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Climate Change, Parasite Infections, and Immune Responses

By Roberta Attanasio

Global climate change noticeably impacts human health—safe drinking water, sufficient food, and secure shelter are threatened by rising sea levels and severe weather events. Heat waves dramatically increase death rates not only from heat strokes, but also from complications arising from cardiovascular, respiratory, and cerebrovascular diseases. Although global warming may bring some localized benefits, such as fewer winter deaths in temperate climates and increased food production in certain areas, the overall health effects of a changing climate are likely to be overwhelmingly negative. For example, climate warming is predicted to increase the transmission of parasite infections. Now, results from a recent study show that host immunity can influence the impact of warming on host–parasite interactions and mitigate its long-term effects.


Photo credit: Robobobobo, CC BY-SA 2.0

For the study (Host immunity shapes the impact of climate changes on the dynamics of parasite infections), researchers focused on soil-transmitted gastrointestinal helminths, also known as parasitic worms. In humans, these worms cause some of the most common parasitic infections worldwide. According to the World Health Organization (WHO), approximately 2 billion people are infected with soil-transmitted helminths globally, mostly in the poorest and most deprived communities. They are transmitted by eggs present in human feces, which in turn contaminate soil in areas where sanitation is poor. However, the researchers focused on two parasitic worms of rabbits, Trichostrongylus retortaeformis and Graphidum strigosum.

In previous studies, the researchers found that, in rabbits, infections from one of the parasites are controlled by the immune response, whereas infections from the other parasite species are not controlled, even though the rabbits do mount an immune response to the parasite. Therefore, the researchers designed the new study to understand the contribution of climate change and immunity on the long-term and seasonal dynamics of infections caused by the two rabbit parasitic worms. They examined samples collected monthly between 1977 and 2002 in Scotland.

The study results show that climate warming—rising temperature and humidity—increases the availability in pastures of the infective stages of both intestinal worms. The intensity of infection increases for the worm not regulated by immunity. In contrast, there is no significant long-term positive trend in the intensity for the immune-controlled worm. Specifically, G. strigosum infection is not controlled by the rabbit immune response. Therefore, the intensity of the parasite infection increases with warming, leading to significant accumulation of G. strigosum in rabbits, mostly in adult rabbits. Why? The rabbits aren’t able to clear the infection caused by G. strigosum with their immune response; therefore, the rabbits accumulate more and more parasites as they age—the result is that older individuals carry most of the infection in the population. However, because T. retortaeformis infection is controlled by the rabbit immune system, the effects of climate on the intensity of infection caused by this worm are mitigated.

Isabella Cattadori, senior author of the study, said in a press releae: “Over the course of 23 years, we saw clear evidence of climate warming at our study site in Scotland. The warmer climate leads to increases in the number of soil-transmitted parasites in the pastures where the rabbits live because the parasites can survive longer in the soil. With more parasites, there is an increased risk of infection, but how this increased risk affects the severity of the infection in the long term depends on the ability of the host to mount an immune response.”

How do these results contribute to the treatment of parasitic worm infections in humans? Cattadori said: “”Our research shows that as climates continue to change, we will need to tailor our treatment of parasite infections based on whether or not the host can mount an effective immune response. When a host’s immune response cannot control the infection, treatment should be targeted at older individuals because they carry the most severe infections. When a host’s immune response can control the infection, treatment should be targeted at younger individuals because they are at the greatest risk.”

The video below provides an overview of the significance of the study.

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Author: Roberta Attanasio

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  1. The article made a very good point in the correlation between climate change and immune response. Whether that being in increasing temperatures and increasing the parasitic population or increasing temperature and weakening the immune response, it is clear a connection is there. It has been proven with multiple things. With different insects passing on different pathogens, such as mosquitoes or ticks, and the increase in nonpathogenic diseases such as Asthma and different allergies. All these have and still are increasing with the increase in climate change. This article just opens a tiny door to the large and harmful amount of damage that climate change is doing: loss of sea ice, accelerated sea level rise, and more intense heat waves. This causes the endangerment of species, economic loss, and increase in heat-related diseases. I would love to and am hoping to see more research to combat not only these individual harmful effects but global warming as a whole. I personally feel more research should be geared to not only what the problem is but also to solving the problem.

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  2. The primary focus of this article is to study how immunity in host cells can influence climate warming on host-parasite interactions. Studies show that as climate rises the severity of parasite infection increases also. One group of rabbits was injected with infections from parasites controlled by the immune response while the other group of rabbits were injected by parasites that were not controlled by immune system. When climate increased the group that was not controlled by immune system were not able to fight off the parasite infection, but the group that was controlled was able to decrease the effects of the parasite more than those that were not controlled. Where there was no control, treatment was targeted towards older adults because they are more likely to be immunocompromised. When there was control, treatment was targeted towards young adults or children because they the chance of contracting the infection is higher for them since they most likely haven’t been exposed. Similarly, treatment is administered against infections today due to the constant change in climate. Another study was performed to show how clams were also being affected in water due to climate changes and parasite infections. What causes the climate changes to have an impact on the contraction of infection is the imbalance caused in body temperature. Once homeostatic is unsteady cells are more prone to infection. Another factor is the genetic make up of the organism; if an organism has a stronger immune system they are better at fighting off the infection than those that are immunocompromised. Researchers are currently trying to see if they can find a correlation to the climate temperatures and the emerging diseases. This way we can be more prepared for the parasites arising and of course possible treatments.


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    • Christina, those were good examples of the different ways on how researchers are trying to find a correlation to the climate temperatures and the emerging diseases. One interesting thought is that we are seeing an increase in emerging diseases because of the change in infectious disease transmission patterns. One that doesn’t involve pathogens but is becoming more and more common is asthma. This could be from the increase in plant pollen or increase in Africa’s ever expanding desert which has the sand blown all the way to the Caribbean islands by the increasing speed of trade winds on the Atlantic. I think it’s safe to say that from the article ‘Climate Change, Parasite Infections, and Immune Responses’, the two you listed and proof by just watching the news that there is definitely a positive correlation. The warmer it gets, the more diseases there are. It is very unfortunate and I think it’s time to start looking for a way to decrease this.

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  3. We are seeing an increase in very sick kids in the emergency department where I work. The running theory that has been heard throughout the department is that we did not really experience a solid winter this year. It is advantageous to humans and animals to experience the brisk, cold winter as it is crucial for the destruction of bacterial cells and viruses. Due to the warmer, almost lack of a winter season and frigid cold the bacteria and viruses have not been wiped out. Similar to the rabbits, small children do not have a sufficient immune response to mount against these bacteria. As they are increasing in numbers, they are able to infect more people and lead to an increase in hospitalizations. Last Friday the ER, out of 400+ children seen, more than 1/3rd of them were admitted to the PICU and critical care units, which is unusual. Most of the patients were having difficulty breathing, required oxygen and were on continuous breathing treatments with little success and relief. As the world gets warmer, this emerging issue affects all living creatures including plants, animals, humans and even marine life. There are many issues with coral bleaching (Link 1) currently occurring in the tropical areas due to a previously symbiotic relationship between corals and their bacterial symbionts zooxanthellae. Similar to the rabbits being able to keep the parasitic infections at bay, the coral and zooxanthellae developed coexistence with one another. The coral provides shelter for the zooxanthellae while the algae perform photosynthesis which the coral benefits from. However, due to the increase in sea water temperatures, the coral is stressed and unable to provide the necessary components to the zooxanthellae for photosynthesis which leads to an expulsion of the algae from the coral. This is what is defined as coral bleaching. The zooxanthellae are what cause the coral pigmentation so as they are expelled from the coral the coral returns to its natural translucent color (which appears white due to the light refraction). Over time, if the balance is not restored the coral succumb to its deprivation of nutrients provided by its symbiont and it dies. This leads to a chain reaction of damaged coral reefs, decrease in numbers of fish and animals living on the coral reefs, lack of food, and oceanic organism decline which as we know has effects on humans as well. The event of coral bleaching can be seen as an immune response the coral activates when it is stressed. The high temperatures create a disruption in their natural calcium stores as well their immune system seems the mount an immune response towards the zooxanthellae leading to its expulsion (Link 2). Climate change affects more than we are currently aware of and through the research on the impacts of animals and parasitic worms and marine biology we are able to forecast some of the consequences of this drastic event. Health organizations as well as environmental advocates need to adjust not only the way in which we protect these plants and animals but adapt how infections are treated and prevented. Understanding the life cycle of parasites and other such organisms can prepare us for the drastic changes that will lead to an increase in infections, hospitalizations and treatment plans. There may come a day when the parasites that currently infect humans in third world countries start thriving in our society due to the increase in climate and ability of them to survive in places they normally would not. The world is changing due to human influence, not in the best way either. It is now up to humans to figure out how to fix and restore what has been damaged, not only for our sake.


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    • Marlena,

      I definitely agree that this past winter has been different from the rest. The temperatures fluctuated every other day, some days being really warm for a winter day, which really affected many people, especially children and the elderly. It is sad to hear that many children were admitted in PICU due to weather conditions beating upon them.

      I wanted to further analyze this and continue by saying that global warming has not only hit the southern states of the United States, but has started moving towards the North Pole. People who have never been exposed to certain diseases have been sent to hospitals, and their immunity is not as built due to no previous exposure. Insects that are not seen during winter came back this past season, and more and more water-borne diseases such as cholera came into presence. Allergy levels were at an all-time high, and people who have never been exposed to allergy had allergy-type symptoms.

      Yes, being a first-world country, we can adapt to new mechanisms to prevent transmission of new diseases, but why succumb to this? I definitely agree that it is us humans that are the main cause of global warming and that there needs to be a way to create better alternative strategies that are more cost-efficient. That way, we can not only help human lives, but also reduce the damage in other important aspects in our ecosystems, such as bleaching in coral reefs.

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    • Marlena,
      I totally agree with you that the cold winter period is beneficial for human and animals because it allows the destruction of bacteria and viruses. To add to your idea, winter is important because as the article that I found mentioned, many insects that are responsible for diseases and other microorganisms are killed with temperatures getting cold.
      However, while cold weather can be beneficial for children, because it would diminish the number of those in the emergency department, we should acknowledge the fact that there is more deaths caused by heart attacks, strokes and other vascular problems, during the cold season because of the increase in blood pressure. Also, with the air getting cold and dry, the flu virus spread rapidly and winter is the season of the flu. Therefore, cold temperatures get rid of some viruses, but it also allow the development of other dangerous one.
      Every season has its advantages and its disadvantages. Global warming is bad for our health, but so is cold weather. Finding a balance weather between them is the key to a great health

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      • Yele,
        While the cold does promote unwanted viruses and conditions that can themselves be detrimental to human health, I am inclined to suggest that the risks associated with warmer climates outweigh those of colder climates. While many people get sick during the winter, there are vaccinations for some of the more common infective agents such as the flu. However, there are not any vaccinations for the helminthic parasitic infections (occurring due to the heat). It is simpler to find a successful vaccination for a virus than it is for a living animal such as parasites. The increasing reproductive rates and life span of these worms can become problematic. The more parasites surviving and reproducing the more likely we are to become infected. It would seem, based on this post and the research done that it is easier to control the effects of cold weather in the long term vs an increasingly warmer climate in terms of health and the ability to fend off parasitic infections. As well, the effects to our environment from the warm have a larger impact on our lives than the cold. The glaciers are melting and the rising sea level can mean more moist environments for other bacteria, viruses and even parasites to thrive in situations that they would not have previously been able to. For example, more still bodies of water lead to an increase in the mosquito population and an increase in malaria spikes in the United States (just a theoretical example). The cascading effects of the increase in global temperature put humans and animals at larger risk for becoming exposed to more and more pathogens that were previously unable to thrive. The global warming that is occurring is quite frightening to me from a scientific and personal standpoint. The adaptations that may arise from this situation can have detrimental consequences we are not currently aware of.



        2) (Video of currently melting glaciers)

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  4. I think the research article brings up a very important point in establishing that host immunity determines the extent of ill-effects global warming can incur regarding parasitic infection.
    However, when we consider parasitic infections, while helminthic infections are one of the most common forms of parasitic infections, they do not account for the highest morbidity rates and are easy to treat affordably.
    Other parasites should be of more concern when regarding the possibility of their territories spreading. If we’re considering North America for example, Chagas disease is being spread into the US increasingly with the reduviid bug being able to live in the warming climate of many southern states. Chagas has no vaccine, and the current treatments are often ineffective at eliminating the entire infection.
    You can also look at the spread of parasitic infections like Malaria. As tropical climates spread due to warming, so too does mosquito territories that bare these terrible disease.

    These parasitic infections are much more serious, much more deadly, and much harder to treat and prevent than helminthic infections. Our efforts should be focused on stopping more pertinent diseases.

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    • Chloe, You make a good point on scientist focusing their efforts on other more deadly disease like malaria or chagas especially with global warming further increasing their vector ranges. A possible reason why parasitic worms are being targeted is that they affect a greater number of people worldwide and worms like ancyclostoma duodenale (hookworm) can lead to severe anemia and death. As the temperature rises, people tend to wear open shoes like flip flops or even walk around barefoot increasing the likelihood of hookworm infection. Similar to the rabbits infected with Trichostrongylus retortaeformis, ascaris lumbricoides infections tend to be more prevalent in the young due to their tendencies to put dirt or unwashed hands in their mouths. This can lead to complications like intestinal blockage, anaphylaxis, respiratory problems or even stunted growth as the worms compete for nutrients. These soil-based helminthes usually go unnoticed for years causing increasingly severe symptoms as time and the worm load increases. Another possible reason these helminthes are focused on could be they are easier to contain as they don’t have vectors and we’ve developed anthelmintic drugs like albendazole against them. It’s easier to start off with easy-to-control parasites like the soil-based helminthes then use the solutions as a model to eradicate the more difficult to control parasites like malaria or chagas.

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  5. This article poses the interesting question of whether or not an increase in climate temperature induces a negative effect on immune response. It proposes that climate warming increases the availability of infective stages of two separate helminths species. The results indicated that the younger population of rabbits were the most immune susceptible to the change in temperature. Is it possible that the increase in temperature lead to a relative increase in breeding times for the parasites? An increase in the number of parasites would in turn increase infections rates seen in this study.
    Could the observed increase in infection be a result of stressed induced temperature response? In the article, “Changes in Hypothalamic-Pituitary-Adrenal Function, Body Temperature, Body Weight and Food Intake with Repeated Social Stress Exposure in Rats” authors showed that when introduced to stressful situations, rats showed an increase in body temperature. Is it possible that the increase in body temperature contributed to the infective rates of the helminths rather than the proposed extrinsic environmental temperature increases studied? In addition, is it possible that an increase in environmental temperatures of the rabbits lead to a decrease in sleep. A lack of sleep has been linked to increases in stress and suppression of the immune system indicated by this study “Sleep and immune function.” If so, in concordance with “Stress, Inflammation, and Short-Term Memory Loss” chronic stress could potentially decrease short term memory loss while also increasing the risk for infection.It would be interesting to examine other immunological implications of stress and sleep deprivation.

    S. Bhatnagar, C. Vining, V. Iyer andV. Kinni. “ Changes in Hypothalamic-Pituitary-Adrenal Function, Body Temperature, Body Weight and Food Intake with Repeated Social Stress Exposure in Rats.”

    Luciana Besedovsky,1,2 Tanja Lange,1,2 and Jan Borncorresponding author1,2
    “Sleep and immune function.” Pflugers Arch. 2012 Jan; 463(1): 121–137.

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  6. I agree that the impact of global warming increase with the levels of parasitic infections, but this is not the only reason as to why the parasite Graphidium Strigosum strives in the wild rabbit population. According to the article on parasitic immunology it showed that the parasites tolerance is also due to rabbits being the natural host of this parasite(1). The experimental design of this research article compared the immune reaction following the infection of two parasites, Graphidium Strigosum and Trichostrongylus Rectortaeformis, in the mucosa membrane .The T. Rectortaeformis elicited both strong systemic and localized immune responses while the Graphidium Strigosum only elicited a systemic immune response and not a localized one. The article concluded that warming climate may be the cause of the rabbit’s inability to fight of this parasitic infection. In another research article a study on the effect of heat waves on the immune system of three stickleback fishes were conducted(2). The body induces fever to warm the body to the leukocytes optimum temperature, so it can inferred that the warmer the temperature the better it would be for the immune system; this study proved that not only are the fishes’ immune system more active at a temperature of 13 degree Celsius but that the exposure to heat wave elicit a long lasting immune disorder in the sticklebacks.

    1. MURPHY, L., et al. “Explaining Patterns Of Infection In Free-Living Populations Using Laboratory Immune Experiments.” Parasite Immunology 33.5 (2011): 287-302. Academic Search Complete. Web. 9 Mar. 2016.

    2. Dittmar, Janine, et al. “Heat And Immunity: An Experimental Heat Wave Alters Immune Functions In Three-Spined Sticklebacks ( Gasterosteus Aculeatus).” Journal Of Animal Ecology 83.4 (2014): 744-757. GreenFILE. Web. 10 Mar. 2016.

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    • As you pointed out, the rabbits are the natural host of the Graphidium Strigosum, which could in turn increase the infection rate seen in this study. The study did mention that the accumulation of Graphidium Strigosum was due to their immune system’s inability to fight the parasite. This inability to combat the parasitic infection lead to a higher concentration in the older population of rabbits.
      While you pose an interesting concept of warming body temperature and an increase in leukocyte optimal activity. However, in the sense of climate change, it may be safe to assume that the current trend of increasing global warming, the temperature on earth could exceed that of the temperature considered for optimal leukocyte activity. As a result, future endeavors may include ways in which to decrease the body’s temperature to a level of optimal leukocyte activity. However, maybe our bodies will adapt to the increase in temperature and develop immune cells equip to resist high temperatures.

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    • Mojid Salawu,

      I was attracted to your article when I read that the rabbits were the natural host of the two parasites in the original post. I’ve always heard of primary or preferred host of pathogens, but not natural. Then I continued reading about the rabbits and stickleback fishes with less efficient immune systems due to increasing temperatures or climates. As an athlete, my initial thought is everything works better if it’s “warmed up.” However, each immune system of organisms has an ideal temperature it likes to work at. So I wanted to find an organism or animal that had the opposite reaction to temperature than your stickleback fishes. But something even more interesting came up; the level of specificity of an immune response can rely on the temperature of a fish’s environment. A study proposed that fish depend on a more general response when temperatures are low, and a more precise response when temperatures are high (1). The study was done on Perca fluviatilis and a few other species, but a lot more support needs to be given for this proposal to become a trend among fish as a whole. Even though fish and rabbits live in completely different environments and temperatures, I have to wonder if the rabbit’s inability to fight off the Graphidium Strigosum is due to more specific response, while the more general response could fight off the infection better. That could be a stretch but if the response became to specific, and allowed the parasitic infection to elude the immune response, a more general response could attack it better. For example, a more general response would be our own innate immune system. It senses a foreign molecule and immediately attacks. The adaptive immune system may generate a stronger or more precise response, but if it takes 1-2 weeks to do so the infection could outrun the attack or avoid the new specificity. If the infection outruns the response, this could cause the older rabbits to have a higher amount of parasites in the body as stated in the original post. The immune system is so fragile in any organism as mentioned before, and temperature seems to effect it in many different ways. I immediately had the opposite reaction to your post, warmer is better, but that’s evidently not always the case.


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  7. There is clear evidence of the negative impact that global warming and climate change have on our environment. As mentioned in the study, one of those impacts is the rise of soil-borne parasitic worm infections because of favorable environmental conditions that allow the organisms to thrive. Parasitic worms are not the only disease causing insects who benefit from the continuously increasing global temperatures.
    Mosquitos are known for thriving in warm climates and seasons. They are also infamous for transmitting nasty viruses like west nile and dengue. In regions like the tropics where temperatures easily reach 100degreesF or more, transmission of mosquito-borne diseases is year-round. However, in regions with seasonal climate changes, transmission is highest within the warmest months of the year; June-August for the northern hemisphere and December-February for the southern hemisphere. In seasonal regions, global warming increases the time during which transmission occurs allowing the mosquitoes to infect more of the population. In addition, mosquitoes that are indigenous to warm climate regions are finding seasonal regions suitable for living, which brings more species of mosquitoes with more diseases.

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    • Global warming has taken a turn on the worse when it comes to humans and lifestyle. Throughout the years, we have indeed faced more heat waves and dramatic changes in weather, which has impacted humans as a whole. Since temperatures have risen to almost a point of no return, vectors such as mosquitoes have transmitted more pathogens, causing recurrences in diseases that were once thought to not be a threat any longer.

      To further off of this, other pathogens such as water-borne pathogens have given a rise to water-borne diseases. This is because the water temperatures have increased so high that these pathogens are successfully transmitting diseases in human hosts. These can be passed through seafood or transportation through ships, which is key in our lifestyle. In third-world countries, pathogens that are transmitted fecal-orally are thriving because sanitation is not advanced, and the water systems are not at their best. This is giving rise to new and recurrent enteroviral diseases.

      To investigate and analyze this, a survey was done between 1990 and 2015. Here, climate changes were recorded, as well as how society responded to those changes. It was observed that many outbreaks had occurred after heavy or extreme weather events (i.e. El Nino). People were unable to cope with the events along with the post-viral outbreaks, and as the years have gone, an increased number of extreme weather events and outbreaks occurring simultaneously were observed. These weather changes could have been due to the dramatic changes in weather, causing a rise in pathogenic diseases along with it.

      At this rate, is there a way to predict these extreme events and potentially out-beat global warming? Not only is human immunity is affected, but factors surrounding humans, such as agriculture, have been hit hard with this. If this continues any further, people will start facing more health problems, and more casualties will arise. If parasites such as G. strigosum and T. retortaeformis are thriving in rabbits due to global warming, then what is the chance that these parasites will further adapt and infect humans? If we can predict further global warming changes and take actions against it, then it is possible that these recurring outbreaks and new viruses will stop emerging and spreading globally.

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    • Rmichel, I am so happy you brought up this point because it just further points out how real and scary global warming is. Not only are parasites likes T. retortaeformis and G. strigosum infecting rabbits, but we as human beings have a continuous enemy that has been infecting us since the being of time, the mosquitos. Its latest attack has been the Zika virus; something that originated in Uganda but is now slowly creeping into North America. What is really scary is that it’s not just the mosquitos attacking us but other insects, like ticks. As climate change continues, temperatures increase. This works in favor of ticks because now their geographical regions are expanding. Ticks don’t just bite animals such as dogs, cats, deer, etc. but more and more are starting to bite humans too. It’s also alarming that they are not only spreading but becoming more abundant. The most common ticks are American dog ticks and blacklegged tick, which can have as many as five different pathogens in it at one time. It is becoming more and more evident that global warming is not working in our favor and I would love to see more action in trying to combat it because it is slowly killing us.

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  8. The effects of global climate change to our world seem to be underestimated. I must admit that, I personally, never paid attention to the catastrophic consequences global warming could have until I read this article. After the 75°F November Georgia experienced at the beginning of winter this year, I think many can agree that the effects of global climate change are becoming very evident. While global climate change seems to be snowballing, and putting a complete stop to global warming does not seem feasible, it is important to understand what we should expect. This study focuses on the increased risk of infection of rabbits caused by two parasites G. strigosum and T. retortaeformis. The attributes the rise of infection to two factors: high temperatures due to global climate change and the rabbits’ ability to produce a long-term infection based on their ability to produce an immune response. While T. retortaeformis is regulated by the rabbits’ immune responses, G. strigosum not.

    It is important to understand that although the article mentions that infection is very common in contaminated areas where sanitation is poor, this infection could impact anyone around the world particularly at this moment in time as millions of people migrate and export/import goods across the world everyday. A study points out that with this constant shift in temperatures coming about from the effects of global climate change cause animals to migrate and bring their parasites along with them too, spreading the possibility of infection even more.

    With that being said, it is crucial to put this article in the context of human lives. As winters get shorter and summers become longer, how could humans be confident that the meat and vegetables they purchase will not grown on helminth-infested soils and later imported to their local grocery store? Since no vaccination against helminth parasitic infections exist, would this be the right time to crack down on devising a vaccine against parasitic infections? Perhaps targeting parasites that cannot be controlled by human immune systems? If the world continues to be look the other way on global warming, we could be dealing with a parasitic pandemic…

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    • I agree with you on coming up with vaccines or ways to deal with parasitic infections in general due to climate changes. Warmer weather are the optimum temperature for most parasites including the helminth worm to thrive in. And since most parasites have evolved mechanisms to avoid our immune system, devising a plan now to deal or control the spread of the infection would prevent an epidemic from occurring. Climate change in general is affecting populations at large and not only young or old people. We are all prone to parasitic infection and the severity of infection is based on the state of an individual’s immune system. But sometimes even people with healthy immune system still fail to clear the infection. And with warmer weather coming, this should be alarming because we all are going to be at risk. Furthermore, Terrestrial parasites should not only be our only concern, but we should also turn our attention to aquatic parasites. People tend to be close to water during warmer weather and aquatic parasites host switching due to climate change is concerning. So therefore, I think it would be a good idea to also raise awareness on aquatic parasites so that people could take precautionary measures. And this in turn could also help reduce high incidence of parasitic infections due to climate changes. After all, parasites are ubiquitous.

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      • We know that early exposure to helminth infections provide greater immunity later in life, and so vaccination development is not far off or impossible, and indeed some already do exist.
        Further, helminth infections are easy to avoid with proper health education and sanitation improvements.. and so I don’t feel that helminthic infections should be a major concern with global warming. Despite being so common, they are easy to treat and easy to avoid, and thus minor efforts could be used to halt their progress (at least on a human scale).
        While there may not be many helminth-centered prophylactics available, there are plenty of very effective treatments such as albendazole and other benzimidazole derivatives.

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      • SM,

        You mentioned an important fact about water-borne diseases and how it will be more prevalent, now that is closer to summer. People will definitely be near water, and without proper water sanitation and hygiene, they will catch not only diseases like malaria, but also diseases such as schistosomiasis and legionellosis. Both are found in warm climates during hot seasons, and both unfortunately do not have vaccines to prevent or cure the disease it brings. Water treatments are taking place in local areas, but I hope that scientists can find a way to target highly-populated areas such as beaches and create treatment plans so that the spread of these types of diseases in this climate can significantly reduce.

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    • I agree with that the fact parasitic infection can have global repercussions in that transmission of the parasite can occur through transportation of contaminated soil used for human produce, cattle food, etc. However, I’m not sure if I agree that right now specifically would be a good time to “crack down” on devising a plan for vaccines that target parasites that cannot be controlled by humans. Helminths are strongly immunomodulatory. The problem lies in the fact that many helminths have defense mechanisms that allow them to evade the immune response as a host. Often times, the pathogenicity of parasites is a result of this evasion of the immune system. Rather then look for preventative measures targeting non-immunogenic parasites capable of infecting humans, I think further research on the mechanism of evasion by these parasites would be more beneficial. Information gathered from evasion mechanisms can then be applied to vaccine research, and/or treatment.

      Another thing to keep in mind is the fact that the information derived from animal model studies of parasite infection must be taken with a light hand as that information may not apply to humans. Application of the results from the study to humans should be done lightly. The notion that the wild rabbits in the older generation carrying more severe infection as a result of no immune response to G. strigosum does not necessarily apply for humans because humans are capable of producing a strong response to parasite infections. Additional factors may play into the dynamic that exists between the older population of rabbits and increased infection severity.

      Additionally, antibody and cell- mediated responses are an important factor in parasite infection, but the adaptive immune response is what limits the susceptibility to infection. Upon reading the blog post: A “Priming” Mechanism Contributes to Immunological Memory in T Cells, natural killer cells seem to be a likely avenue of research against parasite infections as the activation of NK cells is a response to the innate immune system. If NK cells are possibly capable of “priming,” as suggested in the post, then perhaps a focus on NK cells in response to parasite infection would be beneficial to study.

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      • I agree that vaccine development should not be a primary concern at the moment, but that’s not to say that some sort of therapeutic or treatment-based measure should not be taken. According to the linked WHO page, a periodic treatment of helminth infections is already available to those who are highly susceptible. Also, a good method of prevention is to thoroughly wash and cook food before eating. For the most part this preventative measure already takes place in more developed countries so the issue is more localized to less developed countries. That being said, there shouldn’t be much of a concern for increased helminth infections as a result of climate change. A review article touches on the mechanism of immune evasion by parasites. If the mechanism by which helminths avoid immune attacks should continue to be studied, it is important to focus on the activity of IgE and eosinophils, as they become highly prevalent during a parasitic infection.

        The above observation that climate change influences the migration of helminth vectors to areas where these parasites were not previously prevalent is interesting and should be studied further. It’s possible for a new parasite to be introduced to a new area. Since it is unlikely that anyone from that area has been exposed to that parasite, the consequences can be fairly lethal. It’s true that carrying the results of a study based on rabbits and two very specific helminths to a human context is rather premature, but increasing the scope of possibilities in terms of potential new parasites should be heavily considered.

        Immunological modulation and evasion by helminth parasites in human populations

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  9. The lack of immunity leading to a severe infection in the older population may not be the only reason for the positive correlation between infection severity in the older population of rabbits and rising climate change. Studies show heat stress has been positively correlated to a weakened immune response. A study showed heat stress (and humidity) in hens resulted in significant decrease in body weight, feed consumption, and egg production. White blood cells count decreased, and mortality rates were higher among hens exposed to heat compared to the control group. Another study showed weakened innate immunity response and increase virulence in mice infected with Influenza virus H5N1 when exposed to chronic heat. If innate immunity is weakened, the adaptive innate response will also be affected, and thus the ability to provide a strong immune response under warmer conditions.

    The rate of rising global climate has been directly affected by humans. Changes in habitat for wild rabbits due to deforesting, fire, etc. could cause the wild population of rabbits to migrate, allowing for the interaction with new species of parasites. Stress hormones released due to changing environments in conjugation with the actual temperature change can significantly impact a rabbit’s immune system, ESPECIALLY in the older population. Perhaps the increase in infection in the older generation is due to the profound effect the heat has on the immune system? Perhaps the “non-immunogenic” parasite does indeed produce an immune response in the older population of rabbits but they cannot effectively clear the infection due to the stronger impact the heat has on their aged immune system. Global warming significantly impacts human health, and its affect can also be observed in animals. The increase in infection severity in response to rising climate warming may be a product of longer surviving infectious parasites in conjugation with the lack of immune response in wild rabbits, but there are other factors that may explain the increase in infection severity primarily among older generations. It would be interesting to study/observe exactly how the immune system recognizes the immunogenic Trichostrongylus retortaeformis parasite, as the information regarding biology and life cycle of the non-immunogenic Graphidium strigosum is scarce.

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