The concept of Vector-borne diseases, also known as arboviral diseases or arthropod-borne virus diseases, is transmitted to humans or animals by blood-feeding arthropod vectors that comprise organisms including mosquitoes, ticks and fleas. These small vectors carry pathogens like bacteria, parasites and viruses that affect humans and also cause a number of diseases.
In the ongoing changes happening all around the increasing effects of climate change, the circulation of these diseases has become a significant concern. This concern is severe in regions like tropical and subtropical areas. Climate change has a substantial role in promoting a shift among Vector-borne diseases, which raises alarm bells for global health consequences.
Grounded understanding of Vector-borne diseases
One of the few yet common Vector-borne diseases are dengue fever, malaria, Zika virus, Lyme disease as well as chikungunya. These diseases primarily circulate by mosquitoes (aedes, anopheles), ticks and fleas. These small insects and parasites act as vectors for specific pathogens and make tropical and subtropical weather susceptible to outbreaks.
Vectors are taking an expanded place and increasing their habitats with the Earth’s temperatures rising because of human-induced climate change. Areas that were once too cold for these organisms are now becoming warmer, which helps them to survive and reproduce in new regions. These expansions of vector habitat are a prominent factor in the growing incidence of Vector-borne diseases all around.
How does climate change affect Vector-borne diseases?
Climate changes lead to pathogen/vector adaptations, and this causes shifts or expansions in their geographic regions (giving way to Vector-borne diseases). It is found that climate change can have a direct influence on the environmental factors that support the proliferation of vectors. Climate change affects Vector-borne diseases in a number of ways –
Rising temperatures
Warmer temperatures accelerate the life cycles of vectors/pathogens they carry. It is primarily noticed in parasites like mosquitoes, and higher temperatures speed up their reproduction rate along with the maturation of pathogens, including the malaria parasite. Stating this means that mosquitoes are able to transmit diseases more frequently. This is why the chances of Vector-borne diseases get higher in areas previously unaffected.
Increased rainfall
There are many vectors, particularly mosquitoes, have rely on stagnant water for breeding. Increased rainfall, which is driven by changing weather patterns, has the likelihood to increase more water accumulation. This offers an ideal condition for vectors to reproduce. Heavy rains, followed by warm weather, create the perfect breeding environment for mosquitoes that cause Vector-borne diseases.
Prolonged warm seasons
Climate change is extending the length of warm seasons. It allows vectors to thrive for longer periods. Colder winters would kill off mosquito populations in the past, and this would reduce the spread of Vector-borne diseases. It is saddening that milder winters in regions now allow mosquitoes to survive year-round. Due to this reason, it contributes to the persistence of diseases including dengue fever and malaria.
Droughts
While droughts may seem like they would reduce Vector-borne diseases, the reality is complex or different. This is primarily seen in urban areas where droughts increase the risk of mosquito-borne disease, where they reduce the flushing of eggs as well as immature mosquitoes out of sewers and drains. The occurrence of droughts is the reason that forces people in urban areas to store water. Storing of water leads to stagnant water sources where mosquitoes find a way to breed. The rise in mosquitoes and fewer preventive measures at home give way to Vector-borne diseases.
The global health effects of climate-driven Vector-borne diseases
The resurgence in Vector-borne diseases because of climate change leads to serious consequences for global health. These diseases have the ability to cause illnesses, disability and even deaths among vulnerable populations. In addition to the direct health effects, Vector-borne disease places a burden on healthcare systems, economics and communities.
Malaria
Malaria is a parasitic disease transmitted by the Anopheles mosquito. It remains one of the deadliest Vector-borne diseases. The datasets accumulated from the World Health Organisation (WHO) showed that in 2020, the estimated number of malaria deaths stood at 617,000. These death rates majorly occurred in sub-Saharan Africa.
Climate change contributes to the increasing geographic range of malaria, which is observed in highland areas – Africa, Asia and South America. In these regions, temperatures were too cool and became a way of survival for Anopheles Mosquitoes. Warming temperatures are creating a sense of comfort for malaria transmissions and putting millions of people at risk in areas which were previously known to be unaffected by Vector-borne diseases.
Dengue fever
Dengue fever is another mosquito-borne disease that has seen a dramatic increase over decades. The Aedes aegypti mosquito cause dengue fever, where the dengue virus is transmitted to humans through the bites of infected female mosquitoes. The Aedes aegypti is a female mosquito that thrives in warm and tropical environments. As temperatures rise, this mosquito species is expanding its range into parts of Europe and North America. In these areas, the symptoms of Vector-borne diseases are relatively higher in nature.
As per WHO’s projection, it is ascertained that half of the world’s population is now at risk of dengue. The health organization estimated indications that 390 million dengue virus infections are occurring per year, of which 96 million manifest clinically. This highlights the seriousness of Vector-borne diseases.
Zika virus
The Zika virus (alternatively ZIKV) is transmitted by the same mosquito, Aedes aegypti spreading dengue as well as chikungunya. It also gets acceleration by Aedes albopictus mosquitoes between humans and non-human primates. These parasites also offer to Vector-borne diseases. Zika virus caused international outrage in 2015 and 2016 when outbreaks in America were linked to severe birth defects in newborns. Climate change has also contributed to the spread of the Zika virus because it creates favourable conditions for the Aedes mosquito to thrive and breed. Climate change can improve the reproduction of this virus in Aedes spps. Mosquito population and results in intensified ZIKV/Zika virus outbreaks.
Lyme disease
Lyme disease, or Lyme borreliosis, is the most commonly transmitted tick-borne infection. Yes, unlike the other three diseases, malaria, dengue and Zika, Lyme disease is caused by ticks. This disease is divided into three stages – early localised, early disseminated and late. Ticks are expanding their range in higher latitudes with rising temperatures, due to which leads to an increase in this disease. The United States and Europe are the dampest infectious locations that come at the forefront of this disease.
The Centers for Disease Control and Prevention (CDC) estimates that nearly 476,000 people might be diagnosed and treated for Lyme disease every year in the US. On the contrary, 200,000 cases are diagnosed in Western Europe each year. For climate change, it could be expected to increase the tick population and lengthen Lyme disease. It is because of warmer weather that gives more rise to active ticks and contributes to the increased transmission of Vector-borne diseases.
Who is at risk or vulnerable to Vector-borne diseases?
While climate-driven Vector-borne diseases can affect anyone, there are people who are more susceptible to the effects of these diseases.
Low-income communities
There are people in developing countries, who have limited access to healthcare, clean water as well as sanitation. These people are vulnerable, and this makes it difficult to prevent and treat Vector-borne diseases. This is most notable in sub-Saharan Africa, South America and South Asia, where vectors find favorable environmental conditions.
Pregnant women
A pregnant woman and her foetus are saddenedly vulnerable to Vector-borne diseases. The mosquito-borne disease malaria can cause severe complications during pregnancy and lead to low birth weight along with increased infant mortality. Global climate change is also affecting the incidence and geographic spread of many of these diseases. The effects might differ regionally but the intensification of disease can remain the same, though seeing diminution.
Children
Vector-borne diseases account for more than 17 per cent of all infectious diseases, and these cause around 700,000 deaths per year, either because of parasites, viruses or bacteria. Children aged five years have experienced rising infection due to malaria, where approximately 219 million cases were seen globally, resulting in deaths of 400,000 every year.
Adults
Similar Vector-borne diseases were observed among adults by 31 per cent. As per sources, adults are more susceptible to these diseases than children, which stood at 9 per cent. Among adults, the diseases cause symptoms which are nausea, encephalitis, headache, fatigue, etc. Individuals who are immunocompromised have a higher risk of becoming ill due to such diseases. This means that people with weakened or low immune systems, especially those already suffering from chronic illnesses, are at higher risk of illness and death from these diseases.
What are the mitigation and adaptive approaches to control Vector-borne diseases?
The preventive measures could be a unified approach in order to address Vector-borne diseases. These measures can be minimized in the context of climate change by maintaining them.
Vector-control programs
Effective vector control programs should be mandated for the reduction of the spread of Vector-control diseases. The emphasis on
- Insecticide-treated bed nets to prevent mosquito bites.
- Indoor residual spraying with insecticides.
- Larval control through the elimination of standing water where mosquitoes breed.
These programs will be required to be adapted to changing environmental conditions brought about by climate change.
Considering improved surveillance and early warning systems
Actions following early warning can be mindfulness to control the spreading nature of pathogens. Their detection based on monitoring the presence as well as the spatial distribution of the pathogens can be significant to projecting further spread of infections. This can be taken into account using predictive modelling. Ongoing surveillance would also be major to monitor the spread of Vector-borne diseases, thus lessening its outbreak. Early warning systems like temperature and rainfall patterns in climate data can help anticipate this before occurrence.
Public health education
There can be different measures offering the public to take care of their health. These can be behavioural health, personal protection, medical attention, vaccination as well as water and sanitation.
Behavioural change
The WHO works to educate common people on how to protect themselves from vectors to not get affected by Vector-borne diseases, including awareness and community mobilization.
Personal care
The attention to wearing long-sleeves and pants covering legs in infected areas can come in handy to not get infected by Vector-borne diseases. Also, using mosquito repellent creams, coils, mats, and liquids should be mandated as personal protection, especially among infants or young children.
Water and sanitation
Individuals should improve storing water at home. They can also improve sanitation to help control Vector-borne diseases.
Vaccinations
Parents should get their children vaccinated. These can vary as per infection – Dengue vaccine (children aged 9 to 16), and Japanese Encephalitis vaccine (aged two months and up).
Food storage
Housemakers should keep food covered in the kitchen and avoid eating outside.
Medical attention
Observing any symptoms among people, be it children, adults or old people, like a high fever, severe headache, rash, joint pain, or flu-like symptoms, should immediately seek medical attention.
Climate change mitigation
Rooting in the main cause of the rise of Vector-borne diseases is the ultimatum that needs global, collective efforts to mitigate climate change. There is a need to reduce greenhouse gas emissions. This can be achieved through the transition to renewable energy sources and, at the same time promote sustainable land use practices.
Global impact and what are the regions at risk
In Africa, namely Somalia, Chad and Syria, malaria remains a deadly vector-borne disease in the continent. Warmer temperatures are expanding malaria’s reach and it pushes into higher altitude regions that were once too cold for the disease. The WHO has warned that Africa could see millions of cases of malaria with the progression of climate change. In 2022, the continent was home to 94 per cent of malaria cases and deaths 580,000 cases caused by Vector-borne diseases.
In South and Southeast Asia, these landmarks are considered hotspots for Vector-borne diseases, including ZIKV and chikungunya. The combination of heavy rainfall, urbanisation along with poor-water management had led to repeated outbreaks. In India and Bangladesh, being developing countries, these regions experience temperature, due to which it contributes to disease spread.
Although Europe and North America were once considered safe from many Vector-borne diseases, these locations are now seeing an uptick in cases. It is sourced that warmer summers and milder winters have allowed diseases – West Nile virus and Lyme disease to take root in parts of Canada, the US and Europe.
In Latin America and the Caribbean, the Zika virus continues to pose a threat across these regions, making first headlines in 2015. Moreover, Dengue fever and chikungunya remain the most prevalent arbovirus in these regions. These highlight the regional vulnerability to Vector-borne diseases.
FAQ
What are Vector-borne diseases?
Vector-borne diseases are illnesses caused by pathogens and parasites transmitted to humans by vectors. These are mosquitoes, fleas and ticks.
How are Vector-borne diseases transmitted?
Vector-borne diseases are transmitted when a vector, supposedly a mosquito or tick, bites an infected person/animal and later transmit the pathogen to a healthy person through another bite.
What are the common symptoms of Vector-borne diseases?
The symptoms of Vector-borne diseases can vary depending on the disease but the commonalities are fever, headache, muscle or joint pain, fatigue as well as nausea. Severe cases can result in critical conditions, and these can be organ failure, hemorrhage fever and neurological issues.
What are the promising ways to prevent Vector-borne diseases?
Preventive measures can include using insect repellents, wearing long-sleeved clothing, and sleeping under mosquito nets. Vaccine also exists for some diseases like yellow fever but not all.
Which regions are most affected by Vector-borne diseases?
Tropical and subtropical regions are most susceptible to Vector-borne diseases. The parts of Africa, Asia and South America are most affected because of warm climates that support vector breeding. However, due to climate change, these diseases are also appearing in previously unaffected areas.
