PERSUASIVE ESSAY
The Spread of Vector-Borne Diseases is a Growing Concern
Why does it seem as if there are more outbreaks of vector-borne diseases than at any point in recent memory? There may have been more outbreaks in the past that went unnoticed but, increasingly it may seem that new disease outbreaks are happening at an alarming rate and diseases are spreading into areas previously unaffected or thought to be safe from threats. An outbreak of a disease requires various conditions in order to be able to successfully spread and to infect as many people as possible. For instance, the increasing concern over vector-borne diseases from mosquitoes and ticks and how a changing climate will affect the spread of vector-borne diseases remains an important aspect of addressing a changing climate.
Mosquito-borne diseases have ancient roots. Over centuries, efforts to contain it have proven unsuccessful, as it has been unnervingly resilient and maddeningly adaptive to containment efforts. The roots of the history of the mosquito-borne disease begin in Africa where, “An ancestor form (Aedes aegypti formosus) is still present [sic], whereas a domestic form (Aedes aegypti) has spread across almost all tropical and subtropical countries during the past centuries. Its population increases especially in areas where household water storage in containers is common” (Mehlhorn 36). The Aedes aegypti spread across the world after originating in Africa, much like humans. For instance, during the slave trade when Africans were transported by ships to the New World, mosquitoes and the diseases they transmitted were also introduced to the New World.
We can also review the origins of the Aedes aegypti mosquito by studying its living ancestor. Professor of Parasitology, Heinz Mehlhorn, at the Heinrich-Heine-Universität Düsseldorf states that “Mosquitoes have inhabited the globe for more than 100 million years. In the course of evolution, they were able to adjust their biology to a great variety of environmental conditions and reproduce in almost all aquatic habitats” (Mehlhorn 31). Their adaptive ability is remarkable and is a concern as we attempt to find ways to combat them. Mosquitoes have been adapting to changes in climate for millions of years. This, unfortunately, means that mosquitoes have had ample time to adapt to various climates and have the ability to respond to changes in the environment due to their ability to survive in all different kinds of habitats.
Mosquitoes have the ability to survive in unfavorable circumstances for long periods of time. “The most remarkable ability of these species is that the eggs can survive desiccation and dryness for months or sometimes even years and can thus survive long periods with unfavorable living conditions. In general, these species possess [sic] high ecological potency and can rapidly adapt to new habitats” (Mehlhorn 31). Mehlhorn points out that many of the factors that limit the spread of most living things do not affect mosquitoes as much. Mosquitoes have adapted to different conditions and are able to survive for long periods of time in adverse climates. This gives mosquitoes a distinct advantage over other insects because they have the ability to quickly spread across different climates which makes them difficult to eliminate (Mehlhorn 31). As a result of mosquitoes’ ability to adapt to circumstances, mosquito-borne diseases are also difficult to eradicate.
Many of the diseases that are currently found in the tropics were once found in other places around the world. “At one time many of today’s tropical diseases also occurred in temperate regions since many of the same risk factors occurred [sic] there. Today, [sic] industrial development and technological advances, including medical ones, have lessened the impact of these diseases in industrialized countries... Malaria and other mosquito-borne infections were once widespread in the United States” (“The Impact of Tropical Diseases”). Many diseases that are now prominent in the tropics used to be prominent in temperate climates. If the global climate were to become more tropical, then it would become easier for tropical diseases to spread past the current tropical regions of the planet. Tropical climates have greater amounts of rainfall, which leads to excessive amounts of water that are breeding grounds for mosquitoes. This, of course, means that these diseases could become prominent again in temperate climates. Areas previously unaccustomed to receiving large amounts of rainfall could become hotbeds for the spread of mosquito-borne disease.“Increased rainfall and surface water also provide breeding grounds for the mosquito. Climate change may thus wreak a considerable change in [sic] the distribution of the disease” (Martens 536). Martens describes how increases in water coverage around which mosquitoes can breed around will result in greater numbers of mosquitoes. This means that the more the climate changes, the greater the spread vector-borne diseases will have because as the number of mosquitoes increases, the amount that vector-borne disease spreads increase as well.
A changing climate can affect how mosquitoes hibernate and how efficiently mosquito-borne diseases spread. “Climate change affects the hibernation [sic] of many species. Insects and spiders are particularly impacted because they often have reproductive processes that are very temperature sensitive. Mosquitoes have already adjusted their hibernation” (Fry 456). While other insects are more affected by changes in climate, mosquitoes have evolved to be able to adapt to changing climate conditions. Since mosquitoes have already adjusted their hibernation pattern, they are better adapted to survive in different conditions. Pim Martens explains that, “The spread of the disease is thus limited by conditions that favor the vector and the parasite” (Martens 536). She goes on to explain that, “The malaria mosquito is most comfortable at about 20 to 30 degrees Celsius [sic] and at a relative humidity of at least 60 percent. Furthermore, the malaria parasite develops more rapidly inside the mosquito as the temperature rises, and development ceases entirely below about 15 degrees” (Martens 536). As Pim Martens points out in American Scientist, Malaria and other vector-borne diseases can benefit from increases in global temperature. The mosquito that is responsible for the transmission of the malaria parasite requires a certain temperature and humidity in order to thrive.
Vector-borne diseases are not just spread by mosquitoes, as they are also spread by ticks. Ticks have similar preferences to mosquitoes in terms of what they prey upon. Ticks spread several diseases ranging from minor to severe. One of the main diseases that are spread by ticks is Lyme disease. “Lyme is listed as one of the diseases that will be fueled by global climate change, along with cholera, dengue fever [sic], and malaria. U.S. Global Climate Change Research Program predicted with ‘high confidence’ in 2016 that a warmer world would promote ticks carrying Lyme [sic] disease to come out earlier in the spring and move generally northward” (Pfeiffer 51). In essence, Pfeiffer explains how a warmer climate would result in an increase in the range of areas where ticks could spread Lyme disease (Pfeiffer 51).
During our current era, climate change may pose a significant threat to human populations. Climate change could lead to changes in weather patterns, increases in tropical weather conditions, and likely increases in the population of ticks and mosquitoes and the vector-borne diseases that they spread. One of the primary threats to human populations is health-related complications resulting from the spread of vector-borne diseases. Given their historical adaptability and resilience, the threat that vector-borne pose is a global concern. While we may seem to understand the basic mechanisms at work behind the spread of vector-borne diseases, scientists are still struggling to combat the spread of these vector-borne diseases. Many different vector-borne diseases require different conditions in order to thrive, but climate change is creating conditions favorable to the spread of disease.
Annotated Bibliography
Fry, Juliane. The Encyclopedia of Weather and Climate Change: A Complete Visual Guide.
Hinkler Books, 2010.
This book describes climate change and its implications on the weather. This book can prove my thesis by demonstrating the link between climate change and the increase in the mosquito population.
Martens, Pim. “How Will Climate Change Affect Human Health? The Question Poses
a Huge Challenge to Scientists. Yet the Consequences of Global Warming of
Public Health Remain Largely Unexplored.” American Scientist, vol. 87, no. 6,
1999, pp. 534–541. JSTOR, www.jstor.org/stable/27857937.
This article describes how a changing climate would pose a threat to human health. This article supports my thesis by explaining how the incidence of the disease could increase.
Mehlhorn, Heinz. Arthropods as Vectors of Emerging Diseases. Springer Berlin, 2014.
This book describes the need to combat the spread of emerging diseases including vector-diseases spread by mosquitoes and ticks. This book supports my thesis because it describes how
Pfeiffer, Mary Beth. Lyme The First Epidemic of Climate Change. Island Press, 2018.
This book describes how the spread of Lyme Disease can be used to monitor the effects and speed of climate change. This book supports my thesis by describing how Lyme Disease is affected by climate change.
“The Impact of Tropical Diseases.” ASTMH, American Society of Tropical Medicine and
Hygiene, www.astmh.org/education-resources/tropical-medicine-q-a/impact.
This article describes how diseases found in tropical parts of the world can spread to the United States with devastating results.