Purulent Vaginal Discharge (PVD) in Dairy Cows: Diagnosis, Clinical Significance, and Treatment

Purulent vaginal discharge (PVD) is a common postpartum reproductive disorder that deserves routine attention during herd reproductive examinations. Typically identified 4–6 weeks after calving, PVD is characterized by the presence of muco-purulent or purulent discharge within the cranial vagina. Although it is readily detected during clinical examination, the condition is often underdiagnosed despite its clear association with reduced reproductive performance^1,2,3. 

For practicing veterinarians, recognizing PVD as a distinct clinical entity is essential for accurate diagnosis, timely treatment, and effective herd-level reproductive management. 

Recognizing PVD in Clinical Practice 

PVD is defined by the appearance of vaginal exudate containing more than 50% pus, usually identified during examinations performed approximately one month after calving. The diagnosis is based on the visual characteristics of the discharge rather than laboratory testing. 

While some variation exists regarding the optimal diagnostic threshold, discharge that is clearly muco-purulent or purulent consistently identifies cows at greater risk of reduced reproductive performance. The most appropriate diagnostic threshold may vary depending on the interval from calving and the breeding system being used^1,4,5. 

Routine postpartum reproductive examinations provide an ideal opportunity to identify affected cows before breeding begins. 

Why Accurate Terminology Matters 

One of the most important clinical messages is that PVD should not automatically be interpreted as endometritis. 

Although both conditions may occur in the same cow, they frequently exist independently. Many cows with PVD do not have concurrent cytological endometritis, and agreement between the two conditions at a single examination is poor^1,4,5. 

Similarly, PVD is rarely associated with vaginitis. Instead, the discharge most commonly reflects infection involving the uterus and/or cervix¹. 

For this reason, the term "clinical endometritis" should not be used unless endometritis has been confirmed by concurrent endometrial cytology⁶. Using precise terminology improves communication, treatment decisions, and interpretation of reproductive records. 

Understanding the Underlying Infection 

Microbiological findings indicate that PVD is associated with active bacterial infection rather than sterile inflammation. 

Affected cows demonstrate reduced diversity within the uterine microbiota together with increased abundance of organisms such as Trueperella, Fusobacterium, and Porphyromonas species^7,8. Among these, Trueperella pyogenes has shown the strongest and most consistent association with PVD in culture-based investigations¹. 

Differences in the reproductive tract microbiota can also be detected early in the postpartum period, suggesting that microbial changes precede the clinical appearance of disease⁷. 

Treatment Considerations 

Because PVD reflects active bacterial infection in many cases, local antimicrobial therapy remains an appropriate treatment option. 

Repeated clinical experience supports the use of intrauterine cephapirin for improving reproductive outcomes in affected cows¹. 

By comparison, prostaglandin F2α treatment has generally shown limited or no advantage, although cows with both PVD and a corpus luteum may respond similarly to either treatment approach¹. 

Treatment decisions should therefore be guided by accurate diagnosis rather than relying on hormonal therapy alone. 

Practical Clinical Insights 

PVD is straightforward to diagnose during routine postpartum examinations and should be incorporated into herd reproductive monitoring protocols. Herds with 5% or more affected cows are more likely to experience reduced pregnancy rates at first insemination, making regular surveillance valuable for identifying herd-level reproductive constraints¹. 

Monitoring the prevalence of PVD, applying consistent diagnostic criteria, and treating eligible cases with approved intrauterine antimicrobial therapy can help veterinarians strengthen postpartum reproductive management while supporting improved reproductive performance across the herd. 

References 

1. LeBlanc SJ. Postpartum reproductive disease and fertility in dairy cows. animal. 2023 May 1;17:100781. https://www.sciencedirect.com/science/article/pii/S1751731123000770 

2. Hay MJ, Gunn AJ, Abuelo A, Brookes VJ. The effect of abnormal reproductive tract discharge on the calving to conception interval of dairy cows. Frontiers in veterinary science. 2019 Oct 22;6:374. https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2019.00374/pdf 

3. Moraes JG, Silva PR, Mendonça LG, Okada CT, Chebel RC. Risk factors for purulent vaginal discharge and its association with reproductive performance of lactating Jersey cows. Journal of Dairy Science. 2021 Dec 1;104(12):12816-29. https://www.sciencedirect.com/science/article/pii/S0022030221008560 

4. McDougall S, Aberdein D, Bates A, Burke CR. Prevalence of endometritis diagnosed by vaginal discharge scoring or uterine cytology in dairy cows and herds. Journal of dairy science. 2020 Jul 1;103(7):6511-21. https://www.sciencedirect.com/science/article/pii/S0022030220303416 

5. Kelly ET, McAloon CG, O'Grady L, Duane M, Somers JR, Beltman ME. Reproductive tract disease in Irish grazing dairy cows: Retrospective observational study examining its association with reproductive performance and accuracy of 2 diagnostic tests. Journal of dairy science. 2022 Jun 1;105(6):5471-92. https://www.sciencedirect.com/science/article/pii/S0022030222002284 

6. Pascottini OB, Van Schyndel SJ, Spricigo JW, Rousseau J, Weese JS, LeBlanc SJ. Dynamics of uterine microbiota in postpartum dairy cows with clinical or subclinical endometritis. Scientific reports. 2020 Jul 23;10(1):12353. https://www.nature.com/articles/s41598-020-69317-z.pdf 

7. Miranda-CasoLuengo R, Lu J, Williams EJ, Miranda-CasoLuengo AA, Carrington SD, Evans AC, Meijer WG. Delayed differentiation of vaginal and uterine microbiomes in dairy cows developing postpartum endometritis. PloS one. 2019 Jan 10;14(1):e0200974. https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0200974&type=printable 

8. Pascottini OB, Van Schyndel SJ, Spricigo JW, Rousseau J, Weese JS, LeBlanc SJ. Dynamics of uterine microbiota in postpartum dairy cows with clinical or subclinical endometritis. Scientific reports. 2020 Jul 23;10(1):12353. https://www.nature.com/articles/s41598-020-69317-z.pdf