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New study finds emerging pathogen inside brown locusts

17 February 2025 | Story Andre Damons | Photo Supplied

Prof Carolina Pohl-Albertyn — Prof Carlien Pohl-Albertyn is the NRF SARChI Research Chair in Pathogenic Yeasts at the UFS.

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 study, ‘South African brown locusts, Locustana pardalina, hosts 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. The research started in April 2022, when 20 gregarious (swarming) adult locusts were collected during a large 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. “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,” Prof Pohl-Albertyn said.

“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

One of the C. auris strains was studied in more detail. This strain was not resistant to disinfectants but showed 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.

Prof Pohl-Albertyn, also a Professor of Microbiology in the UFS Department of Microbiology and Biochemistry, says, “Healthy humans are not at great risk for infection by this yeast and there is currently no proof that ingestion may be harmful to them. This is unfortunately not the case for people with compromised immune systems or who are seriously ill. However, few susceptible people come into direct contact with the locusts in South Africa.”

She added that there are treatment options available, using other antifungal drugs, but C. auris can become resistant to all the currently available antifungal drugs.

Importance of the study

“The fact that locusts are a food source for other animals, such as birds, could lead to eventual distribution of the yeast to people. In other countries, wild locusts are a food source for humans and there more direct transmission may be possible,” Prof Pohl-Albertyn said.

She explained that this study tries to answer questions regarding the natural hosts of this emerging pathogen and how it may facilitate the spread of the pathogen to the rest of the environment. The study is one part of the puzzle regarding how new pathogens may emerge from the environment and spread to people.

“One of the questions in the field of pathogenic yeasts is how C. auris was able to emerge as a pathogen in several different countries in a relatively short period. It is well known as a hospital-acquired pathogen, but it is not known where in the environment it occurs naturally, and which environmental factors may have shaped its evolution and ability to cause human infections. This has implications for the prevention of the spread of this specific yeast species, as well as our preparedness for new pathogenic yeasts that may be emerging from the environment.”

News Archive

Is milk really so well-known, asks UFS’s Prof. Osthoff

2011-03-17

Prof. Garry Osthoff
Photo: Stephen Collett

Prof. Garry Osthoff opened a whole new world of milk to the audience in his inaugural lecture, Milk: the well-known (?) food, in our Department of Microbial, Biochemical and Food Biotechnology of the Faculty of Natural and Agricultural Sciences.

Prof. Osthoff has done his research in protein chemistry, immuno-chemistry and enzymology at the Council for Scientific and Industrial Research (CSIR) in Pretoria and post-doctoral research at the Bowman-Grey School of Medicine, North Carolina, USA. That was instrumental in establishing food chemistry at the university.

He is involved in chemical aspects of food, with a focus on dairy science and technology. He is also involved in the research of cheese processing as well as milk evolution and concentrated on milk evolution in his lecture. Knowledge of milk from dairy animals alone does not provide all the explanations of milk as food.

Some aspects he highlighted in his lecture were that milk is the first food to be utilised by young mammals and that it is custom-designed for each species. “However, mankind is an opportunist and has found ways of easy access to food by the practice of agriculture, where plants as well as animals were employed or rather exploited,” he said.

The cow is the best-known milk producer, but environmental conditions forced man to select other animals. In spite of breeding selection, cattle seem not to have adapted to the most extreme conditions such as high altitudes with sub-freezing temperatures, deserts and marshes.

Prof. Osthoff said the consumption of the milk as an adult is not natural; neither is the consumption of milk across species. This practice of mankind may often have consequences, when signs of malnutrition or diseases are noticed. Two common problems are an allergy to milk and lactose intolerance.

Allergies are normally the result of an immune response of the consumer to the foreign proteins found in the milk. In some cases it might help to switch from one milk source to another, such as switching from cow’s milk to goat’s milk.

Prof. Osthoff said lactose intolerance – the inability of adult humans to digest lactose, the milk sugar – is natural, as adults lose that ability to digest lactose. The symptoms of the condition are stomach cramps and diarrhoea. This problem is mainly found in the warmer climates of the world. This could be an indication of early passive development of dairy technology. In these regions milk could not be stored in its fresh form, but in a fermented form, in which case the lactose was pre-digested by micro-organisms, and the human population never adapted to digesting lactose in adulthood.

According to Prof. Osthoff, it is basically the lactose in milk that has spurred dairy technology. Its fermentation has resulted in the development of yoghurts and all the cheeses that we know. In turn, the intolerance to lactose has spurred a further technological solution: lactose-free milk is currently produced by pre-digestion of lactose with enzymes.

It was realised that the milks and products from different species differed in quality aspects such as keeping properties and taste. It was also realised that the nutritional properties differed as well as their effects on health. One example is the mentioned allergy against cow’s milk proteins, which may be solved by the consumption of goat’s milk. The nutritional benefits and technological processing of milk aroused an interest in more information, and it was realised that the information gained from human milk and that of the few domesticated species do not provide a complete explanation of the properties of milk as food. Of the 250 species of milk which have been studied, only the milk of humans and a few domesticated dairy animals has been studied in detail.

Media Release
15 March 2011
Issued by: Lacea Loader
Director: Strategic Communication
Tel: 051 401 2584
Cell: 083 645 2454
E-mail: news@ufs.ac.za

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