Fruit bats and Ebola, but why?

Ebola transmission and sourceOf all animals, bats and rats are generally considered to carry around numerous pathogens that can infect humans. Rats tend to live close to humans and are still associated with the bubonic plague that swept through Europe in the 14th century, killing almost 25 million people. But why do bats have such a bad reputation?

Well this prejudice against bats is actually not very surprising. Bats can carry a number of pathogens (rabies, Hendra, Marburg, Nipah and indeed also Ebola). These are all viruses that can cause serious disease in humans. Particularly the Ebola virus can be deadly, killing up to 90% of all infected humans.

Who is to blame?

Contrary to rats, bats do not like to live near humans. But humans are, especially in the tropics, constantly expanding into bat habitat. This – of course – increases the risks of humans coming into contact with these animals. This is not the bats fault, but it does explain the rise of incidences of humans infected with pathogens via bats.

Why bats?

Whether a bat lives in a cave or in a tree, it will always live there with other bats, lots of other bats. Sleeping close together to keep their bodies warm, and in the process creating the perfect conditions for pathogens to spread between animals.

On top of that, bats have a very sophisticated immune system to keep them healthy. Not only does this immune system protect them from dying from many pathogens, it also protects against cancer/DNA damage. Unlike birds, bats have thin but relatively heavy bones, hence the amount of energy required to fly is huge. And where energy is used, free radicals are produced. To prevent this reactive waste from damaging DNA, bats have evolved a very sophisticated and effective immune system. Apart from the immune system, there is another trick; when bats fly their body temperature rises to about 40C. Most viruses and bacteria are eliminated at these temperatures. In fact raising body temperature (fever) is an important part of the human body to overcome pathogens. But unfortunately there are bacteria and viruses that can cope, or learn to cope, with these high temperatures.  These tolerant pathogens are then very difficult for the human body to combat.

Are all bats bad?

As long as you don;t run around poking bats with sticks you are very unlikely to ever get bit by one in the first place. Bats are too afraid of humans to come close and too busy doing important work such as catching mosquitos and pollinating fruit trees. And then again, most bats do not carry zoonotic disease.

Worth watching is this MinuteEarth animated video about bats and disease: