Rats are once again in the news, thanks to recent research, showing that the black death in medieval Europe may have been carried by gerbils rather than black rats.
Another study has indicated that farming expansion in east Africa is attracting plague-carrying rats and increasing the risk of transmission to humans.
These new findings on the role of rodents in the transmission of plague in Europe and Africa highlight some of the serious problems rodents can cause for people. Indeed, the impact of the plague on human civilisation makes it the single most important human disease in history, transforming the economy of medieval Europe through influencing social relations, culture, religion and politics.
Some have argued the effects of the black death helped “reset” European civilisation and contributed to the subsequent Renaissance and European expansionism in later centuries.
The disease-carrying potential of rodents continues to be a major socioeconomic issue, and is particularly acute in tropical developing countries, where people are living in closer proximity to rodents because of poor-quality housing, infrastructure and sanitation. Plague still exists in many parts of the world, with most human cases reported in Africa nowadays.
There are more than 60 other human diseases in which different species of rodent are involved either as reservoirs or vectors. Rat-borne contagions including leptospirosis can be a massive burden on healthcare systems in developing countries, but they can also often be under-reported through misdiagnosis or lack of clinical recognition.
This is because the symptoms of many rat-borne diseases (high fever) are not easily distinguished from those of more familiar conditions, including malaria or dengue.
There is also growing evidence that diseases in which rats are implicated have been severely underdiagnosed globally, and that the true burden of rodents on human health is likely to be much greater than is currently accepted by clinicians, researchers, donors and governments.
This lack of awareness and understanding of the impact of rodents on our health and livelihoods originates directly from our behaviour and cultural attitudes to them. Through generations of negative experiences, rats are ingrained in our psyches as bad, scary animals much like snakes, spiders and bats. We loathe rats and find it easier to sweep them from our thoughts than deal with the issues that make them problematic.
Do we really want to know all the bad things rats are doing, such as eating and contaminating our food with their urine and faeces? With acknowledgement of the problems comes a responsibility to resolve them, when often we are not quite sure how to lessen the impact of rodents and do not have adequate resources to do so.
“Rats are too clever to control” has become a mantra that excuses individuals and society. Instead focusing our attention on problems, we are more comfortable talking about. We continue to be horrified and disgusted by rats and yet often feel powerless to do anything about them. These ingrained attitudes and beliefs about rodents as a nasty, intractable problem are preventing society from overcoming quite significant problems they cause to our health and agriculture.
Despite the bad press rats get, however, there is much to be said in their favour. For many, rodents are a source of joy, entertainment and companionship. Look no further than Mickey Mouse and the hundreds of books and films in which rodents are the main protagonists. Cuddly toy rodents can be found in many children’s bedrooms, and living rodents such as rats, mice, gerbils, hamsters and guinea pigs are kept as domestic pets.
Although we tend to focus on the pests – house mice, black and brown rats – the majority of rodent species have little human interaction and are important components of ecosystems and food webs. For example, some rodents are important for pollinating certain plants, and without them many ecosystems would quickly collapse.
Whether or not we agree with how animals have been used as experimental models in laboratory research, particularly for drug discovery and to understand human diseases, we should not deny the contribution that rats and mice have made to scientific and medical advances. Without their sacrifices, we would not have the quality of life we have today.
Rodents also contribute positively to our lives in unexpected ways. For example, we are exploiting their acute sense of smell by training rodents to detect TNT in order to help clear landmines. They are also being used to help screen for tuberculosis as they can easily smell TB in patients’ sputum samples. Many other jobs that are currently done by dogs, including drug enforcement and border control, may in the near future be done by rats.
So do rats deserve their bad press? The answer, inevitably, is: yes and no. However, most of the bad press is really humanity’s own fault through failing to take responsibility for how we have transformed the world in ways that favour certain rodent pest species. Perhaps, in a strange zoomorphism, people can be the worst kind of rats.