The Impact of Climate Change on Aedes aegypti Behavior in Latin America and the Caribbean

by Shannon O’Neill

Climate change in Latin America and the Caribbean (LAC) has impacted precipitation and temperatures, which have been associated with increases in seasonal outbreaks of dengue fever. However, such correlations are often speculative due to the complexity of interactions involved in vector-borne diseases. Researchers Chadee and Martinez (2015) focused on the adaptive behaviors of the Aedes aegypti mosquito in efforts to fill some of the research gaps typically associated with the research of these diseases. This mosquito is a successful vector for various vector-borne diseases, including dengue fever, Zika virus, and chikungunya, and has shown adaptive behaviors. This research will provide the information to create better vector control strategies that can be applied in order to limit climate change impacts on the resurgence of these diseases. Continue reading

Manmade Triggers Behind the Zika Virus

by Katy Schaefer

It seems that every year has its own health crisis. In the past ten years, we have seen panic from SARS, Mad Cow Disease, Bird and Swine Flu just to name a few.This year seems to be the year of the Zika Virus. Although the disease changes all the time, the panic is always the same. People want to know where it comes from, how it can be treated, and how it can be transmitted. But these aren’t the questions we should be asking. What we really need to know is what is causing the disease and is there a way we can make ourselves less susceptible to it? Recently scientists have been looking into the rising rates of diseases like Zika and Malaria and have found a surprising result. We might be doing this to ourselves, here’s how.

The first confirmed case of the Zika virus came out of Brazil in May of 2015. It is passed through mosquito bites and common symptoms include fever, rash, joint pain, and conjunctivitis. Hospitalization is uncommon, but there is currently no cure and there were reported links between the disease and birth defects in children born to infected mothers. However, most cases of Zika have been sprouting up primarily in South America, the Caribbean, and Africa. Researchers want to know why here, and why now? It is becoming clear that human intervention in the natural environment is impacting not only the viruses that infect our communities, but the insects that spread them.

The Aedes aegypti mosquito, also infamously known for spreading diseases like dengue and yellow fever, is also carrying and spreading Zika. This particular mosquito thrives in unique environments. “It doesn’t live in the ground, or in swamps, or any other kinds of places where you would normally find mosquitoes… So humans have created an environment for it to proliferate, by having all of these water containing containers around, and the mosquito has adapted so well…it’s really kind of a human parasite. It’s like the cockroach of the mosquito world” said Durland Fish, professor of microbial diseases at Yale University. Namely, they survive in tires, cans, and plastic containers. These are symptoms of not only poverty, but environmental degradation. However, the poor aren’t the only people being affected. The mosquitos can live in flower pots or water collected on a pool cover. Of course there are other factors that contribute to the spread of diseases like this, such as planes that can carry people and their diseases across oceans. Poverty that limits peoples ability to prevent and treat illness in a timely fashion to keep it from disseminating. But it’s more about the fact that while these factors have been discussed very openly, the environmental causes have been neglected.

An often looked over cause is the building of dams. While there have been widespread complaints about the ways damming a river might effect its ecosystem, with regards to the spread of disease, it is most problematic in that it brings people and disease together. Schitsomiasis is spread by parasite crying snails that live in freshwater. The Schistosomiasis outbreak in Ghana was catastrophic and widely blamed on the emergence of a dam. “More than 200 million people are infected worldwide. In terms of impact, this disease is second only to malaria as the most devastating parasitic disease. Schistosomiasis is considered one of the Neglected Tropical Diseases (NTDs)” (http://www.cdc.gov/parasites/schistosomiasis/). Malaria alone is responsible for 1.1 million deaths per year and the building of dams only exacerbate the issue. Because the water is still and calm once it has been dammed, it acts as a habitat for the mosquitos.

Another trigger for the spread of diseases like Zika has been the rampant cutting down of forests. The removal of trees that used to act as a sort of barrier between people, animals, and insects. With the massive removal of these trees, the way that we interact with these living creatures is changing, and making humans more susceptible to disease. “In Malaysian Borneo over the past few years, scientists started to suspect that’s what was happening when they noticed an uptick in a form of malaria, caused by the parasite Plasmodium knowlesi, historically found mainly in macaques. In the last decade, research has shown that P. knowlesi has become the leading cause of human malaria in the region” (Chelsea Harvey). Although the parasite is found in macaques, it is still passed by mosquitos that live on, or near them. Scientists concluded that it was an environmental disturbance that brought people and these parasites together. And indeed it was, “forest clearing and development are actually causing people and mosquitoes and macaques to be in much closer contact than before” said Kimberly Fornace, research fellow at the London School of Hygiene and Tropical Medicine. Because of something called the “edge effect”, when ecosystems experience a high level of change at the edges of the habitat, these are also the most critically challenged areas when it comes to the spread of disease, where people and macaques come into contact. Additionally, the fact that these deforested areas tend to be hotter is affecting the spread of these diseases. Because they lack the cooling benefit of the trees, certain parts of the mosquito life cycle have been changing. In particular, the blood feeding and egg laying cycle of female Anopheles gambiae is shortened by up to 52%, greatly affecting the overall population of the insect.

Lastly, climate change has been influencing the survivable temperatures globally, broadening the regions that these mosquitos can live in. “Globally, temperature increases of 2-3ºC would increase the number of people who, in climatic terms, are at risk of malaria by around 3- 5%, i.e. several hundred million,” concludes the WHO. “Further, the seasonal duration of malaria would increase in many currently endemic areas.” Beyond this, mosquitos reproduce more quickly, and bite more frequently in the heat.

It is clear that there is a relationship between the environment and the spread of diseases like Schitsomiasis, Zika, and Malaria. The rising temperatures have expanded the regions that mosquitos are able to occupy. the damming of rivers has created massive pools of still water that not only attract mosquitoes, but bring parasite infected snails to the people that swim in it. Yet, it is still one of the least talked about factors in the spread of disease. It has become clear that we need to think about disease from a more ecological standpoint. Rather than rushing into the vaccination process, we should think more critically about the environmental factors that could be preventative. With these diseases in particular, it all comes down to the mosquitos, and treating them is just about as important as treating the people.

 

LINKS: https://www.washingtonpost.com/news/energy-environment/wp/2016/02/03/the-hidden-environmental-factors-behind-the-spread-of-zika-and-other-deadly-diseases/

https://www.washingtonpost.com/news/energy-environment/wp/2015/12/21/by-cutting-down-forests-humans-may-be-giving-themselves-malaria/?tid=a_inl

http://www.cdc.gov/zika/geo/index.html

The Influence of Climate Change on global distributions of Dengue and Chikungunya Vector Species

by Kaylee Anderson

The global distribution of human cases of dengue and other mosquito-transmitted disease presents a serious health problem, especially considering the diseases have spread significantly in recent years. Although there is considerable research on the global distribution of these diseases, there is a second concern: range expansion by vector species. In recent years, the two main mosquito vectors, Aedes aegypti and albopictus have spread to more regions, including lower and middle latitudes, introducing ‘forest diseases’ to humans. Ae. aegypti is thought to be responsible for most massive outbreaks of dengue, so its future geographical distribution is important to predict. Continue reading

How Trees Calm Us Down

by Paola Salomon

Roger Ulrich perceived a pattern among patients that were recovering from gallbladder surgery at a hospital in a suburban area of Pennsylvania. The patients whose rooms overlooked a green area with deciduous trees were being discharged a day sooner than those whose rooms were facing a wall. But how can the trees positively affect patients in a hospital by just looking at them? A psychology professor, Mac Berman, led the study with the help of researchers in the United States, Canada, and Australia. The study compares two large data sets from Toronto. “The first measures the distribution of green space, as determined from satellite imagery,” while the second “measures health, as assessed by a detailed survey of ninety-four thousand respondents.” These are results reported by Alex Hutchinson in a 2015 New Yorker piece. They showed that “an additional 10 trees on a given block corresponded to a one-per-cent increase in how healthy nearby residents felt.” The cost of planting new trees is high, yet it was estimated that people would feel seven years younger. Continue reading

Climate Change as a Public Health Issue

by Shannon O’Neill

The World Health Organization (WHO) estimates that roughly half of the world’s population is at risk of infection by vector-borne disease. Furthermore, vector-borne diseases are responsible for one-sixth of illness and disability throughout the world, killing at least one million people each year. Vector-borne diseases tend to highlight socioeconomics differences and problems, as they increase health inequalities, with developing countries having a 300 times greater mortality rate from them. These countries do not have the resources for preventative care or to manage outbreaks. Additionally, vector-borne diseases tend to paralyze health systems and substantially decrease tourism. Though some efforts to control vector-borne diseases have been quite successful, these diseases still pose a major threat to the world as re-emergence becomes more likely owing to greater organism drug resistance and other changing environmental factors. Continue reading

Hayfever in the UK Extends to Autumn Months

by Kaylee Anderson

Hayfever is one of the most common allergic conditions, affecting as many as 10 million people in the United Kingdom. It is most well-known to be triggered by ragweeds in the United States and by grasses in the UK. Ragweeds were introduced to Europe in the 19th century, rapidly spreading by 1940.

It is believed that the threshold for clinical symptoms of hayfever is as low as 1-3 ragweed pollen grains/m3, which is significantly lower than other well-known pollen allergens, like grass and birch. Continue reading

The Effect of Climate Change on the Ixodes Tick Success Rate of Transmitting Lyme Disease

by Shannon O’Neill

The potential for a rapid increase of the geographical distribution of ticks and tick-borne pathogens with increasing temperatures is a major public health issue. Therefore, the relationships between the tick, pathogen, hosts, and each of their environments must be better understood in order to effectively manage future outbreaks. Climate change is often considered to be a driving force of increased tick-borne disease. However, the effects of climate on disease are difficult to distinguish from other potential causes. Ostfeld and Brunner (2015) specifically studied the Ixodes tick that spreads Lyme disease in an effort to discern why this tick and the pathogens it transmits have continued to increase with warmer temperatures. The researchers first identified environmental factors for the current tick distribution, then used these factors as a predictor of future suitable tick habitats with climatic changes. Finally, they looked at how various environmental factors sustain both tick populations and the pathogens they transmit. Continue reading