Exposure and Risk Factors to Coxiella burnetii, Spotted Fever Group and Typhus Group Rickettsiae, and Bartonella henselae among Volunteer Blood Donors in Namibia

Abstract

BackgroundThe role of pathogen-mediated febrile illness in sub-Saharan Africa is receiving more attention, especially in Southern Africa where four countries (including Namibia) are actively working to eliminate malaria. With a high concentration of livestock and high rates of companion animal ownership, the influence of zoonotic bacterial diseases as causes of febrile illness in Namibia remains unknown.Methodology/Principal FindingsThe aim of the study was to evaluate exposure to Coxiella burnetii, spotted fever and typhus group rickettsiae, and Bartonella henselae using IFA and ELISA (IgG) in serum collected from 319 volunteer blood donors identified by the Blood Transfusion Service of Namibia (NAMBTS). Serum samples were linked to a basic questionnaire to identify possible risk factors. The majority of the participants (64.8%) had extensive exposure to rural areas or farms. Results indicated a C. burnetii prevalence of 26.1% (screening titre 1∶16), and prevalence rates of 11.9% and 14.9% (screening titre 1∶100) for spotted fever group and typhus group rickettsiae, respectively. There was a significant spatial association between C. burnetii exposure and place of residence in southern Namibia (P<0.021). Donors with occupations involving animals (P>0.012), especially cattle (P>0.006), were also significantly associated with C. burnetii exposure. Males were significantly more likely than females to have been exposed to spotted fever (P<0.013) and typhus (P<0.011) group rickettsiae. Three (2.9%) samples were positive for B. henselae possibly indicating low levels of exposure to a pathogen never reported in Namibia.Conclusions/SignificanceThese results indicate that Namibians are exposed to pathogenic fever-causing bacteria, most of which have flea or tick vectors/reservoirs. The epidemiology of febrile illnesses in Namibia needs further evaluation in order to develop comprehensive local diagnostic and treatment algorithms.

From Q Fever to Coxiella burnetii Infection: a Paradigm Change

“…Q fever seroprevalence rates in humans varied from 1% in Chad (52) to 16% in Egypt (53). More recently, a seroprevalence study among blood donors in Namibia identified a 26% seropositivity rate (54). In an agropastoral region of Algeria, seroprevalence rates of 15%, with peaks up to 30% in villages where the disease is hyperendemic, have been observed (55).…”

Vector-borne diseases of small companion animals in Namibia: Literature review, knowledge gaps and opportunity for a One Health approach

“…The presence of SFG rickettsiae species has not yet been reported in Namibian dogs and cats; however, serological evidence has been reported in human populations (Noden & Van der Colf 2013 ; Noden et al . 2014b ). While the main tick reservoir or vector species in Africa for R. conorii and R. africae is probably R. sanguineus (Walker et al .…”

“… 1998 ) and Namibia (Noden et al . 2014b ). Vectored by the cat flea, C. felis , or the rat flea, X. cheopis (Laudisoit et al .…”

“…The relatively high seropositivity rates in healthy human blood donors (Noden et al . 2014b ) suggest that infected fleas exist in close proximity to pet owners, but few veterinarians in Namibia even mention fleas on dogs and cats. Further study is needed to identify areas of Namibia most prone to domestic flea infestations and the possibility of flea-borne rickettsiae among canine and feline populations and local flea populations.…”

Development of a loop-mediated isothermal amplification (LAMP) assay for rapid screening of ticks and fleas for spotted fever group rickettsia

“…Reports continue to demonstrate that these tick- and flea-borne pathogens are impacting human and animal populations in low resource countries which lack technical and material capabilities. Often, these countries are not aware that these pathogens are circulating in their populations [ 1 , 3 , 7 , 8 ]. In recent years, increased funding and research focus has shifted to the development of point-of-care diagnostics that will detect the causative agents of neglected tropical diseases [ 6 ].…”