Microbiota Analysis of an Environmental Slurry and Its Potential Role as a Reservoir of Bovine Digital Dermatitis Pathogens

Abstract

At present, very little information exists regarding what role the environmental slurry may play as an infection reservoir and/or route of transmission for bovine digital dermatitis (DD), a disease which is a global problem in dairy herds. To investigate whether DD-related bacteria belong to the indigenous microbiota of the dairy herd environment, we used deep amplicon sequencing of the 16S rRNA gene in 135 slurry samples collected from different sites in 22 dairy farms, with and without DD-infected cows. Both the general bacterial populations and digital dermatitisassociated Treponema were targeted in this study. The results revealed significant differences in the bacterial communities between the herds, with only 12 bacterial taxa shared across at least 80% of all the individual samples. These differences in the herd microbiota appeared to reflect mainly between-herd variation. Not surprisingly, the slurry was dominated by ubiquitous gastrointestinal bacteria, such as Ruminococcaceae and Lachnospiraceae. Despite the low relative abundance of spirochetes, which ranged from 0 to 0.6%, we were able to detect small amounts of bacterial DNA from DD-associated treponemes in the slurry. However, the DDassociated Treponema spp. were detected only in samples from herds with reported DD problems. These data indicate that treponemes involved in the pathogenesis of DD are not part of the normal environmental microflora in dairy herds without clinical DD and, consequently, that slurry is not a primary reservoir of infection.IMPORTANCE Bovine digital dermatitis (DD), a dermal disease which causes lameness in dairy cattle, is a serious problem worldwide. To control this disease, the infection reservoirs and transmission routes of DD pathogens need to be clarified. The dairy herd slurry may be a pathogen reservoir of DD-associated bacteria. The rationale for the present study was, therefore, to examine whether DD-associated bacteria are always present in slurry or if they are found only in DD-afflicted herds. The results strongly indicated that DD Treponema spp. are not part of the indigenous slurry and, therefore, do not comprise an infection reservoir in healthy herds. This study applied next-generation sequencing technology to decipher the microbial compositions of environmental slurry of dairy herds with and without digital dermatitis.

Relationships among bedding materials, bedding bacterial composition and lameness in dairy cows

“…The core bacteria which have been identified in DD lesions are genus Treponema, Mycoplasma, Fusobacterium, Porphyromonas, and Dichelobacter [12,13]. DD-associated Treponema was reported to present in the housing facility of the dairy herds with clinical DD history [14,15]. However, except for traditional pathogens such as Treponema, different bedding materials may selectively promote the survival and growth of other bacterial taxa related to DD lesions.…”

Molecular detection of Treponema species organisms in foremilk and udder cleft skin of dairy cows with digital dermatitis

“…among our samples. Identification of the potential reservoirs for DD Treponema was the main concern in many previous studies (Evans et al 2012(Evans et al , 2016Klitgaard et al 2017). Numerous number of reservoirs for Treponema spp.…”

“…Further reservoirs and hosts for Treponema have been also documented including non-pedal bovine regions such as oral cavity, bovine rectum, bovine gastrointestinal tract contents, and slurry, confirming the presence of different hosts and environmental reservoirs for Treponema other than the foot tissue or DD lesions. (Edwards et al 2004;Evans et al 2012;Klitgaard et al 2017).…”

Missing pieces of the puzzle to effectively control digital dermatitis

“…The literature has also evaluated the role that early or active host‐associated DD lesions play as a primary reservoir of infectious organisms. Multiple studies have demonstrated that the quantitative levels of DD‐associated treponemes are higher in host‐associated tissues (including rectum, gingiva, rumen, DD lesions) than in environmental samples collected from dairy environments (Evans, Timofte et al., ; Klitgaard, Strube, Isbrand, Jensen, & Nielsen, ; Rock, Krull, Gorden, Shearer, & Plummer, ). However, low numbers of DD‐associated Treponema spp can be identified in dairy farm slurry on farms with endemic DD when using deep sequencing‐based phylogenomic approaches (Klitgaard et al., ; Rock et al., ).…”

“…Multiple studies have demonstrated that the quantitative levels of DD‐associated treponemes are higher in host‐associated tissues (including rectum, gingiva, rumen, DD lesions) than in environmental samples collected from dairy environments (Evans, Timofte et al., ; Klitgaard, Strube, Isbrand, Jensen, & Nielsen, ; Rock, Krull, Gorden, Shearer, & Plummer, ). However, low numbers of DD‐associated Treponema spp can be identified in dairy farm slurry on farms with endemic DD when using deep sequencing‐based phylogenomic approaches (Klitgaard et al., ; Rock et al., ). Likewise, there is evidence from multiple groups that foot trimming equipment can be contaminated with treponemes and may act as a source of infection between animals and farms (Rock et al., ; Sullivan et al., ).…”