scholarly journals Quantifying Malaria Acquired During Travel and Its Role in Malaria Elimination on Bioko Island

2021 ◽  
Author(s):  
Daniel T Citron ◽  
Carlos A Guerra ◽  
Guillermo A García ◽  
Sean L Wu ◽  
Katherine E Battle ◽  
...  
Keyword(s):  
Malaria Elimination ◽  
Malaria Prevalence ◽  
Equatorial Guinea ◽  
Bioko Island ◽  
Posterior Probability Distribution ◽  
Urban City ◽  
Prevalence Estimates ◽  
Prophylactic Vaccination ◽  
The Impact ◽  
Local Transmission

Abstract Background Malaria elimination is the goal for Bioko Island, Equatorial Guinea. Intensive interventions implemented since 2004 have reduced prevalence, but progress has stalled in recent years. A challenge for elimination has been malaria infections in residents acquired during travel to mainland Equatorial Guinea. We quantify how off-island contributes to remaining malaria prevalence on Bioko Island, and investigate the potential role of a pre-erythrocytic vaccine in making further progress towards elimination. Methods We simulated malaria transmission on Bioko Island using a model calibrated based on data from the Malaria Indicator Surveys (MIS) from 2015-2018, including detailed travel histories and malaria positivity by rapid-diagnostic tests (RDTs), as well as geospatial estimates of malaria prevalence. Mosquito population density was adjusted to fit local transmission, conditional on importation rates under current levels of control and within-island mobility. We evaluated the impact of two pre-erythrocytic vaccine distribution strategies: mass treat and vaccinate, and prophylactic vaccination for off-island travelers. We propagated uncertainty through the model through an ensemble of simulations fit to the Bayesian joint posterior probability distribution of the geospatial prevalence estimates. Results The simulations suggest that in Malabo, an urban city containing 80\% of the population, there are some pockets of residual transmission, but a large proportion of prevalence is attributable to malaria importation by travelers. Outside of Malabo, prevalence was mainly attributable to local transmission. We assess the uncertainty in the local transmission vs. importation to be lowest within Malabo and highest outside. Using a pre-erythrocytic vaccine to protect travelers would have larger benefits than using the vaccine to protect residents of Bioko Island from local transmission. In simulations, mass treatment and vaccination had short-lived benefits, as malaria prevalence returned to current levels as the vaccine's efficacy waned. Prophylactic vaccination of travelers resulted in longer-lasting reductions in prevalence. These projections were robust to underlying uncertainty in prevalence estimates. Conclusions The modeled outcomes suggest that the volume of malaria cases imported from the mainland is a partial driver of continued endemic malaria on Bioko Island, and that continued elimination efforts on must account for human travel activity.

scholarly journals Quantifying malaria acquired during travel and its role in malaria elimination on Bioko Island

2021 ◽  
Author(s):  
Daniel T Citron ◽  
Carlos A Guerra ◽  
Guillermo A García ◽  
Sean L Wu ◽  
Katherine E Battle ◽  
...  
Keyword(s):  
Malaria Elimination ◽  
Malaria Prevalence ◽  
Equatorial Guinea ◽  
Bioko Island ◽  
Posterior Probability Distribution ◽  
Urban City ◽  
Prevalence Estimates ◽  
Prophylactic Vaccination ◽  
The Impact ◽  
Local Transmission

AbstractBackgroundMalaria elimination is the goal for Bioko Island, Equatorial Guinea. Intensive interventions implemented since 2004 have reduced prevalence, but progress has stalled in recent years. A challenge for elimination has been malaria infections in residents acquired during travel to mainland Equatorial Guinea. We quantify how off-island contributes to remaining malaria prevalence on Bioko Island, and investigate the potential role of a pre-erythrocytic vaccine in making further progress towards elimination.MethodsWe simulated malaria transmission on Bioko Island using a model calibrated based on data from the Malaria Indicator Surveys (MIS) from 2015-2018, including detailed travel histories and malaria positivity by rapid-diagnostic tests (RDTs), as well as geospatial estimates of malaria prevalence. Mosquito population density was adjusted to fit local transmission, conditional on importation rates under current levels of control and within-island mobility. We evaluated the impact of two pre-erythrocytic vaccine distribution strategies: mass treat and vaccinate, and prophylactic vaccination for off-island travelers. We propagated uncertainty through the model through an ensemble of simulations fit to the Bayesian joint posterior probability distribution of the geospatial prevalence estimates.ResultsThe simulations suggest that in Malabo, an urban city containing 80% of the population, there are some pockets of residual transmission, but a large proportion of prevalence is attributable to malaria importation by travelers. Outside of Malabo, prevalence was mainly attributable to local transmission. We assess the uncertainty in the local transmission vs. importation to be lowest within Malabo and highest outside. Using a pre-erythrocytic vaccine to protect travelers would have larger benefits than using the vaccine to protect residents of Bioko Island from local transmission. In simulations, mass treatment and vaccination had short-lived benefits, as malaria prevalence returned to current levels as the vaccine’s efficacy waned. Prophylactic vaccination of travelers resulted in longer-lasting reductions in prevalence. These projections were robust to underlying uncertainty in prevalence estimates.ConclusionsThe modeled outcomes suggest that the volume of malaria cases imported from the mainland is a partial driver of continued endemic malaria on Bioko Island, and that continued elimination efforts on must account for human travel activity.

scholarly journals Quantifying malaria acquired during travel and its role in malaria elimination on Bioko Island

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Daniel T. Citron ◽  
Carlos A. Guerra ◽  
Guillermo A. García ◽  
Sean L. Wu ◽  
Katherine E. Battle ◽  
...  
Keyword(s):  
Malaria Elimination ◽  
Malaria Prevalence ◽  
Equatorial Guinea ◽  
Bioko Island ◽  
Posterior Probability Distribution ◽  
Urban City ◽  
Prevalence Estimates ◽  
Prophylactic Vaccination ◽  
The Impact ◽  
Local Transmission

Abstract Background Malaria elimination is the goal for Bioko Island, Equatorial Guinea. Intensive interventions implemented since 2004 have reduced prevalence, but progress has stalled in recent years. A challenge for elimination has been malaria infections in residents acquired during travel to mainland Equatorial Guinea. The present article quantifies how off-island contributes to remaining malaria prevalence on Bioko Island, and investigates the potential role of a pre-erythrocytic vaccine in making further progress towards elimination. Methods Malaria transmission on Bioko Island was simulated using a model calibrated based on data from the Malaria Indicator Surveys (MIS) from 2015 to 2018, including detailed travel histories and malaria positivity by rapid-diagnostic tests (RDTs), as well as geospatial estimates of malaria prevalence. Mosquito population density was adjusted to fit local transmission, conditional on importation rates under current levels of control and within-island mobility. The simulations were then used to evaluate the impact of two pre-erythrocytic vaccine distribution strategies: mass treat and vaccinate, and prophylactic vaccination for off-island travellers. Lastly, a sensitivity analysis was performed through an ensemble of simulations fit to the Bayesian joint posterior probability distribution of the geospatial prevalence estimates. Results The simulations suggest that in Malabo, an urban city containing 80% of the population, there are some pockets of residual transmission, but a large proportion of infections are acquired off-island by travellers to the mainland. Outside of Malabo, prevalence was mainly attributable to local transmission. The uncertainty in the local transmission vs. importation is lowest within Malabo and highest outside. Using a pre-erythrocytic vaccine to protect travellers would have larger benefits than using the vaccine to protect residents of Bioko Island from local transmission. In simulations, mass treatment and vaccination had short-lived benefits, as malaria prevalence returned to current levels as the vaccine’s efficacy waned. Prophylactic vaccination of travellers resulted in longer-lasting reductions in prevalence. These projections were robust to underlying uncertainty in prevalence estimates. Conclusions The modelled outcomes suggest that the volume of malaria cases imported from the mainland is a partial driver of continued endemic malaria on Bioko Island, and that continued elimination efforts on must account for human travel activity.

scholarly journals Infection importation: a key challenge to malaria elimination on Bioko Island, Equatorial Guinea

2015 ◽  
Vol 14 (1) ◽  
Author(s):  
John Bradley ◽  
Feliciano Monti ◽  
Andrea M Rehman ◽  
Christopher Schwabe ◽  
Daniel Vargas ◽  
...  
Keyword(s):  
Malaria Elimination ◽  
Equatorial Guinea ◽  
Bioko Island

scholarly journals Incidence of Plasmodium falciparum malaria infection in 6-month to 45-year-olds on selected areas of Bioko Island, Equatorial Guinea

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Vicente Urbano Nsue Ndong Nchama ◽  
Ali Hamad Said ◽  
Ali Mtoro ◽  
Gertrudis Owono Bidjimi ◽  
Marta Alene Owono ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Control ◽  
Malaria Infection ◽  
Age Groups ◽  
Control Measures ◽  
Equatorial Guinea ◽  
Safety And Efficacy ◽  
Bioko Island ◽  
Malaria Vaccines

Abstract Background Extensive malaria control measures have been implemented on Bioko Island, Equatorial Guinea over the past 16 years, reducing parasite prevalence and malaria-related morbidity and mortality, but without achieving elimination. Malaria vaccines offer hope for reducing the burden to zero. Three phase 1/2 studies have been conducted successfully on Bioko Island to evaluate the safety and efficacy of whole Plasmodium falciparum (Pf) sporozoite (SPZ) malaria vaccines. A large, pivotal trial of the safety and efficacy of the radiation-attenuated Sanaria® PfSPZ Vaccine against P. falciparum is planned for 2022. This study assessed the incidence of malaria at the phase 3 study site and characterized the influence of socio-demographic factors on the burden of malaria to guide trial design. Methods A cohort of 240 randomly selected individuals aged 6 months to 45 years from selected areas of North Bioko Province, Bioko Island, was followed for 24 weeks after clearance of parasitaemia. Assessment of clinical presentation consistent with malaria and thick blood smears were performed every 2 weeks. Incidence of first and multiple malaria infections per person-time of follow-up was estimated, compared between age groups, and examined for associated socio-demographic risk factors. Results There were 58 malaria infection episodes observed during the follow up period, including 47 first and 11 repeat infections. The incidence of malaria was 0.25 [95% CI (0.19, 0.32)] and of first malaria was 0.23 [95% CI (0.17, 0.30)] per person per 24 weeks (0.22 in 6–59-month-olds, 0.26 in 5–17-year-olds, 0.20 in 18–45-year-olds). Incidence of first malaria with symptoms was 0.13 [95% CI (0.09, 0.19)] per person per 24 weeks (0.16 in 6–59-month-olds, 0.10 in 5–17-year-olds, 0.11 in 18–45-year-olds). Multivariate assessment showed that study area, gender, malaria positivity at screening, and household socioeconomic status independently predicted the observed incidence of malaria. Conclusion Despite intensive malaria control efforts on Bioko Island, local transmission remains and is spread evenly throughout age groups. These incidence rates indicate moderate malaria transmission which may be sufficient to support future larger trials of PfSPZ Vaccine. The long-term goal is to conduct mass vaccination programmes to halt transmission and eliminate P. falciparum malaria.

scholarly journals Elucidating the Local Transmission Dynamics of Highly Pathogenic Avian Influenza H5N6 in the Republic of Korea by Integrating Phylogenetic Information

Pathogens ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 691
Author(s):  
Dae-Sung Yoo ◽  
Byungchul Chun ◽  
Kyung-Duk Min ◽  
Jun-Sik Lim ◽  
Oun-Kyoung Moon ◽  
...  
Keyword(s):  
Avian Influenza ◽  
Highly Pathogenic Avian Influenza ◽  
Transmission Dynamics ◽  
Republic Of Korea ◽  
Transmission Risk ◽  
Highly Pathogenic ◽  
Pathogenic Avian Influenza ◽  
The Republic ◽  
The Impact ◽  
Local Transmission

Highly pathogenic avian influenza (HPAI) virus is one of the most virulent and infectious pathogens of poultry. As a response to HPAI epidemics, veterinary authorities implement preemptive depopulation as a controlling strategy. However, mass culling within a uniform radius of the infection site can result in unnecessary depopulation. Therefore, it is useful to quantify the transmission distance from infected premises (IPs) before determining the optimal area for preemptive depopulation. Accordingly, we analyzed the transmission risk within spatiotemporal clusters of IPs using transmission kernel estimates derived from phylogenetic clustering information on 311 HPAI H5N6 IPs identified during the 2016–2017 epidemic, Republic of Korea. Subsequently, we explored the impact of varying the culling radius on the local transmission of HPAI given the transmission risk estimates. The domestic duck farm density was positively associated with higher transmissibility. Ring culling over a radius of 3 km may be effective for areas with high dense duck holdings, but this approach does not appear to significantly reduce the risk for local transmission in areas with chicken farms. This study provides the first estimation of the local transmission dynamics of HPAI in the Republic of Korea as well as insight into determining an effective ring culling radius.

The family Lecithoceridae (Lepidoptera, Gelechioidea) from Bioko Island (Equatorial Guinea), with descriptions of five new species

Zootaxa ◽  
2021 ◽  
Vol 4995 (3) ◽  
pp. 581-593
Author(s):  
KYU-TEK PARK ◽  
TIMM KARISCH
Keyword(s):  
New Species ◽  
Equatorial Guinea ◽  
Bioko Island ◽  
The Family ◽  
First Time ◽  
A New Species

Five new species belonging to the subfamily Torodorinae of Lecithoceridae are described from Bioko Island (Equatorial Guinea), based on specimens which were collected during a short expedition on the island by the second author in 1994. The new species are three species of the genus Thubdora Park, 2018 (T. biocoica sp. nov., T. vernaculella sp. nov., and T. angustiala sp. nov.), and a new species of Ptilothyris Walsingham, 1891and Dragmatucha Meyrick, 1908 respectively (Ptylothyris ruicheensis sp. nov.; and Dragmatucha vulcaniella sp. nov.). In addition, Thubdora bilobella Park, 2018 is reported for the first time from Equatorial Guinea. Images for adults and the genitalia of all species are given.  

scholarly journals Contribution of Asymptomatic Plasmodium Infections to the Transmission of Malaria in Kayin State, Myanmar

2018 ◽  
Vol 219 (9) ◽  
pp. 1499-1509 ◽  
Author(s):  
Victor Chaumeau ◽  
Ladda Kajeechiwa ◽  
Bénédicte Fustec ◽  
Jordi Landier ◽  
Saw Naw Nyo ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Entomological Inoculation Rate ◽  
Fold Increase ◽  
Estimating Equation ◽  
Malaria Prevalence ◽  
Pcr Analysis ◽  
Asymptomatic Malaria ◽  
Asymptomatic Infections ◽  
Greater Mekong Subregion ◽  
The Impact

Abstract Background The objective of mass antimalarial drug administration (MDA) is to eliminate malaria rapidly by eliminating the asymptomatic malaria parasite reservoirs and interrupting transmission. In the Greater Mekong Subregion, where artemisinin-resistant Plasmodium falciparum is now widespread, MDA has been proposed as an elimination accelerator, but the contribution of asymptomatic infections to malaria transmission has been questioned. The impact of MDA on entomological indices has not been characterized previously. Methods MDA was conducted in 4 villages in Kayin State (Myanmar). Malaria mosquito vectors were captured 3 months before, during, and 3 months after MDA, and their Plasmodium infections were detected by polymerase chain reaction (PCR) analysis. The relationship between the entomological inoculation rate, the malaria prevalence in humans determined by ultrasensitive PCR, and MDA was characterized by generalized estimating equation regression. Results Asymptomatic P. falciparum and Plasmodium vivax infections were cleared by MDA. The P. vivax entomological inoculation rate was reduced by 12.5-fold (95% confidence interval [CI], 1.6–100-fold), but the reservoir of asymptomatic P. vivax infections was reconstituted within 3 months, presumably because of relapses. This was coincident with a 5.3-fold (95% CI, 4.8–6.0-fold) increase in the vector infection rate. Conclusion Asymptomatic infections are a major source of malaria transmission in Southeast Asia.

scholarly journals Bayesian estimation of Earth's climate sensitivity and transient climate response from observational warming and heat content datasets

2021 ◽  
Vol 12 (2) ◽  
pp. 709-723
Author(s):  
Philip Goodwin ◽  
B. B. Cael
Keyword(s):  
Climate Sensitivity ◽  
Future Climate ◽  
Climate Feedback ◽  
Future Climate Change ◽  
Climate Projections ◽  
Climate Response ◽  
Ocean Heat Uptake ◽  
Transient Climate Response ◽  
Posterior Probability Distribution ◽  
The Impact

Abstract. Future climate change projections, impacts, and mitigation targets are directly affected by how sensitive Earth's global mean surface temperature is to anthropogenic forcing, expressed via the climate sensitivity (S) and transient climate response (TCR). However, the S and TCR are poorly constrained, in part because historic observations and future climate projections consider the climate system under different response timescales with potentially different climate feedback strengths. Here, we evaluate S and TCR by using historic observations of surface warming, available since the mid-19th century, and ocean heat uptake, available since the mid-20th century, to constrain a model with independent climate feedback components acting over multiple response timescales. Adopting a Bayesian approach, our prior uses a constrained distribution for the instantaneous Planck feedback combined with wide-ranging uniform distributions of the strengths of the fast feedbacks (acting over several days) and multi-decadal feedbacks. We extract posterior distributions by applying likelihood functions derived from different combinations of observational datasets. The resulting TCR distributions when using two preferred combinations of historic datasets both find a TCR of 1.5 (1.3 to 1.8 at 5–95 % range) ∘C. We find the posterior probability distribution for S for our preferred dataset combination evolves from S of 2.0 (1.6 to 2.5) ∘C on a 20-year response timescale to S of 2.3 (1.4 to 6.4) ∘C on a 140-year response timescale, due to the impact of multi-decadal feedbacks. Our results demonstrate how multi-decadal feedbacks allow a significantly higher upper bound on S than historic observations are otherwise consistent with.

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