Blood-sucking assassin bugs transmit the causative agents of the widespread Chagas disease in Central and South America. Since the disease can cause severe symptoms and there is as yet no vaccine against the causative trypanosoma parasites, the main focus at present is to fight assassin bugs and kill them with insecticides. The parasitologists and infection biologists Fanny Eberhard and Prof. Sven Klimpel from the Goethe University Frankfurt, the Senckenberg Society for Nature Research and the LOEWE Center for Translational Biodiversity Genomics, in collaboration with scientists from the Instituto René Rachou in Belo Horizonte, Brazil, have now investigated how Chagas -Trypanosomes change the bacterial community in the gut of assassin bugs. To do this, they used genetic analyzes with which they were able to compare the composition of the bacterial community in the bug's intestine, the microbiome, before and after infection with the pathogen (metagenomic shotgun sequencing).
According to estimates by the World Health Organization (WHO), between six and seven million people worldwide, mainly in Central and South America, are infected with trypanosomes of the species Trypanosoma cruzi. The unicellular (protozoal) parasites cause Chagas disease (American trypanosomiasis), which is unremarkable in the acute phase: only in every third case do the infected develop symptoms at all, which can then also be unspecific, such as fever, hives and swollen lymph nodes . But the parasites remain in the body, and many years later, chronic Chagas disease can become life-threatening, with abnormal enlargement of the heart and progressive paralysis of the gastrointestinal tract.
Chagas trypasomaniacs are transmitted by blood-sucking predatory bugs of the insect subfamily Triatominae. With their sting, they pick up the trypanosomes that settle in the intestines of the assassin bugs. Through the droppings, which the bedbugs usually deposit next to the sting, they excrete the pathogen, which is often unintentionally rubbed into the wound when scratching the severely itchy sting.
When examining how Chagas' trypansosomes change the bacterial community in the gut of assassin bugs, the parasitologists and infection biologists found that the diversity of bacteria in the bug's gut decreased significantly after infection. The researchers also managed to identify four types of bacteria that probably assume important functions for the assassin bug, such as the synthesis of B vitamins.
Fanny Eberhard explains: “Vitamin B is one of the nutrients that blood-sucking insects do not receive through their blood meals. Vitamin B-producing bacteria are therefore very important for assassin bugs, occur in practically all individuals and also remain in the assassin bug gut for generations. Such bacteria are therefore potentially suitable for being equipped with genes for antibodies against Chagas trypanosomes.”
Prof. Sven Klimpel continues: “Ultimately, it is our goal that the assassin bugs defend themselves against Chagas trypanosomes and in this way the infection of humans is prevented. However, before one can endow bacteria with such properties and then release assassin bugs with those bacteria, we need to better understand what the ecology of the assassin bug gut looks like and how the profound interactions between host, pathogen and microbiome take place. Our work makes an essential contribution to this.”