Although it might seem far-fetched, and like the stuff of which science-fiction movies are made, fungi can, and do, infect human brains, with fungal infections contributing to about 1.5m deaths a year.
In The Conversation, scientific researcher Rachael Dangarembizi writes that fungi are present everywhere in our environment: in the air, in the soil, in decaying plant material, on our skin, and even in the gut as part of our natural flora.
She writes:
Microscopic, disease-causing fungi can invade various parts of the body, leading to a range of symptoms and health problems.
As a neurobiologist who has been studying fungal infections of the brain for 10 years, I was part of a team that recently published a review discussing the emergence, and re-emergence, of fungal infections in Africa, especially in sub-Saharan Africa.
We concluded that Africa is suffering from a silent, but costly, epidemic of deadly fungal infections, primarily driven by a high burden of HIV infections, lack of access to quality healthcare, and unavailability of effective antifungal drugs.
What are fungal infections?
For the greater part of history, fungal infections were never a threat to human health, mainly because most of them cannot survive the warm human body temperature of 37°C. However, climate change and other environmental pressures have led to the emergence of species of fungi that are capable of surviving at human body temperatures.
Even then, our immune systems are quite capable of fighting against fungal infections. For instance, our bodies can create localised acidic environments, limit micronutrient availability and release antimicrobial agents.
However, when the immune system is weakened, fungi are able to evade our defences and avoid detection. They can generate bioactive agents which help them evade or adjust to the host immune response. Some adapt to survive in hostile, low-nutrient and low-oxygen environments.
Immunocompromised people are at risk of developing serious or life-threatening fungal diseases. Africa accounts for 67% of the global burden of HIV, and opportunistic fungal diseases are on the rise.
One example is cryptococcal meningitis, which emerged with the HIV pandemic in the late 1980s. Today, sub-Saharan Africa contributes about 73% of all global cases and deaths resulting from the disease.
Cryptococcal meningitis is caused by the fungus Cryptococcus neoformans, found in soil and bird droppings. Infection occurs when someone inhales fungal spores. It first leads to the development of a lung infection and later a fatal brain infection.
Cryptococcal meningitis is a leading cause of adult meningitis in sub-Saharan Africa and it’s associated with almost 20% of all Aids-related deaths. Effective treatments are unaffordable and inaccessible for most affected people.
Costs range between US$1 400 and US$2 500 per patient for a full two-week antifungal treatment course.
The development of cheaper drugs has been hindered by a limited understanding of how the fungus causes such extreme damage in the brain.
Another example of an HIV-related opportunistic fungal disease is pneumocystis jirovecii pneumonia. It’s caused by a ubiquitous, airborne fungus Pneumocystis jirovecii, passed on from person to person.
Pneumocystis hardly causes trouble in people with healthy immune systems, but they act as reservoirs and pass the infection to those with poor immune systems, who may develop serious symptoms including fever, a dry cough and trouble with breathing.
Pneumocystis jirovecii pneumonia occurs in 15%-20% of HIV patients who present with respiratory problems.
The diagnosis of pneumocystis jiroveci pneumonia is expensive and requires a well-equipped laboratory. In Africa’s poor urban and rural healthcare facilities this will be a challenge. The fungus, P. jirovecii, is also extremely difficult to culture, which limits diagnosis and research.
Growing burden
In our review, we found various factors driving the emergence and re-emergence of fungal threats. They include climate change, the spread of immunosuppressive diseases, medical advances such as organ transplants (the immune system is suppressed to minimise rejection), the use of immunosuppressants to manage inflammatory diseases, and the use of antibiotics.
While these factors are not unique to Africa, the burden of fungal diseases and the number of people who succumb to them is much greater.
The Covid pandemic seems to have made the global fungal burden worse. For instance, recent studies have shown that people who were infected with Covid and have recovered are vulnerable to infection with a fungus called mucormycosis, also known as the black fungus.
Covid-induced lung damage, high blood sugar, and the steroids often used to treat it, are all predisposing factors to black fungus infection.
With a reduced capacity to clear fungal spores and a reduced immune response, thanks to the steroids, the fungus can gain entry and infect the sinuses and facial bones, eventually moving to the brain.
But don’t we have antifungal drugs?
Most of those affected by fungal infections live in rural or poor urban settlements.
With poorly funded and overburdened healthcare systems, many African countries are not well prepared to deal with fungal infections. Additionally, some of the WHO-recommended antifungal drugs – such as flucytosine – are unavailable in most African countries. Ineffective and even rather toxic drugs are sometimes used instead.
The emergence of drug-resistant fungal strains is also a growing threat. Of great concern is the rise in multi-drug resistant Candida species, azole-resistant Aspergillus species and clinically resistant Cryptococcus.
Management strategies
Fungal threats are adding pressure to overburdened health systems with a limited arsenal of treatment options.
Healthcare professionals, scientific researchers, policymakers and governments must address the gaps in the diagnosis and management of fungal infections. This will help to improve capacity to deal with them.
Rachael Dangarembizi is a neuroinfections researcher, Division of Physiological Sciences, University of Cape Town.
Study details
Emerging and re-emerging fungal threats in Africa
Rachael Dangarembizi, Sean Wasserman, Jennifer Claire Hoving.
Published in Parasite Immunology on 29 September 2022
Abstract
The emergence of deadly fungal infections in Africa is primarily driven by a disproportionately high burden of human immunodeficiency virus (HIV) infections, lack of access to quality health care, and the unavailability of effective antifungal drugs. Immunocompromised people in Africa are therefore at high risk of infection from opportunistic fungal pathogens such as Cryptococcus neoformans and Pneumocystis jirovecii, which are associated with high morbidity, mortality, and related socioeconomic impacts. Other emerging fungal threats include Emergomyces spp., Histoplasma spp., Blastomyces spp., and healthcare-associated multi-drug resistant Candida auris. Socioeconomic development and the Covid-19 pandemic may influence shifts in epidemiology of invasive fungal diseases on the continent. This review discusses the epidemiology, clinical manifestations, and current management strategies available for these emerging fungal diseases in Africa. We also discuss gaps in knowledge, policy, and research to inform future efforts at managing these fungal threats.
Parasite Immunology article – Emerging and re-emerging fungal threats in Africa (Open access)
See more from MedicalBrief archives:
CDC reports a rise in multidrug-resistant fungus
Regulatory approval of flucytosine just a first step in treating of cryptococcal meningitis
Inside India’s ‘black fungus’ mucormycosis wards
Mucormycosis: The deadly ‘black fungus’ afflicting COVID-19 patients in India
Regimen change may halve cryptococcal meningitis deaths