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Human intervention in the natural environment of Panama, such as deforestation and agriculture, not only affects biodiversity, but also increases the risk of infection with the pathogen that causes tropical Chagas disease, which can affect both animals and humans. This is shown by the results of a study by wildlife ecologists from Ulm University, which has been published in the scientific journal "One Health". The researchers analysed small mammals in various habitats: from pristine rainforests to commercial timber plantations. The study provides new insights into how land use and changes in biodiversity can contribute to the spread of zoonotic pathogens
When night falls in Panama's forests, the time of the opossums begins. The marsupials, which have spent the day sleeping in trees, climb down the trunks and search for fruit, frogs or eggs on the ground. The omnivores often carry a hazardous parasite - the Chagas disease pathogen. A new study by Ulm University has now shown: The more humans intervene in nature, the more host animals are infected with Trypanosoma cruzi, and the more the tropical disease spreads.
"Our results show how human influence affects the diversity of wild animals - and how the loss of biodiversity changes the dynamics of pathogens," says first author Dr Magdalena Meyer from the Institute of Evolutionary Ecology and Conversation Genomics at Ulm University. For their study, the researchers examined more than 800 small mammals at 23 locations in a region around the Panama Canal - in pristine rainforests, on protected islands, in fragmented forest patches and in teak monocultures.
Opossums are spreading - and increasing the risk of infection
The researchers found that the composition of the wildlife communities changed. In disturbed habitats, it was primarily the adaptable opossums that prevailed. Because the marsupials are particularly susceptible hosts, the Chagas pathogen also benefited from this. "The reinforced spread of opossums increases the hazard of the pathogen jumping to livestock, pets or humans," explains Dr Meyer. At the same time, the scientists observed that the genetic diversity of another host species - the spiny rat - decreases in disturbed habitats. This also favours the spread of the pathogen.
The results of the study, which was published in the scientific journal "One Health", have direct implications for health protection: millions of people worldwide are affected by Chagas disease, particularly disadvantaged population groups in Latin America. However, this neglected tropical disease receives little international attention. "Our research impressively shows how closely human, animal and environmental health are linked within the meaning of the One Health approach," emphasises study leader Professor Simone Sommer. "The best protection against the spread of such diseases is the preservation of intact ecosystems with their natural biodiversity."
The study was funded as part of the DFG Priority Programme "Ecology and Species Barriers in Novel Viral Diseases".
About Chagas disease
Chagas disease is caused by the single-celled parasite Trypanosoma cruzi. The main vectors are blood-sucking predatory bugs, which usually pass on the pathogen via faeces or urine when they bite humans or animals in search of blood meals. In addition to humans, more than 180 wild and domestic animal species can serve as hosts, which makes combating the disease particularly difficult. According to the World Health Organisation, six to seven million people are infected worldwide, with around 75 million people living in risk areas - mainly in Latin America. If left untreated, the infection can lead to severe heart or digestive problems, which can be life-threatening. Although there are drugs that are effective in the early stages of the disease, there is no vaccine. The disease is currently spreading - favoured by climate change, which is creating new environmental conditions in which the predatory bug can establish itself as a vector.
Dr Magdalena Meyer, Institute of Evolutionary Ecology and Conversation Genomics, Mail: magdalena.meyer@uni-ulm.de
Magdalena Meyer, Georg Eibner, Alexander Christoph Heni, Kerstin Wilhelm, Simone Sommer: Changes in biodiversity drive trypanosome infections of wildlife in Panama.
One Health, Volume 21, 2025, 101113, ISSN 2352-7714.
DOI: https://doi.org/10.1016/j.onehlt.2025.101113
Opossums had the highest infection rates with Trypanosoma cruzi in the area studied
Source: Alexander Heni
Copyright: Alexander Heni
During the fieldwork in Panama, the researchers set 300 live traps at each of the 23 sites
Source: Ruben Gunzenhäuser
Copyright: Ruben Gunzenhäuser
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Opossums had the highest infection rates with Trypanosoma cruzi in the area studied
Source: Alexander Heni
Copyright: Alexander Heni
During the fieldwork in Panama, the researchers set 300 live traps at each of the 23 sites
Source: Ruben Gunzenhäuser
Copyright: Ruben Gunzenhäuser
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