Estimating leptospirosis incidence using hospital-based surveillance and a population-based health care utilization survey in Tanzania.

BACKGROUND: The incidence of leptospirosis, a neglected zoonotic disease, is uncertain in Tanzania and much of sub-Saharan Africa, resulting in scarce data on which to prioritize resources for public health interventions and disease control. In this study, we estimate the incidence of leptospirosis in two districts in the Kilimanjaro Region of Tanzania. METHODOLOGY/PRINCIPAL FINDINGS: We conducted a population-based household health care utilization survey in two districts in the Kilimanjaro Region of Tanzania and identified leptospirosis cases at two hospital-based fever sentinel surveillance sites in the Kilimanjaro Region. We used multipliers derived from the health care utilization survey and case numbers from hospital-based surveillance to calculate the incidence of leptospirosis. A total of 810 households were enrolled in the health care utilization survey and multipliers were derived based on responses to questions about health care seeking in the event of febrile illness. Of patients enrolled in fever surveillance over a 1 year period and residing in the 2 districts, 42 (7.14%) of 588 met the case definition for confirmed or probable leptospirosis. After applying multipliers to account for hospital selection, test sensitivity, and study enrollment, we estimated the overall incidence of leptospirosis ranges from 75-102 cases per 100,000 persons annually. CONCLUSIONS/SIGNIFICANCE: We calculated a high incidence of leptospirosis in two districts in the Kilimanjaro Region of Tanzania, where leptospirosis incidence was previously unknown. Multiplier methods, such as used in this study, may be a feasible method of improving availability of incidence estimates for neglected diseases, such as leptospirosis, in resource constrained settings.

Comparing actual and perceived causes of fever among community members in a low malaria transmission setting in northern Tanzania.

OBJECTIVE: To compare actual and perceived causes of fever in northern Tanzania. METHODS: In a standardised survey, heads of households in 30 wards in Moshi, Tanzania, were asked to identify the most common cause of fever for children and for adults. Responses were compared to data from a local hospital-based fever aetiology study that used standard diagnostic techniques. RESULTS: Of 810 interviewees, the median (range) age was 48 (16, 102) years and 509 (62.8%) were women. Malaria was the most frequently identified cause of fever, cited by 353 (43.6%) and 459 (56.7%) as the most common cause of fever for children and adults, respectively. In contrast, malaria accounted for 8 (2.0%) of adult and 6 (1.3%) of paediatric febrile admissions in the fever aetiology study. Weather was the second most frequently cited cause of fever. Participants who identified a non-biomedical explanation such as weather as the most common cause of fever were more likely to prefer a traditional healer for treatment of febrile adults (OR 2.7, P < 0.001). Bacterial zoonoses were the most common cause of fever among inpatients, but no interviewees identified infections from animal contact as the most common cause of fever for adults; two (0.2%) identified these infections as the most common cause of fever for children. CONCLUSIONS: Malaria is perceived to be a much more common cause of fever than hospital studies indicate, whereas other important diseases are under-appreciated in northern Tanzania. Belief in non-biomedical explanations of fever is common locally and has important public health consequences.

Chikungunya and dengue fever among hospitalized febrile patients in northern Tanzania.

Consecutive febrile admissions were enrolled at two hospitals in Moshi, Tanzania. Confirmed acute Chikungunya virus (CHIKV), Dengue virus (DENV), and flavivirus infection were defined as a positive polymerase chain reaction (PCR) result. Presumptive acute DENV infection was defined as a positive anti-DENV immunoglobulin M (IgM) enzyme-linked immunsorbent assay (ELISA) result, and prior flavivirus exposure was defined as a positive anti-DENV IgG ELISA result. Among 870 participants, PCR testing was performed on 700 (80.5%). Of these, 55 (7.9%) had confirmed acute CHIKV infection, whereas no participants had confirmed acute DENV or flavivirus infection. Anti-DENV IgM serologic testing was performed for 747 (85.9%) participants, and of these 71 (9.5%) had presumptive acute DENV infection. Anti-DENV IgG serologic testing was performed for 751 (86.3%) participants, and of these 80 (10.7%) had prior flavivirus exposure. CHIKV infection was more common among infants and children than adults and adolescents (odds ratio [OR] 1.9, P = 0.026) and among HIV-infected patients with severe immunosuppression (OR 10.5, P = 0.007). CHIKV infection is an important but unrecognized cause of febrile illness in northern Tanzania. DENV or other closely related flaviviruses are likely also circulating.