Measuring the accuracy of gridded human population density surfaces: A case study in Bioko Island, Equatorial Guinea.

BACKGROUND: Geospatial datasets of population are becoming more common in models used for health policy. Publicly-available maps of human population make a consistent picture from inconsistent census data, and the techniques they use to impute data makes each population map unique. Each mapping model explains its methods, but it can be difficult to know which map is appropriate for which policy work. High quality census datasets, where available, are a unique opportunity to characterize maps by comparing them with truth. METHODS: We use census data from a bed-net mass-distribution campaign on Bioko Island, Equatorial Guinea, conducted by the Bioko Island Malaria Elimination Program as a gold standard to evaluate LandScan (LS), WorldPop Constrained (WP-C) and WorldPop Unconstrained (WP-U), Gridded Population of the World (GPW), and the High-Resolution Settlement Layer (HRSL). Each layer is compared to the gold-standard using statistical measures to evaluate distribution, error, and bias. We investigated how map choice affects burden estimates from a malaria prevalence model. RESULTS: Specific population layers were able to match the gold-standard distribution at different population densities. LandScan was able to most accurately capture highly urban distribution, HRSL and WP-C matched best at all other lower population densities. GPW and WP-U performed poorly everywhere. Correctly capturing empty pixels is key, and smaller pixel sizes (100 m vs 1 km) improve this. Normalizing areas based on known district populations increased performance. The use of differing population layers in a malaria model showed a disparity in results around transition points between endemicity levels. DISCUSSION: The metrics in this paper, some of them novel in this context, characterize how these population maps differ from the gold standard census and from each other. We show that the metrics help understand the performance of a population map within a malaria model. The closest match to the census data would combine LandScan within urban areas and the HRSL for rural areas. Researchers should prefer particular maps if health calculations have a strong dependency on knowing where people are not, or if it is important to categorize variation in density within a city.

The Equatoguinean Malaria Vaccine Initiative: From the Launching of a Clinical Research Platform to Malaria Elimination Planning in Central West Africa.

Fifteen years of investment in malaria control on Bioko Island, Equatorial Guinea (EG), dramatically reduced malaria-associated morbidity and mortality, but the impact has plateaued. To progress toward elimination, EG is investing in the development of a malaria vaccine. We assessed the unique public-private partnership that has had such a significant impact on malaria on Bioko Island and now added a major effort on malaria vaccine development. As part of a $79M commitment, the EG government (75%) and three American energy companies (25%) have invested since 2012 greater than $55M in the Equatoguinean Malaria Vaccine Initiative (EGMVI) to support clinical development of Sanaria® PfSPZ vaccines (Sanaria Inc., Rockville, MD). In turn, the vaccine development program is building human capital and physical capacity. The EGMVI established regulatory and ethical oversight to ensure compliance with the International Conference on Harmonization and Good Clinical Practices for the first importation of investigational product, ethical approval, and conduct of a clinical trial in Equatoguinean history. The EGMVI has completed three vaccine trials in EG, two vaccine trials in Tanzania, and a malaria incidence study, and initiated preparations for a 2,100-volunteer clinical trial. Personnel are training for advanced degrees abroad and have been trained in Good Clinical Practices and protocol-specific methods. A new facility has established the foundation for a national research institute. Biomedical research and development within this visionary, ambitious public-private partnership is fostering major improvements in EG. The EGMVI plans to use a PfSPZ Vaccine alongside standard malaria control interventions to eliminate Pf malaria from Bioko, becoming a potential model for elimination campaigns elsewhere.

Spatial and temporal variability of the Glossina palpalis palpalis population in the Mbini focus (Equatorial Guinea).

BACKGROUND: Human African Trypanosomiasis is a vector-borne parasitic disease. The geographical distribution of the disease is linked to the spatial distribution of the tsetse fly. As part of a control campaign using traps, the spatial and temporal variability is analysed of the glossina populations present in the Mbini sleeping sickness foci (Equatorial Guinea). RESULTS: A significant drop in the annual mean of the G. p. palpalis apparent density was noted from 2004 to 2005, although seasonal differences were not observed. The apparent density (AD) of G. p. palpalis varies significantly from one biotope to another. The fish dryers turned out to be zones with the greatest vector density, although the AD of G. p. palpalis fell significantly in all locations from 2004 to 2005. CONCLUSION: Despite the tsetse fly density being relatively low in fish dryers and jetties, the population working in those zones would be more exposed to infection. The mono-pyramidal traps in the Mbini focus have been proven to be a useful tool to control G. p. palpalis, even though the activity on the banks of the River Wele needs to be intensified. The application of spatial analysis techniques and geographical information systems are very useful tools to discriminate zones with high and low apparent density of G. p. palpalis, probably associated with different potential risk of sleeping sickness transmission.

Impact of different strategies to control Plasmodium infection and anaemia on the island of Bioko (Equatorial Guinea).

BACKGROUND: On the island of Bioko (Equatorial Guinea), insecticide-treated nets (ITNs) have been the main tool used to control malaria over the last 13 years. In 2004, started an indoor residual spraying (IRS) campaign to control malaria. The purpose of this study is to asses the impact of the two control strategies on the island of Bioko (Equatorial Guinea), with regards to Plasmodium infection and anaemia in the children under five years of age. METHODS: Two transversal studies, the first one prior to the start of the IRS campaign and the second one year later. Sampling was carried out by stratified clusters. Malaria infection was measured by means of thick and thin film, and the packed cell volume (PCV) percentage. Data related to ITN use and information regarding IRS were collected. The Pearson's chi-square and logistic regression statistical tests were used to calculate odds ratios (OR). RESULTS: In the first survey, 168 children were sampled and 433 children in the second one. The prevalence of infection was 40% in 2004, and significantly lower at 21.7% in 2005. PCV was 41% and 39%, respectively. 58% of the children surveyed in 2004 and 44.3% in 2005 had slept under an ITN. 78% of the dwellings studied in 2005 had been sprayed. In the 2005 survey, sleeping without a mosquito net meant a risk of infection 3 times greater than sleeping protected with a net hanged correctly and with no holes (p < 0.05). CONCLUSION: IRS and ITNs have proven to be effective control strategies on the island of Bioko. The choice of one or other strategy is, above all, a question of operational feasibility and availability of local resources.

[Epidemiological investigation of imported falciparum malaria in Longlin County, Guangxi Zhuang Autonomous Region].

Among 41 people returned from Equatorial Guinea, 16 persons were infected with Plasmodium falciparum (39.02%) in Longlin County, Guangxi Zhuang Autonomous Region from October 2011 to February 2012. Among the 16 cases, Plasmodiumfalciparum was found in their blood smears of 15 cases, and 1 patient was diagnosed clinically as falciparum malaria. All the 41 people were once suffered from malaria and they received antimalarial drugs when they were in Equatorial Guinea. These imported malaria cases received the standard treatment and the foci were sprayed with insecticides. No secondary malaria cases were found. In conclusion, the measures of imported malaria control are effective. The persons returned from Equatorial Guinea have a high risk of malaria; therefore, it is necessary to strengthen the monitoring of malaria for the floating population from high malaria prevalent areas.

Corporate philanthropy and conflicts of interest in public health: ExxonMobil, Equatorial Guinea, and malaria.

Equatorial Guinea, the most prosperous country in Africa, still bears a large malaria burden. With massive wealth from oil reserves, and nearly half its population living in island ecotypes favourable for malaria control, only poor governance can explain continued parasite burden. By financially backing the country's dictator and other officials through illicit payments, the oil company ExxonMobil contributed to the state's failure. Now ExxonMobil, having helped perpetuate malaria in Equatorial Guinea, gives money to non-governmental organizations, charitable foundations, and universities to advocate for and undertake malaria work. How, and on what terms, can public health engage with such an actor? We discuss challenges in the identification and management of conflicts of interest in public health activities. We reviewed the business and foundation activities of ExxonMobil and surveyed organizations that received ExxonMobil money about their conflict of interest policies. Reforms in ExxonMobil's business practices, as well as its charitable structure, and reforms in the way public health groups screen and manage conflicts of interest are needed to ensure that any relationship ultimately improves the health of citizens.

Marked increase in child survival after four years of intensive malaria control.

In malaria-endemic countries in Africa, a large proportion of child deaths are directly or indirectly attributable to infection with Plasmodium falciparum. Four years after high coverage, multiple malaria control interventions were introduced on Bioko Island, Equatorial Guinea, changes in infection with malarial parasites, anemia, and fever history in children were estimated and assessed in relation to changes in all-cause under-5 mortality. There were reductions in prevalence of infection (odds ratio [OR] = 0.31, 95% confidence interval [CI] = 0.2-0.46), anemia (OR = 0.11, 95% CI = 0.07-0.18), and reported fevers (OR = 0.41, 95% CI = 0.22-0.76) in children. Under-5 mortality fell from 152 per 1,000 births (95% CI = 122-186) to 55 per 1,000 (95% CI = 38-77; hazard ratio = 0.34 [95% CI = 0.23-0.49]). Effective malaria control measures can dramatically increase child survival and play a key role in achieving millennium development goals.

[Epidemiology of human trypanosomiasis in the Luba focus, in Equatorial Guinea]. / Epidemiología de la Tripanosomiasis Humana en el foco de Luba, en Guinea Ecuatorial.

In Equatorial Guinea, the human trypanosomiasis, after an intensive surveillance beginning in the 30's, seemed to be controlled by the end of the 60's. A lack of surveillance provoked a surge of different foci, confirmed in 1982 by the spontaneous presentations of sick in the hospitals of the old foci. These processes have been observed in the Luba focus (ex San Carlos) on the island of Bioko (ex Fernando Poo). The situation was grave in 1985 and a survey was organized by the "Centro de Control de la Tripanosomiasis" (Ministerio de Sanidad de Guinea Ecuatorial--Agencia Española de Cooperación Internacional) to delimit the focus, to evaluate the presence of the disease in the different villages, to know the characteristics and the distribution of the vector, and evaluate the impact of the mono-pyramidal trap as the method of anti-vectorial control. The results have been obtained and presented in the conclusion.