title: Brucellosis in northern Tanzania: Investigating the epidemiology of human infection and evaluating diagnostic test performance in animal hosts
Creators: name: Bodenham, Rebecca F.
Publisher: name: University of Glasgow
Year: 2020
Subjects: subject: brucellosis; zoonotic disease; pastoralist; risk factor; active surveillance; diagnostics; prevention and control

description: Brucellosis is a widespread neglected zoonotic disease. It can cause severe and prolonged illness in people, as well as impacting on animal health and productivity. Brucellosis is endemic in much of sub-Saharan Africa (SSA). The global burden of brucellosis is suspected to be highest in SSA, where there are many livestock-keeping communities. Cattle, sheep and goats are common maintenance hosts of zoonotic Brucella spp. Pastoralist communities in frequent contact with these livestock species are at increased risk of infection. This study was performed to improve our understanding of the epidemiology of brucellosis in Tanzania through: a risk factor analysis for human acute brucellosis cases; trialling an active surveillance approach to identify additional cases through household screening in a high-risk population; and latent class analyses to evaluate diagnostic test performance in different animal hosts. In Chapter 2, questionnaire data were collected from febrile patients attending a rural hospital in the Ngorongoro Conservation Area (NCA), Tanzania. Risk factors associated with acute brucellosis were: having herded cattle, sheep and/or goats in the past 12 months; and decreasing age in years. In Chapter 3, active surveillance in the form of screening household members of febrile patients for exposure to Brucella spp. was implemented in the NCA. Screening household members of febrile patients with acute brucellosis led to identification of additional acute cases. However, the study did not find a significant association between the Brucella spp. exposure of household members and the household member who sought care at hospital. In Chapter 4, Bayesian latent class analyses were used to evaluate the Rose Bengal plate test (RBT) and the competitive enzyme-linked immunosorbent assay (cELISA) for the diagnosis of livestock brucellosis in northern Tanzania. Sensitivity was variable across livestock models, RBT sensitivity was comparable to cELISA in the bovine model and greater than cELISA in ovine and caprine models. RBT and cELISA specificity was essentially comparable in all livestock models. Conducting parallel RBT and cELISA testing optimised diagnostic test performance in all livestock models. These novel findings can inform the development and implementation of effective, evidence-based brucellosis prevention and control measures in SSA. Improved knowledge of acute human brucellosis risk factors is important in understanding temporally relevant risks associated with active infection and is a vital tool in developing interventions that prevent transmission. Active surveillance by screening household members requires further study but may prove too resource-intensive for routine implementation in Tanzania. However, it can provide valuable data on disease burden for the population that do not reach a healthcare facility, as well as assist in targeting prevention and control measures towards high-risk populations. In livestock, a parallel RBT and cELISA diagnostic testing approach, potentially implemented at the herd/flock level, would be more effective than using either test alone or serial approaches. Using these data, identification of a national sampling and testing approach can guide the development of a surveillance strategy which is a crucial step towards improving our understanding of brucellosis burden across livestock-keeping settings in Tanzania and wider SSA.