Comparison of Two Detailed Models of Aedes aegypti Population Dynamics

The success of control programs for mosquito-­borne diseases can be enhanced by crucial information provided by models of the mosquito populations. Models, however, can differ in their structure, complexity, and biological assumptions, and these differences impact their predictions. Unfortunately, it is typically difficult to determine why two complex models make different predictions because we lack structured side-­by-­side comparisons of models using comparable parameterization. Here, we present a detailed comparison of two complex, spatially explicit, stochastic models of the population dynamics of Aedes aegypti, the main vector of dengue, yellow fever, chikungunya, and Zika viruses. Both models describe the mosquito?s biological and ecological characteristics, but differ in complexity and specific assumptions. We compare the predictions of these models in two selected climatic settings: a tropical and weakly seasonal climate in Iquitos, Peru, and a temperate and strongly seasonal climate in Buenos Aires, Argentina. Both models were calibrated to operate at identical average densities in unperturbedconditions in both settings, by adjusting parameters regulating densities in each model (number of larval development sites and amount of nutritional resources). We show that the models differ in their sensitivityto environmental conditions (temperature and rainfall) and trace differences to specific model assumptions.Temporal dynamics of the Ae. aegypti populations predicted by the two models differ more markedly under strongly seasonal Buenos Aires conditions. We use both models to simulate killing of larvae and/or adults with insecticides in selected areas. We show that predictions of population recovery by the models differ substantially, an effect likely related to model assumptions regarding larval development and (director delayed) density dependence. Our methodical comparison provides important guidance for model improvement by identifying key areas of Ae. aegypti ecology that substantially affect model predictions, and revealing the impact of model assumptions on population dynamics predictions in unperturbed and perturbed conditions.Fil: Legros, Mathieu. University of North Carolina; Estados UnidosFil: Otero, Marcelo Javier. Universidad de Buenos Aires; ArgentinaFil: Romeo Aznar, Victoria Teresa. Universidad de Buenos Aires; ArgentinaFil: Solari, Hernan Gustavo. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Gould, Fred. National Institutes of Health; Estados UnidosFil: Lloyd, Alun L.. National Institutes of Health; Estados Unido

Determinants and Differentials of Maternal Reproductive Health Outcomes in Nigeria: A Review of National Demographic Health Survey Data from 1999 to 2013

Women in Sub-Saharan Africa face significant clinical and socio-demographic challenges that translate to poor health outcomes including high maternal morbidity and mortality. Nigeria being the most populous nation in Africa bears a significant burden of both communicable and non-communicable diseases. This study aimed to determine the trends and differentials in indices fuelling poor health outcomes in Nigeria. The study was a review and trend analysis of maternal reproductive health indicators obtained from the Nigeria National Demographic and Health Survey (NDHS) data from 1990 to 2013 including secondary data from WHO, UNICEF and the World Bank. The life expectancy at birth was 54.5 years with an estimated infant mortality rate of 75 per 1000 live births, child mortality rate of 88 per 1,000 live births, under-5 mortality rate of 157 per 1,000 live births and a maternal mortality ratio (MMR) of 545 per 100,000 live births. Contraceptive prevalence was 22% among women in the wealthiest quintile and 3% among those in the poorest quintile.  Only 3% of women with no education used modern contraception as compared to 24% of women with tertiary education. Most of the maternal deaths were due to preventable causes which were largely related to poverty, inimical socio-cultural beliefs and practices as well as clinical factors like haemorrage, hypertension, and indirect causes like inadequate human resource for health, user charges, cultural pregnancy/childbirth beliefs and myths. A community-based participatory research using both qualitative and quantitative methods may shed more light on the non-clinical factors fueling high MMR in Nigeria. Keywords: Maternal and Child Health, maternal mortality, contraceptio

Malariometric indices among Nigerian children in a rural setting

Malaria contributes to high childhood morbidity and mortality in Nigeria. To determine its endemicity in a rural farming community in the south-south of Nigeria, the following malariometric indices, namely, malaria parasitaemia, spleen rates, and anaemia were evaluated in children aged 2-10 years. This was a descriptive cross-sectional survey among school-age children residing in a rubber plantation settlement. The children were selected from six primary schools using a multistaged stratified cluster sampling technique. They were all examined for pallor, enlarged spleen, or liver among other clinical parameters and had blood films for malaria parasites. Of the 461 children recruited, 329 (71.4%) had malaria parasites. The prevalence of malaria parasitaemia was slightly higher in the under fives than that of those ≥5 years, 76.2% and 70.3%, respectively. Splenic enlargement was present in 133 children (28.9%). The overall prevalence of anaemia was 35.7%. Anaemia was more common in the under-fives (48.8%) than in those ≥5 years (32.8%). The odds of anaemia in the under fives were significantly higher than the odds of those ≥5 years (OR = 1.95 [1.19-3.18]). Malaria is highly endemic in this farming community and calls for intensification of control interventions in the area with special attention to school-age children

A public–private partnership model to reduce tuberculosis burden in Akwa Ibom State – Nigeria

Background: Tuberculosis (TB) infection and spread are preventable, and TB disease is curable depending on the individual and community knowledge of causes of the disease, mode of prevention and cure. Objective: Following a previous program carried out in 2006 in Akwa Ibom State (AKS) of Nigeria that focussed on creating awareness about TB and educating the communities on appropriate care-seeking attitudes, an intervention to reduce the burden of the disease in 18 communities of the State was carried out over a period of one year (2010–2011). The program was phased and was comprised of three components: educational intervention, TB case detection and integration into the State National Tuberculosis and Leprosy Control Programme (NTBLCP), as well as laboratory capacity building. Methods: Standard pretested questionnaires were administered to community residents to test their knowledge, attitudes and practices concerning TB. Information about causes, symptoms and prevention of TB was disseminated in community town halls, churches, markets and schools. Individuals who were coughing for three weeks or more were investigated for TB following clinical examination by a physician. Three sputum samples (spot-morning-spot) were obtained from each individual and examined microscopically for the presence of acid-fast bacilli (AFB) using the Ziehl-Neelsen staining technique. Those with positive AFB results were integrated into the existing NTBLCP TB treatment facilities for immediate commencement of Directly-Observed Therapy Short Course (DOTs). Treatment outcome was monitored by retesting patients’ sputum after 2, 5 and 7 months. Two new laboratories were facilitated while existing laboratory capacity was built by providing higher resolution microscopes, power-generating plants, refrigerators and locally-fabricated incinerators. The program was facilitated by a public–private partnership. Effective Health Care Alliance Research Programme (Nigeria), in collaboration with Nigeria National Petroleum Cooperation and Mobil Producing Nigeria Unlimited (NNPC/MPN) Joint Venture, utilized health personnel from the Akwa Ibom State NTBLCP who conducted laboratory testing and supervised the treatment. Results: The 916 responses to the questionnaires showed that 549/841 (65%) correctly identified that TB is airborne, and 759/871 (86%) were aware that TB could be cured by anti-TB medication. Responses to care-seeking attitudes were provided by 123 respondents. Of this number, fear of stigmatization was the reason for 31% (38) seeking care in unorthodox facilities, while 43% (53) did not believe that orthodox medicine could cure their symptoms. Of the 374 detected cases, 9 did not commence treatment. Hence, 365 cases were placed on DOTs; 36 defaulted while 11 died or failed to convert after the seventh month. At the end of month 8, cure was achieved for 318 (87.1%) of the cases. Conclusion: Though the previous intervention might have helped to increase the knowledge of the respondents about TB in the community and helped to improve their care-seeking attitudes, sustaining active case finding through Public–Private Partnership can go a long way to reduce TB burden, especially in rural communities where health care systems are generally weak or inadequate

A public–private partnership to reduce tuberculosis burden in Akwa Ibom State, Nigeria

Background: Tuberculosis (TB) infection and spread are preventable, and TB disease is curable depending on individual and community knowledge of causes of the disease, mode of prevention and cure. An earlier educational intervention carried out in Akwa Ibom State (AKS) of Nigeria in 2006 created awareness of the disease and improved utilization of orthodox medical facilities of residents in 34 communities who had symptoms of TB. Objective: The overall aim of this program is to reduce the burden of TB disease in 18 communities of AKS through educational intervention, TB case detection and integration into the State National Tuberculosis and Leprosy Control Programme (NTBLCP), as well as build laboratory capacity to improve TB case detection and control. Methods: Prior to the educational intervention in each community, standard pretested questionnaires were administered to residents to test their knowledge, attitudes and practices concerning TB. Information about causes, symptoms and prevention of TB was disseminated in community town halls, churches, markets and schools. Individuals who were coughing for three weeks or more were investigated for TB following clinical examination by a physician. Three sputum samples (spot-morning-spot) were obtained from each individual and examined microscopically for the presence of acid-fast bacilli (AFB) using the Ziehl–Neelson staining technique. Those with positive AFB results were integrated into the existing NTBLCP treatment facilities for immediate commencement of Directly-Observed Therapy Short Course (DOTS). Treatment outcome was monitored by retesting patients' sputum after two, five and seven months. Two new laboratories were facilitated while existing laboratory capacity was built by providing higher resolution microscopes, power generating plants, refrigerators, locally-fabricated incinerators and furnishing of staff offices. The program was facilitated by a public–private partnership. Effective Health Care Alliance Research Programme (EHCARP-Nigeria), in collaboration with Nigeria National Petroleum Cooperation and Mobil Producing Nigeria Unlimited (NNPC/MPN) Joint Venture, utilized health personnel from the Akwa Ibom State NTBLCP who conducted laboratory testing and supervised the treatment. Results: The 916 responses to the questionnaires showed that 65.3% (549/841) correctly identified that TB is airborne, and 86% (749/871) were aware that TB could be cured by anti-TB medication. Responses to care-seeking attitudes were provided by 123 respondents. Of this number, fear of stigmatization was the reason for 31% (38) seeking care in unorthodox facilities, while 43.1% (53) did not believe that orthodox medicine could cure their symptoms. Of the 374 detected cases, 9 did not commence treatment. Hence, 365 were placed on DOTS; 36 defaulted, while 11 either died or failed to convert after the seventh month. At the end of month 8, cure was achieved for 87.1% (318). Conclusion: Although the previous intervention may have contributed to the good knowledge about TB and care-seeking attitudes displayed by respondents in the communities, sustaining active case finding through public–private partnership can go a long way to reduce TB burden, especially in rural communities where healthcare systems are generally weak or inadequate. Adequate funding of TB control activities is critical in eliminating TB as a public health problem, and the private sector participation such as this is a welcome development

Dengue vector management using insecticide treated materials and targeted interventions on productive breeding-sites in Guatemala

Background In view of the epidemiological expansion of dengue worldwide and the availability of new tools and strategies particularly for controlling the primary dengue vector Aedes aegypti, an intervention study was set up to test the efficacy, cost and feasibility of a combined approach of insecticide treated materials (ITMs) alone and in combination with appropriate targeted interventions of the most productive vector breeding-sites. Methods The study was conducted as a cluster randomized community trial using “reduction of the vector population” as the main outcome variable. The trial had two arms: 10 intervention clusters (neighborhoods) and 10 control clusters in the town of Poptun Guatemala. Activities included entomological assessments (characteristics of breeding-sites, pupal productivity, Stegomyia indices) at baseline, 6 weeks after the first intervention (coverage of window and exterior doorways made of PermaNet 2.0 netting, factory treated with deltamethrin at 55 mg/m2, and of 200 L drums with similar treated material) and 6 weeks after the second intervention (combination of treated materials and other suitable interventions targeting productive breeding-sites i.e larviciding with Temephos, elimination etc.). The second intervention took place 17 months after the first intervention. The insecticide residual activity and the insecticidal content were also studied at different intervals. Additionally, information about demographic characteristics, cost of the intervention, coverage of houses protected and satisfaction in the population with the interventions was collected. Results At baseline (during the dry season) a variety of productive container types for Aedes pupae were identified: various container types holding >20 L, 200 L drums, washbasins and buckets (producing 83.7% of all pupae). After covering 100% of windows and exterior doorways and a small number of drums (where the commercial cover could be fixed) in 970 study households, tropical rains occurred in the area and lead to an increase of the vector population, more pronounced (but statistically not significant) in the control arm than in the intervention arm. In the second intervention (17 months later and six weeks after implementing the second intervention) the combined approach of ITMs and a combination of appropriate interventions against productive containers (Temephos in >200 L water drums, elimination of small discarded tins and bottles) lead to significant differences on reductions of the total number of pupae (P = 0.04) and the House index (P = 0.01) between intervention and control clusters, and to borderline differences on reductions of the Pupae per Person and Breteau indices (P = 0.05). The insecticide residual activity on treated curtains was high until month 18 but the chemical concentration showed a high variability. The cost per house protected with treated curtains and drum covers and targeting productive breeding-sites of the dengue vector was $ 5.31 USD. The acceptance of the measure was generally high, particularly in families who had experienced dengue. Conclusion Even under difficult environmental conditions (open houses, tropical rainfall, challenging container types mainly in the peridomestic environment) the combination of insecticide treated curtains and to a less extent drum covers and interventions targeting the productive container types can reduce the dengue vector population significantly