Abstract
ObjectiveThis study aimed to evaluate bacterial and host factors causing a fever in cows with metritis. For that, we investigated uterine microbiota using a metagenomic sequencing of the 16S rRNA gene (Study 1), and immune response parameters (Study 2) in metritic cows with and without a fever.Principal Findings (Study1)Bacterial communities were similar between the MNoFever and MFever groups based on distance metrics of relative abundance of bacteria. Metritic cows showed a greater prevalence of Bacteroidetes, and Bacteroides and Porphyromonas were the largest contributors to that difference. A comparison of relative abundance at the species level pointed to Bacteroides pyogenes as a fever-related species which was significantly abundant in the MFever than the MNoFever and Healthy groups; however, absolute abundance of Bacteroides pyogenes determined by droplet digital PCR (ddPCR) was similar between MFever and MNoFever groups, but higher than the Healthy group. The same trend was observed in the total number of bacteria.Principal Findings (Study2)The activity of polymorphonuclear leukocyte (PMN) and the production of TNFα, PGE2 metabolite, and PGE2 were evaluated in serum, before disease onset, at 0 and 3 DPP. Cows in the MNoFever had decreased proportion of PMN undergoing phagocytosis and oxidative burst compared with the MFever. The low PMN activity in the MNoFever was coupled with the low production of TNFα, but similar PGE2 metabolite and circulating PGE2.Conclusion/SignificanceOur study is the first to show a similar microbiome between metritic cows with and without a fever, which indicates that the host response may be more important for fever development than the microbiome. Bacteroides pyogenes was identified as an important pathogen for the development of metritis but not fever. The decreased inflammatory response may explain the lack of a febrile response in the MNoFever group.
Highlights
Metritis is an inflammatory disease in the uterus within 21 days after parturition that affects the cow’s welfare and leads to decreased milk yield, decreased reproductive performance, and economic loss [1,2,3]
We found that the uterine microbiota composition at the phylum and genus level, the total bacterial load, and the absolute numbers of B. pyogenes were very similar between metritic cows with and without a fever
Similar to our recent observations in metritic cows with a fever [15], the uterine microbiota of metritic cows without a fever was dominated by the phyla Bacteroidetes and Fusobacteria
Summary
Metritis is an inflammatory disease in the uterus within 21 days after parturition that affects the cow’s welfare and leads to decreased milk yield, decreased reproductive performance, and economic loss [1,2,3]. It has been proposed that cows with an abnormally enlarged uterus, a fetid watery red-brownish uterine discharge, and a fever be classified as puerperal metritis, whereas the term, metritis should be used for cows with delayed uterine involution and a fetid discharge in the absence of a fever [4]. Only cows with a fever have been evaluated for approval of new antibiotics for treatment of metritis [7,8]. The difference in cure rate could be due to differences in the microbiota associated with fever, which could affect the response to antibiotic treatment
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