Explore the rare and deadly fungal infection blastomycosis and its journey through mammalian lungs, skin, intestines, and brain. Learn about the role of pathogenic fungi in the transition from dinosaurs to mammals, and how our warm-bloodedness protects us from fungal infections. Discover the ecological and global distribution of blastomycosis, and the potential impact of climate change on its growth. This episode has it all - dinos, dogs, deep time, and deadly outbreaks!
Blastomycosis, caused by Blastomyces species, is a rare but potentially deadly fungal infection that can affect various organs in the body.
Understanding the ecological traits of fungal pathogens in their natural habitats can provide insights into their pathogenicity and aid in the development of new antifungal treatments.
The emergence of endothermy in mammals has provided a significant advantage in protecting against systemic fungal infections, although it comes at an energetic cost.
Deep dives
Blastomycosis: A Challenging Fungal Infection
Blastomycosis is a fungal infection caused by Blastomyces dermatitidis and Blastomyces gilchristii. The disease can affect various organs in the body, with pulmonary infections being the most common. Pulmonary blastomycosis can range from minor pneumonia to severe acute respiratory distress syndrome. Skin involvement is also common, manifesting as nodules, plaques, ulcers, or abscesses. Other sites of infection include the bones, genitourinary tract, and central nervous system. The fungus is thermally dimorphic, existing as a mold in the environment and transforming into yeast in the host. The infection is challenging to diagnose and treat, requiring prolonged antifungal therapy. While blastomycosis can affect immunocompetent individuals, those with compromised immune systems are at higher risk for severe infections and mortality. The ecological traits of blastomyces, such as thermotolerance and evasion of host immune responses, contribute to its pathogenicity. Understanding the natural ecology and interactions with other microbes in the environment can help in the development of new antifungal treatments.
Fungal Infections and Ecological Perspectives
Fungal infections pose a significant global burden, with millions of cases and deaths reported each year. Many fungal pathogens are opportunistic, causing infections in immunocompromised individuals or inadvertently infecting humans. Understanding the ecological traits of these fungi in their natural habitats, such as soil, can provide insights into their pathogenicity. Traits like thermotolerance, adaptability to varying oxygen levels, and effective evasion of predators or competitors contribute to their success in the environment and their ability to infect humans. Exploring the microbial interactions and microbial products in these ecosystems can help in the development of new antifungal treatments. Unlike viral and bacterial pathogens, fungi exhibit unique pathogenic traits that require a different approach to diagnosis, treatment, and risk assessment.
The Evolution and History of Blastomycosis
Blastomycosis, caused by Blastomyces species, has likely existed for millions of years. The fungal genus Blastomyces emerged about 150 million years ago. Blastomycosis cases may have occurred in prehistoric communities based on skeletal remains. However, blastomycosis was officially identified and described by Thomas Casper Gilchrist in the late 1800s. At that time, fungi were classified within the plant kingdom, but Gilchrist correctly recognized blastomycosis as a fungal infection. The understanding of fungal pathogens in humans was still developing, and blastomycosis was one of the first fungi identified as a human pathogen. The disease's history and prevalence in North America highlight the need for early diagnosis and treatment of this challenging fungal infection.
Endothermy as a Defense against Fungal Infections
The emergence of endothermy in mammals, characterized by the constant maintenance of body temperature, has provided a significant advantage in protecting against fungal infections. Most fungi are adapted to thrive in environmental temperatures, while mammals maintain higher body temperatures that are too hot for the majority of fungal pathogens to handle. This trait, known as endothermy, serves as a defense mechanism against systemic infections, as mammalian immune systems, particularly macrophages, effectively combat these pathogens. While endothermy provides protection, it comes at an energetic cost, as mammals require higher energy consumption to maintain their body temperature. Nevertheless, the evolution of endothermy remains a complex interplay between thermoregulation, enhanced aerobic capacity, and parental care.
Blastomycosis and Environmental Adaptation
Blastomycosis, caused by the Blastomyces dermatitidis fungus, is an environmental pathogen mainly found in the United States, particularly in the Midwest, Southeast, East, and parts of Canada. It is also reported in several regions in Africa and India. The fungus thrives in damp, sandy soils with a high presence of rotting wood, often near lakes or rivers. The epidemiology of blastomycosis is challenging to determine due to under-reporting and limited data, as it is not a reportable disease in most areas. The prevalence of blastomycosis is seasonally influenced, with higher case numbers in autumn and spring. With the anticipated effects of climate change, including increased rainfall and higher temperatures, there may be changes in the distribution and incidence of blastomycosis. This highlights the importance of understanding the impact of environmental changes on fungal infections and their potential public health implications.
Fungal infections don’t often make an appearance on this podcast, but when they do, you know you’re in for a wild ride. In this episode, we explore the rare but potentially deadly fungal infection blastomycosis. We trace the journey of Blastomyces spores as they depart from their cozy homes of decomposing wood and make their way first into mammalian lungs before possibly moving into the skin, intestines, and brain. How and why these fungi can be so deadly is our next stop, one that takes us into an unexpected direction: the fall of dinosaurs, the rise of mammals and the role that pathogenic fungi played in this transition. We delve into why comparatively few fungi are pathogenic to humans and how our warm-bloodedness may protect us. But, as we discuss in the episode’s conclusion, that protection may be weakened as our warming planet selects for fungi that can tolerate increasing temperatures. Dinos, dogs, deep time, and deadly outbreaks - this episode has it all.
