Preventing yellow fever epidemics in Asian megacities: how can cities control mosquito-transmitted diseases?

The COVID-19 pandemic has reminded us of the ever present threat from infectious diseases, this includes the ones we know about already and future unknowns. The mosquito-transmitted disease yellow fever has claimed thousands of lives over the centuries and it hasn't gone away. It is still endemic in tropical areas of Africa and Latin America, where it is kept at bay through constant surveillance, mass vaccination campaigns and some natural immunity within local populations. Despite this there are serious outbreaks from time to time. The Aedes mosquitoes capable of transmitting the virus from person to person, are now widespread in warmer countries worldwide, moreover they thrive in urban areas. With increased international movement, the fear is that infected travellers could unwittingly introduce the virus into countries where people have little or no immunity. Densely populated Asian megacities are a major concern. There are simple measures citizens can take to protect themselves and their homes from the bite of infected mosquitoes, but city leaders must be at the forefront of a coordinated response bringing together diverse stakeholders to ensure a robust and sustainable defence.

CHARACTERIZING MOVEMENT PATTERNS OF NOMADIC PASTORALISTS AND THEIR EXPOSURE TO RIFT VALLEY FEVER IN KENYA

The role of animal movement in spreading infectious diseases is highly recognized by various legislations and institutions such as the World Organisation for Animal Health and the International Animal Health Code. The increased interactions at the nexus of human-animal-ecosystem interface have seen an unprecedented introduction and reintroduction of new zoonotic diseases with high socio-economic impacts such as the COVID-19 pandemic. Rift Valley fever (RVF) is a zoonotic disease that affects both humans and animals and is transmitted by Aedes mosquitoes or through contact with the body fluids of infected animals. This study seeks to characterize movement patterns of pastoralist and how this movement behaviour increases their susceptibility to RVF virus exposure. We levarage on a rapidly growing field of movement ecology to monitor five herds collared from 2013 – 2015 in an RVF endemic semi-arid region in Kenya. The herds were also sampled for RVF antibodies to assess their exposure to RVF virus during the rainy seasons. adehabitatLT package in R was used to analyze the trajectory data whereas the first passage time (FPT) analysis was used to measure the area utilized in grazing. Sedentary herds grazed within 15km radius while migrating herds presented restricted space use patterns during the dry seasons and transient movement during the start and end of the rainy season. Furthermore, RVF virus antibodies were generally low for sedentary herds whereas the migrating herds recorded high levels during their transition periods. This study can be used to identify RVF risk zones for timely and targeted management strategies.

Listen to the shopkeeper.

His mosquito control project heading for failure, a field entomologist recalls how a chance encounter led to a Eureka moment.

Predictors of Dengue Preventive Practices Based on Precaution Adoption Process Model among Health Care Professionals in Northwest of Iran

Background: Dengue fever as a mosquito-borne disease, has rapidly spread due to climate change, globalization, and human behavior. Iran is prone to dengue fever, as its vector recently has been found in the country. This study aimed to assess predictors of dengue preventive practices based on Precaution Adoption Process Model (PAPM) factors in West Azerbaijan province, northwest of Iran. Methods: This cross-sectional study conducted on 405 health professionals of communicable disease sector who were interested in study participation. Data-gathering instrument was an online researcher-made questionnaire consisting of demographic characteristics (11 items), questions based on PAPM, and dengue preventive practices (85 items). Content validity and reliability of the instrument, content validity ratio, content validity index, and Cronbach a were utilized, respectively. Descriptive, analytical, and regression analysis using SPSS and STATA were examined. Results: Regression analysis revealed that awareness of appropriate actions for dengue prevention was a stronger predictor of preventive practice in borderline and appropriate categories (ß= 4.09, p< 0.001) and (ß= 4.42, p< 0.001), re - spectively. Among factors of PAPM, beliefs about precaution effectiveness and difficulty in borderline (ß= 1.04, p= 0.04) and appropriate (ß= 1.12, p= 0.03) groups had direct and significant relation with dengue preventive practice. Conclusion: The highest mean score of beliefs about hazard likelihood and severity factor was related to dengue prevention. Therefore, theory-based interventions that address beliefs about precaution effectiveness and difficulty can lead to assistance in acting. To improve dengue preventive practices, a well-designed promotive intervention that addresses associated factors in a context-specific manner is essential.

Individuals and Externalities in Economic Epidemiology: A Tension and Synthesis

Both standard economic and public choice approaches to epidemiology ignore the role individuals play in disease prevention. Whereas the standard economic approach recognizes that people respond to changing prevalence rates, the standard public choice approach suggests they succumb to free-riding and collective-action problems. But the literature on collective action and the private provision of public goods suggests people can resolve collection-action problems in response to changing prevalence rates, especially when doing so lowers transaction costs. The insights of that literature suggest that decisions related to migration, housing, and community-and related markets that influence those decisions-influence mosquito control and, potentially, malaria prevalence rates.

Driving down malaria transmission with engineered gene drives.

The last century has witnessed the introduction, establishment and expansion of mosquito-borne diseases into diverse new geographic ranges. Malaria is transmitted by female Anopheles mosquitoes. Despite making great strides over the past few decades in reducing the burden of malaria, transmission is now on the rise again, in part owing to the emergence of mosquito resistance to insecticides, antimalarial drug resistance and, more recently, the challenges of the COVID-19 pandemic, which resulted in the reduced implementation efficiency of various control programs. The utility of genetically engineered gene drive mosquitoes as tools to decrease the burden of malaria by controlling the disease-transmitting mosquitoes is being evaluated. To date, there has been remarkable progress in the development of CRISPR/Cas9-based homing endonuclease designs in malaria mosquitoes due to successful proof-of-principle and multigenerational experiments. In this review, we examine the lessons learnt from the development of current CRISPR/Cas9-based homing endonuclease gene drives, providing a framework for the development of gene drive systems for the targeted control of wild malaria-transmitting mosquito populations that overcome challenges such as with evolving drive-resistance. We also discuss the additional substantial works required to progress the development of gene drive systems from scientific discovery to further study and subsequent field application in endemic settings.

Handwashing stations in Nepal: Role of wealth status in establishing handwashing stations at home

Handwashing has been proven to be effective at preventing several infectious diseases. This study aims to find out the role of wealth status in establishing handwashing stations in the households of Nepal. This study used secondary data from Nepal Demographic Health Survey in 2016 to assess the association between households' wealth status and handwashing stations. The findings displayed a significant association between the age of the household head, residence place, ecological zone, province, wealth status, having a mosquito net, having a radio and TV in the respondent's household, and fixed handwashing stations at their households at p < 0.001 level. Wealth status has significant effect on fixed handwashing stations (adjusted odds ratio [aOR] = 12.699;95% confidence interval [CI] = 10.120–15.935;p < 0.001) in the households. The households with the poorest wealth status (aOR = 9.718;95% CI = 7.387–12.785;p < 0.001), mountain ecological zone (aOR = 1.325;95% CI = 1.098–1.599;p < 0.01), Madhesh province (aOR = 2.967;95% CI = 2.405–3.658;p < 0.001) were significant predictors for not having fixed handwashing stations even after inclusion of socio‐covariates. Correspondingly, the presence of mosquito net (aOR = 0.795;95% CI = 0.692–0.913; p < 0.01), presence of a radio (aOR = 0.758;95% CI = 0.671–0.857;p < 0.001), and presence of a TV (aOR = 0.762;95% CI = 0.667–0.871;p < 0.001) had a significant effect on fixed handwashing stations at their households even after inclusion of socio‐covariates. The study found households with the poorest wealth quintiles, mountain ecological zone, and Madhesh and Karnali provinces had low fixed handwashing stations. The study suggests more leading interventions to improve public health in this region.Alternate :洗手能有效预防多种传染病。本研究旨在分析财富状况对尼泊尔家庭建立洗手台一事产生的作用。本研究使用2016年尼泊尔人口统计健康调查(NDHS)数据，评估家庭财富状况与洗手台之间的关联。研究结果显示，受访家庭户主的年龄、居住地、生态区、省份、财富状况、拥有蚊帐、收音机和电视机，这些因素与家庭拥有固定洗手台之间存在显著相关性，p=<0.001。财富状况对家庭拥有固定洗手台一事产生显著效果，调整后比值比（aOR）=12.699；95%置信区间 (CI) =10.120‐15.935，p=<0.001。财富状况最差的家庭（aOR=9.718；95% CI=7.387‐12.785，p=<0.001）、山地生态区（aOR=1.325，95% CI=1.098‐1.599，p=<0.01）、摩提舍省（aOR=2.967, 95% CI= 2.405‐3.658, p=<0.001) 是家庭没有固定洗手台的重要预测物，即使在包含社会协变量后也是如此。相应地，拥有蚊帐 (aOR=.795;95% CI=.692‐.913, p=<0.01)、收音机 (aOR=.758;95% CI=.671‐.857, p= <0.001) 和电视 (aOR=.762;95% CI=.667‐.871, p=<0.001) 对家庭拥有固定洗手台一事产生显著效果，即使在包含社会协变量后也是如此。研究发现，最贫困的财富五分位家庭、山地生态区、摩提舍省和卡尔纳利省的固定洗手台位置较低。本研究建议采取更多重要的干预措施来改善该地区的公共卫生。Alternate :El lavado de manos es efectivo para prevenir varias enfermedades infecciosas. El estudio tiene como objetivo averiguar el papel del estado de riqueza en el establecimiento de estaciones de lavado de manos en los hogares de Nepal. Este estudio utilizó datos secundarios de la Encuesta de salud demográfica de Nepal (NDHS) de 2016 para evaluar la asociación entre el estado de riqueza de los hogares y las estaciones de lavado de manos. Los hallazgos mostraron una asociación significativa entre la edad del jefe de hogar, el lugar de residencia, la zona ecológica, la provincia, el nivel de riqueza, tener mosquitero, tener radio y televisión en los hogares de los encuestados con estaciones fijas de lavado de manos en sus hogares a un ivel de p = <0,001. El estado de riqueza tiene un efecto significativo en las estaciones fijas de lavado de manos cociente de probabilidades ajustado (aOR) = 12,699;Intervalo de confianza (IC) del 95% =10.120‐15.935, p = <0.001, en los hogares. Los hogares con el estado de riqueza más pobre (aOR = 9.718;95% IC = 7.387‐12.785, p = <0.001), zona ecológica de montaña (aOR = 1.325, 95% IC = 1.098‐1.599, p = <0.01), provincia de Madhesh (aOR = 2.967, IC 95%= 2.405‐3.658, p = <0.001), fueron predictores significativos de no tener estaciones fijas de lavado de manos aún después de la inclusión de socio‐covariables. Así mismo, presencia de mosquitera (ORa = .795;IC 95%=.692‐.913, p = <0.01), presencia de radio (ORa = .758;IC 95%=.671‐.857, p = <0.001) y la presencia de un televisor (aOR = .762;95% IC = .667‐.871, p = <0.001) tuvieron un efecto significativo en las estaciones fijas de lavado de manos en sus hogares incluso después de la inclusión de socio‐covariables. El estudio encontró que los hogares con los quintiles de riqueza más pobres, la zona ecológica montañosa, Madhesh y la provincia de Karnali tenían estaciones de lavado de manos fijas bajas. El estudio sugiere más intervenciones líderes para mejorar la salud pública en esta región.Alternate :Key PointsHandwashing effectively reduces the spread of several infectious diseases, including COVID‐19.This paper uses secondary data from Nepal's Demographic Health Survey in 2016 to assess the association between households' wealth status and having handwashing stations.There exists a significant association between the age of the household head, place of residence, ecological zone, province, wealth status, and having a mosquito net/radio/TV in the house, and the likelihood of having fixed handwashing stations.The lowest proportions of fixed handwashing stations were found in the poorest households, in the mountains, among the Madheshi ethnicity, and based in Karnali province.Promoting handwashing stations may need additional public health interventions to overcome underlying inequalities at a population level.

Zika virus ‘harms baby brain collagen development’

Speed read New study helps understand effects of Zika virus on foetal brain development Vaccine progress continues, despite COVID-19 challenge But Aedes aegypti is adapting to new environments Zika virus can hamper vital collagen development in the brains of babies whose mothers were infected with the disease while pregnant, new research reveals, as the search for a vaccine continues. The research shows that a vaccine that aims to neutralise mature Zika virus particles could be effective, says co-author Ted Pierson, chief of the Laboratory of Viral Diseases at the National Institute of Allergy and Infectious Diseases in the United States. The mosquito is moving faster than epidemiologists expected and there are smaller outbreaks occurring in southern parts of Brazil. “Since Zika is not an endemic disease in these regions, the population has no natural defences against it,” Spilki warns.

Scientists eye gene drive technology to combat malaria

Speed read Innovation must be ramped up to tackle malaria, scientists urge Gene drive technology could reduce mosquito populations Pace of malaria innovation has slowed, say experts Scientists are hoping that adoption of gene drive technology could reduce mosquito populations as they call for new innovations in the fight against malaria, a fatal disease widespread in Sub-Saharan Africa. The World Health Organization (WHO) says the Africa region accounted for around 94 per cent of all global malaria cases and deaths in 2019. Fredros Okumu, entomologist and director of science, Ifakara Health Institute, Tanzania “It is a cost-effective way to cut down malaria vectors, and is simple to implement because the mosquitoes themselves do the work,” said Birungi during a Roll Back Malaria Partnership virtual boot camp on malaria control innovation on 15 November.

In Silico Study and Excito-Repellent Activity of Vitex negundo L. Essential Oil against Anopheles gambiae

(1) Background: Essential oil from Vitex negundo is known to have repellent and insecticidal properties toward the Anopheles gambiae and this is linked to its monoterpene and sesquiterpene content. In this work, an effort is made to delineate the constitution of V. negundo essential oil (VNEO) and their interaction with odorant-binding proteins (OBPs) of A. gambiae and hence access its repellent efficiency as cost-effective and safer malaria vector control alternatives. (2) Methods: Anopheles species authentication was performed by genomic DNA analysis and was subjected to behavioral analysis. GC-MS profiling was used to identify individual components of VNEO. Anopheles OBPs were obtained from the RCSB protein data bank and used for docking studies. Determination of ligand efficiency metrics and QSAR studies were performed using Hyper Chem Professional 8.0.3, and molecular dynamics simulations were performed using the Desmond module. (3) Results: GC-MS analysis of VNEO showed 28 compounds (monoterpenes, 80.16%;sesquiterpenes, 7.63%;and unknown constituents, 10.88%). The ligand efficiency metrics of all four ligands against the OBP 7 were within acceptable ranges. β-selinene (−12.2 kcal/mol), β-caryophellene (−9.5 kcal/mol), sulcatone (−10.9 kcal/mol), and α-ylangene (−9.3 kcal/mol) showed the strongest binding affinities for the target proteins. The most stable hydrophobic interactions were observed between β-selinene (Phe111 and Phe120), Sulcatone (Phe54 and Phe120), and α-ylangene (Phe111), while only sulcatone (Tyr49) presented H-bond interactions in the simulated environment. (4) Conclusions: Sulcatone and β-caryophyllene presented the best log p values, 6.45 and 5.20, respectively. These lead phytocompounds can be used in their purest as repellent supplement or as a natural anti-mosquito agent in product formulations.

The COVID-19 Pandemic: An Opportunity to Assess the Global Health Status

According to WHO: "As long as one child is infected all countries are at risk to get 200,000 new cases per year" [6, 7]. * TB claims 1.5 million lives each year. Three million cases were missed by the detection systems and the funding to combat the disease was back to the 2016 level that year [8-10]. * The number of cholera cases remains high and many are not reported. [...]it can be re-introduced into many countries like it was in Haiti in the 2010 [11-13]. * Due to the sylvatic cycle in Africa yellow fever cannot be realistically eradicated [14-17]. * Because of the cattle and wild animal reservoirs of Trypanosoma rhodesiense in East Africa, sleeping sickness cannot be practically eradicated. * In 2007, WHO announced a renewed strategy to eliminate Chagas' disease by 2010. The main problems linked to the elimination of malaria have not been tackled like: deforestation, agricultural expansion, infrastructure development, the biological differences in Anopheles species adapted to different landscapes, human and mosquito migrations, travelers, climate change [24-26]. * The discovery of a dog-fish cycle in Chad renders a lasting elimination of dracunculiasis improbable [27-28]. Most worrisome are the trends for the diseases mentioned above and there is no sign of imminent or short term eradication. [...]lack of capacity is the main obstacle to adequate healthcare in developing countries [30]. * Quantitatively, data are dismal [31]. * Quality wise, the gap is huge and increasing [32]. * Unfortunately, the evolution in various places is not toward improvement particularly in Sub-Saharan Africa. * Questions have not been raised on the unreliable origin and misutilization of resources.

PREGNANCY ASSOCIATED SARS-COV-2 AND ZIKA INFECTIOUS CONDITIONS – RECENT DATA AND OUTCOMES

Since the Zika virus outbreak in the United States, Centers for Disease Control and Prevention (CDC) concluded that among people with confirmed or possible Zika virus infection during pregnancy, Zika-associated birth defects occured in 5% of babies [4]. According to cohorts from Colombia, Puerto Rico, and French Guiana, the cumulative risk of ZIKV infection for pregnant women living in epidemic areas ranged from 21 to 44 percent [5]. Blood donors who were asymptomatic and Zika virus RNA positive were found in Florida and Texas in 2017 [7]. [...]Zika virus sexual transmission is possbile from both asymptomatic and symptomatic infections through genital, oral and anal intercourse [7]. According to these data, pregnant women in the US are more likely than non-pregnant women of reproductive age to get SARS-CoV-2 infection and accompanying symptoms [12].

Ontogenetic Transfer of Microplastics in Bloodsucking Mosquitoes Aedes aegypti L. (Diptera: Culicidae) Is a Potential Pathway for Particle Distribution in the Environment

The uptake and accumulation of microplastics (MPs) by bloodsucking mosquitoes Aedes aegypti L., carriers of vector-borne diseases, were investigated in the laboratory. In the experimental group, polystyrene (PS) particles were registered in insects of all life stages from larvae to pupae and adults. Ae. aegypti larvae readily ingested MPs with food, accumulating on average 7.3 × 106 items per larva in three days. The content of PS microspheres significantly decreased in mosquitoes from the larval stage to the pupal stage and was passed to the adult stage from the pupal without significant loss. On average, 15.8 items were detected per pupa and 10.9 items per adult individual. The uptake of MPs by Ae. aegypti did not affect their survival, while the average body weight of mosquitoes of all life stages that consumed PS microspheres was higher than that of mosquitoes in the control groups. Our data confirmed that in insects with metamorphosis, MPs can pass from feeding larvae to nonfeeding pupae in aquatic ecosystems and, subsequently, to adults flying to land. Bloodsucking mosquitoes can participate in MP circulation in the environment.

Needs Assessment of Southeastern United States Vector Control Agencies: Capacity Improvement Is Greatly Needed to Prevent the Next Vector-Borne Disease Outbreak

A national 2017 vector control capacity survey was conducted to assess the United States’ (U.S.’s) ability to prevent emerging vector-borne disease. Since that survey, the southeastern U.S. has experienced continued autochthonous exotic vector-borne disease transmission and establishment of invasive vector species. To understand the current gaps in control programs and establish a baseline to evaluate future vector control efforts for this vulnerable region, a focused needs assessment survey was conducted in early 2020. The southeastern U.S. region was targeted, as this region has a high probability of novel vector-borne disease introduction. Paper copies delivered in handwritten envelopes and electronic copies of the survey were delivered to 386 unique contacts, and 150 returned surveys were received, corresponding to a 39% response rate. Overall, the survey found vector control programs serving areas with over 100,000 residents and those affiliated with public health departments had more core capabilities compared to smaller programs and those not affiliated with public health departments. Furthermore, the majority of vector control programs in this region do not routinely monitor for pesticide resistance. Taken as a whole, these results suggest that the majority of the southeastern U.S. is vulnerable to vector-borne disease outbreaks. Results from this survey raise attention to the critical need of providing increased resources to bring all vector control programs to a competent level, ensuring that public health is protected from the threat of vector-borne disease.

First detection of WNV RNA presence in field-collected mosquitoes in Cyprus.

West Nile virus (WNV) infections have increased over recent years to the extent that WNV has become one of the most widespread arboviruses in the world, with potential consequences for both human and animal health. While much is known about WNV and the vectors that transmit it from their primary hosts across continental Europe, little is known about the epidemiology of the disease on the island of Cyprus. In this study, the aim was to investigate the prevalence of WNV infection in potential mosquito vectors for the first time in the Republic of Cyprus, using WNV surveillance of mosquitoes. Mosquitoes were collected in 2019, during which an outbreak in humans had occurred, and sampled mosquitoes were then examined for WNV infection by testing them for the presence of WNV RNA. Of 126 mosquito pools tested, one pool, containing Culex pipiens mosquitoes sampled from the Nicosia district, was found to be positive for the presence of WNV RNA. The positive pool found in this study represents the first demonstration of WNV in mosquitoes in Cyprus and confirms that human cases in Cyprus are likely the result of transmission via local Culex mosquitoes.

SARS-CoV-2 and Arthropods: A Review.

The emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) that led to the unprecedented COVID-19 pandemic exemplifies how a lack of understanding and preparedness for emerging viruses can result in consequences on a global scale. Statements that SARS-CoV-2 could not be transmitted by arthropod vectors were made without experimental support. Here we review laboratory-based research, field studies, and environmental studies to evaluate the potential for the virus to be transmitted either biologically or mechanically by arthropods. Based on these data, we conclude that transmission by arthropods is highly unlikely to play a significant epidemiological role in the transmission of SARS-CoV-2.

Dengue fever-a worldwide study

Nowadays, after coronavirus COVID 19, dengue fever is a problem of human beings that is spread by the Aedes aegypti mosquitoes. If proper protection arrangements from the particular mosquitoes are not done, this problem may lead to a pandemic. The main problem of this fever is that the starting symptoms are the same as viral fever as high fever, myalgia, muscular and joint pain, hemorrhagic episodes, and cutaneous rash. The purpose of this manuscript is to aware people of this health problem. Near the rain season, the problems of mosquitoes are increased. The awareness of the people could prevent this disease. In this manuscript, an analytic study on the worldwide dengue fever has been made. It is observed that after 2010, the cases of dengue fever are increased continuously. People should keep neat and clean their surroundings and cover maximum part of the body. © 2021 The authors.

“Best of Both World”: The Amalgamation of Fuzzy Delphi Method with Nominal Group Technique for Dengue Risk Prioritisation Decision-Making

Introduction. Dengue remains a public health threat. Clarifying the characteristics of future threats and prioritising intervention towards the highest risk potential can help to control and prevent dengue outbreaks. However, obtaining a consensus from panels of experts is certainly challenging due to the relative subjectivity of experience. Therefore, this article incorporates the fuzzy Delphi method (FDM) within a nominal group technique (NGT) as a multicriteria decision-making tool for (1) describing the characteristics of socioecological attributes (SEAs) with a high risk of causing dengue outbreak and (2) ranking those SEAs as priorities for intervention. Material and Methods. Experts were recruited using a purposive sampling technique. Informed consent was obtained before the start of the study. The NGT process began with an introductory presentation of dengue SEA by the moderator, followed by “silent generation.” Next, each participant provided information in a round-robin fashion. Ideas were collected by the moderator and displayed publicly. All experts were given ample time and space to contribute and justify their ideas without interruption during the discussion step to yield agreeable SEA characteristics. Ultimately, FDM was incorporated in the voting step to ensure rigorous analysis. The study was approved by an ethical committee before its commencement. Results. A total of 10 field experts participated in the study, with a median experience of 7.5 years working on a dengue team. The common characteristics of SEA prone to cause dengue outbreaks were the presence of human-made containers, in high quantities, left unattended, and covered from direct sunlight. Apart from that, all eight SEAs passed the triangulation of fuzzy numbers and defuzzification processes. The average fuzzy numbers ranged between 0.500 and 0.780, and the threshold value (d) ranged from 0.055 to 0.196. Of the potential risk factors identified, experts ranked illegal dumping sites as the most important, followed by old and unused items and construction sites. Conclusion. The NGT process successfully helped to obtain a consensus among the expert panels in describing SEA characteristics. Nevertheless, the integration of FDM offered a robust analysis that validated their ranking in dengue risk prioritisation. Therefore, we strongly recommend the application of FDM to be incorporated in any public health decision-making process.

Research in brief

Vimentin in SARS-CoV-2 entry Extracellular vimentin, a structural protein widely expressed in endothelial cells in the vascular system, enables SARS-CoV-2 entry into human cells say researchers who found that knockdown of vimentin significantly reduced SARS-CoV-2 infection of human endothelial cells, whereas overexpression of vimentin with ACE2, the entry receptor for SARS-CoV-2, significantly increased the infection rate. According to the study's lead author, the situation has changed little for children in Africa since the study was done. The study's researchers allowed no-CTL4 and intact-CTL4 mosquitoes to feed on human blood samples laced with Plasmodium falciparum parasites.