Roadside flowerpots probably accelerated the spread of rat lungworm Angiostrongylus spp. in Norway rats

Abstract

We detected a zoonotic parasite, the rat lungworm Angiostrongylus spp. in Norway rats Rattus norvegicus that were collected in February each year from 2015 to 2020 outside buildings in a 21-hectare business district in Yokohama. The infection rate of the parasite in rats that were two months old or older jumped from 4.9% in 2015 to 28.6% in 2017 when flowerpots were set along the roadside, but it decreased to nearly 7% in 2018 and 2019 and to 0% in 2020 when those flowerpots were removed. It is likely that the rate increased because the flowerpots supplied intermediate hosts of the lungworm, i.e., slugs and snails with habitats.