Menu Close
An Australian cockroach on a white background.

Invasive species: biggest threat may be the most uncertain – disease

Showering celebrities with cockroaches, spiders and other exotic bugs might have seemed fun in Australia, but it’s a different story when the bushtucker trials move to Wales. Police are investigating I’m a Celebrity, Get Me Out Of Here because of concerns that non-native wildlife used in the ITV reality show – said to include cockroaches, whip scorpions, mealworms and crayfish – may be escaping into the Welsh countryside.

The UK is at constant risk of invasion by animals, plants, and microbes that haven’t evolved here. We can appreciate their potential environmental impact by comparing invasive species with oil spills. The effect of an oil spill is largely determined by the total amount of fuel that leaks, but it can be cleaned up and over time it becomes less severe. But when an alien species enters a new environment and is able to survive, its population can grow out of control and continue to spread and affect ecosystems long after the first release, eventually becoming difficult to control.

If even a few insects or spiders were to make it into the Welsh countryside, their population could grow and compete with – or even eat – native wildlife. This is what keeps invasive species biologists up at night. Nests belonging to the invasive Asian hornet have been recorded at least three times in the UK. If this species were to gain a foothold, it could pose a major health risk to people and decimate native bee populations.

You only need to visit your local park to see what a successful invasion can mean for native wildlife. You might spot an invasive grey squirrel, but you’re far less likely to see a native red squirrel almost anywhere in the UK. The key to grey squirrels colonising the British Isles wasn’t simply that they turned up and pushed the reds out. The greys used biological warfare – transmitting a deadly disease to red squirrels called the squirrel pox virus.

This is the unknown factor that scientists fear most. We can anticipate and prepare for an invasive species that acts as a new predator or competitor for native wildlife. But how do we begin to prepare for the myriad diseases that they might carry?

Hitchhikers on invasive species

Invasive species can carry all kinds of diseases. If an animal or plant brings with it an unfamiliar virus, bacteria or other microorganism, it might infect local species. The crayfish plague, caused by a fungal parasite carried by invasive signal crayfish from North America, has killed large numbers of the UK’s native white clawed crayfish. When crayfish plague hits a stream or river, you’ll know within the day as dead crayfish wash up.

While a spokesperson for I’m a Celebrity, Get Me Out Of Here was reported as insisting that the bugs they use aren’t likely to cause a problem in the wild, first impressions can be deceiving. We can’t predict how a non-native species will behave in a new environment.

Our work at the National Horizons Centre of Teesside University explores how invasive parasites, such as viruses and bacteria, evolve and interact with native species when introduced to somewhere new. Their spread and impact can vary depending on the type of parasite and the species it infects. In some cases, like the squirrels and crayfish, the disease can cause no symptoms in the invasive host, but can kill the native species.

Read more: Invasive species: why Britain can't eat its way out of its crayfish problem

In others, diseases can actually control the invaders, and stop them from causing too much damage. The invasive demon shrimp caused a great deal of alarm when it was discovered in the UK in 2012. We recently discovered a novel nudivirus, which appears to alter the behaviour of demon shrimp in their non-native habitat, making infected animals more active and potentially increasing their ability to spread both the virus and themselves. But we’ve also found parasites that can control the population by making the shrimp sick, including a spore-forming fungus known as Cucumispora ornata. These examples highlight the critical role invisible hitchhikers play in the invasion process, either exacerbating or limiting the colonising capabilities of their animal hosts.

A small, pale shrimp suspended in water.
Demon shrimp may not look like much, but they could spell bad news for native crustaceans. Jack Perks/Shutterstock

Despite their obvious importance, we know worryingly little about these parasites in invasive arthropods – the invertebrate animals which include insects, arachnids and crustaceans. That leaves us in the dark about the potential diseases new invaders can carry. Less than a third of invasive species we studied have been screened for parasites, and there remains a lot of uncertainty around how diverse these parasites are, which invasive species can carry them and whether their introductions could harm native wildlife.

The furore around I’m a Celebrity’s non-native insects should set an example. Other industries, including the trade in ornamental species and tourism, have adjusted to accommodate the risk of spreading invasive species. Now we need much better security measures for television programmes that use wildlife, to prevent non-native species escaping sets and ending up on our doorsteps.

Want to write?

Write an article and join a growing community of more than 183,800 academics and researchers from 4,961 institutions.

Register now