After the pandemic is before the pandemic – and it’s our own fault. Using the example of the hendra virus, a study shows how we could better get the threat posed by zoonoses under control.
Although many complex relationships in ecosystems have been known for a long time, they do not prevent us from further intervening in them – without having an eye on the consequences. A current example provides an in Nature published Study from Australia.
Deadly hendravirus
The team led by Peggy Eby from the University of New South Wales focused their research on the zoonotic Hendravirus, also called equine morbillivirus. The cloaked RNA-Virus was first isolated from horses and humans in Hendra, Australia, in 1994. The main hosts are flying foxes, whose infection is asymptomatic. Horses become intermediate hosts by coming into contact with fruit bats’ saliva or excrement. This can happen, for example, by spitting out fruit or fruit stones on the paddock when flying foxes sleep in stables or help themselves to drinkers and feeding troughs. Infected horses develop loss of appetite and respiratory infections with fever, which lead to death in the majority of the animals within a week. If humans come into contact with nasal discharge, saliva, urine or blood from horses, they too can become infected. The incubation period is one to three weeks. So far so known.
| follow the channel pin for further infectiology topics. consequences |
Less space = more proximity = greater risk
In their publication, however, the authors show an exciting connection that we as humans have a direct influence on. In the investigated area in Australia, the flying foxes usually migrate long distances between flowering eucalyptus trees to get their food – the nectar of the flowers. In summer many trees bloom, in winter the food sources are scarce. During these periods of hunger, which last several weeks, the flying foxes change their usual behavior, form small groups temporarily and eat fruit in gardens and agricultural regions. So you spend significantly more time around people and pets.
When enough trees bloom again, they return to their usual behavior. Up until 2002, the phases observed by the researchers, which lasted several weeks, with more proximity to humans did not pose a problem – there were no infections with hendraviruses. In 2002, however, a turning point appeared to have been reached. At the start of the study, around 70 percent of the flying foxes’ habitats had already been destroyed, according to the authors. In the period up to 2018, however, the animals lost another third of their habitat – and with them their natural food sources. The trees also blossomed because of the climatic changes fewer. The winter contingency program became the norm. The flying fox population stayed in small groups and always got their food close to humans. As a result, as of 2006, Hendravirus outbreaks occurred in horses and humans in 80 percent of the years.
Animals adapt
During that time, 84 of the 112 infected horses and four out of seven infected humans died. The researchers were also able to observe that this mechanism is reversible. If, in some years, more of the remaining eucalyptus trees blossomed again, the animals behaved as before and flew to their original food sources. In those years, the group around Eby did not record any infections either. The authors emphasize that their data confirm what has long been warned of: the destruction and use of wild animal habitats makes new zoonoses more likely.
Also in Report of the World Biodiversity Council It says: “The causes of pandemics are the same global environmental changes that are also driving biodiversity loss and climate change.” According to the report, there are up to 1.7 million undetected viruses in the animal kingdom, of which 827,000 are potentially infecting humans be able. The experts write: “The pandemic risk is driven by the exponentially increasing anthropogenic changes.” It is wrong to blame wild animals for the occurrence of diseases, “because the emergence or spread of these diseases is caused by human activities and the effects of these activities on the environment.”
Image source: Doruk Yemenici, unsplash