Phil Christopher, CRRU, reminds professionals to take the opportunity to explain why we control rats, by looking at the zoonotic diseases rodents carry.

"Whenever possible, take the opportunity to explain why we control rats because, even though it's self-evident to us, there will always be influential people against the use of rodenticides."

This invaluable advice came from the late Jonathan Peck, long time Killgerm figurehead, in the early days of the Campaign for Responsible Rodenticide Use. As many readers will know, he was uniquely instrumental in starting and representing CRRU until his untimely passing in 2013.

Jonathan's wise words came to mind recently while reading about research that identified a number of human disease organisms carried by rats in a public park just north of Paris city centre. The park hosts a farm, circus, horse livery and about two million visitors a year.

Of rat bodies analysed, 88% carried at least two such pathogens, and another 10% carried one. Five different species of Leptospira were found, all capable of causing serious human disease, including Weil's.

Three more genera (plural of genus) of zoonotic bacteria were Bartonella, Rickettsia and Francisella. These are variously responsible for human illnesses affecting heart or lungs, liver or kidneys, brain and central nervous system, lymph nodes or skin.

Of rat bodies analysed, 88% carried at least two such pathogens, and another 10% carried one. Five different species of Leptospira were found, all capable of causing serious human disease, including Weil's.

Some serious cases can be fatal, while many cause fever, headache and debilitation that can be slow or impossible to overcome.

Although not found in this study, the roll call of familiar rat-borne agents of human or farm animal diseases also includes Salmonella, Toxoplasma, Cryptosporidium, Pasteurella, Listeria, Hantavirus and Campylobacter.

Among other relevant findings, 56% of rats, which were trapped live and euthenased, carried a common resistance mutation and 48% carried rodenticide residues. This is despite the use of anticoagulant rodenticides being prohibited throughout the park.

Together with a high genetic diversity among rats analysed, the report suggests this indicates significant migration into the park from its surroundings.

Source*: Desvars-Larrive A, et al (2017). Population genetics, community of parasites, and resistance to rodenticides in an urban brown rat (Rattus norvegicus) population. PLoS ONE 12(9): e0184015.

Source: CRRU press release