Scientists have discovered an “abundant” amount of potentially disease-causing yeasts in the digestive tracts of brown locust samples collected from swarms near Middelburg in 2022, the largest outbreak ever recorded in the region.
A new study by researchers from the University of the Free State (UFS), the National Health Laboratory Service, and the University of Venda has confirmed for the first time that common brown locusts are carriers of pathogenic yeasts that can cause severe infections in humans — especially in people with compromised immune systems or who are seriously ill.
The Dispatch extensively reported about the destruction caused by major swarms in 2021 and 2022, which Agri Eastern Cape president Peter Cloete said had been the largest recorded locust outbreak ever.
The swarm spread through Addo, Pearston, Aberdeen, Jansenville, Graaff-Reinet, Cradock, Middelburg, Somerset East, Tarkastad, Dikeni and Stutterheim.
In April 2021, The Herald reported how Sterkfontein farmer Jannie Louw, 36, watched as his crops were wiped out in less than three hours by a locust swarm.
The insects reached the Buffalo City Metro region in May.
Graaff-Reinet, Cradock, Richmond and Middelburg had been plagued by locusts since the start of the year.
Parts of the swarm made it through East London, with the brown insects fluttering about the parking lot of the Daily Dispatch.
The study — “South African brown locusts, Locustana pardalina, host fluconazole-resistant, Candidozyma (Candida) auris (Clade III)” — highlights for the first time the presence of the pathogenic (disease-producing) fungal yeast C. auris in the digestive tract of the locusts, and shows their potential in disseminating this emerging pathogen.
Research started in April 2022, when 20 gregarious (swarming) adult locusts were collected during the locust outbreak which occurred from September 2021 to May 2022 in the semi-arid Eastern Karoo region in the Eastern Cape.
The study is still under peer review.
According to Prof Carlien Pohl-Albertyn, National Research Foundation (NRF) SARChI Research Chair in Pathogenic Yeasts, three C. auris strains were isolated from three different adult locusts, two of which also harboured strains of another potentially pathogenic yeast, Candida orthopsilosis.
Pohl-Albertyn said: “The fact that we were able to isolate C. auris from 15% of the sampled locusts, using non-selective media and a non-restrictive temperature of 30°C, may indicate that C. auris is abundant in the locusts and that specific selective isolation is not mandatory.
“Interestingly, C. auris was isolated from the fore- and hindgut of the locusts.
“Isolation from the foregut, which is dedicated to food intake and storage, filtering and partial digestion, indicates that C. auris was probably obtained by the locusts via feeding activities.
“Isolation from the hindgut confirms that C. auris can survive the digestive processes in the midgut and is likely to be released back into the environment via faeces.”
Healthy humans are not at great risk, explained Pohl-Albertyn, who is also a professor of microbiology in the UFS department of microbiology and biochemistry.
“Healthy humans are not at great risk for infection by this yeast and there is now no proof that ingestion may be harmful to them,” she said.
“This is unfortunately not the case for people with compromised immune systems or who are seriously ill.”
One of the C. auris strains was studied in more detail.
According to UFS, the strain is not resistant to disinfectants, but shows decreased susceptibility to the common antifungal drug fluconazole.
“This is a characteristic of this yeast species and thus not surprising.
“Most of the emerging pathogenic yeasts show this intrinsic resistance.
“This highlights the urgent need to discover and develop new antifungal drugs.”
Pohl-Albertyn said treatment options were available, using other antifungal drugs, but C. auris could become “resistant to all the now available antifungal drugs”.
“The fact that locusts are a food source for other animals, such as birds, could lead to eventual distribution of the yeast to people.”
Daily Dispatch