Recent Irish research investigated rodent pest resistance to anticoagulant rodenticide

Research examining the possibility of resistance to anticoagulant rodenticides has been carried out on Irish Norway Rats (also known as Brown Rats) and House mice. Resistance to some anticoagulant rodenticides in rats and mice has been detected in parts of central and southern England and south-west Scotland, as well as in populations of these species in other European countries. However, until now, no data was available on the occurrence in Ireland of such resistance. The results have been published in the on-line journal Springer Nature Scientific Reports.

This research work was completed by the Molecular Virology Laboratory of the Department pf Agriculture working with the Campaign for Responsible Rodenticide Use Ireland and with selected Pest Control Companies.

Although the number of rat samples available for analysis was less than planned, no genetic evidence was found of the occurrence and distribution of mutations associated with Norway rat resistance to anticoagulant rodenticides in the Eastern region of Ireland.  Given the absence of mutations associated such resistance, it can be concluded that there is a high probability that these are true negative findings or that the prevalence of resistance is very low. This is important because the use of anticoagulants in attempts to control rodent pests that have developed resistance to them, unnecessarily exposes wildlife to poisoning with rodenticides.

In the case of House mice, evidence of resistance to anticoagulant rodenticides was found following screening for six different mutations associated with anticoagulant resistance. There was widespread presence of two separate mutations in House mice samples taken from the east of Ireland. Biological testing would be required to establish the extent to which those mutations have conferred field resistance to the House mouse populations concerned. However, it is highly likely that such field resistance is present in House mouse populations, in at least the Eastern Region of Ireland.

Rodent pests are vectors or carry vectors of many serious human and animal diseases, cause significance spoilage, losses of food and feed as well as damage to buildings and infrastructure. There are more than 200 rodenticide products authorised for use in Ireland, and in excess of 60 companies provide pest control services in Ireland.  There is a clear need for further research to establish the extent and distribution of anticoagulant resistance in populations of rodent pests on the island of Ireland.

The full article can be read at https://www.nature.com/articles/s41598-018-22815-7.

For more information on the Campaign for Responsible Rodenticide Use in Ireland log on to www.crru.ie  or call Eanna Ni Lamhna on 087 6147506.