Impact Assessment of Repeated Mass Ivermectin Treatment on Onchocerciasis in Abia State, Nigeria

The impact assessment of repeated mass ivermectin treatment on onchocerciasis in Abia state, south eastern Nigeria was carried out between June and September 2011, using skin snipping method. Abia state is made up of 17 Local Government Areas, eight of which are endemic for onchocerciasis (2 hyper-endemic and 6 meso-endemic LGAs). The study captured the two LGAs of the state that were rated as hyper-endemic by REMO assessment and had been receiving treatment since 1995. Out of 547 individuals skin snipped, only 3 (0.55%) were infected with microfilariae of Onchocerca volvulus, and this occurred in one community Amiyi-Obilohia. The distribution of infection showed that 0.50% of the infected were males while 0.58% were females. The overall age specific prevalence showed that infection only occurred in individuals 60 years and above, who were low compliers and were not treated during the last treatment period. A CMFL of 0.28 mf/mg obtained is an indication that ivermectin is an effective microfilaricide. Key words: Impact assessment, Repeated, mass, ivermectin, treatment, Onchocerciasis

Gravity Inversion of the Gongola Basin Fault Structures Using the Step Model

Gravity anomalies with step-like appearance are often attributed to fault structures. Analysis of gravity anomalies due to such structures is then tantamount to solving the four fault parameters: depth to the surface, sediment thickness, density contrast and the fault dip. In this research, a gravity inversion using the step model was carried out to simultaneously estimate the four parameters of the faulted bed. The model assumes a configuration that the basin is filled with homogeneous sediments. Three characteristic curves were adopted for estimating the fault parameters.Analysis of the residual anomaly profiles of the fault structures showed that the fault structures were independent of the strike length. The estimated depth to the surface and the sediment thickness yielded the basement depth. The basement depth obtained from the gravity profiles showed a maximum basement depth of 1.0 km in the south-western part, and 7.0 km in the north-eastern part of the project area. The estimated basement depth yielded plausible geological model that corroborates with depth obtained using seismic and well information. The computed density contrast was used in the determination of density contrast and rock density maps of the basin. This helped in defining the basin into zones of sedimentary, basement complex and granite pluton

Few Losses to Follow-up in a Sub-Saharan African Cancer Cohort via Active Mobile Health Follow-up

Accurate survival estimates are needed for guiding cancer control efforts in sub-Saharan Africa, but previous studies have been hampered by unknown biases due to excessive loss to follow-up (LTFU). In the African Breast Cancer-Disparities in Outcomes Study, a prospective breast cancer cohort study, we implemented active mobile health follow-up, telephoning each woman or her next-of-kin (NOK) trimonthly on her mobile phone to update information on her vital status. Dates of every contact with women/NOK were analyzed from diagnosis in 2014-2017 to the earliest of September 1, 2018, death, or 3 years postdiagnosis. The cumulative incidence of being LTFU was calculated considering deaths as competing events. In all, 1,490 women were followed for a median of 24.2 (interquartile range (IQR), 14.2-34.5) months, corresponding to 8,529 successful contacts (77% of total contacts) with the women/NOK. Median time between successful contacts was 3.0 (IQR, 3.0-3.7) months. In all, 71 women (5.3%) were LTFU at 3 years: 0.8% in Nigeria, 2.2% in Namibia, and 5.6% in Uganda. Because of temporary discontinuity of active follow-up, 20.3% of women were LTFU after 2 years in Zambia. The median time to study notification of a death was 9.1 (IQR, 3.9-14.0) weeks. Although the present study was not a randomized controlled trial, in this cancer cohort with active mobile health follow-up, LTFU was much lower than in previous studies and enabled estimation of up-to-date and reliable cancer survival

Evaluating the Stability and Adequacy of NIGNET for the Definition of Nigerian Geodetic Reference Frame

A set of Continuously Operating Reference Stations (CORS) distributed all over Nigeria constitutes the Nigerian GNSS Reference Network referred to as NIGNET. Global Navigation Satellite System (GNSS) is a system that uses satellites for autonomous position determination, and is a critical component of the modern-day geodetic infrastructure and services. Using CORS provide geodetic controls of comparable accuracy and a better alternative to the classical geodetic network. As the NIGNET infrastructure is utilised for different geodetic applications, it has become necessary to evaluate the suitability of the network data for the definition of a geodetic reference frame (GRF). This study utilised the technique of Precise Point Positioning (PPP) in position estimation, and time series analysis for temporal monitoring of the network. The sufficiency and adequacy of the NIGNET data archive was also evaluated against that of an International GNSS Service (IGS) Station. The temporal stability of the station coordinates measured in terms of standard deviations varied between 10 mm and 22 mm. This analysis suggests a relative stability required for Tiers 1 and 2 CORS in line with the IGS standards. Based on this reported stability, it is concluded that NIGNET is fit for purpose in defining the Nigerian Geodetic Reference Frame. However, despite the good data quality observed, the adequacy of the network has been compromised by infrastructural failures and lack of continuity in data transmission. Accordingly, it is recommended that both practical and policy measures required to ensure the realisation of the goal of the network should be implemented