Research Summary - 2
Assessment of the validity of on-farm tests to diagnose uterine infection in dairy cows
| Date/Time: |
9/13/2024
12:00
|
| Author: |
José Denis-Robichaud |
| Clinic: |
Independent researcher |
| City, State, ZIP: |
Amqui, QC G5J2N5 |
J. Denis-Robichaud, DVM, MSc, PhD, Dipl. ACVPM
1
;
N. Barbeau-Grégoire, MSc
2
;
M.-L. Gauthier, DVM, MSc, Dipl. ACVM
3
;
S. Dufour, DVM, PhD
2
;
J.-P. Roy, DVM, MSc, Dipl. ECBHM
2
;
S. Buczinski, DVM, MSc, Dipl. ACVIM
2
;
J. Dubuc, DVM, MSc, DVSc
2
;
1Independent researcher, Amqui, Québec, G5J 2N5, Canada
2Faculté de médecine vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, J2S 2M2, Canada
3Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec, Saint-Hyacinthe, Québec, J2S 2M2, Canada
Introduction:
Dairy cows commonly experience uterine bacterial infections
post-calving, which can lead to reproductive tract inflammation. While
diagnosing uterine infection requires bacteriological culture, on-farm
identification of inflammation is quicker. Moreover, antimicrobial treatment
has shown positive impacts on reproductive performance of cows identified with
inflammation of the reproductive tract. In the face of antimicrobial resistance
concerns, however, the diagnostic of uterine infection might become essential. In this prospective cross-sectional study, our aim was to assess the
diagnostic validity of various tests for identifying uterine infection (UI) in
dairy cows, and to evaluate their utility under different scenarios.
Materials and methods:
From July 2020 to April 2023, we sampled cows between 29 and 43 (DIM) in
seven dairy herds. We evaluated six diagnostic methods: laboratory bacteriological
culture, Petrifilm, Tri-Plate, luminometry, purulent vaginal discharge (PVD),
and esterase. The vaginal discharge was assessed using a Metricheck, and uterine
samples, for the bacteriological (laboratory, Petrifilm, and Tri-Plate) and esterase
test, were collected using uterine cytobrushes. Test results were dichotomized
using thresholds of ≥ 3 (mucopurulent discharge) for PVD, ≥ 2 (moderate amount
of leukocytes or more) for esterase, ≥ 100 CFU/mL for the laboratory culture,
and of ≥ 1 CFU on at least one of the medium for Tri-Plate. For Petrifilm and
luminometry, multiple thresholds were tested (Petrifilm: 100 to 350 CFU/mL;
luminometry: 50 to 300 relative light units). We estimated sensitivity and
specificity of each test using Bayesian latent class models. Additionally, we
devised ten scenarios reflecting real-world farm conditions, exploring the
predictive values and misclassification cost terms (MCT) at different UI prevalences
(0.20, 0.40, and 0.60) and for different false-negative to false-positive
ratios.
Results:
A total of 326 uterine samples were analyzed. Among the tests,
laboratory culture demonstrated the highest sensitivity (0.87; 95%BCI = 0.77-0.97)
and specificity (0.71; 95%BCI = 0.58-0.86), while PVD exhibited the lowest
sensitivity (0.05; 95%BCI = 0.01-0.10). Notably, PVD showed consistently low
PVs and high MCT across all scenarios, indicating its inadequacy for UI
identification. Laboratory culture consistently exhibited high PVs and low MCT,
suggesting its reliability in most situations. However, esterase and on-farm
bacteriological tests (Petrifilm and Tri-Plate) did not yield comparable
results. Interestingly, luminometry showed potential, particularly when
considering scenarios where the consequences of treating a healthy cow outweighed
those of leaving a cow with UI untreated.
Significance:
Our findings underscore the limitations of current on-farm diagnostic tools (PVD and esterase) in accurately identifying cows with UI. While laboratory culture emerges as the most valid test, its practical implementation on dairy farms may pose challenges. The luminometry showed promise, but would require further research to optimize its utility for judicious UI treatment.
