Super-rats arrive in Spain

British scientists have identified rats and mice that are immune to the most commonly used rodenticides – anticoagulants.

Some 78% of rats and 95% of house mice have genes that mean they can tolerate anticoagulant, according to the Daily Mirror newspaper. These usually kill the rodent by causing internal bleeding but this is not happening in Britain. However, such super rodents are already present in Europe, including Spain, and the United States.

According to Jacinto Díez, communications director of the company Rentokil, "anticoagulants were until a few years ago a very effective method to control the population".

European legislation has greatly restricted the use of anticoagulants. The current method of combating rat and mouse infestations involves controls that do not include the use of anticoagulants. "Because of all this, the battle that we had won before is now at a stalemate," Díez said.

Díez said to prevent a rodent infestation it is not only necessary to apply biocides, but also "it is necessary to adopt preventive measures to prevent them from entering an area and, if they do, to ensure that the conditions for their development do not exist". Cleanliness and tidiness, for example, in a warehouse are fundamental, because rodents "have a tremendous capacity for adaptation when it comes to finding food or shelter".

During the pandemic the Rentokil expert said that the closure of bars, shops and businesses, coupled with the absence of people on the streets, "made the rats more confident and they left the sewers to colonise other areas. An effect we are still suffering from”.