How vampire bats became bloodthirsty decoded

Vampire bats have an unusual community of gut microbes which may help them digest blood, a study suggests.
The furry creatures feed exclusively on blood, a mode of feeding unique among mammals.
It has therefore been long suspected that vampire bats have highly specific evolutionary adaptations, which would be documented in their genome.
Scientists, including those from the German Leibniz Institute for Zoo and Wildlife Research (IZW), analysed the genome of vampire bats and the microorganisms that live in their gut.
They analysed how much the viruses contained in the blood may affect the vampire bats.
The results demonstrate that the microbiome plays an essential part in tackling nutritional and non-nutritional challenges posed by blood meals and improving resistance to viral infections.

The common vampire bat (Desmodus rotundus) belongs to a small group of bat species that are adapted to a blood-based diet (sanguivory).

Feeding only on blood poses a big challenge, as this diet is low in vitamins, lipids and glucose and has a high salt content.
A blood diet also exposes these animals to a large variety of blood-borne pathogens, including viruses.
Researchers sequenced and analysed both the vampire bat genome and its microbiome to investigate specific adaptations of vampire bats to sanguivory.
They discovered that the vampire bat microbiome is very different from other carnivorous, insectivorous or frugivorous bats.

The adaptations to feeding on blood conferred by both the genome and the microbiome include the ability to tackle nitrogen waste and increased osmotic pressure, iron assimilation and changes in immunity.
In a second study, researchers from the Leibniz-IZW and colleagues examined the presence of viruses in populations of vampire bats and cattle from the same geographic region.
The surprising insight was that bats and cattle did not share pathogenic viruses.
In general, vampire bats carried far fewer retroviruses, for example, than other bats or other mammals.
"In vampire bats, the microbiome not only helps to process a nutrient-poor diet, which is difficult to digest by the host, it also contributes to host defense against blood borne viruses," said Marina Escalera-Zamudio, a former PhD student at the Leibniz-IZW and currently a postdoctoral fellow at Oxford University.

"This is a really good example of the interdependency between the host and its bacterial community during the evolutionary process," said Escalera-Zamudio.
Both studies suggest that host ecology and species-specific adaptations must be taken into consideration to determine the risk that a bat species poses in transmitting viruses.