confirmed by detection of R. africae DNA in about 6% of acutely ill febrile patients (Ndip et al, 2004b).…”

“…The agent was later isolated in A. hebraeum ticks in Zimbabwe in 1990, and in 1992, the first isolate from a patient was obtained Kelly et al, 1994). The pathogen has been detected in many other African countries including Senegal , Ethiopia (Stephany et al, 2009) and Cameroon (Ndip et al, 2004a;Ndip et al, 2004b). In the following, we give a synopsis of our current knowledge of African tick bite fever in Cameroon.…”

“…However, these tests are not very reliable in distinguishing species because cross-reactivity may be observed among the SFG rickettsiae. However, some authors have proposed that a fourfold or greater titer for R. africae compared to other species is confirmatory Ndip et al, 2004a). The western immunoblot assay can also be used to detect antibodies against species-specific OmpA and OmpB proteins.…”

Tick-Borne Rickettsioses around the World: Emerging Diseases Challenging Old Concepts

“…Despite high seroprevalence to R. africae among native Africans, nearly all acute cases of ATBF described in the literature have occurred in European or American travelers (145,205,273). Recently however, Ndip et al reported cases of ATBF documented by serology (26 patients) and molecular techniques (7 patients) among indigenous patients in Cameroon (212,213).…”

Silent circulation of arboviruses in Cameroon

“…Unfortunately, after the last (1976) publication of these surveys, there was a 25-year gap before Fontenille and Toto reported the introduction of the Aedes albopictus, a potential new vector of DF and YF into southern Cameroon (6)(7)(8). Later, Ndip et al (9) Kuniholm et al (10) and Demanou et al (11), reported prevalence of antibodies (Abs) to some arboviruses in the serum of febrile patients in Cameroon, and Peyrefitte et al, isolated the CHIKV from a patient. In this survey, we sought to further investigate the latent circulation of arboviruses, characterise the agents and assess the risk of infection in Cameroon, with reference to the Fako Division ( Figure 1).…”