Isolation of Rhodococcus equi from the gastrointestinal contents of earthworms (family Megascolecidae)

Abstract

Rhodococcus equi was isolated from the gastrointestinal contents of earthworms (family Megascolecidae) and their surrounding soil collected from pastures of two horse‐breeding farms in Aomori Prefecture, outdoor pig pens, forest in Towada campus, orange groves and forest where wild boars (Sus scrofa) are established in Tanabe, Wakayama Prefecture. The number of R. equi in the lower gastrointestinal contents of 23 earthworms collected from our campus was significantly larger than that of the upper gastrointestinal content. The mean numbers of R. equi from the gastrointestinal contents of earthworms collected from the various places were 2·3‐fold to 39·7‐fold more than those of the surrounding soil samples. In all, 1771 isolates from the earthworms and 489 isolates from the soil samples were tested for the presence of vapA and vapB genes using polymerase chain reaction. At the horse‐breeding farm N, 9 of the 109 isolates (8·3%) from the earthworms and 7 of the 106 isolates (6·6%) from the soil samples were positive for the vapA gene. At the University’s forest, one of the 250 isolates (0·4%) from the gastrointestinal contents of the earthworm was positive for the vapB gene. These results revealed that R. equi can be found in significant quantities in the gastrointestinal contents of earthworms, suggesting that they act as an accumulator of R. equi in the soil environment and as a source or reservoir of animal infection.

Science‐in‐brief: The 6th Havemeyer Workshop on Rhodococcus equi—A decade‐long journey in advancing research into a major equine pathogen (2012–2023)

“…Evidence exists of biological vectors within the biota of the soil and the gut of foals that can enable virulent R. equi to proliferate and perhaps protect the organism from being exposed to environmental stresses. 8,9 Foals, especially those with clinical signs, shed high concentrations of virulent R. equi in their faeces. Further, their dams can shed high concentrations into the environment.…”

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): antimicrobial‐resistant Rhodococcus equi in horses

“…R. equi is ubiquitously distributed in soil and there is no evidence that the disease can be transmitted from animal to animal. Thus, although R. equi can be isolated from several animal species, including the gastrointestinal contents of earthworms (Annelida; Megascolecidae) (Takai et al., 2021 ), none of them is regarded as a disease reservoir.…”

Virulence plasmids in clinical isolates of Rhodococcus equi from sick foals in the Netherlands

“…Rhodococcus equi is widespread, inhabits the soil and colonizes the intestine of grazing animals and omnivores, and more recently, it was isolated from the earthworm's gastrointestinal contents (Takai et al . 2022). Rhodococcus equi also infects other mammals, including pigs, cattle, goats, cats, dogs and humans (Vázquez‐Boland and Meijer 2019).…”

“…Rhodococcus equi is a well-known bacterial pathogen first described in a Swedish foal in 1923 as the causative agent of pyogranulomatous pneumonia and lung abscesses in foals aged less than 6 months (Magnusson 1923). Rhodococcus equi is widespread, inhabits the soil and colonizes the intestine of grazing animals and omnivores, and more recently, it was isolated from the earthworm's gastrointestinal contents (Takai et al 2022). Rhodococcus equi also infects other mammals, including pigs, cattle, goats, cats, dogs and humans (V azquez-Boland and Meijer 2019).…”