BackgroundReported malaria cases continue to decline globally, and this has been attributed to strategic implementation of multiple malaria control tools. Gains made would however need to be sustained through continuous monitoring to ensure malaria elimination and eradication. Entomological inoculation rate (EIR) is currently the standard tool for transmission monitoring but this is not sensitive enough, especially in areas of very low transmission. Transmission estimation models based on seroconversion rates (λ) of antibodies to Plasmodium falciparum blood stage antigens are gaining relevance. Estimates of λ, which is the measure of transmission intensity, correlate with EIR but are limited by long-term persistence of antibodies to blood stage antigens. Seroprevalence of antibodies to sporozoite antigens may be better alternatives since these antigens usually have shorter immune exposure times. The aim of this study was to develop transmission estimation models based on the seroprevalence of antibodies to two P. falciparum sporozoite antigens (CSP, CelTOS) and compare with models based on the classical blood stage antigen AMA1.MethodsAntibody levels in archived plasma from three cross-sectional surveys conducted in 2009 in a low transmission area of Southern Ghana were assessed by indirect ELISA. Seroprevalence of antibodies against CSP, CelTOS and AMA1 were fitted to reversible catalytic models to estimate λ and corresponding seroreversion rates (ρ) for each antibody.ResultsOf the three models developed, the anti-CSP model predicted a 13-fold decrease in λ four years prior to the time of sampling (2009). Anti-AMA1 antibodies formed at a four-fold greater rate compared to that of anti-CelTOS antibodies, and anti-CSP antibodies during the period of decreased λ. In contrast, anti-AMA1 antibodies decayed at a five-fold slower rate relative to that of anti-CSP antibodies while anti-AMA1 and anti-CelTOS antibody decay rates were not significantly different. Anti-CSP antibodies were relatively short-lived as they formed at an 11.6-fold slower rate relative to their decay during the period of decreased λ.ConclusionsThese features of anti-CSP antibodies can be exploited for the development of models for predicting seasonal, short-term changes in transmission intensity in malaria-endemic areas, especially as the elimination phase of malaria control is approached.

Purpose The management of external debt among highly indebted poor countries (HIPCs) in Africa still remains a challenge despite numerous packages and attempts to ameliorate the consequences of such odious debt. The purpose of this paper is to establish the factors that contribute to the growth rate of external debt and how these factors respond to shocks to external debt growth rate in Africa. Design/methodology/approach Data were obtained from 24 African countries and analyzed using a panel vector autoregression estimation methodology. Findings The study found that external debt growth rates respond positively to unit shock or changes in government investment spending, consumption spending, and domestic borrowings over a long period of time. In the medium term, external debt growth rates respond negatively to shocks in tax revenue, inflation, and output growth rates. The paper also provides empirical support that external debt may be consumed rather than invested among HIPCs in Africa. Research limitations/implications The findings of this paper are limited to only HIPCs in Africa. Practical implications This study has some few debilitating implications for external debt management among HIPCs in Africa. First, the paper suggests that debt repayment may be a problem. This is largely because external debt is consumed rather than invested. External debt sustainability needs a holistic approach in less developed countries. The findings place much emphasis on improvements in gross domestic product and tax revenues as the principal routes out of the debt doldrums. However, this option must be exploited with great caution as there is ample evidence that these poor countries increase their external borrowing capacities with improvements in economic outlook. Originality/value This paper fills a research gap that identifies specific components of government deficit budgets that may be contributing to the growth rate of external debts among HIPCs.

Background-Rapid but simple diagnostic tool for detecting drug resistant