Malaria Control Methods: Genetic Variation and Immune Responses
Advisor: Karen Allendoerfer
Internship Location: University of Maryland
Onsite Mentor: Matthew Laurens
Countless species of Anopheles mosquitoes transmit malaria, and in different capacities. What variation in their genetics allows mosquito species to have different immune responses to Plasmodium parasites in different regions? There has been a resurgence of reported cases in recent years, with even the United States having recorded homegrown malaria cases for the first time in 20 years. The widespread use of antimalarial drugs, such as chloroquine and artemisinin-based therapies, has led to the selection of resistant strains, rendering some treatments less effective over time. This project’s goal is to use research based on the genetic variation in Anopheles and their immune responses, relative to geography, to develop a proposal of a potential combination of vector control strategies for malaria regulation.
Project Blog
Post 1: 1: Introduction
Hello! This is the first blog post for my senior project about malaria control methods and the potential development of a novel system. This week I’ll be providing an introduction to my project, including some background on malaria recently, why I chose the specific areas of study I did, and what my end product will be.
Background
Countless species of Anopheles mosquitoes transmit malaria, and in different capacities. What variation in their genetics allows mosquito species to have different immune responses to Plasmodium parasites in different regions? The World Malaria Report revealed that an estimated 247 million people were infected with malaria in 2021, and there were approximately 619,000 deaths because of the disease. Malaria is a deadly infectious disease that disproportionately affects some of the most marginalized populations in the world, and there has been a resurgence of reported cases within the United States in more recent years, with an approximate 9% increase in cases in 2021 as opposed to those in 2019. Malaria remains a global health challenge, and it is crucial to understand the ecology of mosquitoes and the genetic variation within their populations to develop precise control methods.
One significant issue is the concern regarding the rise and dissemination of drug-resistant strains of the malaria parasite, especially Plasmodium falciparum, responsible for the majority of malaria-related fatalities. The widespread utilization of antimalarial drugs like chloroquine and artemisinin-based therapies has resulted in the emergence of resistant strains, diminishing the effectiveness of certain treatments over time. The genetic diversity among mosquito populations contributes to their resilience against traditional control measures. The renewed interest in malaria underscores the pressing need to address its impact on vulnerable populations and reassess control methods in light of past challenges by refocusing on the transmissions. A more thorough understanding of mosquito genetics and ecology is imperative for designing targeted interventions that can effectively address the specific challenges posed by mosquito populations.
Goal
My project’s goal is to use research based on the genetic variation in Anopheles and their immune responses relative to geography, to 1) conduct extensive research in the realm of malaria under the Anopheles genus of mosquitoes, and 2) create a proposal of a novel solution developing a new vector control method based on existing solutions with the goal of regulating malaria transmissions. By integrating genetic, immune, and ecological factors, my research will aim to offer a more holistic perspective on malaria control. This approach could contribute to the development of newer sustainable vector control methods that consider the dynamic nature of mosquito populations relative to location and environment. My product will be a report detailing my findings, with the methodology behind a proposal of my combination of malaria control methods that I find to be most effective in regards to the region of the world I expect to focus on. With this final report, I hope to better understand why the genetic variation in certain mosquito species allows for increased transmission to humans as well as their own immune responses to the parasites carrying the disease.
Post 2: 2: Literature & Data Sourcing
Hello! During week 2 of my senior project researching malaria and mosquitoes, I finished writing the introduction and have begun writing the literature review for my final report. The literature currently consists of my findings from articles I’ve read from my research into malaria and mosquitoes including prior to beginning this project. Two books that I’ve included and reviewed are Pandemic: Tracking contagions, from cholera to coronaviruses and beyond by Sonia Shah and Influenza: The Hundred-Year Hunt to cure the deadliest disease in history written by Dr. Jeremy Brown. These are not directly malaria related, however their concepts are integral to my research and interest in the field.
I’ve also started to gather data from online sources, and this has been a slow process taking up a large portion of my time. I have anticipated this being the primary challenge in my senior project, as it revolves around sourcing necessary data from online articles and scholarly references. While plenty of data relating to malaria exists online, the varied spectrum of topics I am covering—such as genetics, ecology, and anatomy—may cause issues due to the potentially limited amount of specific, publicly available data in regards to what I plan on focusing on.
I've also been able to narrow down some of the species, or subgenus of Anopheles mosquitoes, I intend to concentrate on. I have quite a few, such as Anopheles janconnae and Anopheles marajoara, which have the largest overlap with the distribution of Plasmodium falciparum. Plasmodium falciparum is known as one of the deadliest species of parasites transmitting malaria in humans, causing falciparum malaria. These species are among those which I intend to focus on, and in the next week I will be narrowing options based on region and population.
Thanks for reading, come back next week for the species verdict (hopefully)!
Post 3: 3: Location & Species
Hello! During week 3 of my senior project, I chose the region and species I will be focusing my targeted control method/ combination of methods on, which is the Anopheles culicifacies, one of the most prevalent major vectors for malaria transmission in Pakistan, and the Indian subcontinent in general.
In Pakistan, malaria is most often found in the provinces of Khyber Pakhtunkhwa, Balochistan, and Sindh. Plasmodium infections in Pakistan are generally attached to Plasmodium vivax, the most frequent cause of malaria recurring. Plasmodium falciprum, as I mentioned last week, is another prevalent parasite species in Pakistan, causing 36% of infections while P. vivax are responsible for approximately 64%. I have not run across any significant issues in this area of research, however I did pause data gathering to narrow down species before continuing, as I am now unsure of what data I will actually make use of. I may simply end up focusing on transmissions and the effectiveness of control methods rather than the comparison of species in Pakistan.
After many environmental changes in recent years, part of what I will be expanding and researching more on next week, Pakistan has witnessed a surge in malaria cases. As for what piqued my interest in the region of Pakistan, there has been a jump from half a million cases in 2021 to over 2.5 million in 2022 according to the World Malaria Report 2023. Most other countries with a high prevalence of malaria have had this issue for many years consistently and with generally either slow recovery or no significant change in cases. Pakistan has had a recent increase, and more than countries like Nigeria, Uganda, or the Democratic Republic of the Congo, which together account for over 50% of the malaria cases globally.
Thanks for reading my week 3 blog! During week 4 I will be focusing on the environment in Pakistan and the spike in malaria cases, as well as why certain species are more common in Pakistan as opposed to where malaria is more prominent in countries in Africa. Come back next week for more progress on my report and beginning genetic variation research as well as a first look into ecology.
Post 4: 4: Floods & Waterborne Diseases
Hello! During week 4 I worked on the Methods section of my current rough draft report and focused on the recent significant changes in Pakistan’s environment that caused the spike in malaria cases and why certain mosquito species were more prevalent than others. Essentially, the species that are most recognized are those that thrive in polluted water bodies. The species Anopheles culicifacies, my focus for this project, are able to adapt to several different water bodies like clean water, rice fields, and polluted water pools. This allows them to flourish in many different regions in Pakistan, and just as much during the flooding, my second area of research this week.
To summarize my research in the Pakistan environment and reasoning behind the sudden increase in malaria cases, Pakistan dealt with some of the worst flooding it has experienced in its history during the summer of 2022. The total damages reached to over USD 14.9 billion, and the estimated need for reconstruction is at least USD 16 billion. The floods destroyed many of the water systems in place, so contaminated water was all that was accessible to millions of people. Contaminated water itself is not responsible for malaria, but mosquitoes lay their eggs in stagnant water. Clogged drains and improperly stored water containers can become a breeding ground for these mosquitoes.
Consuming contaminated water can lead to waterborne diseases such as typhoid and diarrhoea, which significantly weaken a person’s immune system. Half of the 33 million people affected by the floods were children, and their weakened immune systems were even more likely to contract malaria if bitten because many were also malnourished. These childrens’ susceptibility to waterborne diseases initiates a repeating cycle of malnutrition and increased infection because of the floods.
In the more populated areas like the Punjab province, industrialization led to improved health systems while better water management and rice cultivation practices helped mitigate the stagnant pools where malaria-carrying mosquitoes reproduce. As these areas were removed, the focus turned to more rural and remote regions, such as the Khyber Pakhtunkhwa, Sindh, and Balochistan provinces.
Thanks for reading my week 4 blog! Come back next week for my updates where I will mainly focus on making progress on my report and beginning research on current vector control methods.
Post 5: 5: Report Progress & Control Methods
Hello! This week’s blog is a bit different from previous weeks because there is much less I am able to share. I spent the majority of this week working on my report, fixing sections I’ve done, adding to them, and just expanding based on information I learned last week. I did continue with Pakistan’s environment and researching more into the specific areas, such as the Sindh and Balochistan provinces, where malaria was more prevalent, however much of the information is similar and I find it not necessary to expand upon here. In essence, this week was mostly writing, detailing my report, and adding graphics.
As I said last week, this week I did begin looking at vector control methods and found that there is minimal data on Pakistan in regards to different control methods soon and how effective they are. Much of the research is about how many cases there are, and some general strategies used to combat this outbreak, nothing extensive nor specific enough for me to have made a lot of progress. There is not much work-around for this predicament, so I will simply continue this next week and will hopefully improve my findings. While my efforts this week did not go to waste, it was tedious and finding malaria control methods around the globe that could be applicable is likely my goal, regardless of whether or not I find sufficient information from articles and reports online in the coming week for blog 6.
Thanks for reading this week’s blog! Next week I’ll have more to report on being able to identify globally successful malaria control methods that could be adaptable to specific regions within Pakistan. Whether sufficient data becomes available for Blog 6 this coming week remains uncertain, but my focus will be on uncovering more specific and applicable control methods.
Post 6: 6: Tafenoquine & Climate Change
Hello! During week 6 I continued my progress on the report but began research into malaria control methods both around the world and efforts uniquely implemented into Pakistan’s progress in vector control.
Pakistan's battle against the recent surge in malaria cases involves a combination of established control methods and an innovative treatment option. The primary control methods Pakistan is using are insecticide treated nets, used indoors to repel mosquitoes and reduce transmission. Additionally, increased accessibility to rapid tests and treatment has helped many more vulnerable communities with less access to funding for care. These are methods that are also commonly used in other regions; one specifically used in Pakistan in the past year is tafenoquine. Tafenoquine is a single-dose radical cure, newly licensed, that is used for prophylaxis of malaria and vivax malaria. Vivax malaria is transmitted via plasmodium vivax, the parasite that transmits malaria most prevalently in Pakistan (I’ve expanded upon this in previous weeks).
Regarding the environment, the primary cause of the floods in Pakistan, which as I’ve explained in previous blog posts are responsible for the sudden spike in malaria cases, is climate change. This much is evident enough, as rising temperatures in the north have accelerated the melting of glaciers and ice caps, causing excessive water flow in rivers and streams, leading to floods in these regions. In the southern parts, the change to warmer temperatures of the Indian Ocean are what led to unprecedented rains in Pakistan. This is to say that one control method that could prevent this in the future would be floodplain management. This would be effective by implementing building embankments, improving drainage systems, and promoting early warning systems to lessen the impact of future floods on current or known mosquito breeding grounds.
Thanks for reading this week’s blog! Next week I’ll be continuing my progress on the rough draft of my paper, though I don’t think I have to keep mentioning it. I’ll still be researching more into vector control methods that could be adaptable to regions like the Khyber Pakhtunkhwa, Sindh, and Balochistan provinces within Pakistan. This will likely continue for a while longer, and I can only recap a small amount in these blogs, but data gathering and knowing what data to gather in the first place is still an issue, so I’ll be continuing with what is working for now. See you next week!
Post 7: 7/8: Larvicide & Drones
Hello! Instead of publishing twice, I’ll summarize what I did in week 7 as well as week 8 as I was sick and traveling during week 7 so content-wise there wasn’t much to expand upon. I continued my progress on the report, and will likely be done next week and ready to edit into a final draft. I also continued research into malaria control methods specific to Pakistan, along with floodplain management.
Utilizing larvicide, a biological or chemical insecticide designed to kill mosquito larvae before their mature stage, is a strategy that could be very helpful for Pakistan, especially because it can target areas while being time-saving. Drone-based larviciding, using drones that can carry tanks with larvicide. Focusing these efforts on stagnant water that was created by the floods affecting northern and southern Pakistan could be extremely helpful in significantly reducing mosquito populations and breeding grounds, and preventing transmission outbreaks. Drones can also reach inaccessible breeding sites without having to send medical professionals to rural areas with limited facilities. Some of the areas, such as the Sidh or Balochistan province, may be more high-risk and drones eliminate the need for personnel to travel while being generally more accurate than ground surveys for data. Overall, drone-based larviciding offers a new, unique approach for Pakistan to combat malaria, particularly in the aftermath of the floods that have created widespread mosquito breeding grounds. By leveraging this technology and addressing additional challenges that contributed to the malaria transmission spike, such as the environment and guarantee that drones would raise concerns amongst local communities, Pakistan can help make its fight against malaria more efficient and successful by use of drone based larviciding.
Thanks for reading this week’s blog! Next week I’ll still continue my paper as well as larvicide research. I am slightly behind in terms of my paper, so that will be taking my time this coming week to get that edited later. (I was meant to publish this blog post earlier, but it seems I forgot to actually hit the submit button) See you next week!
Post 8: 9: Microbial Larvicide & Spinosyns
Hello! During Week 9, I did research surrounding the larvicide vector control method that I introduced last week. I continued my progress on the report, but I haven’t yet finished it because of the new information I’m adding each week. This report will likely remain unfinished until I don’t have time to add new information, and will only be wrapped up the final week we have for research.
To find environmentally-safe and tested larvicides, my research this week has led me to focus on microbial larvicides and spinosyns. These are derived from bacteria that act as pesticides and target mosquito larvae. The main types used for malaria control are Bacillus thuringiensis israelensis (Bti) and Lysinibacillus sphaericus (Bs). Bti produces a toxin that interrupts the biological processes of the gut of mosquito larvae during digestion. It is highly effective against Anopheles mosquitoes that transmit malaria. The Bs type of microbial larvicide is a bacterium that produces proteins which damage the gut of mosquito larvae, resulting in their death. Environmental complications such as excess wind and rain can hinder their effectiveness, so the heavy rains that were part of the cause of the malaria outbreak in Pakistan would make matters worse for the use of microbial larvicide.
Spinosyns, derived from the fermentation of the bacteria Saccharopolyspora spinosa, have the main active ingredient spinosyn A, which targets the mosquito nervous system and interferes with nerve cell communication. They are considered to have low impact on non-target organisms compared to traditional chemical insecticides, giving them a benefit in terms of not harming the environment. Some things to consider are that although they are safer than most insecticides, spinosyns still have the potential to harm beneficial insects like bees at higher concentrations. They can also be expensive and require frequent applications when in sunlight, requiring a much larger budget than may be available.
Thanks for reading this week’s blog! I’ll still be making progress on my report this coming week, but will leave more of that to the week after for final editing instead of slow progress during week 10. See you next week!
Post 9: 10: Bs & Bti
Hello! During week 10, the majority of the time was spent designing and putting together a draft presentation for practice presentations with my advisor. I did additional research on the bacteria that are used in microbial larvicides, typically used for malaria control.
Bacillus thuringiensis israelensis, the gram-positive, soil-dwelling bacteria, is used predominantly against mosquito larvae, particularly those of the Anopheles species that transmit malaria. Bti produces protein crystals during sporulation (spore formation), which produce a potent toxin called cry toxins. These toxins kill larval midgut cells by causing an osmotic shock leading to cell lysis, which is when the cell membrane is destroyed to release genetic material of some sort or the organelles within the cell. When mosquito larvae ingest Bti spores or Cry toxins while feeding, the toxins specifically bind to receptors in the larval gut lining, allowing for selective larvicidal action. Bs, or Lysinibacillus sphaericus joins Bti as a gram-positive bacteria breaking down mosquito larvae. Bs also relies on spores for its larvicidal activity. These spores germinate in the mosquito larval gut. After germination, it releases a combination of insecticidal proteins that damage the larval gut lining and kills the larvae. Bs shows effectiveness against a broader range of mosquito species compared to Bti. This complementary action makes it a very valuable addition to vector control strategies. A limitation of the effectiveness of these larvicides is that their success depends on proper application to ensure optimal reach and impact on mosquito breeding sites.
Thanks for reading this week’s blog! This blog was just mentioning the progress I’ve made in terms of research, but working on the presentation and report will take most of my time from now on. I likely won’t be doing much more research on these control methods other than to fill in gaps and make final conclusions, but that’s saved for my report. Next week is the final time I’ll be making progress, I’ll have finished my report (hopefully), and begin working on final edits. See you next week!
Post 10: 11: Environmental Impact & Biodegradability
Hello! During week 11 I’ve been trying to cut down my report to only what I feel is necessary and working on my presentation. I’ve also added more detail and information on microbial larvicide, such as the impact environmentally, so I'll expand on that section in this blog.
Microbial larvicides like Bacillus thuringiensis israelensis (Bti) and Lysinibacillus sphaericus (Bs) generally only target mosquito larvae. They have an indiscernible impact on other insects in the environment as opposed to other insecticides, such as chemicals. Bti and Bs are also biodegradable, breaking down into harmless components in the environment. Additionally, many mosquito breeding sites are stagnant water bodies or wetlands, so although chemical insecticides can contaminate these environments, and harm fish, frogs, and beneficial bacteria, microbial larvicides degrade naturally and pose minimal threat to aquatic ecosystems.
Unlike chemical insecticides that can harm a wide range of insects and other organisms, microbial larvicides target mosquito larvae through unique procedures (which I expand on in my report), leaving other beneficial insects like pollinators and predators unharmed. There is a reduced risk to wildlife because chemical insecticides build up, which is a threat to wildlife like birds, fish, and mammals that feed on insects that inject toxic substances, while microbial larvicides obviously don’t have the same harmful effect, being bacteria. The reduced threat helps maintain a healthy ecosystem and supports biodiversity, thereby reducing the risk of long-term environmental damage by the larvicides. Regarding resistance, mosquitoes are also less likely to develop resistance to microbial larvicides because they target the biological processes of mosquito larvae, making it harder for them to develop resistance mechanisms.
The use of microbial larvicide in other malaria stricken areas, such as several parts of Africa, has led to major decreases in transmission. Compounds including synthetic organic chemicals, bacterial larvicides, spinosyns, and insect growth regulators that I’ve mentioned before are used as larvicides [1]. Unfortunately, little information is available on the efficacy and effectiveness of the majority of these larvicides in Africa because of the lack of knowledge on implementing methods and the intensive effort needed for its monitoring. Therefore, I would believe the impact in Pakistan would be great, but there is no proper data available to confirm that. Thanks for reading this week’s blog! Next week is my final blog, and it will be after the senior project presentations. This week has presentation practices, and I’ll hopefully cut down my report enough. See you next week!