Is Climate Change affecting the abundance of disease?
In this post, I will be presenting information that I found through literature that supports climate change affecting the abundance of diseases. Also, a PowerPoint is attached. I presented this in Dr. Sutton’s Ecosystem Science and Management at Tennessee State University in November of 2018. Please use the information to continue your knowledge expansion and reference accordingly!
WARNING: LENGTHY POST BUT HIGHLY EDUCATIONAL
Climate change is increasing the occurrence of diseases, affecting ecosystems across the world. This poses a great threat to biodiversity, survival of wildlife, and food production.
We know the implications of climate change – the how and why. Diseases are not completely overlooked, but it needs to addressed more often.
There are factors that can easily identify climate change; warmer and shorter winters, changes in hydrology, and when it comes to plants: “…the adaptive potential of plant and pathogen populations may prove to be one of the most important predictors of the magnitude of climate change effects” (Das et al 2016).
This proclamation is supported by a commonly known idea called the Disease triangle. It is composed of susceptible host, favorable environments, and the pathogens. The “…change in temperature and other climatic factors make the plants more vulnerable to pathogens that are currently not important, owing to unfavorable climate” (Das et al 2016).
We have discussed how climate change has affected animal phenology by either delaying or hastening plant growth out of sync with animal reproduction seasons. That results in young deaths, such as the reindeer calves. The same happens to plants, but in terms of being susceptible to diseases from stress: “phenology and physiology of the host are also affected by climate change, thereby affect its virus susceptibility and virus ability to infect” (Das et al 2016).
With an increase of global temperature, the range of plants being able to grow in other places is increasing. But with the shipping of plants to different climatic regions, their pathogens tend to follow. “Pathogens will follow their migrating hosts and because of their rapid response to small environmental changes, they may provide good early warning of impending climate change” (Chakraborty et al 1998). If a pathogen is infecting a plant where it has not been reported before, you can tell about how the environment is changing based on what disease was found.
Climate change presents many challenges to plant disease management:
–Demand for food and production yield: The global population growth means we have to find a way to support the people, and in supporting the population an “increasing demands for total, safe, and diverse foods (are needed) to support the blooming global population and its improving living standards; (thus) reducing production potential in agriculture due to competition for land in fertile areas and exhaustion of marginal arable lands”. Global growth intensifies global climate change, which will only then increase environmental problems.
–Depletion of natural resources: Our ways of agriculture are “deteriorating ecology of agro-ecosystems and depletion of natural resources” which is unsustainable. Depletion of natural resources can set off a domino effect where when a certain component is gone, it affects the other, and so on and so forth that will increase disease occurrence and create stress for plants.
-Risk of epidemics: The “increased risk of disease epidemics resulting from agricultural intensification and monocultures” is seen every day. This is basically an iteration of the demand for food and production yield. The demand has increased each year, when means that the maintenance of the crops is left to chemical treatments which not only degrade the environment but it creates resistance in diseases because of the genetic recombination that will be discussed later in the presentation.
-“Resistant” cultivars/varieties: almost futile – in nature “host plant and pathogens are constantly changing with pathogens evolving net pathogenicity to overcome host defense systems and plants evolving to reduce pathogen attack” (Das et al 2016); “importantly, many fungi are flexible in their ability to undergo genetic recombination, hybridization or horizontal gene transfer, causing the clonal emergence of pathogenic lineages also allowing the formation of novel genetic diversity leading to the genesis of new pathogens” (Fisher et al 2012).
With winters becoming warmer and shorter, the “down time” for disease populations to be reduce barely makes an impact on the population.
Ahanger et al 2013 states “climate change may alter the growth stage, development rate, pathogenicity of infectious agents, and the physiology and resistance of the host plant”. A longer growth stage, advancement of development rates, and stress of the plants from extreme temperatures create extreme changes that “…may result in geographical distribution, increased overwinter, changes in population growth rates, increases in the number of generations, extension of the development that season, changes in crop-pest synchrony, changes in interspecific interactions and increased risk of invasion by migrant pests” (Ahanger et al 2013).
The higher CO2 concentrations can result “in greater fungal spore production” and the “evolutionary forces act on massive pathogen populations boosted by a combination of increased fecundity and infectious cycles under favorable microclimate” (Ahanger et al 2013).
The “plant of structural diversity and habitat complexity can influence the composition, abundance, and distribution of animals that play important roles in the transmission cycles of some human diseases” (Pongsiri et al 2009).
Forestry:
“have been losses to individual tree species due to new pathogens such as Phytophthora ramorum” (Boland et al 2004)
Chestnut Blight (Cryphonectria parasitica), White Pine blister rust (Cronartium ribicola), Dutch Elm disease (Ophiostoma ulmi), beech bark disease (Cryptococcus fagisuga insect and Neonectria canker fungi)
Soil-borne pathogens:
“High moisture favors foliar diseases and some soil-borne pathogens such as Phytophthora, Pythium, R. Solani, Sclerotium rolfsii” (Das et al 2016)
Wildlife: hit button for quote about wildlife first
“Many fungi in the phylum Ascomycota are common soil organisms and are tolerant of salinity with the consequences that, when they enter the marine system through freshwater drainage, they are able to infect susceptible hosts such as corals, sea otters, and the nest of loggerhead sea turtles (Fusarium solani)” Fisher et al 2012
“The best studies in fungal isolate that can affect both animals and plants is Fusarium oxysporum f. sp. Lycopersici which can kill both immunodepressed mice and tomato plants” Sexton, Howlett 2006
Cattle Plague (rinderpest virus)
New races:
“Given that the rate of intra- and inter-lineage recombination among fungi will be proportional to the contact rates between previous geographically separate populations and species, these data from across plant and animal fungal pathosystems suggest that the further evolution of new races is inevitable given current rates of homogenization of previously allopatric, geographically separate, fungal lineages” Fisher et al 2012
Human Health:
“An extreme example is the genus Fusarium, with species that cause diseases in thousands of plant species as well as in animals, including humans” Sharon, Shlezinger 2013
From https://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-fusarium-infection:
Some clinical manifestations in immunocompetent patients are keratitis, onychomycosis, deep cutaneous infections; in immunocompromised patients are sinusitis, pneumonia, cutaneous lesions, fungemia, and disseminated disease.
The difference between immunocompetent and immunocompromised is competent means that the immune system is functional while compromised means that the immune system has been impaired by a disease or treatment. Examples of immunocompromised patients are: AIDS, cancer, transplants. Examples of immunocompetent patients is us.
“The soil-borne fungus Chaetomium globosum can infect plant roots endophytically without inducing disease symptoms and can control infection by some plant-pathogenic fungi. The airborne spores of this fungus can cause invasive diseases with life-threatening symptoms, such as pneumonia, in immune-compromised patients” Sexton, Howlett 2006
“Fungal secondary metabolites are widely recognized for their toxic, mutagenic, and carcinogenic impacts on vertebrates, and the production of aflatoxin by Aspergillus flavus on contaminated grain and peanuts that is stored in damp conditions is connected to increasing numbers of aflatoxin-induced liver cancers world-wide” Fisher et al 2016
Primarily linked to citrus plants and tobacco, but is now infesting vegetables, medicinal herbs, watersheds, forest trees, recycling irrigation water, and woody ornamentals (Panabieres et al 2016)
It is found on over five continents with a host range of 255 species and can withstand many different climates (Panabieres et al 2016)
Reproduction features are called sporangiophores which are sensitive to the environment – when humidity, temperature, and other favorable conditions are present, it will release zoospores. Zoospores swim freely in water. This is how it moves from site to site and is the primary pathway for genetic recombination (Panabieres et al 2016)
Phytophthora nicotianae is a hemibiotrophic pathogen – it forms an intimate relationship with the host plant cells then it causes the host cell to die. P. nicotianae inhibits the plant response pathways, and begins to suffocate the cells. (Panabieres et al 2016, Kong et al 2017)
Increase stress tolerance:
“Increased emphasis should be placed on breeding plants for environmental stress tolerance as drought stress increases” Boland et al 2004
New Identification Techniques:
“New techniques that enhance the identification and development of host tolerance or resistance to biotic and abiotic diseases will be important in facilitating this adaptation” Boland et al 2004
Consider species selection:
“Because of the long-lived nature of trees, and accordingly the limited degree to which adaptation can occur, it will be increasingly necessary to consider these impacts in forest management including species selection, breeding, and site selection” Boland et al 2004
Microbial populations:
“Microbial populations or control agents also affect the plant-pathogen relationship” Das et al 2016
Evaluate efficacy:
“To cope with the predicted climate change, one can evaluate the efficacy of current physical, chemical, and biological control methods and also by adapting new tools and techniques” Das et al 2016
“First, there is a need to evaluate under climate change the efficacy of current physical, chemical, and biological control tactics, including disease-resistant cultivars, and secondly, to include climate scenarios in all research aimed at developing new tools and tactics” Das et al 2016
Understand pathogenesis and epidemic principles:
“Thus while an understanding of the pathogenesis and epidemic principles of plant pathogen and genetics, biological and physiological mechanisms of host plant defenses is important, so too is the knowledge of interactions with other microbial populations, and the ecological niche of the pathogen” Dun-chun et al 2016
Assess food security:
“Future plant disease management should aim to strengthen food security for a stable society while simultaneously safeguarding the health of associated ecosystems and reducing dependency on natural resources” Dun-chun et al 2016
“Providing safe and adequate food for society is always the most important task of plant disease management. Plant disease management should strive to ensure food security and social standards by increasing crop productivity, reducing food contamination by microbial toxins, and guaranteeing the supply of diverse and reasonable food prices” Dun-chun et al 2016
From Mary Oliver’s Upstream: “Teach the children. We won’t matter so much, but the children do. Show them daises and the pale hepatica. Teach them the taste of sassafras and wintergreen. The lives of the blue sailors, mallow, sunbursts, the moccasin flowers. And the frisky ones – inkberry, lamb’s quarters, blueberries. And the aromatic ones – rosemary, oregano.
Give them peppermint to put in their pockets as they go to school. Give them the fields and the woods and the possibility of the world salvaged from the lords of profit. Stand them in the stream, head them upstream, rejoice as they learn to love this green space they live in, its sticks and leaves and then the silent, beautiful blossoms.
Attention is the beginning of devotion.”






Courtesy of Dr. Byl PowerPoint on September 19, 2018