Mosquitoes are small, seemingly innocuous insects that can have a big impact on our lives. While many people associate them with itchy and annoying bites, mosquitoes are also carriers of diseases that affect millions of people worldwide. Today we will delve into the world of mosquito bites, exploring what they are, the chemical reactions they cause, and most importantly, how to prevent them. We will also touch upon some of the dangerous diseases transmitted by mosquitoes and how climate and weather play a role in their prevalence.
What are mosquito bites?
Mosquito bites are the result of female mosquitoes using their specialised mouthparts to pierce our skin and feed on our blood. Unlike their male counterparts, female mosquitoes require the nutrients found in blood to develop their eggs. When a mosquito bites, it injects its saliva into the bite site. This saliva contains a cocktail of proteins and enzymes that serve as anticoagulants, preventing our blood from clotting while the mosquito feeds. The body's immune system recognises these foreign proteins and mounts a response, leading to the characteristic itching, redness and swelling associated with mosquito bites.
The chemistry behind the itch
The chemical reaction at the heart of a mosquito bite is a fascinating process. Mosquitoes use proteins in their saliva to inhibit our blood from clotting, essentially creating a steady flow of blood for their meal. However, this interaction also triggers our body's immune response, which releases histamines. These histamines cause the blood vessels near the bite to dilate and become more permeable, allowing immune cells to reach the site of the bite. While this process is essential for our body's defence, it's what makes mosquito bites so itchy and uncomfortable.
By understanding this interaction, we can discern what the stages of a mosquito bite are. When a mosquito first pierces the skin, one may not even notice. Their saliva contains a numbing agent that keeps their intrusion nearly painless together with the tiny size of the wound. As the mosquito continues to feed, it injects its saliva. This is the critical moment when it introduces those anticoagulants into the bloodstream. As mentioned earlier, the immune system recognises the foreign proteins in the mosquito's saliva and starts releasing histamines to combat them. Consequently, the "bite area" becomes red, swollen and itchy. Scratching it can further aggravate the itching and increase the risk of infection.
In saying this, if one is bitten by a mosquito, the "bite area" should be washed with soap and water to reduce the chance of infection. Furthermore, applying an over-the-counter anti-itch cream or ointment can help soothe the itching and decrease inflammation. It is immensely important to try and resist the urge of scratching the area, to prevent any further irritation and the potential introduction of new pathogenic bacteria.
Preventing mosquito bites
Prevention is key when it comes to mosquito bites. Effective strategies include using mosquito repellent containing DEET, picaridin or other recommended ingredients. Wearing long-sleeved clothing and pants can significantly reduce the amount of exposed skin. Installing screens on windows and doors helps keep mosquitoes out of one's home too. Moreover, eliminating breeding sites by emptying stagnant water in containers around one's property can significantly reduce the mosquito population in one's area. Additionally, exercising such precautions is of paramount importance when travelling/living in countries, where mosquitoes are prone to being vectors for specific diseases like malaria.
Mosquitoes and disease
Mosquitoes are not just irritating pests; they are also vectors for a variety of serious and deadly diseases, posing a significant global health threat. According to the World Health Organisation (WHO), mosquito-borne diseases cause over 700,000 deaths each year.
One of the most devastating mosquito-borne diseases is malaria. Caused by the Plasmodium parasite, malaria affects over 200 million people annually, resulting in approximately 400,000 deaths. Malaria is most prevalent in sub-Saharan Africa, but it is also found in other parts of the world, including Asia, South America and the Middle East.
Another major mosquito-borne disease is yellow fever. Yellow fever is a viral infection that can cause severe symptoms, including fever, headache, muscle pain, jaundice and bleeding. Yellow fever is found in tropical and subtropical regions of Africa and South America, and it is estimated to cause over 200,000 cases and 30,000 deaths annually.
Dengue fever is another widespread mosquito-borne disease. Dengue is caused by four different viruses and is transmitted by Aedes mosquitoes. Dengue fever can cause a range of symptoms, from mild flu-like symptoms to severe dengue haemorrhagic fever and dengue shock syndrome. Dengue is found in over 120 countries and territories, and it is estimated to cause over 390 million infections and 20,000 deaths annually.
Zika virus is another mosquito-borne disease that has emerged as a global concern in recent years. Zika is primarily transmitted by Aedes mosquitoes and can cause mild symptoms such as fever, rash, headache and muscle pain. However, Zika can have devastating consequences for pregnant women, as it can cause birth defects in their newborns. The Zika virus outbreak in 2015-2016 raised alarm worldwide, and while the outbreak has subsided, monitoring and prevention remain essential, particularly for pregnant women.
West Nile virus is another mosquito-borne disease that is prevalent in various regions, including North America, Europe and Asia. West Nile virus is transmitted by Culex mosquitoes and can cause a range of symptoms, from mild flu-like symptoms to severe neurological illness. In the United States alone, thousands of cases of West Nile virus are reported each year.
Each of these mosquito-borne diseases presents unique challenges and risks to affected populations. Control efforts often involve a combination of strategies, including vaccination, mosquito control programmes and public health campaigns to raise awareness and encourage personal protection measures. These diseases underscore the critical importance of ongoing research, international cooperation and public health initiatives to combat the global threat posed by mosquitoes and the diseases they carry.
In addition to the diseases mentioned above, mosquitoes can also transmit other diseases such as chikungunya fever, Japanese encephalitis and lymphatic filariasis. Mosquito-borne diseases are a major public health concern and it is important to take steps to protect yourself from mosquito bites.
The role of climate and weather
As we broaden our perspective, it's essential to consider the role of climate and weather in the mosquito equation. Mosquitoes thrive in warm, humid conditions, making tropical and subtropical regions ideal breeding grounds. However, climate change is altering mosquito distribution patterns, potentially exposing new populations to diseases previously unseen in their regions.
Furthermore, extreme weather events, such as heavy rainfall and flooding, create additional breeding sites for mosquitoes. Stagnant water is an open invitation for these insects to multiply, further increasing the risk of disease transmission.
Conclusion
In conclusion, while mosquito bites may seem like minor annoyances, they are part of a much larger, interconnected web of biological and environmental factors. Understanding the intricacies of mosquito biology, the diseases they transmit and the environmental conditions that facilitate their proliferation is essential for safeguarding ourselves and our communities. Armed with knowledge and proactive measures, we can better protect ourselves from these buzzing threats and their potentially dire consequences.
Renald Blundell is a biochemist and biotechnologist with a special interest in Natural and Alternative Medicine. He is a professor at the Faculty of Medicine and Surgery, University of Malta
Emma Camilleri is currently a fourth-year medical student at the University of Malta