Abstract
BackgroundQ fever is a common cause of febrile illness and community-acquired pneumonia in resource-limited settings. Coxiella burnetii, the causative pathogen, is transmitted among varied host species, but the epidemiology of the organism in Africa is poorly understood. We conducted a systematic review of C. burnetii epidemiology in Africa from a “One Health” perspective to synthesize the published data and identify knowledge gaps.Methods/Principal FindingsWe searched nine databases to identify articles relevant to four key aspects of C. burnetii epidemiology in human and animal populations in Africa: infection prevalence; disease incidence; transmission risk factors; and infection control efforts. We identified 929 unique articles, 100 of which remained after full-text review. Of these, 41 articles describing 51 studies qualified for data extraction. Animal seroprevalence studies revealed infection by C. burnetii (≤13%) among cattle except for studies in Western and Middle Africa (18–55%). Small ruminant seroprevalence ranged from 11–33%. Human seroprevalence was <8% with the exception of studies among children and in Egypt (10–32%). Close contact with camels and rural residence were associated with increased seropositivity among humans. C. burnetii infection has been associated with livestock abortion. In human cohort studies, Q fever accounted for 2–9% of febrile illness hospitalizations and 1–3% of infective endocarditis cases. We found no studies of disease incidence estimates or disease control efforts.Conclusions/Significance C. burnetii infection is detected in humans and in a wide range of animal species across Africa, but seroprevalence varies widely by species and location. Risk factors underlying this variability are poorly understood as is the role of C. burnetii in livestock abortion. Q fever consistently accounts for a notable proportion of undifferentiated human febrile illness and infective endocarditis in cohort studies, but incidence estimates are lacking. C. burnetii presents a real yet underappreciated threat to human and animal health throughout Africa.
Highlights
Coxiella burnetii, a zoonotic bacterial pathogen found worldwide except in New Zealand, is transmitted to humans through direct contact with milk, urine, feces, or semen from infected animals as well as inhalation of aerosolized particles from animal placentas, parturient fluids, aborted fetuses, and environmental dust [1]
In light of recent findings establishing Q fever as an important cause of severe febrile illness in northern Tanzania [11,12] and growing awareness of the potential economic impact of infection in animals, we systematically reviewed the existing literature on the epidemiology of C. burnetii infection among humans and animals in Africa
We considered the following serologic tests and minimum antibody titer cut-offs for C. burnetii phase I and/or phase II antigen as acceptable evidence of infection in humans and animals based on expert consensus: complement fixation (CF) .1:10 for animals [20] and $1:4 for humans, microscopic agglutination test (MAT) $1:4 for humans and animals, indirect fluorescent antibody (IFA) $1:25 for animals and $1:40 for humans, and ELISA validated against one of the above methods [20,21,22,23]
Summary
A zoonotic bacterial pathogen found worldwide except in New Zealand, is transmitted to humans through direct contact with milk, urine, feces, or semen from infected animals as well as inhalation of aerosolized particles from animal placentas, parturient fluids, aborted fetuses, and environmental dust [1]. While infection by C. burnetii in humans can be asymptomatic, symptomatic infection, known as Q fever, can present as an acute undifferentiated febrile illness with the possibility of focal manifestations, such as hepatitis and pneumonia. Infection by C. burnetii has been demonstrated in many animal species, but the principle reservoirs are thought to be sheep, goats, and cattle. In these livestock species infection is often asymptomatic but can cause abortion and reduce reproductive efficiency [1,6]. Q fever is a common cause of febrile illness and community-acquired pneumonia in resource-limited settings. The causative pathogen, is transmitted among varied host species, but the epidemiology of the organism in Africa is poorly understood. We conducted a systematic review of C. burnetii epidemiology in Africa from a ‘‘One Health’’ perspective to synthesize the published data and identify knowledge gaps
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