Question: Can diseases spread from one animal to another, for example can a disease from a giraffe spread to give it to the elephant?

Bethany Dearlove answered on 13 Jun 2014:

Yes, diseases can spread between different animals – and from animals into humans. Such diseases are known as ‘zoonotic’ diseases. It’s not easy to make the ‘jump’ into a new animal host though, as species have different biological features that the disease has to overcome – for example, different immune systems, organs and body temperatures. In addition, the two species have to come into contact and interact in some way – this could be through shared environment, social contact, or even a predator eating infected prey.

To begin with, a few microbes will gain the ability (perhaps through a single mutation) to be able to transfer into the new host and survive, but with little or no further transmission. Occasionally, some of these will survive to spread into another individual, and another…and another, until there is sustained transmission between members of the new host species. You might have heard of avian or bird flu. This is a type of influenza (flu) that is naturally found in birds, and then occasionally makes the jump of being able to infect humans – sometimes causing global scale epidemics.

The main bacteria I work on, Campylobacter, is also zoonotic. Some strains of Campylobacter are only found in a single host species, but others are found in multiple species. It is these ones – that can infect chicken, cows and pigs – which are the main ones that also go on to infect humans. I’m using sequence data to try and understand how these strains can switch so easily between hosts (or whether they actually don’t, and it just appears that they do), so we can better identify how it gets into humans. So far, it looks like chickens are the main culprit – though it’s not a problem as long as you cook it properly!