Malaria Research

Mosquitos   |   Alternative Perspective

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Deadly Mothers: How Mosquitoes, a Unique Species of Fly, Became the World’s Most Lethal Creatures

          Living with mosquitoes can be unbearable, and their impact on daily life may be hard for some to comprehend. These insects buzz, bite, and itch throughout the day, making it difficult for people to sleep at night, especially with the added challenge of humidity and mosquito-induced ASMR in the ear. Despite these struggles, people adapt and find ways to coexist with them.

         Contrary to popular belief, mosquitoes are not bloodthirsty parasites intent on destroying humanity. Female mosquitoes, which exhibit remarkable maternal instincts, feed on human blood to obtain essential nutrients for their offspring’s yolk development. Males, on the other hand, often rely on nectar for their sugar intake. These mothers are selective about their egg-laying sites, ensuring the best chance of success for their young.

         As members of the fly family, mosquitoes typically consume liquid meals. Female mosquitoes are particularly fond of human blood due to its high protein and lipid content, which is crucial for yolk development. Furthermore, Anopheles females are discerning about their egg-laying habitats. While most mosquitoes lay eggs in stagnant water, Anopheles species can also thrive in running water sources. Their aquatic larvae breathe air and feed on organic matter in the water for about two weeks before metamorphosing into adult mosquitoes.

TLDR; Living with mosquitoes is challenging, as they buzz, bite, and itch, making sleep difficult. Yet, people adapt and coexist with them. Female mosquitoes feed on human blood for offspring development, while males consume nectar. As part of the fly family, mosquitoes consume liquid meals and lay eggs in specific habitats. Anopheles species can thrive in both stagnant and running water, with larvae developing into adults in about two weeks.

Plasmodium Species Exploit Anopheles Mosquitoes as Vectors for Human Transmission

        Plasmodium species experience multiple life stages throughout their lifespan. Sporozoites, one stage of the Plasmodium life cycle, mature in the midgut epithelium of female mosquitoes. The parasite then travels from the midgut epithelium to the mosquito's salivary glands. Mosquitoes possess a long, segmented proboscis covered by a protective sheath that penetrates the skin. Humans are an attractive food source for mosquitoes due to our lack of fur or hair, providing easy access to superficial blood vessels within the reach of the proboscis. After the mosquito finishes feeding, it releases a numbing agent from its salivary glands, which simultaneously allows sporozoites to enter the host's bloodstream

TLDR; Malaria parasites go through different stages inside female mosquitoes before moving to their salivary glands. Mosquitoes use a needle-like mouthpart to reach our blood vessels. After feeding, they release a substance that lets the parasites enter our bloodstream

Strengthening Mosquito Control Measures to Aid in Malaria Eradication

         Common ideas for eradicating malaria often involve the use of insecticides like DDT or more futuristic strategies. DDT, a well-known contact poison, is sprayed on house walls, causing bioaccumulation of organochlorine in mosquitoes. However, DDT is unique in its resistance to degradation by sunlight, causing it to persist in the environments where it is used.
         Mosquitoes, like other insects, have an exoskeleton. Tiny holes, called spiracles, pierce the exoskeleton, enabling DDT and other insecticides to enter their bodies. Mosquitoes also groom themselves regularly, which creates another avenue for DDT exposure. DDT acts as a nerve agent, impairing the mosquito’s nervous system.
         In Brazil, sterile male mosquitoes were released into the wild to mate with females. As a result, the sterile eggs laid by the females did not hatch, temporarily reducing the overall mosquito population.

TLDR; Efforts to fight malaria often use insecticides like DDT, which sticks around in the environment and affects mosquitoes through their exoskeleton or grooming. DDT harms their nervous system. In Brazil, releasing sterile male mosquitoes helped temporarily reduce their population, as their eggs couldn’t hatch.

Malaria’s Persistence Despite Mosquito Elimination Efforts

         An important consideration is that even if mosquitoes were successfully eliminated, another vector could take their place. Successful species thrive due to their adaptability to changing ecological environments. If mosquitoes were to lose their effectiveness, a different species might emerge to replace them as a Plasmodium zoonotic vector. Chris D. Thomas’ book, “Inheritors of the Earth: How Nature is Thriving in an Age of Extinction,” discusses the concept of successful species and the reasons leading to this success. This perspective contrasts with more alarming works, such as Elizabeth Kolbert’s “The Sixth Extinction: An Unnatural History” and David Wallace-Wells’ “The Uninhabitable Earth.” Adopting an optimistic perspective towards science, instead of a negative one, can lead to a clearer understanding of reality, especially when considering the improbable nature of our existence—yet, against the odds, we are here.

TLDR; If mosquitoes were wiped out, another species might take over as a disease-spreading vector. Adaptable species thrive in changing environments. Chris D. Thomas’ book promotes optimism in understanding nature, unlike more alarming works. A positive outlook on science helps us better understand our improbable existence.

Tropical Environments and Disease Transmission

         Tropical and subtropical regions are well-known transmission hotspots not only for sporozoan Plasmodium parasites but also for various other pathogens. These regions are home to vectors responsible for spreading protists, viruses, bacteria, and nematodes. Apart from malaria, mosquitoes transmit the causative agents for dengue, yellow fever, onchocerciasis (river blindness), cutaneous leishmaniasis (open skin lesions), filariasis (elephantiasis), and the notorious trypanosomiasis (sleeping sickness).

TLDR; Tropical and subtropical areas have a lot of disease-causing organisms. Mosquitoes in these regions can spread many diseases other than malaria, like dengue, yellow fever, onchocerciasis, cutaneous leishmaniasis, filariasis, and trypanosomiasis.

Vector Interactions with Human Hosts in Disease Transmission

         Anopheles mosquitoes stand out as vectors because they do not simply transfer Plasmodium parasites through mechanical transmission, like cutting key lime pie with the same knife you just used to cut chocolate cake. Instead, they use biological transfer, a more complex interaction between the pathogen and the vector. Plasmodium parasites successfully reproduce in the mosquito’s midgut epithelium before being transmitted to human hosts.
         Malaria impacts both humans and other animals, but human malaria is unique in its single-cycle disease pattern. This characteristic is uncommon among insect-borne diseases, as it necessitates the coevolution of the pathogen, vector, and Homo sapiens. Unlike other diseases, such as the plague, which depends on rats, or yellow fever, which requires monkeys, malaria operates independently, relying exclusively on humans as its host.
         Usually, a vector transmits a disease from an animal to a human when humans encroach on natural areas containing animals that serve as disease reservoirs. For example, Aedes bromeliae feeds on both humans and primates in Uganda and can transfer jungle yellow fever to humans. In contrast, the primary host reservoir for malaria is just Homo sapiens.

TLDR; Anopheles mosquitoes are different from other mosquitoes because they transfer the malaria parasite through a more complicated biological process. Malaria only affects humans and has a unique way of spreading that requires a close relationship between the parasite, the mosquito, and humans. Unlike other diseases, malaria only relies on humans as its host. Mosquitoes usually transmit diseases when humans go into areas where animals that carry the disease live, but malaria is only found in humans.

The Role of the Proboscis in Mosquito Injections

         When infected mosquitoes feed on human blood, they transfer Plasmodium parasites. Although it may seem simple – a mosquito lands, inserts its needle-like mouthpart, and draws blood – the process is more intricate than it appears.
         A mosquito’s mouth, called a proboscis, is a highly specialized feeding structure with an internal bundle of tubes (fascicle) surrounded by soft tissue known as the labium. At the tip of the labium are two sensory organs called labella that help locate the ideal feeding spot.
          As the female mosquito prepares to bite, tiny serrated structures called maxillae pierce the skin. Similar to what ants and other insects use for feeding, mosquito maxillae are simply elongated. Working alongside the maxillae are mandibles that keep tissues apart, like retractors. Once the mosquito has cut deep enough, a secondary sensory organ called the labrum probes for blood. Connected to the labrum is the hypopharynx, which secretes saliva that serves as an anti-inflammatory lubricant for the proboscis and prevents blood clotting.
         The fascicle then draws blood up through the labrum into the mosquito’s stomach, where red blood cells are stored and water is expelled through the insect’s rear end.

TLDR; When mosquitoes bite and feed on human blood, they use a specialized feeding structure called the proboscis, which has many different parts that work together to pierce the skin and draw up the blood. This process is more complicated than it seems and involves different organs and secretions that help the mosquito feed and prevent blood clotting.

PBS’s YouTube channel DeepLook has a video on the science of the proboscis, linked

DeepLook | Mosquitos

Embracing Mosquito Adaptations for Advancements in Disease Control

         As previously stated, mosquitoes are not blood-sucking parasites acting with malicious intent. In fact, few, if any, species purposefully harm their host as it would be counterproductive to their own survival. Mosquitoes are simply carrying out their biological role, completely unaware of the protozoan transmission they facilitate. Delving deeper into mosquito behavior might even reveal fascinating traits that could make them more likable—perhaps. However, it’s crucial to remember that Anopheles species serve as the transmission vector for a deadly disease that affects individuals, families, and communities daily.

 Faculty contributor(s)

• Dr. Altfeld, an entomologist who helped me understand malaria from a insect's point of view.
• Dr. Miller, a botanist who spent time explaining the niche environments mosquitoes occupy.
• Dr. Alava, a physician who helped me understand why mosquitoes are terrible to live with.