Matthew B Thomas

• Professor at Pennsylvania State University

Mosquito infection experiments that characterise how sporogony changes with temperature are increasingly being used to parameterise malaria transmission models. In these experiments, mosquitoes are exposed to a range of temperatures, with each group experiencing a single temperature. Diurnal temperature variation can, however, affect the sporogonic...

There is concern that increases in temperature due to climate change could lead to shifts in the dynamics and distribution of mosquito vectors. Many current models assume there are average thermal performance curves for a given vector species transmission. However, this one-size-fits-all assumption ignores the potential for local adaptation to crea...

The distribution and abundance of ectothermic mosquitoes are strongly affected by temperature, but mechanisms remain unexplored. We describe the effect of temperature on the transcriptome of Anopheles stephensi, an invasive vector of human malaria. Adult females were maintained across a range of mean temperatures (20 °C, 24 °C and 28 °C), with dail...

The abundance and distribution of ectotherms is being shaped at unprecedented scales by human-induced climate change. Unraveling molecular adaptations to thermal variation is prescient. Vector-borne diseases are of particular concern and although mosquitoes are responsible for most of the 621 million cases annually, their response to temperature is...

Despite concern that climate change could increase the human risk to malaria in certain areas, the temperature dependency of malaria transmission is poorly characterized. Here, we use a mechanistic model fitted to experimental data to describe how Plasmodium falciparum infection of the African malaria vector, Anopheles gambiae, is modulated by temp...

Most models exploring the effects of climate change on mosquito‐borne disease ignore thermal adaptation. However, if local adaptation leads to changes in mosquito thermal responses, “one size fits all” models could fail to capture current variation between populations and future adaptive responses to changes in temperature. Here, we assess phenotyp...

Malaria is a life-threatening disease caused by Plasmodium parasites transmitted by Anopheles mosquitoes. In 2021, more than 247 million cases of malaria were reported worldwide, with an estimated 619,000 deaths. While malaria incidence has decreased globally in recent decades, some public health gains have plateaued, and many endemic hotspots stil...

Background Attractive targeted sugar bait (ATSB) is a novel approach to vector control, offering an alternative mode of insecticide delivery via the insect alimentary canal, with potential to deliver a variety of compounds new to medical entomology and malaria control. Its potential to control mosquitoes was recently demonstrated in major field tri...

Malaria transmission is strongly influenced by traits such as mosquito life expectancy, vector competence, and the Extrinsic Incubation Period (EIP, which is the development time of the parasite inside the mosquito). Even though these traits are known to be shaped by environmental temperature and there is considerable concern that climate change co...

Malaria transmission is strongly influenced by traits such as mosquito life expectancy, vector competence, and the Extrinsic Incubation Period (EIP, which is the development time of the parasite inside the mosquito). Even though these traits are known to be shaped by environmental temperature and there is considerable concern that climate change co...

Background Eave tube technology is a novel method of insecticide application that uses an electrostatic coating system to boost insecticide efficacy against resistant mosquitoes. A series of previous experiments showed encouraging insecticidal effects against malaria vectors. This study was undertaken to assess the effects of the eave tube approach...

Background A better understanding of vector distribution and malaria transmission dynamics at a local scale is essential for implementing and evaluating effectiveness of vector control strategies. Through the data gathered in the framework of a cluster randomized controlled trial (CRT) evaluating the In2Care (Wageningen, Netherlands) Eave Tubes str...

Background In recent years, the downward trajectory of malaria transmission has slowed and, in some places, reversed. New tools are needed to further reduce malaria transmission. One approach that has received recent attention is a novel house-based intervention comprising window screening (S) and general house repairs to make the house more mosqui...

Background Attractive targeted sugar bait (ATSB) is a novel approach to vector control, offering an alternative mode of insecticide delivery via the alimentary canal, with potential to deliver a variety of compounds new to medical entomology and malaria control. Its potential to control mosquitoes was recently demonstrated in major field trials in...

The In2Care EaveTube is a house modification designed to block and kill malaria mosquitoes using an electrostatic netting treated with insecticide powder. A previous study demonstrated prolonged duration of effective action of insecticide-treated electrostatic netting in a semi-field setting. As part of a cluster randomized controlled trial (CRT) o...

Mathematical models of vector-borne infections, including malaria, often assume age-independent mortality rates of vectors, despite evidence that many insects senesce. In this study we present survival data on insecticide-resistant Anopheles gambiae s.l. from experiments in Côte d’Ivoire. We fit a constant mortality function and two age-dependent f...

Abstract Background A study was conducted prior to implementing a cluster-randomized controlled trial (CRT) of a lethal house lure strategy in central Côte d’Ivoire to provide baseline information on malaria indicators in 40 villages across five health districts. Methods Human landing catches (HLC) were performed between November and December 2016,...

[This corrects the article DOI: 10.1371/journal.pntd.0005568.].

Background There is a pressing need to improve understanding of how insecticide resistance affects the functional performance of insecticide-treated nets (ITNs). Standard WHO insecticide resistance monitoring assays are designed for resistance surveillance and do not necessarily provide insight into how different frequencies, mechanisms or intensit...

Background: A study was conducted prior to implementing a cluster randomised controlled trial (CRT) of a lethal house lure strategy in central Côte d’Ivoire and aimed to provide baseline information on malaria vectors in 40 village clusters. Methods: Human landing catches (HLC) was performed between November-December 2016, capturing mosquitoes indo...

The In2Care® EaveTube is a house modification designed to block and kill malaria mosquitoes using an electrostatic netting treated with insecticide powder. A previous study demonstrated prolonged duration of effective action of insecticide-treated electrostatic netting in a semi-field setting. As part of a cluster randomized controlled trial (CRT)...

Background There is evidence that the knockdown resistance gene ( Kdr ) L1014F and acetylcholinesterase-1 gene ( Ace-1 R ) G119S mutations involved in pyrethroid and carbamate resistance in Anopheles gambiae influence malaria transmission in sub-Saharan Africa. This is likely due to changes in the behaviour, life history and vector competence and c...

Mathematical models of vector-borne infections, including malaria, often assume age-independent mortality rates of vectors, despite evidence that many insects senesce. In this study we present survival data on insecticide-resistant Anopheles gambiae s.l. from field experiments in Côte d’Ivoire. We fit a constant mortality function and two age-depen...

Background: There is a pressing need to improve understanding of how insecticide resistance affects the functional performance of Insecticide Treated Nets (ITNs). Standard WHO insecticide resistance monitoring assays are designed for resistance surveillance and do not necessarily provide insight into how different frequencies, mechanisms or intensi...

The mosquito Aedes aegypti is the primary vector of many disease-causing viruses, including dengue (DENV), Zika, chikungunya, and yellow fever. As consequences of climate change, we expect an increase in both global mean temperatures and extreme climatic events. When temperatures fluctuate, mosquito vectors will be increasingly exposed to temperatu...

Background There is evidence that the Kdr L1014F and Ace-1R G119S mutations involved in pyrethroid and carbamate resistance in Anopheles gambiae influence malaria transmission in sub Saharan Africa. This is likely due to changes in behavior, life history, vectorial competence and capacity. In the present study, performed as part of a two-armed clus...

From 2004 to 2019, insecticide-treated bednets (ITNs) have been the most effective tool for reducing malaria morbidity and mortality in sub-Saharan Africa. Recently, however, the decline in malaria cases and deaths has stalled. Some suggest that this inertia is due to increasing resistance in malaria vectors to the pyrethroid insecticides used for...

Despite its epidemiological importance, the time Plasmodium parasites take to achieve development in the vector mosquito (the extrinsic incubation period, EIP) remains poorly characterized. A novel non-destructive assay designed to estimate EIP in single mosquitoes, and more broadly to study Plasmodium – Anopheles vectors interactions, is presented...

Background New vector control tools are required to sustain the fight against malaria. Lethal house lures, which target mosquitoes as they attempt to enter houses to blood feed, are one approach. Here we evaluated lethal house lures consisting of In2Care (Wageningen, Netherlands) Eave Tubes, which provide point-source insecticide treatments against...

Housing improvement such as blocking eaves and screening windows can help in reducing exposure to indoor biting mosquitoes. The impacts of physical barriers could potentially be boosted by the addition of a mechanism that kills mosquitoes as they attempt to enter the house. One example is to combine household screening with EaveTubes, which are ins...

Despite its epidemiological importance, the time Plasmodium parasites take to achieve development in the vector mosquito (the extrinsic incubation period, EIP) remains poorly characterized. A novel non-destructive assay designed to estimate EIP in single mosquitoes, and more broadly to study Plasmodium – Anopheles vectors interactions, is presented...

Routine monitoring of occurrence, levels and mechanisms of insecticide resistance informs effective management strategies, and should be used to assess the effect of new tools on resistance. As part of a cluster randomised controlled trial evaluating a novel insecticide-based intervention in central Côte d'Ivoire, we assessed resistance and its und...

Many important endemic and emerging diseases are transmitted by vectors that are biting arthropods. The functional traits of vectors can affect pathogen transmission rates directly and also through their effect on vector population dynamics. Increasing empirical evidence shows that vector traits vary significantly across individuals, populations, a...

Innovations promise a better future, which may generate feelings of hope and inspire advocacy. Some innovations are more communal in nature: attempting to address a social problem, through community engagement and wide-spread adoption. For such innovations, the social processes that involve collective aspects of community life may play important ro...

Insecticide-treated bed nets reduce malaria transmission by limiting contact between mosquito vectors and human hosts when mosquitoes feed during the night. However, malaria vectors can also feed in the early evening and in the morning when people are not protected. Here, we explored how the timing of blood feeding interacts with environmental temp...

Background: There is substantial concern that the spread of insecticide resistance will render long-lasting insecticide-treated nets (LLINs) ineffective. However, there is limited evidence supporting a clear association between insecticide resistance and malaria incidence or prevalence in the field. We suggest that one reason for this disconnect i...

The relationship between Plasmodium falciparum gametocyte density and infections in mosquitoes is central to understanding the rates of transmission with important implications for control. Here, we determined whether field relevant variation in environmental temperature could also modulate this relationship. Anopheles stephensi were challenged wit...

Background: There is growing interest in the potential to modify houses to target mosquitoes with insecticides or repellents as they search for human hosts. One version of this 'Lethal House Lure' approach is the In2Care® EaveTube, which consists of a section of polyvinyl chloride (PVC) pipe fitted into a closed eave, with an insert comprising ele...

The relationship between Plasmodium falciparum gametocyte density and infections in mosquitoes is central to understanding the rates of transmission with important implications for control. Here, we determined whether field relevant variation in environmental temperature could also modulate this relationship. Anopheles stephensi were challenged wit...

Mosquito‐borne diseases cause a major burden of disease worldwide. The vital rates of these ectothermic vectors and parasites respond strongly and nonlinearly to temperature and therefore to climate change. Here, we review how trait‐based approaches can synthesise and mechanistically predict the temperature dependence of transmission across vectors...

The rate of malaria transmission is strongly determined by parasite development time in the mosquito, known as the extrinsic incubation period (EIP), since the quicker parasites develop, the greater the chance that the vector will survive long enough for the parasite to complete development and be transmitted. EIP is known to be temperature-depende...

A number of studies report changes in the biting time of malaria mosquitoes following the introduction of long-lasting insecticide-treated bed nets (LLINs). Here, we explored whether timing of blood feeding interacts with environmental temperature to influence the vector competence of Anopheles mosquitoes for the human malaria parasite, Plasmodium...

The rate of malaria transmission is strongly determined by parasite development time in the mosquito, known as the extrinsic incubation period (EIP), since the quicker parasites develop, the greater the chance that the vector will survive long enough for the parasite to complete development and be transmitted. EIP is known to be temperature depende...

Vectors are responsible for the transmission of many important endemic and emerging diseases. The functional traits of these animals have important consequences for pathogen transmission, but also for fitness and population dynamics of the vectors themselves. Increasing empirical evidence suggests that vector traits vary significantly at time scale...

Background The malaria Eradication Research Agenda (malERA) has identified human-to-mosquito transmission of Plasmodium falciparum as a major target for eradication. The cornerstone for identifying and evaluating transmission in the laboratory is standard membrane feeding assays (SMFAs) where mature gametocytes of P. falciparum generated in vitro a...

Abstract Background The widespread emergence of insecticide resistance in African malaria vectors remains one of the main challenges facing control programmes. Electrostatic coating that uses polarity to bind insecticide particles is a new way of delivering insecticides to mosquitoes. Although previous tests demonstrated the resistance breaking pot...

Abstract Background: Eave tubes are a type of housing modification that provide a novel way of delivering insecticides to mosquitoes as they attempt to enter the house. The current study reports on a series of semi-field studies aimed at improving the understanding of how eave tubes might impact mosquito mortality and behaviour. Methods: Experiment...

Background: Access to long-lasting insecticidal nets (LLINs) has increased and malaria has decreased globally, but malaria transmission remains high in parts of sub-Saharan Africa and insecticide resistance threatens current progress. Eave tubes are a new tool for the targeted delivery of insecticides against mosquitoes attempting to enter houses....

Background: Environmental factors such as temperature, relative humidity and their daily variation influence a range of mosquito life history traits and hence, malaria transmission. The standard way of characterizing environmental factors with meteorological station data need not be the actual microclimates experienced by mosquitoes within local t...

The time it takes for malaria parasites to develop within a mosquito, and become transmissible, is known as the extrinsic incubation period, or EIP. EIP is a key parameter influencing transmission intensity as it combines with mosquito mortality rate and competence to determine the number of mosquitoes that ultimately become infectious. In spite of...

This study documents an investigation into the adoption and diffusion of eave tubes, a novel mosquito vector control, during a large-scale scientific field trial in West Africa. The diffusion of innovations (DOI) and the integrated model of behavior (IMB) were integrated (i.e., innovation attributes with attitudes and social pressures with norms) t...

Evaluating the risk of emergence and transmission of vector-borne diseases requires knowledge of the genetic and environmental contributions to pathogen transmission traits. Compared to the significant effort devoted to understanding the biology of malaria transmission from vertebrate hosts to mosquito vectors, the strategies that malaria parasites...

In spite of widespread insecticide resistance in vector mosquitoes throughout Africa, there is limited evidence that long lasting insecticidal bed nets (LLINs) are failing to protect against malaria. Here, we showed that LLIN contact in the course of host-seeking resulted in higher mortality of resistant Anopheles spp. mosquitoes than predicted fro...

Malaria transmission is known to be strongly impacted by temperature. The current understanding of how temperature affects mosquito and parasite life history traits derives from a limited number of empirical studies. These studies, some dating back to the early part of last century, are often poorly controlled, have limited replication, explore a n...

Data from each temperature group from pilot experiment. Data for proportion of infectious mosquitoes on each day of salivary gland dissections during pilot experiment. (XLSX)

Comparison of survival model distributions across block for 30°C, 32°C, and 34°C. Comparison of survival models built using the R package flexsurvusing 3 survival distributions (Gompertz, Weibull, and exponential) commonly used in studies of mosquito mortality across block and temperature for 30°C through 34°C. Bolded models represent the best fit...

Nonlinear models for post-truncated data for 30°C, 32°C, and 34°C. Nonlinear exponential models used for each block and temperature combination for instances where a decrease in proportion of infectious mosquitoes was observed. Models represent the description of the curve only for data points past the point of truncation (day of peak proportion of...

Parameters for binary logistic regression sporogony model. Parameter values (g, k, tm) for best fit model listed for and each block separately. Bolded numbers are predicted values, with 95% confidence intervals in parentheses. (XLSX)

Predicted EIP10, EIP50, and EIP90 values. Predicted values and 95% confidence intervals (in parentheses) for EIP10, EIP50, and EIP90 from the binary logistic regression model for each block and temperature combination as parameterized in S10 Table. EIP, extrinsic incubation period. (XLSX)

Calculation of negative exponential mortality rates for relative vectorial capacity from reduced Gompertz curves. (DOCX)

Dynamic transmission potential model schematic. (TIF)

Dynamics of survival and infection at 30°C. Dynamics of survival (purple line) and the proportion of mosquitoes alive and infectious (orange line) for each replicate cup and block in the 30°C treatment used to mathematically analyze the possibility of differential mortality. (TIF)

Pairwise log-rank tests between temperature across both blocks. Results of post-hoc pairwise log-rank statistics across both blocks, comparing all temperatures to each other across blocks. (XLSX)

Pairwise log-rank tests between temperatures within block 1. Results of post-hoc pairwise log-rank statistics across temperature in experimental block 1, comparing all temperatures to each other. Bold italics represent groups not statistically different from each other. (XLSX)

Pairwise log-rank tests between temperature and block. Results of post-hoc pairwise log-rank statistics across temperature and block, comparing all temperatures to each other between each block. Bold italics represent groups not significantly different from each other. (XLSX)

Comparison of survival model distributions across block for 21°C, 24°C, and 27°C. Comparison of survival models built using the R package flexsurv using 3 survival distributions (Gompertz, Weibull, and exponential) commonly used in studies of mosquito mortality across block and temperature for 21°C through 27°C. Bolded models represent the best fit...

Experimental design schematic. (TIFF)

Dynamics of survival and infection at 32°C. Dynamics of survival (purple line) and the proportion of mosquitoes alive and infectious (orange line) for each replicate cup and block in the 32°C treatment used to mathematically analyze the possibility of differential mortality. Replicate cup 4 in experimental block 1 was discarded due to sugar pad bei...

Dynamics of survival and infection at 34°C. Dynamics of survival (purple line) and the proportion of mosquitoes alive and infectious (orange line) for each replicate cup and block in the 32°C treatment used to mathematically analyze the possibility of differential mortality. Replicate cup 4 in experimental block 1 was discarded due to sugar pad bei...

Pairwise log-rank tests between temperatures within block 2. Results of post-hoc pairwise log-rank statistics across temperature in experimental block 2, comparing all temperatures to each other. (XLSX)

Gonotrophic cycle for first clutch of eggs. Data for number of females laying the first clutch of eggs and the mean gonotrophic cycle length for each temperature for the first clutch. (XLSX)

Calculations for rVC using EIP10 and EIP90. Values for relative vectorial capacity using minimum estimate for EIP (defined here as EIP10, or time to 10% of maximum proportion infectious) and the maximum estimate for EIP (EIP90, or time to 90% of maximum proportion infectious). EIP, extrinsic incubation period. (XLSX)

Comparison of nonlinear models for performance of traits across temperature. Comparison of nonlinear models for performance of traits across temperature for the data presented in this paper and the data used in Mordecai et al. 2013. The R2 refers to our empirical data and the corresponding best fit models. (XLSX)

Pairwise log-rank tests between blocks across temperature. Results of post-hoc pairwise log-rank statistics across all temperatures, comparing temperatures between block. (XLSX)

Gonotrophic cycle data from second clutch. Data for number of females still alive after laying the first clutch of eggs, the number that laid a second clutch of eggs, and the mean gonotrophic cycle length for each temperature for the second clutch of eggs. (XLSX)

Mating success data across temperatures. Mating success across each temperature in gonotrophic cycle/biting rate experiment. A successful mating was considered either successful oviposition or the presence of sperm in dissected spermathecae, in the case a female did not lay eggs over the course of the experiment. (XLSX)

Differential mortality calculations. Mathematical analysis for the possibility of differential mortality or recovery. Each temperature x block x cup combination was analyzed using a Gompertz distribution with ‘surviving’ and ‘surviving and infectious’ as categorial covariates. Each combination was analyzed beginning at the day of peak prevalence an...

Key to contemporary management of diseases such as malaria, dengue, and filariasis is control of the insect vectors responsible for transmission. Insecticide-based interventions have contributed to declines in disease burdens in many areas, but this progress could be threatened by the emergence of insecticide resistance in vector populations. Insec...